The document discusses computed tomography (CT) scanning. It begins by introducing CT and comparing it to conventional radiography. CT provides more accurate diagnostic information by reconstructing 3D structures from multiple 2D projections, unlike conventional radiography which produces 2D shadow images. The document then covers key aspects of CT scanning including the components involved in data acquisition, the reconstruction process, and parameters such as slice thickness and radiation dose. It also describes advances in CT technology over generations from narrow single detector scans to modern multi-detector scanners.
Magnetic Resonance Angiography and techniquesAlwineAnto
This document discusses MR angiography techniques and vascular abnormalities. It begins by outlining the major vascular systems in the human body. It then describes various vascular abnormalities like stenosis, aneurysms, and arterial venous malformations. The document goes on to explain different MR angiography pulse sequences like TOF, CE MRA, and PC MRI. It provides details on TOF MRA principles and advantages/disadvantages. Common artifacts seen on TOF MRA like shine-through and susceptibility artifacts are also outlined. Finally, the document discusses CE MRA techniques including test bolus timing and advantages/disadvantages compared to TOF MRA.
presentation on ultrasound elastography-introduction ,techniques,physics,application, interpretation and future prospects.sourced from multiple articles.
Dual energy CT utilizes two different x-ray spectra to characterize tissues. It can help address challenges with single energy CT like lesion detection and image noise. Dual energy CT works by analyzing how materials attenuate x-rays differently at various energies, allowing differentiation of substances like iodine and calcium. There are several technical approaches to dual energy CT, including sequential acquisition with two scans, rapid voltage switching between two voltages, and dual-source CT with two tube-detector pairs. Post-processing involves material decomposition and differentiation using image-domain or projection-domain algorithms.
MRI of the breast has certain contraindications including the presence of metallic implants, those unable to lie prone, or with large body habitus. Normal breast tissue may enhance asymmetrically, so scheduling during days 7-20 of the menstrual cycle can provide less enhancement. Dedicated breast coils are used with patients lying prone, and protocols involve unilateral or bilateral imaging with pre-and post-contrast sequences to analyze enhancement kinetics. Morphological features like irregular shapes and enhancement kinetics help identify lesions, with Type I curves associated with benign lesions and Type III with malignancy. MRI is useful for screening, determining tumor extent, assessing recurrence or residual disease, and providing information not available from other imaging methods.
Elastography is a noninvasive imaging technique that uses ultrasound to image the elasticity or stiffness of tissues. It works by applying slight pressure and measuring how tissues deform. Hard tissues appear stiffer on elastograms. Elastography has many medical applications including differentiating benign from malignant breast lesions, assessing liver fibrosis, and evaluating prostate lesions. Shear wave elastography provides quantitative stiffness measurements and is the most accurate method. While useful, elastography has limitations such as difficulty imaging large or painful lesions and certain anatomical areas. Overall, elastography provides important clinical information about tissue composition when used along with other imaging tests.
This document provides an overview of breast MRI, including anatomy, techniques, and characteristics of different breast lesions. Breast MRI is very sensitive for cancer detection, especially in dense breasts. Dynamic contrast enhanced MRI is used to evaluate lesion morphology, enhancement patterns, and kinetics. Benign lesions like cysts and fibroadenomas have characteristic appearances, while malignant lesions often appear irregular or spiculated with rapid early enhancement and washout. Non-mass enhancement can indicate cancers like DCIS and requires analysis of distribution and internal pattern. Computer aided diagnosis evaluates kinetic curves but does not replace visual analysis.
K space is the domain where MRI data is stored during acquisition. It represents the spatial frequency content of the image, with each point containing information about the whole image. K space is filled line by line using gradients to encode phase and frequency, with the center lines containing contrast and the outer lines containing resolution. A Fourier transform converts the data into the actual image domain. Understanding k space is important for MRI physics and image reconstruction.
This document provides an overview of MRI instrumentation, sequences, and artifacts. It describes various types of RF coils including surface coils, paired saddle coils, Helmholtz coils, and birdcage coils. It also discusses magnets including permanent magnets, electromagnets, and superconducting magnets. Common MRI sequences such as spin echo, gradient echo, inversion recovery, STIR, fat saturation, proton density, diffusion weighted imaging, and FLAIR are explained.
Magnetic Resonance Angiography and techniquesAlwineAnto
This document discusses MR angiography techniques and vascular abnormalities. It begins by outlining the major vascular systems in the human body. It then describes various vascular abnormalities like stenosis, aneurysms, and arterial venous malformations. The document goes on to explain different MR angiography pulse sequences like TOF, CE MRA, and PC MRI. It provides details on TOF MRA principles and advantages/disadvantages. Common artifacts seen on TOF MRA like shine-through and susceptibility artifacts are also outlined. Finally, the document discusses CE MRA techniques including test bolus timing and advantages/disadvantages compared to TOF MRA.
presentation on ultrasound elastography-introduction ,techniques,physics,application, interpretation and future prospects.sourced from multiple articles.
Dual energy CT utilizes two different x-ray spectra to characterize tissues. It can help address challenges with single energy CT like lesion detection and image noise. Dual energy CT works by analyzing how materials attenuate x-rays differently at various energies, allowing differentiation of substances like iodine and calcium. There are several technical approaches to dual energy CT, including sequential acquisition with two scans, rapid voltage switching between two voltages, and dual-source CT with two tube-detector pairs. Post-processing involves material decomposition and differentiation using image-domain or projection-domain algorithms.
MRI of the breast has certain contraindications including the presence of metallic implants, those unable to lie prone, or with large body habitus. Normal breast tissue may enhance asymmetrically, so scheduling during days 7-20 of the menstrual cycle can provide less enhancement. Dedicated breast coils are used with patients lying prone, and protocols involve unilateral or bilateral imaging with pre-and post-contrast sequences to analyze enhancement kinetics. Morphological features like irregular shapes and enhancement kinetics help identify lesions, with Type I curves associated with benign lesions and Type III with malignancy. MRI is useful for screening, determining tumor extent, assessing recurrence or residual disease, and providing information not available from other imaging methods.
Elastography is a noninvasive imaging technique that uses ultrasound to image the elasticity or stiffness of tissues. It works by applying slight pressure and measuring how tissues deform. Hard tissues appear stiffer on elastograms. Elastography has many medical applications including differentiating benign from malignant breast lesions, assessing liver fibrosis, and evaluating prostate lesions. Shear wave elastography provides quantitative stiffness measurements and is the most accurate method. While useful, elastography has limitations such as difficulty imaging large or painful lesions and certain anatomical areas. Overall, elastography provides important clinical information about tissue composition when used along with other imaging tests.
This document provides an overview of breast MRI, including anatomy, techniques, and characteristics of different breast lesions. Breast MRI is very sensitive for cancer detection, especially in dense breasts. Dynamic contrast enhanced MRI is used to evaluate lesion morphology, enhancement patterns, and kinetics. Benign lesions like cysts and fibroadenomas have characteristic appearances, while malignant lesions often appear irregular or spiculated with rapid early enhancement and washout. Non-mass enhancement can indicate cancers like DCIS and requires analysis of distribution and internal pattern. Computer aided diagnosis evaluates kinetic curves but does not replace visual analysis.
K space is the domain where MRI data is stored during acquisition. It represents the spatial frequency content of the image, with each point containing information about the whole image. K space is filled line by line using gradients to encode phase and frequency, with the center lines containing contrast and the outer lines containing resolution. A Fourier transform converts the data into the actual image domain. Understanding k space is important for MRI physics and image reconstruction.
This document provides an overview of MRI instrumentation, sequences, and artifacts. It describes various types of RF coils including surface coils, paired saddle coils, Helmholtz coils, and birdcage coils. It also discusses magnets including permanent magnets, electromagnets, and superconducting magnets. Common MRI sequences such as spin echo, gradient echo, inversion recovery, STIR, fat saturation, proton density, diffusion weighted imaging, and FLAIR are explained.
This document provides an overview of breast anatomy and mammography techniques. It describes the internal structures of the breast including lobes, lobules, ducts, and connective tissue. Lymph node drainage pathways are explained. Mammography views including craniocaudal, mediolateral oblique, and magnification views are illustrated along with positioning techniques. Breast composition changes with age. Ultrasound techniques and common breast lesions seen on ultrasound are also reviewed. The document concludes with an explanation of BI-RADS assessment categories used in breast imaging.
Mammography Positioning Technique for Additional Views Selin Prasad
This document discusses additional views that can be performed in mammography, including magnification views, spot compression views, and views for patients with breast implants. Magnification views use a smaller focal spot size and elevated breast position to provide higher resolution of areas of interest, though at the cost of increased radiation dose and potential for motion blur. Spot compression views apply targeted compression over areas of concern to spread overlapping tissues and better define lesion features. Views for implants displace the implant posteriorly during compression to exclude it from the image and allow improved visualization of breast tissue.
MRI can detect breast lesions with high sensitivity but has variable specificity in differentiating benign from malignant lesions. MR spectroscopy provides additional metabolic information that can improve specificity by detecting elevated choline levels associated with malignant tumors. Response to chemotherapy can also be assessed non-invasively with MR spectroscopy by monitoring changes in choline levels within 24 hours of treatment. Limitations include difficulty with small lesions, dense breasts, and lactating breasts.
This document discusses various techniques for reducing radiation dose in computed tomography (CT) scans. It outlines strategies such as using automatic exposure control, adjusting scan parameters based on patient size, employing noise-tolerant images when possible, limiting scan lengths and phases, and utilizing newer reconstruction techniques. The goal is to lower radiation dose without compromising diagnostic image quality.
This document discusses breast imaging recommendations and tools. It recommends annual mammography screening starting at age 40 for average risk women, while high risk women may benefit from additional screening with MRI. Digital mammography is the gold standard but has limitations depending on breast density. New tools like tomosynthesis and ultrasound can help address these limitations and provide additional information. The document reviews various breast imaging tools and their uses, as well as risk factors, screening guidelines, and case examples.
MRI uses strong magnetic fields and radio waves to produce detailed images of the inside of the body. Protons in the body align with the magnetic field, and radio waves excite the protons causing them to emit signals. The signals are detected by coils and used to construct an image on a computer. Different tissues can be distinguished based on proton density and relaxation times after excitation. Gradient fields are used to localize the source of the signals within the body.
1. The document describes several medical cases with imaging findings and diagnoses. It discusses abnormalities seen on CT scans and x-rays indicating conditions like diffuse idiopathic skeletal hyperostosis, tuberculous spondylitis, leaking dermoid tumour, Takayasu arteritis, and advanced bronchial carcinoma.
2. Key findings mentioned include flowing osteophytes, ossification of the posterior longitudinal ligament, calcified psoas abscesses, hydronephrosis, widened mediastinum with sternotomy sutures, dissecting aneurysm of the aorta, occlusion of arteries, and diffuse mural thickening of the rectum and colon.
3. The document
This document discusses magnetic resonance angiography (MRA) and its advantages and disadvantages compared to catheter angiography. It describes different MRA techniques including contrast enhanced MRA, time of flight angiography, phase contrast angiography, and non-contrast techniques. It also discusses artifacts that can appear on MRA such as metal artifacts and blooming artifacts. Key features and images of each technique are provided.
MRI uses strong magnetic fields and radio waves to produce detailed images of organs and tissues in the body. Protons in the body align with the magnetic field, and a radio pulse causes them to resonate. Their signals are detected to form images. Different pulse sequences and parameters produce T1-weighted, T2-weighted, or proton density images. Safety concerns include the strong magnetic field and certain implants. Advantages are no radiation, good soft tissue contrast, and multiplanar imaging. Disadvantages include long scan times and high costs.
This document discusses breast MRI protocols, techniques, and the interpretation of findings. It provides details on coil and patient positioning, recommended MRI field strength, and standard breast MRI protocols. It discusses recognizing normal enhancing structures like vessels, nipples, and lymph nodes. Guidelines are presented for analyzing lesion enhancement and characterizing benign masses based on criteria like smooth margins, shape, homogeneous enhancement, fat content, T2 signal, and rim enhancement. Examples of benign findings like fibroadenomas and fat-containing lesions are also described.
This document outlines the protocol for performing CT angiography (CTA) from the cerebral arteries to the lower limbs. It discusses indications for CTA including aneurysms, stenosis, dissections, and more. The preparation, positioning, and scanning protocols are provided for CTA of the head to lower limbs as well as the subclavian arteries. Pediatric protocols are also summarized. The document concludes with examples of CTA findings and references.
Tissue harmonic imaging is an ultrasound technique that provides higher quality images compared to conventional ultrasound by collecting harmonic signals generated in tissues and filtering out transducer-generated fundamental echo signals, resulting in clearer images with improved contrast resolution, reduced artifacts, and better visualization of deeper structures and vessels. While tissue harmonic imaging improves image quality in many clinical applications, it can decrease axial resolution compared to fundamental frequency imaging due to the narrowed signal bandwidth.
1. MRI provides multi-planar, multi-contrast images to study organ structure, function, metabolism, physiology and pathology in a non-invasive manner.
2. When certain atomic nuclei such as hydrogen protons are placed in a strong, static magnetic field, they align with the field. A radiofrequency pulse can then excite the aligned protons, causing them to emit radiofrequency signals as they relax back to equilibrium.
3. T1 relaxation is the recovery of longitudinal magnetization along the magnetic field axis, while T2 relaxation is the loss of transverse magnetization in the plane perpendicular to the magnetic field. Differences in T1 and T2 values between tissues provide image contrast.
MRI uses strong magnets and radio waves to produce detailed images of the body. It has three main components - the scanner, computer, and recording hardware. The scanner contains powerful magnets including static magnetic field coils, gradient coils, and radiofrequency coils. The static magnetic field orients hydrogen atoms in the body. Gradient coils are used to localize tissues and encode spatial information. Radiofrequency coils transmit RF pulses to excite hydrogen atoms and receive their signals. The signals are processed by the computer to produce images based on the relaxation properties of tissues, namely T1 and T2 relaxation times. T1 relates to the rate at which hydrogen atoms realign with the magnetic field after excitation while T2 relates to the rate of signal decay
This document discusses CT image acquisition. It describes how CT scanners work, including the components of a CT scanner like the x-ray tube and detector array. It explains the image acquisition process, from x-ray generation to data collection and processing, and image reconstruction. Key steps include positioning the patient, rotating the x-ray tube, acquiring data projections from different angles, converting analog signals to digital, reconstructing images from the data using algorithms. The document provides an overview of the CT imaging process.
This document discusses the effects of kVp and mAs on various properties of x-ray images. It explains that kVp determines the highest x-ray energy and quality, while mAs determines the quantity of photons and exposure time. Higher kVp and mAs increase spatial resolution, contrast, and signal-to-noise ratio, but also increase radiation dose. The document covers these parameters for screen-film radiography as well as computed tomography, and how they impact visible properties like image noise, contrast, and resolution.
This document provides an overview of elastography, a medical imaging technique that detects differences in tissue stiffness. It discusses various elastography methods including quasi-static ultrasound elastography, which images strain from externally applied stress, and dynamic methods like transient elastography that image shear waves to quantify tissue stiffness. The document outlines early developments in elastography research and commercial applications, limitations of different techniques, and potential future advances.
MRI uses strong magnetic fields and radio waves to generate images of the inside of the body. It works by aligning hydrogen atoms in water molecules and fat in tissues when placed in a magnetic field. Radio waves are then used to stimulate the hydrogen atoms, which emit signals as they relax back to their original positions. These signals can be used to construct detailed images of tissues and organs inside the body. The document discusses key concepts in MRI physics including precession, relaxation times T1 and T2, spin echo and gradient echo sequences, and how varying pulse sequence parameters affects contrast in the resulting images.
Magnetic Resonance Elastography is an advanced imaging technique in MRI. This method is a method of "virtual palpation" of internal organs with the help of MRI.
Computed Tomography and Spiral Computed Tomography JAMES JACKY
1. Computed Tomography / Spiral Computed Tomography
2. Clinical and Principle Operation of Computed Tomography
3. Law and Regulation in Malaysia
4. Radiation Dose
This document provides an overview of breast anatomy and mammography techniques. It describes the internal structures of the breast including lobes, lobules, ducts, and connective tissue. Lymph node drainage pathways are explained. Mammography views including craniocaudal, mediolateral oblique, and magnification views are illustrated along with positioning techniques. Breast composition changes with age. Ultrasound techniques and common breast lesions seen on ultrasound are also reviewed. The document concludes with an explanation of BI-RADS assessment categories used in breast imaging.
Mammography Positioning Technique for Additional Views Selin Prasad
This document discusses additional views that can be performed in mammography, including magnification views, spot compression views, and views for patients with breast implants. Magnification views use a smaller focal spot size and elevated breast position to provide higher resolution of areas of interest, though at the cost of increased radiation dose and potential for motion blur. Spot compression views apply targeted compression over areas of concern to spread overlapping tissues and better define lesion features. Views for implants displace the implant posteriorly during compression to exclude it from the image and allow improved visualization of breast tissue.
MRI can detect breast lesions with high sensitivity but has variable specificity in differentiating benign from malignant lesions. MR spectroscopy provides additional metabolic information that can improve specificity by detecting elevated choline levels associated with malignant tumors. Response to chemotherapy can also be assessed non-invasively with MR spectroscopy by monitoring changes in choline levels within 24 hours of treatment. Limitations include difficulty with small lesions, dense breasts, and lactating breasts.
This document discusses various techniques for reducing radiation dose in computed tomography (CT) scans. It outlines strategies such as using automatic exposure control, adjusting scan parameters based on patient size, employing noise-tolerant images when possible, limiting scan lengths and phases, and utilizing newer reconstruction techniques. The goal is to lower radiation dose without compromising diagnostic image quality.
This document discusses breast imaging recommendations and tools. It recommends annual mammography screening starting at age 40 for average risk women, while high risk women may benefit from additional screening with MRI. Digital mammography is the gold standard but has limitations depending on breast density. New tools like tomosynthesis and ultrasound can help address these limitations and provide additional information. The document reviews various breast imaging tools and their uses, as well as risk factors, screening guidelines, and case examples.
MRI uses strong magnetic fields and radio waves to produce detailed images of the inside of the body. Protons in the body align with the magnetic field, and radio waves excite the protons causing them to emit signals. The signals are detected by coils and used to construct an image on a computer. Different tissues can be distinguished based on proton density and relaxation times after excitation. Gradient fields are used to localize the source of the signals within the body.
1. The document describes several medical cases with imaging findings and diagnoses. It discusses abnormalities seen on CT scans and x-rays indicating conditions like diffuse idiopathic skeletal hyperostosis, tuberculous spondylitis, leaking dermoid tumour, Takayasu arteritis, and advanced bronchial carcinoma.
2. Key findings mentioned include flowing osteophytes, ossification of the posterior longitudinal ligament, calcified psoas abscesses, hydronephrosis, widened mediastinum with sternotomy sutures, dissecting aneurysm of the aorta, occlusion of arteries, and diffuse mural thickening of the rectum and colon.
3. The document
This document discusses magnetic resonance angiography (MRA) and its advantages and disadvantages compared to catheter angiography. It describes different MRA techniques including contrast enhanced MRA, time of flight angiography, phase contrast angiography, and non-contrast techniques. It also discusses artifacts that can appear on MRA such as metal artifacts and blooming artifacts. Key features and images of each technique are provided.
MRI uses strong magnetic fields and radio waves to produce detailed images of organs and tissues in the body. Protons in the body align with the magnetic field, and a radio pulse causes them to resonate. Their signals are detected to form images. Different pulse sequences and parameters produce T1-weighted, T2-weighted, or proton density images. Safety concerns include the strong magnetic field and certain implants. Advantages are no radiation, good soft tissue contrast, and multiplanar imaging. Disadvantages include long scan times and high costs.
This document discusses breast MRI protocols, techniques, and the interpretation of findings. It provides details on coil and patient positioning, recommended MRI field strength, and standard breast MRI protocols. It discusses recognizing normal enhancing structures like vessels, nipples, and lymph nodes. Guidelines are presented for analyzing lesion enhancement and characterizing benign masses based on criteria like smooth margins, shape, homogeneous enhancement, fat content, T2 signal, and rim enhancement. Examples of benign findings like fibroadenomas and fat-containing lesions are also described.
This document outlines the protocol for performing CT angiography (CTA) from the cerebral arteries to the lower limbs. It discusses indications for CTA including aneurysms, stenosis, dissections, and more. The preparation, positioning, and scanning protocols are provided for CTA of the head to lower limbs as well as the subclavian arteries. Pediatric protocols are also summarized. The document concludes with examples of CTA findings and references.
Tissue harmonic imaging is an ultrasound technique that provides higher quality images compared to conventional ultrasound by collecting harmonic signals generated in tissues and filtering out transducer-generated fundamental echo signals, resulting in clearer images with improved contrast resolution, reduced artifacts, and better visualization of deeper structures and vessels. While tissue harmonic imaging improves image quality in many clinical applications, it can decrease axial resolution compared to fundamental frequency imaging due to the narrowed signal bandwidth.
1. MRI provides multi-planar, multi-contrast images to study organ structure, function, metabolism, physiology and pathology in a non-invasive manner.
2. When certain atomic nuclei such as hydrogen protons are placed in a strong, static magnetic field, they align with the field. A radiofrequency pulse can then excite the aligned protons, causing them to emit radiofrequency signals as they relax back to equilibrium.
3. T1 relaxation is the recovery of longitudinal magnetization along the magnetic field axis, while T2 relaxation is the loss of transverse magnetization in the plane perpendicular to the magnetic field. Differences in T1 and T2 values between tissues provide image contrast.
MRI uses strong magnets and radio waves to produce detailed images of the body. It has three main components - the scanner, computer, and recording hardware. The scanner contains powerful magnets including static magnetic field coils, gradient coils, and radiofrequency coils. The static magnetic field orients hydrogen atoms in the body. Gradient coils are used to localize tissues and encode spatial information. Radiofrequency coils transmit RF pulses to excite hydrogen atoms and receive their signals. The signals are processed by the computer to produce images based on the relaxation properties of tissues, namely T1 and T2 relaxation times. T1 relates to the rate at which hydrogen atoms realign with the magnetic field after excitation while T2 relates to the rate of signal decay
This document discusses CT image acquisition. It describes how CT scanners work, including the components of a CT scanner like the x-ray tube and detector array. It explains the image acquisition process, from x-ray generation to data collection and processing, and image reconstruction. Key steps include positioning the patient, rotating the x-ray tube, acquiring data projections from different angles, converting analog signals to digital, reconstructing images from the data using algorithms. The document provides an overview of the CT imaging process.
This document discusses the effects of kVp and mAs on various properties of x-ray images. It explains that kVp determines the highest x-ray energy and quality, while mAs determines the quantity of photons and exposure time. Higher kVp and mAs increase spatial resolution, contrast, and signal-to-noise ratio, but also increase radiation dose. The document covers these parameters for screen-film radiography as well as computed tomography, and how they impact visible properties like image noise, contrast, and resolution.
This document provides an overview of elastography, a medical imaging technique that detects differences in tissue stiffness. It discusses various elastography methods including quasi-static ultrasound elastography, which images strain from externally applied stress, and dynamic methods like transient elastography that image shear waves to quantify tissue stiffness. The document outlines early developments in elastography research and commercial applications, limitations of different techniques, and potential future advances.
MRI uses strong magnetic fields and radio waves to generate images of the inside of the body. It works by aligning hydrogen atoms in water molecules and fat in tissues when placed in a magnetic field. Radio waves are then used to stimulate the hydrogen atoms, which emit signals as they relax back to their original positions. These signals can be used to construct detailed images of tissues and organs inside the body. The document discusses key concepts in MRI physics including precession, relaxation times T1 and T2, spin echo and gradient echo sequences, and how varying pulse sequence parameters affects contrast in the resulting images.
Magnetic Resonance Elastography is an advanced imaging technique in MRI. This method is a method of "virtual palpation" of internal organs with the help of MRI.
Computed Tomography and Spiral Computed Tomography JAMES JACKY
1. Computed Tomography / Spiral Computed Tomography
2. Clinical and Principle Operation of Computed Tomography
3. Law and Regulation in Malaysia
4. Radiation Dose
Computerized tomography (CT) was pioneered by Godfrey Hounsfield and Allan Cormack in the 1970s. CT uses X-rays and computer processing to create cross-sectional images of the body. The first CT scanners used a translate-rotate design, while later generations used multiple detectors and spiral scanning for faster, more detailed imaging. Image reconstruction uses back projection to convert attenuation measurements into pixel values and display slices. CT provides excellent anatomical detail and is widely used for diagnosing conditions of the brain, blood vessels, lungs and other organs.
Basic physics of multidetector computed tomography ( CT Scan) - how ct scan works, different generations of ct, how image is generated and displayed and image artifacts related to CT Scan.
Computed tomography (CT) uses computer-processed X-rays to create cross-sectional images of the body. CT works by rotating an X-ray tube and detectors around the patient, acquiring multiple transmission measurements at different angles to reconstruct a 3D image. Image reconstruction involves algorithms like back projection and filtered back projection that use the transmission data to calculate the attenuation coefficients of different tissues and generate tomographic images representing slices of the body. CT numbers, measured in Hounsfield units, provide standardized values related to tissue density and visibility.
Computed tomography (CT) provides cross-sectional images of the body using X-rays. CT has evolved through several generations with advances in technology. Modern multi-detector CT allows acquisition of multiple slices simultaneously, reducing scan time. Helical or spiral CT involves continuous table movement and X-ray rotation, allowing whole organ or body coverage with minimal artifacts. Pitch relates the table speed to beam width and affects radiation dose and anatomic coverage. CT has advantages over conventional radiography including better contrast resolution and ability to distinguish between tissues.
Computed tomography (CT) uses rotating X-rays and computer processing to create cross-sectional images of the body. CT provides advantages over conventional radiography like distinguishing between tissues with similar densities and detecting differences as small as 0.5% contrast. Modern CT systems use multiple detector rows to acquire multiple slices simultaneously during each rotation, improving coverage and reducing scan time. Advanced techniques like multiplanar reformation and 3D rendering provide additional diagnostic information from CT images. Artifacts can arise from factors like the helical acquisition and differences between detector rows.
CT scanners produce cross-sectional images of the body by using X-rays from different angles to reconstruct tomographic slices. CT scanners rotate an X-ray tube and detector array around the patient, measuring attenuation profiles along rays. These projection data are reconstructed using filtered back projection to produce images with improved contrast compared to radiography but some artifacts. Advances like spiral CT allow faster full-volume imaging but increase patient dose. CT provides anatomical detail but cannot replace modalities like MRI for all clinical needs.
The document summarizes the history and technology of computed tomography (CT) scanners. It describes how CT was developed in the 1970s by Godfrey Hounsfield and Alan Cormack, who were later awarded the Nobel Prize. It outlines the key innovations in each generation of CT scanners, from the first generation's pencil beam geometry to later generations' use of detector arrays and helical scanning, which reduced scan times. The document also discusses the components of a CT scanner, including the x-ray tube, detectors, and techniques for image reconstruction and calibration.
This slide best explains the introduction of CT, basis and types of CT image reconstructions with detailed explanation about Interpolation, convolution, Fourier slice theorem, Fourier transformation and brief explanation about the image domain i.e digital image processing.
Basic Principles and Concepts of Computed Tomography (CT)AayushiPaul1
Computed tomography (CT) uses x-rays and computer processing to create cross-sectional images of the body. The document discusses the basic principles and evolution of CT technology over several generations. Key points include how early CT systems used pencil beams and translations to acquire images, while modern CT uses fan beams, rapid rotations, and multiple detector arrays to provide faster scanning and thinner slices. CT has become an invaluable medical imaging tool due to advances that improve resolution, speed, and lower radiation dose.
CT scan and MRI are the techniques for body imaging. Computed Tomography or Computerized Axial Tomography is commonly referred to as a CT scan.
C- computed (Use of computer) and T- tomography (Greek word “Tomos” means “slice” and “Grapho” means “ To write”
The first commercial CT scanner was invented by Sir Godfrey Hounsfield in United Kingdom.
It is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce images of the inside of the body. It shows detailed images of any part of the body including the bones, muscles, fat, organs and blood vessels.
CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage.
Computed Tomography or Computerized Axial Tomography is commonly referred to as a CT scan.
C- computed (Use of computer) and T- tomography (Greek word “Tomos” means “slice” and “Grapho” means “ To write”
The first commercial CT scanner was invented by Sir Godfrey Hounsfield in United Kingdom.
It is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce images of the inside of the body. It shows detailed images of any part of the body including the bones, muscles, fat, organs and blood vessels.
CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage. Computed Tomography or Computerized Axial Tomography is commonly referred to as a CT scan.
C- computed (Use of computer) and T- tomography (Greek word “Tomos” means “slice” and “Grapho” means “ To write”
The first commercial CT scanner was invented by Sir Godfrey Hounsfield in United Kingdom.
It is a diagnostic imaging procedure that uses a combination of X-rays and computer technology to produce images of the inside of the body. It shows detailed images of any part of the body including the bones, muscles, fat, organs and blood vessels.
CT scans may be performed to help diagnose tumors, investigate internal bleeding, or check for other internal injuries or damage. MRI stands for Magentic Resonance Imaging which is a non-invasive medical imaging test that produces detailed images of almost every internal structure in the human body, including the organs, bones, muscles and blood vessels.
MRI scanners create images of the body using a large magnet and radio waves.
No ionizing radiation is produced during an MRI exam, unlike X-rays. These images give your physician important information in diagnosing your medical condition and planning a course of treatment.
Raymond Damadian, the inventor of the first magnetic resonance scanning machine performed the first full-body scan of a human being in 1977.
The Nobel Prize was awarded to the American chemist, Paul Lauterbur, and the British physicist, Peter Mansfield, for developing a method to represent the information gathered by a scanner as an image. This is fundamental for the way the technology is used today.
This document summarizes key concepts in computed tomography (CT) imaging. It discusses how CT uses x-rays to measure the attenuation of objects along different projection angles to reconstruct cross-sectional images. Specifically, it covers:
1) How monoenergetic and polychromatic x-ray sources are used to measure attenuation projections and the artifacts that can arise from beam hardening and scatter.
2) Different scanning methods like fan beam rotational and fixed detector ring configurations.
3) Emission CT techniques like SPECT and PET that use radioactive tracers.
4) Ultrasound CT and magnetic resonance imaging which use different physical phenomena for tissue imaging and data collection.
5) Artifacts like
LCU RDG 402 PRINCIPLES OF COMPUTED TOMOGRAPHY.pptxEmmanuelOluseyi1
This document provides an outline for a course on principles of computed tomography. It discusses key topics that will be covered, including image digitization, computed radiography, basic CT principles, and care of radiographic equipment. The objectives are for students to understand the principles of image digitization, computed radiography, CT scanning, and components of CT machines. It also explains some of the technical aspects of digital imaging, spatial resolution, CT scanning principles, CT equipment components like the gantry and x-ray tube, and characteristics of ideal x-ray detectors.
The document provides an overview of the fundamentals of CT and MRI imaging. It discusses how CT was introduced in 1972 and revolutionized medical imaging by providing high-quality transverse cross-sectional images of the body without tissue superimposition. It also describes the evolution of CT technology from early generation pencil-beam systems to current helical CT scanners that acquire continuous data as the patient passes through the rotating gantry. Key developments included increasing the number of detectors to acquire wider beams, implementing rotating gantries to speed up scans, and incorporating slip-ring technology to allow continuous 360-degree rotation.
The document discusses the principles of computed tomography (CT) scanning. It describes how CT works by obtaining multiple X-ray transmission views of the patient by rotating an X-ray tube and detector array around the patient. The detector readings are used to reconstruct a CT image composed of pixels representing the linear attenuation coefficients of tissue. Tissue densities are expressed using Hounsfield units scaled relative to water and air. The key components of a CT system that enable image acquisition include the gantry, X-ray tube, detectors, data acquisition system, and computer for image reconstruction.
This document provides an overview of computed tomography (CT) and magnetic resonance imaging (MRI). It discusses the history and development of CT from the early 1970s to present day, including the evolution from first to fifth generation CT scanners. Key aspects of CT technology covered include the basic principles, components like the x-ray tube and detectors, and types of scans like conventional tomography and cone beam CT. The document also briefly introduces magnetic resonance imaging.
Computerized tomography (CT) uses X-rays and digital image processing to generate cross-sectional images of the body. Godfrey Hounsfield invented the first commercially viable CT scanner in 1972. CT scans provide more detailed images than traditional X-rays by using multiple angles to reconstruct cross-sectional slices of the body. Modern CT scanners can obtain these slices quickly, in under one second, allowing imaging of moving structures like the heart.
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The document describes the major components and systems of a computed tomography (CT) scanner. It discusses three main systems: the imaging system, computer system, and image display/recording/storage system. The imaging system includes components like the x-ray tube, generator, collimator, filter, and detector that work together to produce x-rays and detect the attenuated radiation passing through the patient. The computer system receives the digital data and performs image reconstruction. The display system shows the reconstructed images and allows storage and recording. Key components discussed in more detail include the gantry assembly, detectors, and computer processing architecture.
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2. INTRODUCTION
Computed Tomography is a well accepted imaging
modality for evaluation of the entire body.
Computed Tomography(CT) Scan Machines Uses X-
rays, a powerful form of Electromagnetic Radiation.
The images are obtained directly in the axial plane of
varying tissue thickness with the help of a computer.
Some pathology can be seen in saggital or coronal
plane by reconstruction of the images by computer.
CT has undergone several evolutions and nowadays
multi- detectors CT scanners have been evolved which
have better application in clinical field.
3. COMPARISION OF CT WITH
CONVIENTIONAL RADIOGRAPHY
Conventional radiography suffers
from the collapsing of 3D structures
onto a 2D image.
CT gives accurate diagnostic
information about the
distribution of structures inside
the body.
4. COMPARISION OF CT WITH CONVIENTIONAL RADIOGRAPHY.
A conventional X-ray image is basically a shadow.
Shadows give you an incomplete picture of an object's shape.
This is the basic idea of computer aided tomography. In a CT scan machine,
the X-ray beam moves all around the patient, scanning from hundreds of
different angles
5. Comparison of CT with Conventional
Radiography
Radiographic procedure is qualitative and not quantitative
6. ADVANTAGE OF COMPUTED TOMOGRAPHY
OVER CONVIENTIONAL RADIOGRAPHY.
To overcome superimposition of structures.
To improve contrast of the image.
To measure small differences in tissue contrast.
7. TOMOGRAPHY
Imaging of Layer/Slice.
Principle
Images of structures lying above and below the plane
are blurred out due to motion unsharpness while the
structures lying in plane of interest appear sharp in in
the image.
9. PRINCIPLE OF COMPUTED
TOMOGRAPHY
The internal structure of the object can be
reconstructed from multiple projections of the
object.
Mathematically principle of CT was first developed in
1917 by Radon.
Proved that image of unknown object could be
produced if one had several number of projections
throughout the object.
10. VARIOUS PARAMETERS OF CT
SLICE
MATRIX
PIXEL
VOXEL
CT NUMBER
WINDOWING
WINDOW WIDTH
WINDOW LEVEL
PITCH
11. SLICE/CUT
The cross section portion of body which is scanned for
production of CT image is called Slice.
The slice has width and therefore volume.
The width is determined by width of the x rays beam.
12. Cross Sectional Slices
Think like looking into the loaf of bread by cutting into
the thin slices and then viewing the slice individually.
13. MATRIX
The CT image is represented as the Matrix of the
number.
A two dimensional array of numbers arranged in rows
and columns is called Matrix.
Each number represent
the value of the image at
that location.
14. PIXEL
Each square in a matrix is called a pixel.
Also known as picture element.
15. VOXEL
Each individual element or number in the image
matrix represents a three dimensional volume element
in object called VOXEL.
16. CT NUMBER
The numbers in the image matrix is called CT
NUMBER.
Each pixel has a number which represents the x-ray
attenuation in the corresponding voxel of the object.
17. HOUNSFIELD UNITS(HU)
Related to different composition and nature of Tissue.
The CT NUMBER is also known as Hounsfield
units(HU).
Represent the density of tissue.
Different Tissue have different CT number Range in
HU.
18. Air - 1000
Fat -100
Pure water 0
CSF 15
White matter 45
Gray matter 40
Blood 20
Bone/calcification +1000
TISSUE AND CT NUMBER APPROXIMATE
19. WINDOWING is a system where the CT no. range of
interest is spread cover the full grey scale available on
the display system
WINDOW WIDTH –Means total range of CT no.
values selected for gray scale interpretation.
It corresponds to contrast of the image.
WINDOW LEVEL– represents the CT no. selected for
the centre of the range of the no. displayed on the
image. It corresponds to brightness of image .
20. Pitch
The relationship between patient and tube motion is
called Pitch.
It is defined as table movement during each
revolution of x-ray tube divided by collimation
width.
For example: For a 5mm section, if patient moves
10mm during the time it takes for the x-ray tube to
rotate through 360˚, the pitch is 2.
Increasing pitch reduces the scan time and patient
dose.
22. Phase of CT scanning
1.Scanning the patient or data Acquisition
a)X-ray Generator
b)X-ray Tube
c)X-ray Filtration System
d)Detector System
2.Reconstruction
a)Simple back projection
b)Iterative method
c)Analytical method
3.Display
23. DATA ACQUISTION
The scanning process begins with data
acquisition
Data Acquisition refers to a method by
which the patient is systematically
scanned by the X ray tube and detectors
to collect enough information for image
reconstruction
24. Major components of Data Acquisition
System(DAS)
a)X-ray Generators
Generators are located on rotating scan frames within
the CT gantry to accommodate slip Ring.
Power: 50 to 80kw
Frequency: 5 to 50kHz
KVp: 80-120
mA:80-500
25. b) X-ray Tube
Rotating anode x-ray tube with unique cooling.
Small focal spot size (0.6mm) to improve spatial resolution.
Anode heating capacity:1MHU to 7MHU
Cooling rate:1MHU per minute.
c)X-ray Beam Filtration System
CT employs monochromatic beam but radiation from
CT X-ray tube is polychromatic. so, X-ray beam is shaped by
compensation filter.
a)Pre patient Collimators: Reduces the patient dose.
b)Post patient Collimators: Reduces the scattered radiation detectors.
26. Overall Functions of
Collimators.
To decrease scatter
radiation
To reduce patient
dose
To improve image
quality
Collimator width
determines the slice
thickness
27. d)Detectors
The detectors gather information by measuring the x-ray
transmission through the patient.
Two types:
Scintillation crystal detector
(Cadmium tungstate+ Si Photodiode)
Can be used in third and fourth generation scanners
Xenon gas ionisation chamber
Can be used in third generation scanners only
28. 2)Reconstruction
Reproduction of an image from raw data is called
Reconstruction.
A)Simple back projection
The image is created by reflecting the attenuation
profiles back in same direction they were obtained.
29. B)Iterative method
It start with assumption that all point in matrix have
same value and it was compared with measured value
and make correction until Values come with in
acceptable range.
It contain three correction factor
1. SIMULTANEOUS RECONSTRUCTION
2. RAY BY RAY CORRECTION
3. POINT BY POINT CORRECTION
30. C)Analytical Method
Today commonly used .
Two popular method used in that method are:-
1. 2-D FOURIER ANALYSIS
2.FILTERED BACK PROJECTION
31. 2-D FOURIER ANALYSIS
In it any function of time or space can be represented by the
sum of various frequencies and amplitude of sine and
cosine waves.
For example the actual projected image of original object is
more rounded than those shown which would be slowly
simplify and corrected by Fourier transformation.
33. FILTERED BACK PROJECTION
Same as back projection except that the image is filtered,
or Modified to exactly counterbalance the effect of
sudden density Changes , which cause blurring(star
like pattern) in simple back projection.
34.
35. 3)Display
The reconstructed image is displayed on the monitor.
It is a digital image.
It consists of 2D representation of 3D object in the
form of pixels.
CT pixel size is determined by dividing the FOV by
matrix Size which is generally 512*512.
PIXEL SIZE= FOV (mm)/ MATRIX SIZE
36. Generations of CT Scan
First Generation
Narrow pencil beam
Single detector
Detector used is made up of NaI.
Translate –Rotate movements of
Tube- detector combination
Scan time-5mins.
Designed only for evaluation
of brain.
37. First generation CT Scanner
•Head kept enclosed in a water
bath
•Paired detectors
•A reference detector
39. Second Generation
Narrow fan beam
Linear detector array(5 to30)
Translate-Rotate movements of Tube-Detector
combination
Fewer linear movements are needed as there are
more detectors to gather the data.
Between linear movements, the gantry rotated 30o
Scan time~30secs(advantage over first generation)
40. Third Generation
•Rotate(tube)Rotate(detectors)
Motion.
•Pulsed wide fan beam.
•Arc of detectors(600-900)
•Detectors are perfectly aligned
with the X-Ray tube
•Both Xenon and scintillation
crystal detectors can be used
•Scan time< 5secs
•Disadvantage: Ring Artifacts
due to electronic drift between
many detectors.
42. Fourth Generation
Complete circular array of about 1200 to 4800
stationary detectors
Single x-ray tube rotates with in the circular array
of detectors
Wide fan beam to cover the entire patient
Scan time of newer scanners is about ½ s or, <2s.
Designed to address ring artifacts by keeping
detector assembly stationary.
Disadvantage: High cost.
43. Fifth Generation
stationary/stationary
Developed specifically for cardiac tomographic imaging
No conventional x-ray tube; large arc of tungsten encircles
patient and lies directly opposite to the detector ring
Electron beam steered around the patient to strike the
annular tungsten target
Capable of 50-msec scan times; can produce fast-frame-
rate CT movies of the beating heart
44. Electron gun
Large Arcs of tungsten
targets
Detector ring
17 slices per second
45. CT SCAN IN OUR RADIOLOGY
DEPARTMENT.(16 SLICES)
47. TECHNICAL SPECIFICATION
(Hitachi ECLOS 16)
CT scanner mode: Multislice
Slices per rotation: 16
Other rotation speed options: 1.0, 1.5, 2.0, 3.0 seconds
Minimum rotation speed: 0.8 seconds
Gantry diameter: 70 cm
Maximum beam width (cm): 2 cm
Table weight limit: 495 lbs
Table movement range vertically/longitudinally: 42 to 100 cm
vertical, 186 cm horizontal
X-ray generator kV range: 100, 120, 130 kVp
Maximum scan range: 175 cm
X-ray tube heat capacity: 5.0 MHU
Power requirements: 3-phase, 200 Amp max.
48.
49. SPIRAL/HELICAL CT
Spiral/Helical scanning uses third generation or fourth
generation slip ring design.
Spiral computed tomography (or helical computed
tomography) is a computed tomography(CT) technology in
which the source and detector travel along a helical path
relative to the object. Typical implementations involve
moving the patient couch through the bore of the scanner
whilst the gantry rotates. Spiral CT can achieve improved
image resolution for a given radiation dose, compared to
individual slice acquisition. Most modern hospitals
currently use spiral CT scanners.
50. SLIP RING TECHNOLOGY
In conventional CT scanning there was a paused
between each gantry rotation. But in Helical CT, Slip
Ring technology is used which allows continuous
rotation of gantry without interruption.
Slip Rings are electrical conducting brushes and
component of gantry transferring the data or,
electrical energy to and from the stationary part of
gantry to rotating part of gantry for continuous
rotation of gantry.
51. Contd….
There are usually three slip rings made up of
conduction materials(i.e. Sliver and Graphite.)
First Slip Ring provides high voltage power to X-ray
tube.
Second provide low voltage to control system on
rotating gantry and
Third Slip Ring transfers digital data from rotating
detectors arrays.
52.
53. MULTISLICE/MULTIDETECTOR CT
Multidetector computed tomography(MDCT) is a form of
computed tomography (CT) technology for diagnostic
imaging.
In MDCT, a two-dimensional array of detector elements
replaces the linear array of detector elements used in
typical conventional and helical CT scanners. The two-
dimensional detector array permits CT scanners to acquire
multiple slices or sections simultaneously and greatly
increase the speed of CT image acquisition.
Image reconstruction in MDCT is more complicated than
that in single section CT.
54. DUAL SOURCE CT
Dual Source CT (DSCT) is equipped
with two X-ray tubes.
Two corresponding detectors are
oriented in the gantry with an angular
offset of 90 degrees.
ADVANTAGES
1) High temporal resolution(in
response to time domain) for
cardiac imaging without β
blockers which means heart rate
is independent upon temporal
resolution.
2) Less radiation dose even for
obese patient.
3) Faster acquisition time with
shortest breathe hold.
55. DUAL ENERGY CT
Standard computed tomography (CT)
scanners use normal X-rays to make
cross-sectional ‘slice-like’ pictures or
images of the body.
A dual energy CT scanner is fairly new
technology that uses both the normal
X-ray and also a second less powerful X-
ray to make the images.
Two pictures are taken of the same
slice at different energies.(i.e. 80/140KV
,100/140KV Or,70/150KV)
This gives dual energy CT additional
advantages over standard CT for a wide
range of tests and procedures.
Most commonly used for CT
Angiography.
57. PORTABLE CT SCAN
As the world’s first portable, full-body, 32-slice CT (computed
tomography) scanner, BodyTom is a multi-departmental
imaging solution capable of transforming any room in the
hospital into an advanced imaging suite. The system boasts an
impressive 85cm gantry and 60cm field of view, the largest field
of view available in a portable CT scanner.
The battery-powered BodyTom with an innovative internal drive
system can easily be transported from room to room and is
compatible with PACS, planning systems, surgical and robotic
navigation systems.
Uniquely designed to accommodate patients of all sizes,
BodyTom provides point-of-care CT imaging wherever high-
quality CT images are needed, including the operating room,
intensive care unit, radiation oncology suites, and the emergency
department.
58. RADIATION DOSE IN CT
Volume Computed Tomography Dose Index (CTDIvol) is a
standardized parameter to measure Scanner Radiation Output
CTDIvol provides information about the amount of radiation
used to perform the study.
CTDIvol is NOT patient dose
CTDIvol is reported in units of mGy for either a 16-cm
(for head exams) or 32-cm (for body exams) diameter.
AAPM (American Association of Physicts in Medicine)
introduces a parameter known as the Size Specific Dose
Estimate (SSDE) to allow estimation of patient dose based on
CTDIvol and patient size.
For the same CTDIvol, a smaller patient will tend to have a
higher patient dose than a larger patient.