1. MRI physics involves the behavior of spins under magnetic fields and the use of radiofrequency pulses to manipulate spin alignment and generate signals.
2. Different pulse sequences such as spin echo, gradient echo, and inversion recovery use varying combinations of excitation pulses, rephasing gradients, and timing delays to produce images weighted towards T1, T2, proton density or other tissue contrasts.
3. Sequence parameters like repetition time (TR), echo time (TE), and inversion time (TI) determine the relative contributions of T1, T2 and other factors to image contrast.
presentation about bone scintigraphy or bone scan study on nuclear medicine field done by students of nuclear medicine course in deparment of radiological techniques, Qassim univeristy
This document discusses various types of artifacts that can occur in MRI imaging, including equipment-related artifacts like non-uniform signal and phase wrap, as well as patient-related artifacts like susceptibility effects and motion blurring. It provides examples of static magnetic field (B0) inhomogeneity artifacts caused by differences in magnetic susceptibility between tissues. The document also discusses specific artifact reduction strategies, such as improving B0 field shimming, adjusting pulse sequence parameters like echo time, and using parallel imaging techniques to reduce geometric distortion from susceptibility effects. In summary, the document provides an overview of common MRI artifacts and their causes, with a focus on artifacts from magnetic field inhomogeneities and susceptibility differences between tissues.
This document discusses quality control for structural and functional MRI data. It explains that quality control is important for deciding which data to include in a study, diagnosing problems with data acquisition, and fixing issues before scanning new subjects. The document recommends performing quality control early and provides examples of checking for consistency across scans and subjects, as well as metrics to detect motion, artifacts, noise, and information quality in the data.
PET/CT is a medical imaging technique that combines a positron emission tomography (PET) scanner and an x-ray computed tomography (CT) scanner into a single gantry system. This allows it to obtain both functional metabolic information from PET and anatomic information from CT in a single imaging session. The PET data provides physiological functional imaging while the CT data provides accurate structural information. By combining the PET and CT images, diagnostic accuracy and localization of lesions is improved for conditions like cancer, infections, and inflammation. The PET/CT scan involves intravenous injection of FDG, a CT scan, a PET scan, and generation of thousands of fused PET/CT images which are reconstructed, reformatted and analyzed.
1. MRI utilizes the magnetic spin property of protons in hydrogen atoms to produce images.
2. Different pulse sequences such as T1-weighted, T2-weighted, and proton density weighted images provide varying contrast between tissues based on relaxation times.
3. Evaluation of MRI involves determining the optimal pulse sequence, analyzing images for abnormalities, and correlating findings with clinical information.
1. MRI physics involves the behavior of spins under magnetic fields and the use of radiofrequency pulses to manipulate spin alignment and generate signals.
2. Different pulse sequences such as spin echo, gradient echo, and inversion recovery use varying combinations of excitation pulses, rephasing gradients, and timing delays to produce images weighted towards T1, T2, proton density or other tissue contrasts.
3. Sequence parameters like repetition time (TR), echo time (TE), and inversion time (TI) determine the relative contributions of T1, T2 and other factors to image contrast.
presentation about bone scintigraphy or bone scan study on nuclear medicine field done by students of nuclear medicine course in deparment of radiological techniques, Qassim univeristy
This document discusses various types of artifacts that can occur in MRI imaging, including equipment-related artifacts like non-uniform signal and phase wrap, as well as patient-related artifacts like susceptibility effects and motion blurring. It provides examples of static magnetic field (B0) inhomogeneity artifacts caused by differences in magnetic susceptibility between tissues. The document also discusses specific artifact reduction strategies, such as improving B0 field shimming, adjusting pulse sequence parameters like echo time, and using parallel imaging techniques to reduce geometric distortion from susceptibility effects. In summary, the document provides an overview of common MRI artifacts and their causes, with a focus on artifacts from magnetic field inhomogeneities and susceptibility differences between tissues.
This document discusses quality control for structural and functional MRI data. It explains that quality control is important for deciding which data to include in a study, diagnosing problems with data acquisition, and fixing issues before scanning new subjects. The document recommends performing quality control early and provides examples of checking for consistency across scans and subjects, as well as metrics to detect motion, artifacts, noise, and information quality in the data.
PET/CT is a medical imaging technique that combines a positron emission tomography (PET) scanner and an x-ray computed tomography (CT) scanner into a single gantry system. This allows it to obtain both functional metabolic information from PET and anatomic information from CT in a single imaging session. The PET data provides physiological functional imaging while the CT data provides accurate structural information. By combining the PET and CT images, diagnostic accuracy and localization of lesions is improved for conditions like cancer, infections, and inflammation. The PET/CT scan involves intravenous injection of FDG, a CT scan, a PET scan, and generation of thousands of fused PET/CT images which are reconstructed, reformatted and analyzed.
1. MRI utilizes the magnetic spin property of protons in hydrogen atoms to produce images.
2. Different pulse sequences such as T1-weighted, T2-weighted, and proton density weighted images provide varying contrast between tissues based on relaxation times.
3. Evaluation of MRI involves determining the optimal pulse sequence, analyzing images for abnormalities, and correlating findings with clinical information.
This document discusses techniques for fat suppression in MRI. It begins by explaining why fat suppression is useful for tissue characterization and contrast agent visualization. It then covers the molecular and magnetic properties that differ between fat and water, allowing various techniques to exploit these differences. The main techniques discussed are CHEMICAL SHIFT SELECTIVE (CHESS), WATER EXCITATION, DIXON, STIR, SPAIR, and SPIR. Each technique is explained in 1-2 sentences. The document concludes by comparing the techniques and discussing their common clinical applications.
Percutaneous cementoplasty involves injecting acrylic cement into vertebral bodies to prevent collapse and relieve pain in patients with pathologic or compressed vertebrae. It can be used to treat osteoporotic fractures, tumors, and metastases. The procedure is performed under local anesthesia and fluoroscopy guidance. Cement is injected during its viscous phase to prevent leaks. Potential complications include cement leaks into the epidural space, veins, or disk, which can cause cord compression or embolism. The procedure provides pain relief but risks include leak-related complications and infection.
Digital Techniques For Myocardial Perfusion SpectMuhammad Ayub
This document provides an overview of digital techniques for myocardial perfusion SPECT imaging. It describes SPECT equipment components like the gamma camera and workstation. It explains tomographic acquisition parameters and technical considerations. Image processing techniques are covered like filtered back projection, filtering, and iterative reconstruction. Quantitative analysis methods like bullseye displays and segmental analysis are also summarized.
This document summarizes various types of artifacts that can occur in MRI images and their causes and remedies. It discusses artifacts related to patient motion like respiratory and cardiac motion as well as metal implants. It also covers susceptibility artifacts at tissue interfaces, chemical shift artifacts at fat-water boundaries, and partial volume artifacts due to large voxel sizes. Specific artifacts discussed include black lines, zebra stripes, and Moire fringes. For each artifact, the document describes techniques that can be used to reduce or eliminate the artifact, such as breath holding, gating, and improved pulse sequences.
MRI artifacts can occur due to hardware issues, software problems, physiological phenomena or physical limitations of the MRI device. Common artifacts include chemical shift artifacts seen at fat-water interfaces, aliasing artifacts due to an undersized field of view, black boundary artifacts at tissue borders, and motion artifacts from patient movement. Understanding the sources and appearances of artifacts is important for technicians to maintain image quality and avoid confusing artifacts with pathology.
it includes generations and advancement in CT. In generations fifth generation CT is described in detail.
UFC detector, stellar detectors and gemstone detector is also described
straton x-ray tube, MRC, LIMAX and aquillion one xray tube
different techniques used in CT
dual energy CT is also described
Dual energy x-ray absorptiometry (DEXA or DXA) scan is the most effective technique for measuring bone mineral density to diagnose osteoporosis. It uses two low-dose x-ray beams of different energies to generate a two-dimensional image of the bones, subtracting out soft tissue. Bone mineral density measurements are then compared to normal ranges based on age and gender to determine a patient's T-score or Z-score fracture risk. DEXA scans provide a quick, non-invasive, and accurate assessment of bone health with low radiation exposure.
A bone scan uses radioactive tracers to detect areas of increased or decreased bone activity. It can evaluate bone abnormalities throughout the entire skeleton. Some key points:
- Bone scans are useful for detecting cancer metastases, fractures, stress fractures, bone infections, and other bone diseases.
- They have advantages of being able to image the whole body and having relatively low radiation exposure.
- The most common tracer used is technetium-99m MDP, which concentrates in areas of increased bone formation.
- Abnormal findings on bone scans include multiple areas of abnormal uptake indicating cancer metastases, linear areas of uptake indicating fractures, and photopenic defects indicating bone infarcts.
The document discusses inversion recovery MRI sequences. Inversion recovery sequences initially aimed to produce heavy T1 weighting but are now mainly used with fast spin echo sequences to produce T2-weighted images. The sequence begins with an 180-degree inversion pulse to invert spins, followed by a 90-degree excitation pulse after time TI. This produces an echo that can be used to generate T1- or T2-weighted images depending on timing parameters. Variants like fast inversion recovery, STIR, and FLAIR combine inversion recovery with other pulses to suppress signals from fat, fluid, or blood.
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...Arif S
This document provides an overview of diffusion-weighted and perfusion MR imaging techniques for characterizing brain tumors and assessing treatment response. It discusses how perfusion MR imaging can provide physiological information on tumor vascularity and differentiate tumor grades. Diffusion-weighted imaging provides data on water diffusion properties within tumors and surrounding tissue. Together these techniques can help delineate tumor margins, guide biopsy planning, and monitor response to therapies like radiation and anti-angiogenic drugs by detecting changes in vascularity and cellularity. The document reviews the strengths and limitations of these methods compared to histopathology.
The document provides an overview of magnetic resonance imaging (MRI), including how it works, the types of images it can produce, and its applications in various parts of the body. It explains that MRI uses strong magnetic fields and radio waves to align hydrogen protons in the body and produce signals used to form images. Key applications mentioned include neuroimaging, musculoskeletal imaging, and evaluating diseases of the abdomen, blood vessels, heart, breast and fetus.
This document discusses skeletal disorders of metabolic and endocrine origin. It begins by describing the anatomy of mature bone and parts of long bones like the growth plate. It then discusses various causes of rickets and osteomalacia including nutritional rickets, hereditary forms, oncogenic osteomalacia, and drug-induced rickets. The pathology, clinical features, and radiological findings of each condition are described. Other conditions discussed include metabolic chondrodysplasia, hypophosphatasia, atypical axial osteomalacia, and hyperparathyroidism. For each, the document outlines the pathogenesis, clinical presentation, and characteristic radiographic abnormalities.
This document discusses various types of artifacts that can occur in MRI images and their causes and remedies. It covers technique-related artifacts such as chemical shift artifacts, Gibbs artifacts, aliasing artifacts, and magic angle artifacts. It also discusses patient-related artifacts like motion artifacts, metal artifacts, and flow artifacts. System-related artifacts discussed include shimming artifacts, gradient artifacts, and radiofrequency-related artifacts. For each type of artifact, the etiology, manifestation, and tips for remedying the artifact are provided. The document uses images to demonstrate examples of artifacts and their effects on MRI scans.
MRI SCAN - QUESTION AND ANSWER 3 MARKS
This document contains summaries of MRI concepts provided by multiple students, including explanations of spin echo pulse sequences, free induction decay, gradient coils, Larmor frequency, gadolinium contrast media, T1-weighted images, and common MRI artifacts. It also addresses contraindications for MRI studies and provides a brief history of the development of MRI technology.
Basic and advanced mri imaging sequences in brainDev Lakhera
- Conventional MRI brain imaging protocols include T1-weighted, T2-weighted, FLAIR, DWI, and SWI sequences.
- MRI works by applying radiofrequency pulses and magnetic field gradients to manipulate the alignment of hydrogen protons in the body and generate signals used to form images. T1-weighted images highlight tissues like fat and post-contrast lesions, while T2-weighted images highlight fluid.
- Pulse sequences like spin echo and gradient echo are used to generate T1-weighted and T2-weighted images. Modifications like fast spin echo increase scan speed. Contrast between tissues is determined by proton density, T1 and T2 relaxation times.
This document provides an overview of positron emission tomography (PET) scanning techniques. It discusses several non-invasive brain imaging scans conducted on patients, including normal CT and MRI scans but an abnormal PET scan where the patient was found to be dead. The document outlines topics to be covered in a seminar on PET scans, including introductions, principles, instrumentation, procedures, applications and advantages/disadvantages. It provides details on radiopharmaceutical production, PET scan instrumentation, patient preparation including tracer injection, and the imaging process.
Cardiac MRI uses MRI techniques to study the heart's anatomy, physiology, and pathology. It offers improved soft tissue definition compared to other modalities and does not use ionizing radiation. The basic sequences include black blood imaging for anatomy and bright blood imaging for assessing flow and motion. Black blood sequences like spin echo are used while bright blood uses gradient echo. Cine imaging captures motion throughout the cardiac cycle. Contrast-enhanced techniques like perfusion and delayed enhancement imaging are used to identify infarcts and viability. Standard cardiac planes include the short axis, 4-chamber, and 2-chamber views.
Fat suppression MRI techniques suppress the signal from fat tissues to improve visualization of other tissues. The main techniques are STIR, CHESS, SPIR, and SPAIR which use inversion recovery pulses or chemical saturation of fat protons at different resonance frequencies than water. Newer Dixon-based methods extract water-only and fat-only images from multiple echoes acquired at different echo times to achieve fat suppression without sensitivity to magnetic field inhomogeneities. These techniques are used for tissue characterization, detecting contrast enhancement, and reducing chemical shift artifacts.
Time of flight MR angiography produces images of blood vessels without contrast agents. It works by manipulating the longitudinal magnetization of stationary tissues so they do not recover between repetitions, while flowing blood is not affected. It can be performed as 2D or 3D acquisitions, with 2D providing larger coverage but lower resolution and 3D providing higher resolution but smaller coverage area. Parameters like TR, TE, and flip angle must be optimized and techniques like MOTSA can improve results by reducing flow saturation and artifacts.
The document discusses imaging features of malignant bone tumors. It notes that plain radiographs are important for initial diagnosis and can show features like patterns of bone destruction, mineralization, and periosteal reactions that help differentiate benign from malignant lesions. Osteosarcoma is discussed in detail, with its common locations in long bones of adolescents and association with sunburst periosteal reactions and soft tissue masses. Telangiectatic and secondary osteosarcomas are also summarized.
This document discusses techniques for fat suppression in MRI. It begins by explaining why fat suppression is useful for tissue characterization and contrast agent visualization. It then covers the molecular and magnetic properties that differ between fat and water, allowing various techniques to exploit these differences. The main techniques discussed are CHEMICAL SHIFT SELECTIVE (CHESS), WATER EXCITATION, DIXON, STIR, SPAIR, and SPIR. Each technique is explained in 1-2 sentences. The document concludes by comparing the techniques and discussing their common clinical applications.
Percutaneous cementoplasty involves injecting acrylic cement into vertebral bodies to prevent collapse and relieve pain in patients with pathologic or compressed vertebrae. It can be used to treat osteoporotic fractures, tumors, and metastases. The procedure is performed under local anesthesia and fluoroscopy guidance. Cement is injected during its viscous phase to prevent leaks. Potential complications include cement leaks into the epidural space, veins, or disk, which can cause cord compression or embolism. The procedure provides pain relief but risks include leak-related complications and infection.
Digital Techniques For Myocardial Perfusion SpectMuhammad Ayub
This document provides an overview of digital techniques for myocardial perfusion SPECT imaging. It describes SPECT equipment components like the gamma camera and workstation. It explains tomographic acquisition parameters and technical considerations. Image processing techniques are covered like filtered back projection, filtering, and iterative reconstruction. Quantitative analysis methods like bullseye displays and segmental analysis are also summarized.
This document summarizes various types of artifacts that can occur in MRI images and their causes and remedies. It discusses artifacts related to patient motion like respiratory and cardiac motion as well as metal implants. It also covers susceptibility artifacts at tissue interfaces, chemical shift artifacts at fat-water boundaries, and partial volume artifacts due to large voxel sizes. Specific artifacts discussed include black lines, zebra stripes, and Moire fringes. For each artifact, the document describes techniques that can be used to reduce or eliminate the artifact, such as breath holding, gating, and improved pulse sequences.
MRI artifacts can occur due to hardware issues, software problems, physiological phenomena or physical limitations of the MRI device. Common artifacts include chemical shift artifacts seen at fat-water interfaces, aliasing artifacts due to an undersized field of view, black boundary artifacts at tissue borders, and motion artifacts from patient movement. Understanding the sources and appearances of artifacts is important for technicians to maintain image quality and avoid confusing artifacts with pathology.
it includes generations and advancement in CT. In generations fifth generation CT is described in detail.
UFC detector, stellar detectors and gemstone detector is also described
straton x-ray tube, MRC, LIMAX and aquillion one xray tube
different techniques used in CT
dual energy CT is also described
Dual energy x-ray absorptiometry (DEXA or DXA) scan is the most effective technique for measuring bone mineral density to diagnose osteoporosis. It uses two low-dose x-ray beams of different energies to generate a two-dimensional image of the bones, subtracting out soft tissue. Bone mineral density measurements are then compared to normal ranges based on age and gender to determine a patient's T-score or Z-score fracture risk. DEXA scans provide a quick, non-invasive, and accurate assessment of bone health with low radiation exposure.
A bone scan uses radioactive tracers to detect areas of increased or decreased bone activity. It can evaluate bone abnormalities throughout the entire skeleton. Some key points:
- Bone scans are useful for detecting cancer metastases, fractures, stress fractures, bone infections, and other bone diseases.
- They have advantages of being able to image the whole body and having relatively low radiation exposure.
- The most common tracer used is technetium-99m MDP, which concentrates in areas of increased bone formation.
- Abnormal findings on bone scans include multiple areas of abnormal uptake indicating cancer metastases, linear areas of uptake indicating fractures, and photopenic defects indicating bone infarcts.
The document discusses inversion recovery MRI sequences. Inversion recovery sequences initially aimed to produce heavy T1 weighting but are now mainly used with fast spin echo sequences to produce T2-weighted images. The sequence begins with an 180-degree inversion pulse to invert spins, followed by a 90-degree excitation pulse after time TI. This produces an echo that can be used to generate T1- or T2-weighted images depending on timing parameters. Variants like fast inversion recovery, STIR, and FLAIR combine inversion recovery with other pulses to suppress signals from fat, fluid, or blood.
Diffusion-weighted and Perfusion MR Imaging for Brain Tumor Characterization ...Arif S
This document provides an overview of diffusion-weighted and perfusion MR imaging techniques for characterizing brain tumors and assessing treatment response. It discusses how perfusion MR imaging can provide physiological information on tumor vascularity and differentiate tumor grades. Diffusion-weighted imaging provides data on water diffusion properties within tumors and surrounding tissue. Together these techniques can help delineate tumor margins, guide biopsy planning, and monitor response to therapies like radiation and anti-angiogenic drugs by detecting changes in vascularity and cellularity. The document reviews the strengths and limitations of these methods compared to histopathology.
The document provides an overview of magnetic resonance imaging (MRI), including how it works, the types of images it can produce, and its applications in various parts of the body. It explains that MRI uses strong magnetic fields and radio waves to align hydrogen protons in the body and produce signals used to form images. Key applications mentioned include neuroimaging, musculoskeletal imaging, and evaluating diseases of the abdomen, blood vessels, heart, breast and fetus.
This document discusses skeletal disorders of metabolic and endocrine origin. It begins by describing the anatomy of mature bone and parts of long bones like the growth plate. It then discusses various causes of rickets and osteomalacia including nutritional rickets, hereditary forms, oncogenic osteomalacia, and drug-induced rickets. The pathology, clinical features, and radiological findings of each condition are described. Other conditions discussed include metabolic chondrodysplasia, hypophosphatasia, atypical axial osteomalacia, and hyperparathyroidism. For each, the document outlines the pathogenesis, clinical presentation, and characteristic radiographic abnormalities.
This document discusses various types of artifacts that can occur in MRI images and their causes and remedies. It covers technique-related artifacts such as chemical shift artifacts, Gibbs artifacts, aliasing artifacts, and magic angle artifacts. It also discusses patient-related artifacts like motion artifacts, metal artifacts, and flow artifacts. System-related artifacts discussed include shimming artifacts, gradient artifacts, and radiofrequency-related artifacts. For each type of artifact, the etiology, manifestation, and tips for remedying the artifact are provided. The document uses images to demonstrate examples of artifacts and their effects on MRI scans.
MRI SCAN - QUESTION AND ANSWER 3 MARKS
This document contains summaries of MRI concepts provided by multiple students, including explanations of spin echo pulse sequences, free induction decay, gradient coils, Larmor frequency, gadolinium contrast media, T1-weighted images, and common MRI artifacts. It also addresses contraindications for MRI studies and provides a brief history of the development of MRI technology.
Basic and advanced mri imaging sequences in brainDev Lakhera
- Conventional MRI brain imaging protocols include T1-weighted, T2-weighted, FLAIR, DWI, and SWI sequences.
- MRI works by applying radiofrequency pulses and magnetic field gradients to manipulate the alignment of hydrogen protons in the body and generate signals used to form images. T1-weighted images highlight tissues like fat and post-contrast lesions, while T2-weighted images highlight fluid.
- Pulse sequences like spin echo and gradient echo are used to generate T1-weighted and T2-weighted images. Modifications like fast spin echo increase scan speed. Contrast between tissues is determined by proton density, T1 and T2 relaxation times.
This document provides an overview of positron emission tomography (PET) scanning techniques. It discusses several non-invasive brain imaging scans conducted on patients, including normal CT and MRI scans but an abnormal PET scan where the patient was found to be dead. The document outlines topics to be covered in a seminar on PET scans, including introductions, principles, instrumentation, procedures, applications and advantages/disadvantages. It provides details on radiopharmaceutical production, PET scan instrumentation, patient preparation including tracer injection, and the imaging process.
Cardiac MRI uses MRI techniques to study the heart's anatomy, physiology, and pathology. It offers improved soft tissue definition compared to other modalities and does not use ionizing radiation. The basic sequences include black blood imaging for anatomy and bright blood imaging for assessing flow and motion. Black blood sequences like spin echo are used while bright blood uses gradient echo. Cine imaging captures motion throughout the cardiac cycle. Contrast-enhanced techniques like perfusion and delayed enhancement imaging are used to identify infarcts and viability. Standard cardiac planes include the short axis, 4-chamber, and 2-chamber views.
Fat suppression MRI techniques suppress the signal from fat tissues to improve visualization of other tissues. The main techniques are STIR, CHESS, SPIR, and SPAIR which use inversion recovery pulses or chemical saturation of fat protons at different resonance frequencies than water. Newer Dixon-based methods extract water-only and fat-only images from multiple echoes acquired at different echo times to achieve fat suppression without sensitivity to magnetic field inhomogeneities. These techniques are used for tissue characterization, detecting contrast enhancement, and reducing chemical shift artifacts.
Time of flight MR angiography produces images of blood vessels without contrast agents. It works by manipulating the longitudinal magnetization of stationary tissues so they do not recover between repetitions, while flowing blood is not affected. It can be performed as 2D or 3D acquisitions, with 2D providing larger coverage but lower resolution and 3D providing higher resolution but smaller coverage area. Parameters like TR, TE, and flip angle must be optimized and techniques like MOTSA can improve results by reducing flow saturation and artifacts.
The document discusses imaging features of malignant bone tumors. It notes that plain radiographs are important for initial diagnosis and can show features like patterns of bone destruction, mineralization, and periosteal reactions that help differentiate benign from malignant lesions. Osteosarcoma is discussed in detail, with its common locations in long bones of adolescents and association with sunburst periosteal reactions and soft tissue masses. Telangiectatic and secondary osteosarcomas are also summarized.
PARÁMETROS Y FUNCIONES QUE CARACTERIZAN UN HAZ DE RADIACIÓN (FOTONES). PhD. S...Sandra Guzman
Este documento describe los parámetros y funciones que caracterizan un haz de radiación de fotones. Explica conceptos como la penetración del haz en un paciente, el efecto del tamaño y forma del campo, la variación de la dosis absorbida con la distancia a la fuente, la posición de la fuente virtual y las relaciones definidas sobre el eje central. El documento contiene gráficos y ejemplos para ilustrar estos conceptos clave de la dosimetría en radioterapia.
Chiari: Lezione su acceleratori di particelle (2012)Massimo Chiari
Slide delle lezioni su acceleratori di particelle e sorgenti di ioni nell'ambito del corso "Tecniche di analisi con fasci di ioni", corso di Laurea Magistrale in Fisica e Astrofisica, Univ. Firenze AA 2011-2012 (Massimo Chiari, P.A. Mandò)
BSc thesis presentation - Space Navigation - March 2012Alessandro Rosati
BSc final thesis. Mathematical approach to the use of pulsating emitters, located at a finite distance from the observer, in order to define a completely-relativistic navigation system. Based on Professor Angelo Tartaglia research and works.
Bachelor presentation on 7Be solar neutrinos in Borexino Phase IILorenzo Donegà
This is the presentation I gave on my graduation. I graduated with a bachelor of Science in Physics. The goal of my thesis is to measure the interaction rate of 7Be solar neutrino flux in the detector Borexino during Phase II.
Borexino is a huge liquid scintillator detector located at Laboratori Nazionali del Gran Sasso (LNGS) in Italy.
Presentazione tesi su misura di neutrini solari da 7Be nella Fase 2 di BorexinoLorenzo Donegà
Questa è la presentazione della mia tesi triennale, nella quale ho misurato il tasso di interazione dei neutrini solari da 7Be nella Fase II dell'esperimento Borexino.
Borexino è un grande rivelatore a scintillatore liquido attivo dal 2007 e situatio ai Laboratori Nazionali del Gran Sasso.
Applicazioni di Matlab all'analisi di immagini telerilevateMarco Palazzo
Applicazioni di Matlab all'analisi di immagini telerilevate
Marco Palazzo & Lorenzo Vasanelli Presentazione al Convegno "Matematica senza Frontiere" 5-8 Marzo 2003, Lecce
Validazione del Software SELF3D. Suite di Calcolo evoluta con Modello 3D per la Simulazione dell'Induzione Magnetica generata da linee elettriche aeree, interrate e di forma arbitraria.
Info sull'applicativo disponibili a:
https://stilrs.altervista.org/software.html
2. Interazione di qualche forma di energia con la struttura
studiata -> rendere misurabile la distribuzione spazio
temporale di una grandezza fisica di interesse biologico
sorgente
fascio
collimatore
attenuatore
assorbitore
rivelatore
immagine
Tutte le modalità diagnostiche contengono tre componenti: la
SORGENTE, il CAMPO di RADIAZIONE (o fascio radiante), il RIVELATORE.
3. TIPO:
Radiogena (raggi-X),
Radioattiva, Sonora
STATO FISICO-CHIMICO:
Liquida, solida, gassosa
DIMENSIONI:
Volume, fuoco
SPETTRO DI EMISSIONE:
A righe, continuo
TEMPO DI DIMEZZAMENTO:
Finito, indefinito
ENERGIA MEDIA: keV
TIPO EMISSIONE: Continua,
pulsata
ONDE
ELETTROMAGNETICHE:
Onde Radio
Infrarossi
Luce
Ultra Violetti
Raggi X e Raggi Gamma
PARTICELLE:
Positroni, Elettroni,
Protoni, Neutroni
Alfa, Ioni, Atomi,
Molecole
VIBRAZIONI:
Suono, Ultrasuoni
Calore
PRINCIPIO DI RIVELAZIONE:
Chimico, fisico, biologico
STATO FISICO-CHIMICO:
Liquido, solido, gassoso
DIMENSIONI:
Area di rivelazione, spessore
RANGE DINAMICO:
Range di rivelazione delle variazioni di
attenuazione del fascio
RISOLUZIONE TEMPORALE:
Minimo lasso di tempo fra la rivelazione
di due segnali
distinti
RISOLUZIONE SPAZIALE:
Minimo distanza a cui due segnali si
rivelano come distinti
RISOLUZIONE DI CONTRASTO:
Minimo valore a cui due segnali si
rivelano come
distinti fra due zone contigue
TIPO SEGNALE:
Analogico, Digitale
RAPPORTO SEGNALE/RUMORE:
Rapporto segnale con informazione
rispetto al segnale
senza contenuto informativo.
4. In tomografia a raggi-X si usa la misura del coefficiente di attenuazione dei
tessuti per dedurre informazioni diagnostiche sul paziente.
Radiofarmaci gamma:
emissione fotoni di energia
compresa tra 80 e 300 keV
Radiofarmaci beta: emissione
positroni ognuno dei quali si
annichila immediatamente
incontrando un elettrone
della materia producendo una
coppia di fotoni collineari con
energia di 511 keV
La tomografia ad emissione utilizza il processo di decadimento di un
isotopo radioattivo per rilevarne la distribuzione all’interno del corpo
umano.
Il sistema di rivelazione acquisisce i conteggi e li registra in modo che
sulla base di tali informazioni si possa stimare la posizione spaziale degli
atomi emettitori.
99mTc
11C 18F
5. Il rivelatore è un monocristallo di NaI(Tl) di forma cilindrica. La luce prodotta viene
essenzialmente rilevata da un gruppo di sette PMT. La luce raccolta (quindi convertita
per fotoemissione in impulso elettronico) da ogni PM sarà tanto maggiore quanto più il
PM è prossimo all’evento. Le coordinate dell’evento vengono stabilite tramite una
media pesata della quantità di luce raccolta da ogni PM (logica Anger). Il «peso» viene
stabilito con una matrice di impedenze; preamplificatori ‘a soglia’ associati ai fototubi
limitano la media ai soli fototubi che più contribuiscono al segnale.
Per mantenere la correlazione tra le posizioni di emissione dei fotoni gamma e le
coordinate di posizione registrate si impiegano collimatori in modo da selezionare solo
determinate linee di propagazione dei fotoni.
6. Le due teste della gamma camera
sono fatte ruotare attorno al
paziente.
Durante la rotazione si acquisiscono
immagini planari tipicamente ogni
3-6 gradi
La rotazione di 360 gradi permette di
ottenere una ricostruzione 3D
ottimale.
Il tempo necessario per ottenere ogni
proiezione è variabile, ma è tipica
una durata di 15 – 20 secondi.
tempo totale di scansione di circa
15-20 minuti.
Campionamento della radioattività a diversi angoli attorno all'organo in
studio. I profili di radioattività cosi' ricavati vengono elaborati mediante
opportuni algoritmi di ricostruzione perla formazione dell'immagine
tomografica della sezione in studio.
7. viene considerato un evento
quando all’anello di rivelatori
arrivano due fotoni con
l’energia di 511 KeV in
coincidenza
• Cristalli raggruppati in blocchi
• Ogni blocco visto da gruppo di PM (4).
• Blocchi (circa100) organizzati in anelli di
80-90 cm di diametro
• 3-4 anelli per un totale di nr 18-32 anelli
di cristalli ovvero 12000-18000 singoli
cristalli
• => (2nr-1) piani transassiali acquisibili
simultaneamente (da 35 a 63 piani di 4-8
mm di spessore)
• FOV assiale 15 cm
8. La ricostruzione avviene a
partire dal sinogramma in cui
sono raccolte le proiezioni
delle varie sezioni
MA
Dato il sinogramma g, qual è
la distribuzione di f nella zona
di interesse?
Metodi analitici: FBP
Assunzioni:
Propagazione rettilinea
Angolo di vista 180°
Proiezioni equispaziate
Sistema spazioinvariante
Algoritmi iterativi:
Sezione è funzione f(x,y) a cui posso
sovrapporre una griglia quadrata che assume
concentrazione o densità diversa per ogni
elemento della griglia
Obiettivo: ottenere l’immagine di una sezione in
esame partendo dalla conoscenza delle sue
proiezioni lungo varie direzioni
10. Sinogrammi
Ogni sinogramma rappresenta i dati
acquisiti per una determinata fetta da tutti
gli angoli
Ogni LOR corrisponde ad un particolare
pixel la cui posizione nel sinogramma
dipende dall’angolo della coppia di
rivelatori e dalla distanza tra la LOR e il
centro del gantry.
Per ogni coincidenza è determinata la LOR
quindi è incrementato il valore del pixel
corrispondente
File LIST MODE
Vettore unidimensionale m che contiene
il numero di conteggi rivelati da ognuna
delle coppie i di rivelatori [per ognuna
delle LORs possibili] ad ogni intervallo
di tempo.
Non vi è uno specifico raggruppamento
dei dati, acquisizione seriale dei dati.
I valori lungo una riga
del sinogramma
rappresentano le
rivelazioni lungo
LORs parallele.
L’ampiezza della
sinusoide fornisce la
distanza della
rivelazione dal centro
del gantry
La fase della
sinusoide fornisce
l’angolo.
11. SPECT
• Attenuazione: nell’ipotesi di
coefficiente di attenuazione uniforme
nella regione di interesse si calcola il
fattore di attenuazione medio facendo
la media geometrica di proiezioni
opposte acquisite a 180°
• Scatter Compton interno: può essere
stimato sia pre che durante la
ricostruzione
• Risposta sistema collimatore-
detettore: filtro immagini
PET
12. Retroproiezione filtrata
Fourier slice theorem : la trasformata di Fourier della
proiezione della distribuzione di attività f nella direzione
θ ha valori coincidenti con quelli della trasformata di
Fourier 2D di f calcolata lungo la retta di
direzione θ passante per l'origine dello spazio delle
frequenze Il valore dell’attività dell’oggetto in esame lungo
la linea radiale è determinato facendo la trasformata di
Fourier delle proiezioni per tutti gli angoli .
A: PROIEZIONE B: RETROPROIEZIONE
C: IMMAGINE
ORIGINALE
D: DIFFERENZE TRA
IMMAGINE ORIGINALE
E RICOSTRUITA
13. Teorema della convoluzione: Il processo
di convoluzione nel dominio spaziale è
equivalente ad una moltiplicazione nel
dominio di frequenza
Applico un filtro nel dominio delle frequenze:
L’immagine viene divisa nelle sue componenti di
frequenza e il filtro definisce il peso assegnato
ad ognuno dei componenti.
Il sistema di retroproiezione introduce uno sparpagliamento : fretroproiettata(x,y)=f(x,y)⊗d(x,y)
dove d(x,y) è la point spread function
Filtro a rampa limitato (es Shepp Logan;
Hamming): amplifica alte frequenze (dettagli e
rumore)
Filtri passa basso (es di Butterworth; di
Hanning)
Assunzioni per FBP: propagazione rettilinea,
angolo di vista 180°, proiezioni equispaziate,
sistema spazio invariante.!
14. Approccio basato sull’assunzione che la sezione
del corpo in esame sia un array di incognite e che
si possa scrivere un sistema di equazioni
algebriche (lineari) per le incognite in funzione
dei dati misurati (proiezioni).
essenziale quando:
•la propaganzione non è rettilinea
•l’angolo totale di vista è limitato
•le proiezioni non sono equispaziate
•la risposta del sistema non è spazio invariante
Gli algoritmi iterativi utilizzano modelli matematici del funzionamento
dell’apparato di misura.
partendo da una stima dell’immagine corrispondente ad una
distribuzione di attività (uniforme) i passaggi fondamentali sono:
Proiezione della stima corrente per produrre una serie di proiezioni
stimate
Confronto delle proiezioni stimate con le misurate per produrre il set
delle proiezioni di errore ->a rapporto; per differenza
Retroproiezione degli errori di proiezione per trovare la locazione del
pixel nell’immagine che deve essere corretto
Aggiornamento
15.
F(x,y)
pixel dxd
In cui fj è costante
f1 f3f2 f4 f5 f6 f7
gi
gi+1
Assunzione: la concentrazione del radiofarmaco (MBq/mL o mCi/mL) f(r)in ogni posizione r
[xyz]sia un array di incognite e che si possa scrivere un sistema di equazioni algebriche
(lineari) per le incognite in funzione dei dati misurati.
Problemi: A è sparsa, non quadrata, priva di
struttura, malcondizionata.
16. Trovare stima
dell’oggetto f a partire
dai dati g prodotti
dall’apparato descritto
dalla matrice A
sinogramma
noise
Inizializzazione
immagine (FBP)
Per ogni angolo costruzione
proiezione
Confronto proiezioni stimate con quelle misurate
(sinogramma): calcolo errore
Retroproiezione errore
Errore
<soglia
FineSINO
devo risolvere
Matrice A dei pesi aij MA:
-non è quadrata
-dati>incognite
-malcondizionata
-molto sparsa
Per immagine
256x256⇒65.000 incognite
con 65.000 dati
A [65000x65000]
Attenzione il rumore
non è puramente
additivo ma
poissoniano
19. g,A
Criterio di
stop
verificato?
NO
SI
FINE
Iterazioni
su k
Sub iterazioni
su j
j=1,….n
A: Modellizzazione
apparato
C costante>0
Tipicamente le
subiterazioni sono legate
all’angolo di vista.
• Aj sottomatrice
• gj sinogramma relativo
a j
Il fattore di accelerazione
è circa pari al numero di
sottoinsiemi
Criterio diverso a seconda del problema