This document outlines the uses and indications of radiological investigations in surgery. It discusses various diagnostic modalities like X-ray, ultrasound, CT, MRI, Doppler, nuclear imaging and PET scans. The roles of imaging in emergency and elective surgical situations are described. Key uses include assessing trauma, tumors, infections and anatomical abnormalities. Modalities provide diagnostic information to evaluate patient management in a minimally invasive manner with good communication between radiologists and surgeons.
A presentation about Intravenous Urography (Also known as Intravenous Pyeography).
The presentation contains 41 slides, and is divided into 4 parts :
1 - Introduction.
2 - The procedure.
3 - Examples for abnormal findings.
4 - Studies comparing IVU accuracy with KUB & USG with CT Scan.
This presentation was prepared and presented by me in the tutorials of the Radiology Department of Sebha Medical Center.
Focused Assessment with Sonography in Trauma (FAST) in 2017Dr Varun Bansal
FAST , its definition, its modifications, its extensions in various other situations such as pregnancy, in pediatric populations, use in triage of patients. Described extended FAST which include evaulation for pneumothorax, pleural effusion, pericardial effusion. other extensions of FAST such as RUSH, RADIUS.
This presentation include biliary anatomy ,indication, contraindication post op care of percutaneus transhepatic biliary drainage with important technique. and advantage and disadvantage of different technique. This is important for radiologist, radiographers, intervention radiologist radiology resident. Thanks
Description of various ultrasound features of benign and suspicious thyroid nodules with multiple ultrasound systems for risk stratification of malignancy.
A presentation about Intravenous Urography (Also known as Intravenous Pyeography).
The presentation contains 41 slides, and is divided into 4 parts :
1 - Introduction.
2 - The procedure.
3 - Examples for abnormal findings.
4 - Studies comparing IVU accuracy with KUB & USG with CT Scan.
This presentation was prepared and presented by me in the tutorials of the Radiology Department of Sebha Medical Center.
Focused Assessment with Sonography in Trauma (FAST) in 2017Dr Varun Bansal
FAST , its definition, its modifications, its extensions in various other situations such as pregnancy, in pediatric populations, use in triage of patients. Described extended FAST which include evaulation for pneumothorax, pleural effusion, pericardial effusion. other extensions of FAST such as RUSH, RADIUS.
This presentation include biliary anatomy ,indication, contraindication post op care of percutaneus transhepatic biliary drainage with important technique. and advantage and disadvantage of different technique. This is important for radiologist, radiographers, intervention radiologist radiology resident. Thanks
Description of various ultrasound features of benign and suspicious thyroid nodules with multiple ultrasound systems for risk stratification of malignancy.
In this presentation we will discuss about the
Anatomy of Prostate
Technique of Transrectal US
Carcinoma Prostate and
Different modes of prostatic biopsy.
This presentation consist MR procedure of pelvis and hip joint , anatomy and MR planning is shown by picture with positioning block and parameters are included ,it includes basic sequence of both procedures
Role of imaging of diagnosis and management of male infertilityPrasunDas31
MALE INFERTILITY IS ONE OF THE MOST OVERLOOKED AND IGNORED TOPIC.I TRY TO ASSIMILATE ALL PROBABLE IMAGING FEATURE TO CORRECTLY DIAGNOSE IT SO THAT UROSERGEONS CAN PROCEED EASILY.
Acute scrotum is a general term referring to an emergency condition affecting the contents or the wall of the scrotum.
There are a number of conditions that present acutely, predominantly with pain and/or swelling
A careful and detailed history and examination, and in some cases, investigations allow differentiation between these diagnoses. A prompt diagnosis is essential as the patient may require urgent surgical intervention
Testicular torsion refers to twisting of the spermatic cord, causing ischaemia of the testicle.
Testicular torsion results from inadequate fixation of the testis to the tunica vaginalis producing ischemia from reduced arterial inflow and venous outflow obstruction.
The prevalence of testicular torsion in adult patients hospitalized with acute scrotal pain is approximately 25 to 50 percent
Title: Sense of Taste
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the structure and function of taste buds.
Describe the relationship between the taste threshold and taste index of common substances.
Explain the chemical basis and signal transduction of taste perception for each type of primary taste sensation.
Recognize different abnormalities of taste perception and their causes.
Key Topics:
Significance of Taste Sensation:
Differentiation between pleasant and harmful food
Influence on behavior
Selection of food based on metabolic needs
Receptors of Taste:
Taste buds on the tongue
Influence of sense of smell, texture of food, and pain stimulation (e.g., by pepper)
Primary and Secondary Taste Sensations:
Primary taste sensations: Sweet, Sour, Salty, Bitter, Umami
Chemical basis and signal transduction mechanisms for each taste
Taste Threshold and Index:
Taste threshold values for Sweet (sucrose), Salty (NaCl), Sour (HCl), and Bitter (Quinine)
Taste index relationship: Inversely proportional to taste threshold
Taste Blindness:
Inability to taste certain substances, particularly thiourea compounds
Example: Phenylthiocarbamide
Structure and Function of Taste Buds:
Composition: Epithelial cells, Sustentacular/Supporting cells, Taste cells, Basal cells
Features: Taste pores, Taste hairs/microvilli, and Taste nerve fibers
Location of Taste Buds:
Found in papillae of the tongue (Fungiform, Circumvallate, Foliate)
Also present on the palate, tonsillar pillars, epiglottis, and proximal esophagus
Mechanism of Taste Stimulation:
Interaction of taste substances with receptors on microvilli
Signal transduction pathways for Umami, Sweet, Bitter, Sour, and Salty tastes
Taste Sensitivity and Adaptation:
Decrease in sensitivity with age
Rapid adaptation of taste sensation
Role of Saliva in Taste:
Dissolution of tastants to reach receptors
Washing away the stimulus
Taste Preferences and Aversions:
Mechanisms behind taste preference and aversion
Influence of receptors and neural pathways
Impact of Sensory Nerve Damage:
Degeneration of taste buds if the sensory nerve fiber is cut
Abnormalities of Taste Detection:
Conditions: Ageusia, Hypogeusia, Dysgeusia (parageusia)
Causes: Nerve damage, neurological disorders, infections, poor oral hygiene, adverse drug effects, deficiencies, aging, tobacco use, altered neurotransmitter levels
Neurotransmitters and Taste Threshold:
Effects of serotonin (5-HT) and norepinephrine (NE) on taste sensitivity
Supertasters:
25% of the population with heightened sensitivity to taste, especially bitterness
Increased number of fungiform papillae
The prostate is an exocrine gland of the male mammalian reproductive system
It is a walnut-sized gland that forms part of the male reproductive system and is located in front of the rectum and just below the urinary bladder
Function is to store and secrete a clear, slightly alkaline fluid that constitutes 10-30% of the volume of the seminal fluid that along with the spermatozoa, constitutes semen
A healthy human prostate measures (4cm-vertical, by 3cm-horizontal, 2cm ant-post ).
It surrounds the urethra just below the urinary bladder. It has anterior, median, posterior and two lateral lobes
It’s work is regulated by androgens which are responsible for male sex characteristics
Generalised disease of the prostate due to hormonal derangement which leads to non malignant enlargement of the gland (increase in the number of epithelial cells and stromal tissue)to cause compression of the urethra leading to symptoms (LUTS
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
Tom Selleck Health: A Comprehensive Look at the Iconic Actor’s Wellness Journeygreendigital
Tom Selleck, an enduring figure in Hollywood. has captivated audiences for decades with his rugged charm, iconic moustache. and memorable roles in television and film. From his breakout role as Thomas Magnum in Magnum P.I. to his current portrayal of Frank Reagan in Blue Bloods. Selleck's career has spanned over 50 years. But beyond his professional achievements. fans have often been curious about Tom Selleck Health. especially as he has aged in the public eye.
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Introduction
Many have been interested in Tom Selleck health. not only because of his enduring presence on screen but also because of the challenges. and lifestyle choices he has faced and made over the years. This article delves into the various aspects of Tom Selleck health. exploring his fitness regimen, diet, mental health. and the challenges he has encountered as he ages. We'll look at how he maintains his well-being. the health issues he has faced, and his approach to ageing .
Early Life and Career
Childhood and Athletic Beginnings
Tom Selleck was born on January 29, 1945, in Detroit, Michigan, and grew up in Sherman Oaks, California. From an early age, he was involved in sports, particularly basketball. which played a significant role in his physical development. His athletic pursuits continued into college. where he attended the University of Southern California (USC) on a basketball scholarship. This early involvement in sports laid a strong foundation for his physical health and disciplined lifestyle.
Transition to Acting
Selleck's transition from an athlete to an actor came with its physical demands. His first significant role in "Magnum P.I." required him to perform various stunts and maintain a fit appearance. This role, which he played from 1980 to 1988. necessitated a rigorous fitness routine to meet the show's demands. setting the stage for his long-term commitment to health and wellness.
Fitness Regimen
Workout Routine
Tom Selleck health and fitness regimen has evolved. adapting to his changing roles and age. During his "Magnum, P.I." days. Selleck's workouts were intense and focused on building and maintaining muscle mass. His routine included weightlifting, cardiovascular exercises. and specific training for the stunts he performed on the show.
Selleck adjusted his fitness routine as he aged to suit his body's needs. Today, his workouts focus on maintaining flexibility, strength, and cardiovascular health. He incorporates low-impact exercises such as swimming, walking, and light weightlifting. This balanced approach helps him stay fit without putting undue strain on his joints and muscles.
Importance of Flexibility and Mobility
In recent years, Selleck has emphasized the importance of flexibility and mobility in his fitness regimen. Understanding the natural decline in muscle mass and joint flexibility with age. he includes stretching and yoga in his routine. These practices help prevent injuries, improve posture, and maintain mobilit
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
NVBDCP.pptx Nation vector borne disease control programSapna Thakur
NVBDCP was launched in 2003-2004 . Vector-Borne Disease: Disease that results from an infection transmitted to humans and other animals by blood-feeding arthropods, such as mosquitoes, ticks, and fleas. Examples of vector-borne diseases include Dengue fever, West Nile Virus, Lyme disease, and malaria.
Recomendações da OMS sobre cuidados maternos e neonatais para uma experiência pós-natal positiva.
Em consonância com os ODS – Objetivos do Desenvolvimento Sustentável e a Estratégia Global para a Saúde das Mulheres, Crianças e Adolescentes, e aplicando uma abordagem baseada nos direitos humanos, os esforços de cuidados pós-natais devem expandir-se para além da cobertura e da simples sobrevivência, de modo a incluir cuidados de qualidade.
Estas diretrizes visam melhorar a qualidade dos cuidados pós-natais essenciais e de rotina prestados às mulheres e aos recém-nascidos, com o objetivo final de melhorar a saúde e o bem-estar materno e neonatal.
Uma “experiência pós-natal positiva” é um resultado importante para todas as mulheres que dão à luz e para os seus recém-nascidos, estabelecendo as bases para a melhoria da saúde e do bem-estar a curto e longo prazo. Uma experiência pós-natal positiva é definida como aquela em que as mulheres, pessoas que gestam, os recém-nascidos, os casais, os pais, os cuidadores e as famílias recebem informação consistente, garantia e apoio de profissionais de saúde motivados; e onde um sistema de saúde flexível e com recursos reconheça as necessidades das mulheres e dos bebês e respeite o seu contexto cultural.
Estas diretrizes consolidadas apresentam algumas recomendações novas e já bem fundamentadas sobre cuidados pós-natais de rotina para mulheres e neonatos que recebem cuidados no pós-parto em unidades de saúde ou na comunidade, independentemente dos recursos disponíveis.
É fornecido um conjunto abrangente de recomendações para cuidados durante o período puerperal, com ênfase nos cuidados essenciais que todas as mulheres e recém-nascidos devem receber, e com a devida atenção à qualidade dos cuidados; isto é, a entrega e a experiência do cuidado recebido. Estas diretrizes atualizam e ampliam as recomendações da OMS de 2014 sobre cuidados pós-natais da mãe e do recém-nascido e complementam as atuais diretrizes da OMS sobre a gestão de complicações pós-natais.
O estabelecimento da amamentação e o manejo das principais intercorrências é contemplada.
Recomendamos muito.
Vamos discutir essas recomendações no nosso curso de pós-graduação em Aleitamento no Instituto Ciclos.
Esta publicação só está disponível em inglês até o momento.
Prof. Marcus Renato de Carvalho
www.agostodourado.com
micro teaching on communication m.sc nursing.pdfAnurag Sharma
Microteaching is a unique model of practice teaching. It is a viable instrument for the. desired change in the teaching behavior or the behavior potential which, in specified types of real. classroom situations, tends to facilitate the achievement of specified types of objectives.
Knee anatomy and clinical tests 2024.pdfvimalpl1234
This includes all relevant anatomy and clinical tests compiled from standard textbooks, Campbell,netter etc..It is comprehensive and best suited for orthopaedicians and orthopaedic residents.
2. OUTLINE
• Introduction
• Diagnostic modalities in radiology
• Role of radiological imaging in emergency
surgical situation
• Role of radiological imaging in elective surgical
situation
• Conclusion
• Reference
3. Best practice for imaging
• If it is likely to affect patient management
• Localize the clinical problem prior to imaging in order to
reduce over-investigation and excess radiation exposure
• Relevant imaging procedure for the relevant diagnostic
information most easily
• Good communication with the radiologists is key to
ensuring appropriate investigation pathways
4. Diagnostic Modalities in Radiology
• X ray
• USG
• CT Scan
• MRI
• Doppler
• Radio nucleotide imaging
• PET scan
5. Role of radiological imaging in
emergency surgical situation
• X-ray
–Perforation of gas containing hollow viscus
–Intestinal Obstruction
–Tension Pneumothorax / Hemothorax /
Pneumohemothorax
–Fracture
6. • USG
• FAST
• Ruptured ectopic pregnancy
• High resolution USG in acute appendicitis
• CT scan
– Pneumocephalus
–# head
–Subdural hematoma
–Intracerebral hematoma
20. Indication of FAST
• Evaluation of the torso for free fluid
suggesting injury to peritoneal, pericardial,
and pleural cavities, particularly in trauma
• Blunt abdominal trauma
• Stable penetrating trauma
21. Advantages
• Decrease the time to diagnosis for acute
abdominal injury in blunt abdominal trauma
• Helps accurately diagnose and assess degree
of hemoperitoneum
• Noninvasive
• Can be intergrated in 10 or 20 survey
• Can be performed quickly, in clinical arena
• Safe for children and pregnant woman
22. Role of Radiological Imaging in Elective
surgical situation
1. Plain
2. contrast
38. Anterograde urethrography/MCU
• Bladder is filled with contrast via suprapubic or
retrograde catheterization
• Bladder and urethra is assessed during voiding.
Indications:
• Voiding difficulties
• VUR
• Trauma
• Anatomical abnormalities of bladder neck
• Fistula
42. • Barium swallow X-ray -> for oesophagus
• Barium meal X-ray -> for stomach
• Barium follow through -> for small intestine
• Barium enema -> for large intestine
48. Dilatation from small bowel obstruction. The diameter of the bowel is greatly increased. The
feathery mucosal pattern is lost and the folds appear as thin lines traversing the bowel,
known as valvulae conniventes (arrows
51. Drawbacks
• Contrast inadvertently injected outside the vein is
painful and should be carefully guarded against.
• A few patients develop an urticarial rash, which
usually subsides spontaneously.
• Bronchospasm, laryngeal oedema or hypotension
occasionally develop and may be so severe as to
be lifethreatening.
• Intravenous contrast agents may have a
deleterious effect on renal function in patients
with impaired kidneys.
52. Other uses
• To determine the appropriate position of
central venous line, ET tube and Chest tube
53. Ultrasonography (USG)
Principle
• Depends on the generation of high frequency
sound wave(3 and 7 MHz) by transducer
placed on skin
• Sound is reflected by tissue interfaces
• Echoes generated are picked by the same
transducer and converted into an image
• Image is displayed in real time on monitor
57. THERAPEUTIC USES
• USG guided aspiration of hepatic and
pulmonary abscess and cyst
• Focused U/S may be used to break up kidney
stone by lithotripsy
• U/S may be used for cataract treatment by
phacoemulsification
58. Ultrasound scan of gall bladder showing a large
stone inthe neck of the gall bladder
(downward pointing arrow). Note the acoustic
shadow behind the stone (horizontal double-
headed arrow).
Ultrasound scan of longitudinal section
through the liver and right kidney. A cyst
(C) is present in the upper pole of the
kidney.
59.
60. Advantages of USG
• No radiation
• Inexpensive
• Allow interaction with patients
• Superb soft tissue resolution in the near field
• Dynamic studies can be performed
• 1st line inv- hepatic, biliary and renal disease
• Excellent resolution for breast, thyroid and testes
imaging
• Good for soft tissue, including tendons and ligament
• Excellent for cysts and foreign bodies
• Doppler studies allow assessment of blood flow
61. Doppler
• To study cardiovascular system.
• To study vascularity of tumours.
• To study blood flow and velocity in arterial
diseases so as to assess stenosis (its extent,
cause, etc.) like in atherosclerosis, TAO, cervical
rib, aneurysm, A-V fistulas.
• To find out deep venous thrombosis (DVT),
varicose veins,perforator incompetence.
• To study grade of varicocele in males
62.
63.
64. Computed Tomography
• Principle
The x-ray tube and
detectors move
around the patient
enabling a picture
of x-ray absorption
in different parts of
the body to be built
up.
65.
66.
67.
68. Computed Tomography (CT)
Indications
• Trauma like head injury, chest injury, abdomen
trauma. In trauma only plain CT scan is taken.
• Neoplasms: To see the exact location, size,
vascularity,extent and operability. For
example, brain, abdominal, retroperitoneal,
thoracic and spinal tumours.
• Inflammatory conditions, in various sites.For
example, psoas abscess, pseudocyst of
pancreas.
69. Advantages of CT
• High spatial and contrast resolution
• Contrast resolution enhanced by imaging in arterial and/or
venous phases
• Rapid acquisition of images in one breath hold
• Imaging of choice for the detection of pulmonary masses
• Allows global assessment of abdomen and pelvis
• Excellent for liver, pancreatic, renal and bowel pathology
• 3D reconstruction allows complex fracture imaging
• Multiplanar reconstruction and 3D imaging eg CT
angiography and coloscopy
74. Magnetic Resonance Imaging
• radiofrequency pulse at the resonant frequency
of hydrogen
• a proportion of the protons change alignment,
• Following this the protons return (realign) to
their original positions.
• As the protons realign (relax), they induce a
signal
• can be detected and localized by copper coils
placed around the patient.
• An image representing the distribution of the
hydrogen protons can be built up
75.
76.
77.
78.
79. Magnetic resonance Imaging (MRI)
• very useful in intracranial, spinal and musculoskeletal
lesions including joint pathologies.
• It gives direct anatomical sections of the area, with
lesions at a high resolution.
• MR angiogram : done without injecting IV contrast
agents
• Cardiac MRI
• Breast MRI : used in multifocal recurrent cancers.
80. • Magnetic resonance
cholangiopancreatography (MRCP)
a very useful non contrast diagnostic tool
which may replace diagnostic ERCP.
• MR spectroscopy
chemical analysis of elements in a tissue to
differentiate between tumor, inflammation,
and degeneration.
84. Evolving use
• Staging
• MRCP
• MR angiography
• Breast malignancy
• Pelvic malignancy
• Cardiac imaging
85. Adnvantages over USG, Xray and CT
scan
• No ionizing radiation
• Excellent soft tissue contrast
• Best imaging technique for
– Intracranial lesions, specially posteriro fossa lesion
– Spine
– Bone marrow and joint lesions
86. Radionucliotide imaging
ISOTOPE USED FOR
DIAGNOSTIC USES
131I Thyroid disease
60Co Perncicious anemia
24Na Arterial disease
Radioactive diiodoflurescein Brain tumor
THERAPEUTIC USES
131I Hyperthyroidism and thyroid cancer
131I(very high dose) CHF
32P Polycythemia vera and leukemia
198Au Malignant pleaural and peritonial
effusions
87. PET scan
Uses
• To assess myocardial perfusion (82Rb) and
viability (FDG) study.
• Epilepsy—To localize temporal lobe epilepsy
(FDG)
• Cancer imaging—Lung cancer (detection and
staging)
• Colorectal cancer
• Melanoma
• Head and neck cancer and breast cancer
• Musculoskeletal tumors
• Thyroid cancer (I131)
88.
89.
90. ALARA principle: ‘as low as
reasonably achievable’
• Use of appropriate equipment and good technique
• Limiting the size of the x-ray beam to the required
areas,
• Limiting the number of films to those that are
necessary,
• Keeping repeat examinations to a minimum and
ensuring that the examination has not already been
performed.
91. References
• Diagnostic imaging 7th edition
• Bailey and Love’s Short Practice of Surgery,
26th edition
• SRB’s Manual of Surgery 4th edition
• Medscape
Free gas in the peritoneal cavity. On this chest
radiograph, air can be seen under the domes of both
hemidiaphragms. The curved arrow points to the left
hemidiaphragm and the arrow head to the wall of the stomach.
The two vertical arrows point to the diaphragm and upper
border of the liver.
Volvulus of the caecum. The twisted obstructed caecum and ascending colon now lie on the left side of the abdomen and appear as a large gas shadow. There is also extensive small bowel dilatation from obstruction by the volvulus.
Epidural?
Subdural acute/chronic?
Stable penetrating trauma?
EFAST- extended form where includes view of bilateral hemithoraces to access for hemothorax and view of upper bilateral hemithoraces to access for pneumothorax
Pneumothorax lt
Normal plain abdominal film. (a) Normal abdomen. The
arrows point to the lateral borders of the psoas muscles. The
renal outlines are obscured by the overlying colon
Small bowel obstruction due to adhesions. (a) The jejunal loops are markedly dilated and show air–fluid levels in the erect
film. The jejunum is recognized by the presence of valvulae conniventes. (b) The ‘stack of coins’ appearance is well demonstrated in the
supine film. Note the large bowel contains less gas than normal.
Paralytic ileus. There is considerable dilatation of the whole of the large bowel extending well down into the pelvis. Small bowel dilatation is also seen
Correct central line and ET tube placement
As air, bone and other heavily calcified materials absorb
nearly all the ultrasound beam, ultrasound plays little
part in the diagnosis of lung or bone disease. The information
from abdominal examinations may be significantly
impaired by gas in the bowel, which interferes with the
transmission of sound.
Fluid is a good conductor of sound, and ultrasound is,
therefore, a particularly good imaging modality for diagnosing
cysts, examining fluid-filled structures such as the
bladder and biliary system, and demonstrating the fetus in
its amniotic sac. Ultrasound can also be used to demonstrate
solid structures that have a different acoustic impedance
to adjacent normal tissues, e.g. metastases
Ultrasound of normal liver. Transverse scan across the porta hepatis. Ao, aorta; IVC, inferior vena cava; PV, portal vein.
Ultrasound of normal gall bladder. Note the thin wall
and absence of echoes from within the gall bladder. GB, gall
bladder; IVC, inferior vena cava; PV, portal vein
Normal ultrasound of the full bladder (B). Note the
smooth thin bladder wall. The vagina lies posteriorly
Cysts or other fluid-filled structures produce echoes from their walls but no echoes
from the fluid contained within them. Also, more echoes
than usual are received from the tissues behind the cyst, an
effect known as acoustic enhancement. Conversely, with a
calcified structure, e.g. a gall stone (Fig. 1.7), there is a great
reduction in the sound that will pass through, so a band of duodereduced
echoes, referred to as an acoustic shadow, is seen
behind the stone
Sound reflected from a mobile structure shows a variation
in frequency that corresponds to the speed of movement of
the structure. This shift in frequency, which can be converted
to an audible signal, is the principle underlying the
Doppler probe
The Doppler effect can be exploited to image blood
flowing through the heart or blood vessels. Here the sound
is reflected from the blood cells flowing in the vessels (Fig.
1.9). If blood is flowing towards the transducer, the received
signal is of higher frequency than the transmitted frequency,
whilst the opposite pertains if blood is flowing
away from the transducer. The difference in frequency
between the sound transmitted and received is known
as the Doppler frequency shift (Box 1.2). The direction of
blood flow can readily be determined and flow towards the
transducer is, by convention, coloured red, whereas blue
indicates flow away from the transducer.
When a patient is being scanned, the Doppler information
in colour is superimposed onto a standard ultrasound
image (Fig. 1.10).
During the examination, the flow velocity waveform can
be displayed and recorded. As the waveforms from specific
arteries and veins have characteristic shapes, flow abnormalities
can be detected
Frequency shift = 2Fi ×V ×cos theta/c
As c, the speed of sound in tissues, and Fi, the incident
frequency of sound, are constant, and if θ, the Doppler angle,
is kept constant, the frequency shift depends directly on the
blood flow velocity V
Colour Doppler. (a) Normal renal artery. (b) Normal renal vein. (c) Bifurcation of the common carotid artery showing stenosis of
the internal carotid artery. The flowing blood is revealed by colour. The precise colour depends on the speed and direction of the blood
flow. cca, common carotid artery; eca, external carotid artery; ica, internal carotid artery.
The attenuation values are
expressed on an arbitrary scale (Hounsfield units) with
water density being zero, air density being minus 1000
units and bone density being plus 1000 units
Coronal reconstruction of CT of the chest, abdomen and
pelvis. The images were obtained in the axial plane using very
thin sections and then reconstructed into the desired plane – a
coronal plane in this example. The illustrated section is through
the posterior abdomen and shows the kidneys. There is a
retroperitoneal mass (arrow) displacing the left kidney and
causing hydronephrosis.
The range of densities visualized
on a particular image is known as the window width
and the mean level as the window level or window centre
Obstructive hydrocephalus. Axial CT images performed at the level of the lateral ventricles (a) and more inferiorly at the level
of the temporal horns
the nuclei of certain elements align with the magnetic force when placed in a strong magnetic field.
At the field strengths currently used in medical imaging, hydrogen nuclei (protons) in water molecules and lipids are responsible for producing anatomical images. If a radiofrequency pulse at the resonant frequency of hydro-gen is applied, a proportion of the protons change alignment, flipping through a preset angle, and rotate in phase with one another. Following this radiofrequency pulse, the protons return (realign) to their original positions. As the protons realign (relax), they induce a signal which, although very weak, can be detected and localized by copper coilsplaced around the patient. An image representing the distributionof the hydrogen protons can be built up
The strength of the signal depends not only on proton
density but also on two relaxation times, T1 and T2; T1
depends on the time the protons take to return to the axis
of the magnetic field, and T2 depends on the time the
protons take to dephase (also known as T2 decay). A T1-
weighted image is one in which the contrast between
tissues is due mainly to their T1 relaxation properties, while
in a T2-weighted image the contrast is due to the T2 relaxation
Properties
Most pathological
processes show increased T1 and T2 relaxation times
and, therefore, these processes appear lower in signal
(blacker) on a T1-weighted scan and higher in signal intensity
(whiter) on a T2-weighted image than the normal surrounding
tissues.
One
advantage of MRI over CT is that the information can be
directly imaged in any plane. In most instances, MRI
requires a longer scan time (often several minutes) compared
with CT, with the disadvantage that the patient has
to keep still during the scanning procedure. Unavoidable
movements from breathing, cardiac pulsation and peristalsis
often degrade the image.
Diagram of an MRI machine. The
patient lies within a strong magnet (usually
a cylindrical magnet). The radiofrequency
transmitter coils send radiowaves into the
patient and the same coils receive signals from
within the patient. The intensity and source of
these signals can be calculated and displayed
as an image.
MRI of brain. (a) Axial T1-weighted image. (b) Axial
T2-weighted image. (c) Axial T1-weighted image following
gadolinium. Note that the cerebrospinal fluid within the
lateral ventricles is of low signal intensity on T1- and high
signal intensity on T2-weighted images (arrows in (a) and
(b)). Note also that the intensity of the white and grey matter
of the brain differs on the two images. There is a metastasis
from a breast carcinoma (M) in the right occipital pole,
showing oedema around the mass on the T2-weighted image
and enhancement on the post contrast image
The most widely used agents are
gadolinium compounds which only cross the blood–brain
barrier when it is damaged by disease (see Fig. 1.14c), and
which concentrate in tissues and disease processes with a high blood supply
Gadolinium-based contrast agents are generally very
safe and anaphylactic reactions are rare. They are contraindicated
in pregnancy. Also, it has recently been recognized
that patients in renal failure, on dialysis or awaiting liver
transplantation are at risk of developing nephrogenic
systemic fibrosis, which can be fatal. In these patients,
the magnetic resonance scan is done without the use of
gadolinium-based contrast agents.
MRI of a sagittal section of lumbar spine. (a) On this T1 sequence, the spinal cord is grey, cerebrospinal fluid (CSF) is nearly
black and subcutaneous fat is white. (b) T2-weighted sequence. Here the CSF is white. Cortical bone (arrows) returns no signal and
appears as a black line on both sequences. The fat in the bone marrow produces a signal that enables the vertebrae to be visualized.
MRCP. A stone is present in the common bile duct
(arrow) with dilatation of the ducts above it. A normal pancreatic
duct has also been demonstrated (curved arrows).
ERCP.(a) A normal biliary system has been shown by
injecting contrast through a catheter passed from the endoscope
into the common bile duct. The pancreatic duct has also been
filled. (b) A dilated ductal system with numerous large calculi in
the hepatic and common bile ducts. (c) A stricture in the
common bile duct from a cholangiocarcinoma is causing marked
dilatation of the biliary system above it.
Endoscopic ultrasound showing a small polyp in the
gall bladder with no acoustic shadow (arrow).
Cancer uptakes more fluorodeoxyg
By using isotopes of biologically important elements such
as carbon or oxygen, PET can be used to study physiological
processes such as blood perfusion of tissues, and
metabolism of substances such as glucose, as well as
complex biochemical pathways such as neurotransmitter
storage and binding.lucose
F-18 fluorodeoxyglucose (FDG). This is an analogue of
glucose and is taken up by cells in proportion to glucose
metabolism, which is usually increased in tumour cells.
Because muscle activity results in the uptake of FDG, the
patient should rest quietly in the interval between injection
of the FDG and scanning.
FDG-PET scans, maximum intensity projections. (a) Normal isotope distribution. There is intense uptake in the brain and the
neck uptake is in the tonsils. The FDG is excreted by the kidneys. (b) Lymphoma, showing multiple visceral, nodal, bone
and scalp deposits
Positron emission tomography demonstrates biological
function while CT gives anatomical information. If PET and
CT are fused, the lesions detected by PET can be precisely
localized by CT
FDG-PET/CT of lung cancer. (a) Coronal fused image and (b) maximum intensity projection, demonstrating a small left lung
cancer (arrowed in (a)). The remainder of the FDG uptake is physiological.
