Three dimensional (3D) ultrasound is a technique that converts standard 2D grayscale ultrasound images into a volumetric data set. The 3D image can then be reviewed retrospectively. The technique was developed for problem solving (particularly in obstetric/gynecologic exams) and potentially to r...
An opacity projecting over the abdomen has a broad differential. Possibilities to consider include:
ingested, e.g. coins, batteries, bones, etc.
artifacts, e.g. object attached to the cloth of the patient like a safety pin or button
iatrogenic, e.g. haemostatic clips, gastric ...
Abnormal bowel wall attenuation patterns on CT scan can be grouped under five categories:
water halo sign
fat halo sign
The first three patterns are seen on contrast studies.
It is defined as uniform enhancement of th...
Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumours.
Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situations:
Down syndrome: around 80...
Acromiohumeral interval (AHI) is a useful and reliable measurement on AP shoulder radiographs and when narrowed is indicative of rotator cuff tear or tendinopathy.
Measurements of the AHI in the following intervals are suggestive of pathology 1-2:
>12 mm: shoulder dislocation; i...
Acute pelvic pain is a common presenting symptom to the emergency department and radiologist. Pelvic ultrasound with transabdominal and endovaginal approaches are usually the first line imaging modality.
pain of <3 months duration
Patients also often ...
Adult chest radiograph common exam pathology is essential to consider in the build up to radiology exams. The list of potential diagnoses is apparently endless, but there are some favorites that seem to appear with more frequency.
When dealing with the adult chest radiograph in the exam settin...
There are a number of adult chest radiograph set-pieces. These are based on common patterns of disease that are seen on chest radiographs. Make sure that you have relevant differentials for these appearances and a quick aural set-piece for them when they come up.
The imaging characteristics of blood on MRI are variable and change with the age of the blood.
In general, five stages of haematoma evolution are recognised:
isointense on T1
isointense to hyperintense on T2
acute (1 to 2 days)
An air space nodule is a small (few millimeters to 1 cm), ill-defined, nodular opacity that is often centrilobular in location and is non-specific, seen in many conditions. Commonly it represents a focal area of consolidation or peribronchiolar inflammation, and can indicate endobronchial spread...
The alpha angle is a measurement used in the ultrasonographic assessment of developmental dysplasia of the hip (DDH).
The angle is formed by the acetabular roof to the vertical cortex of the ilium and thus reflects the depth of the bony acetabular roof. This is a similar measurement to the acet...
The amniotic fluid index (AFI) is an estimate of the amniotic fluid volume in a fetus. It is part of the fetal biophysical profile.
uterus is divided into four imaginary quadrants with linea nigra and umbilicus acting as the vertical and the horizontal axis respectively
Amniotic fluid volume (AFV) is a function both of the amount of water transferred to the gestation across the placental membrane, and the flux of water across the amnion.
Change in volume through gestation
The AFV undergoes characteristic changes with gestation. It progressively ri...
The Amsterdam wrist rules are validated clinical decision rules for determining which patients require radiographic imaging (wrist radiography) for acute wrist pain following trauma. The initial study evaluated 882 patients and were published in 2015 1. The decision rules assessed different clin...
The anatomic position, also referred to as the standard anatomic position, is the consistent position of the human body in which positional reference is made for anatomical nomenclature. It is not reliant on whether the patient is standing, supine, prone, sitting, etc.
The position is defined a...
Getting a film with anembryonic pregnancy in the radiology fellowship examination is one of the many exam set-pieces that the candidate must be prepared for.
Transabdominal and transvaginal pelvic ultrasound shows a uterus with an intrauterine gestational sac. MSD is 25mm in TV st...
Ankle AP view is part of a three view series of the distal tibia, distal fibula, proximal talus and proximal metatarsals.
the patient may be supine or sitting upright with their leg straighten on the table
the foot is in dorsiflexion
the toes will be pointing directly toward...
Antenatal screening of Down syndrome (and other less common aneuploidies) should be available as a routine component of antenatal care. It allows families to either adjust to the idea of having a child with the condition, or to consider termination of pregnancy.
For a general description of Dow...
Anterior cord syndrome (also known as Beck's syndrome or anterior spinal artery syndrome) is a clinical subset of spinal cord injury syndromes, due to ischaemia/infarction of the anterior two-thirds of the spinal cord, typically sparing posterior third.
Patient present wi...
An aortic nipple is seen in about 10% of PA chest x-rays on the lateral surface of the aortic arch/aortic knob. It represents the left superior intercostal vein.
When prominent, superior vena cava obstruction should be considered (the left superior intercostal vein might be a collateral pathway).
The apical zone is one of the four chest radiograph zones and an important location for missed diagnoses when reporting a frontal chest radiograph and makes up one of the "check areas". It is sometimes thought of as a subdivision of the upper zone.
A solitary pulmonary nodule, according to the Nomenclature Committee of the Fleischner Society, defined as a rounded opacity, well or poorly defined on a conventional radiograph, measuring up to 3 cm in diameter and is not associated with lymphadenopathy, atelectasis, or pneumonia.
A number of differentials must be kept in mind while approaching diffuse pulmonary nodules. Interpretation is easier if nodules are the only abnormality.
These differentials can be narrowed down based on the several criteria:
Based on appearance
This is a basic article for medical students and other non-radiologists
NG tube placement is commonly assessed using a chest radiograph although local protocol may dictate that pH assessment of NG aspirate be used in the first instance to confirm position of the NG tube.
There are recognised l...
Assessment of thyroid lesions is commonly encountered in radiological practice.
hyperplastic / colloid nodule / nodular hyperplasia: 85%
papillary: 60-80% of carcinomas
Ultrasound along with nuclear medicine, is an important modality for assessment of thyroid lesions, and it is also frequently used to guide biopsy. Diagnostic criteria for thyroid nodules continue to evolve with improving ultrasound technology.
The American Thyroid Association (ATA) guidelines for assessment of thyroid nodules are meant to improve inter- and intra-reader consistency during assessment of thyroid nodules on ultrasound, and to facilitate communication with referring endocrinologists.
The 2015 guidelines stress the import...
Abdominal radiographs can be challenging examinations to look at. It is always best to approach radiographs in a systematic way.
Bowel gas pattern
Gas within the bowel forms a natural contrast with surrounding tissues since it has a very low density. Bowel can only be seen if it contains air/g...
Barium swallow is a dedicated test of the pharynx, oesophagus, and proximal stomach, and may be performed as a single or double contrast study. The study is often "modified" to suit the history and symptoms of the individual patient, but it is often useful to evaluate the entire pathwa...
Benign and malignant characteristics of breast lesions at ultrasound allow the classification as either malignant, intermediate or benign based on work published by Stavros et al in 1995.
Malignant characteristics (with positive predictive values)
The big rib sign is a sign to differentiate right and left ribs on lateral chest radiographs.
It exploits a technique of magnification differences on lateral projections between right and left ribs. For example, on right lateral projections the left ribs appear larger than right ribs.
The bimastoid line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.
The bimastoid line is drawn between right and left tip of mastoids. The tip of the odontoid process of C2 normally projects less than or equal to 10 mm...
Blumensaat line is the line drawn alone the roof of intercondylar notch of the femur as seen on lateral radiograph of the knee joint. It can been used for:
indicating the relative position of the patella as normally this line intersects the lower pole of the patella
suggesting ACL injury as th...
Böhler angle, also written as Bohler angle or Boehler angle, is also called as calcaneal angle or tuber joint angle 1, is the angle between two lines tangent to the calcaneus on the lateral radiograph. These lines are drawn tangent to the anterior and posterior aspects of the superior calcaneus....
Breast calcifications are relatively frequently found on mammograms and are indicative of focally active process, however about 80% of these processes are benign. Thus the ability to distinguish these calcifications based on their morphological characteristics, size, number and distribution is i...
Breast density on mammography can significantly vary between individuals. The density is a function of the relationship between radiolucent fat and radiodense glandular tissue.
Breast density varies with age and generally younger women have denser breasts (i.e. more glandular tissue relative to...
Breast echotexture according to the BI-RADS lexicon is usually classified into three categories 1:
parenchymal patterns in breast imaging
Breast MRI is a rapidly growing field, especially in the assessment of high risk women.
Editorial board note: this article is probably outdated, lacks structure and is in need of a major rewrite. If you are interested in refining it you are more than welcome.
T1 C+ (Gd...
Following administration of Gadolinium there can be three possible enhancement kinetic curves for a lesion on breast MRI (these are also applied in other organs such as prostate MRI). These are sometimes termed the Kuhl enhancement curves.
type I curve: progressive enhancement pattern
British Thoracic Society guidelines for pulmonary nodules were published in August of 2015 for the workup of pulmonary nodules seen on CT. They supersede previous Fleischner Society guidelines in the United Kingdom.
They are based initially on identifying whether the nodule being dealt with is...
Bronchogenic cysts and oesophageal duplication cysts are embryological foregut duplication cysts and are also differential diagnosis for a cystic mediastinal mass.
asymptomatic bronchogenic cyst
symptomatic oesophageal cyst in case of peptic ulceration
Plain radiograph ...
Computed tomography of the heart (or cardiac CT) is routinely performed to gain knowledge about cardiac or coronary anatomy, to detect or diagnose coronary artery disease, to evaluate patency of coronary artery bypass grafts or implanted coronary stents or to evaluate volumetry and cardiac funct...
Cardiac MRI consists of using MRI to study heart anatomy and pathology.
Main advantages of cardiac MRI in comparison with other techniques are:
a better definition of soft tissues
use of different types of sequences improves diagnostic accuracy
avoid ionising radiation
Cardiac silhouette refers to the outline of the heart as seen on frontal and lateral chest radiographs and forms part of the cardiomediastinal contour. The size and shape of the cardiac silhouette provide useful clues for underlying disease.
From the frontal projection, t...
The cardiothoracic ratio (CTR) aids in the detection of enlargement of the cardiac silhouette, which is most commonly from cardiomegaly but can be due to other processes such as pericardial effusion.
The CTR is measured on a PA chest x-ray, and is the ratio of maximal ho...
The cases featured in these video lectures are specifically selected to teach important concepts in radiology over a broad range of topics. The tutorials vary in difficulty from basic to advanced. For maximum learning, try the cases for yourself in Radiopaedia quiz mode first.
We love this ser...
Caudate-right lobe ratio (C/RL) is used in the assessment of livers, usually in the setting of cirrhosis, in which there is atrophy of the right lobe with hypertrophy of the caudate lobe.
Method for measuring
image: axial slice immediately below the bifurcation of the main portal vein
There are several causes leading to a perfusion defect on a VQ scan with an acute pulmonary embolus being only one of them:
acute pulmonary embolus
previous pulmonary embolus (including fat embolism, thromboembolism, air embolism, tumour)
vasculitides affecting the pulmonary ...
Cerebroplacental ratio (CPR) is an important obstetric ultrasound tool used as a predictor of adverse pregnancy outcome and is calculated by dividing the Doppler pulsatile indices of the middle cerebral artery (MCA) by the umbilical artery (UA).
The index will reflect mild increased in placenta...
ABCDEFGHI can be used to guide a systematic interpretation of chest x-rays.
Assessment of quality
The quality of the image can be assessed using the mnemonic PIER:
position: is this a supine AP file? PA? Lateral?
inspiration: count the posterior ribs. You should see 10 to 11 ribs with a good...
The chest radiograph zones are useful when describing the location of pathology on a frontal chest radiograph.
The chest radiograph is a 2D representation of a 3D structure. Since the interfaces between the lobes are orientated obliquely, it is often not possible to determine which lobe patholo...
Lines and tubes are an important component chest radiographic evaluation.
Nasogastric (NG) tube
See: nasogastric tube positioning.
NG tube tip ≥10 cm distal to the gastro-oesophageal junction
i.e. below the left hemidiaphragm
insertion into trachea or bronc...
This is a basic article for medical students and other non-radiologists
Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Chest radiographs are frequently performed and a fantastic tool for making diagnoses of acute and chronic co...
Computed tomographic (CT) colonography, also called virtual colonoscopy (VC), is a powerful minimally invasive technique for colorectal cancer screening.
screening test for colorectal carcinoma
colon evaluation after incomplete or unsuccessful conventional colonoscopy
Computed tomographic (CT) gastrography, also called virtual gastroscopy (VG), is a non invasive procedure for the detection of gastric abnormalities.
rapid and non invasive exam
offers information about local tumor invasion, lymph node and distant metastasis in cases of gastric can...
Computed tomography (CT) of the chest is a cross sectional evaluation of the heart, airways, lungs and the mediastinum.
Two key methods of image acquisition includes
routine CT with 5 mm slice thickness for mediastinum and gross evaluation of lungs
high resolution CT (HRCT) with thin section...
The nipple areolar complex is a major aantomic landmark of the breast. It may be affected by variation in its embryological development, breast maturation and also by other benign and malignant conditions.
nipple retraction or inverstion
With the advent of echocardiography, and cardiac CT and MRI, the role of chest radiographs in evaluating congenital heart disease has been largely been relegated to one of historical and academic interest, although they continue to crop up in radiology exams. In most instances a definite diagnos...
The coracoclavicular (CC) distance is an indicator of the integrity of the coracoclavicular (CC) ligament.
The CC distance is assessed on a frontal radiography of the shoulder or clavicle or the coronal projection or a CT or MRI as the distance between the superior cortex...
Coxa magna is the asymmetrical, circumferential enlargement and deformation of the femoral head and neck. Definitions in the literature vary but enlargement with asymmetry >10% in size is a reasonable cut-off for diagnosis 1.
Coxa profunda refers to a deep acetabular socket. On pelvis x-rays it is seen as the acetabular fossa being medial to the ilioischial line. It should be differentiated from protrusio acetabuli, where the femoral head is seen additionally medial to the ilioischial line. Coxa profunda is much more...
Due to the overlap in clinical presentation of Crohn disease (CD) and ulcerative colitis (UC), imaging often has a role to play in distinguishing the two. Distinguishing features include:
CD: small bowel 70-80%, only 15-20% have only colonic involvement
UC: rectal involvement 9...
CT cystography is a variation of the traditional fluoroscopic cystogram. Instead of anterograde opacification of the urinary collecting system (as with CT urography), contrast is instilled retrograde into the patient's bladder, and then the pelvis is imaged with CT.
Computed tomographic (CT) enterography is a non-invasive technique for diagnosis of small bowel disorders.
evaluates the entire thickness of the bowel wall
offers information about the surrounding mesentery, the mesenteric vasculature and the perienteric fat
useful in the assessm...
CT head review will likely be performed differently by the majority of radiologists. So, this is just a proposition of one way to read a CT head.
What it does do is make use of windowing to maximise pickup rate. With PACS, windowing appropriately is simple and there is no excuse for not window...
This is a basic article for medical students and other non-radiologists
CT investigations are performed for a variety of reasons. There are a number of ways to read and look at these scans, and these pages should give some help for what to look for.
There is a lot to take in, with scans includ...
The subdural (blood) window can be used when reviewing a CT brain as it makes intracranial haemorrhage more conspicuous, and may help in the detection of thin acute subdural haematomas that are against the calvarium. It is a wider setting than the standard non-contrast window, and there are a nu...
CT perfusion in ischaemic stroke has become established in most centres with stroke services as an important adjunct, along with CT angiography (CTA), to conventional imaging of the brain with a non-contrast CT scan.
Its advantage is that it is able to delineate ischeamic areas of the brain wh...
Cystography is a fluoroscopic study that images the bladder. It is similar to a voiding cystourethrogram (VCUG), and the difference between the studies is primarily one of emphasis; a cystogram focuses on the bladder and a VCUG focuses on the posterior urethra. The study has been adapted to CT w...
Deductive echocardiography is a step-by-step approach in diagnosing and differentiating congenital heart disease.
position of heart
The deepest (maximal) vertical pocket (DVP) depth is considered a reliable method for assessing amniotic fluid volume on ultrasound 1-2. It is performed by assessing a pocket of maximal depth of amniotic fluid which is free of umbilical cord and fetal parts.
The usually accepted values are:
The OMERACT ultrasound group published a consensus in 2005 of widely accepted definitions of abnormal ultrasound findings in rheumatological diseases:
erosion: an intra-articular discontinuity of the bone surface that is visible in two orthogonal planes
joint effusion: abnormal hypoechoic or a...
The Denver criteria are a set of screening criteria for blunt cerebrovascular injury (BCVI) used to reduce the need for CT angiography and its associated radiation exposure.
The screening protocol criteria 1,3 for BCVI are divided into signs and symptoms of BCVI and risk fa...
Describing a fracture is a basic requirement when making an assessment of a plain radiograph. There are many ways to approach the assessment of the radiograph; this is just one approach.
I: Describe the film
What film (or films) are you looking at? Check the who, what, why, when and where.
Atrial situs refers to the relative position of cardiac atria in relation to abdominal viscera and the midline.
Identification of atrial situs is an important initial step in the antenatal and postnatal diagnosis of cardiac structural and situs anomalies.
Differential diagnosis of lytic bone lesions with septations and trabeculations include
unicameral bone cyst
aneurysmal bone cyst
giant cell tumour
Enlargement of sella turcica can be seen in situations including the following.
empty sella syndrome
slight globular enlargement of the sella with no erosion, destruction or posterior displacement of dorsum sellae
enlargement with erosion of anterior cortex of dorsu...
Well defined solitary osteolytic lesions can be seen with following conditions
subchondral geodes or cysts
unicameral bone cyst
aneurysmal bone cyst
epidermoid inclusion cyst
non ossifying fibrom...
Subcutaneous calcification can be associated with a number of disorders. The list includes:
basal cell nevus syndrome
as a manifestation of systemic lupus erythematosus
Diffuse pulmonary nodules are usually seen as multiple pulmonary nodular opacifications on a HRCT chest scan. They can signify disease processes affecting either the interstitium or the airspace. They can range from a few millimetres to up to 1 cm and when very small and numerous there can be so...
The digastric (or biventer) line has been described and used to evaluate basilar invagination on frontal skull plain film and coronal recontructed CT image.
The digastric line is drawn between right and left digastric grooves. The tip of the odontoid process and atlanto-occipital joint normall...
Elbow radiographs are common plain films that are obtained frequently in the emergency department.
anterior humeral line
drawn down the anterior surface of the humerus
should intersect the middle 1/3 of the capitellum
if it doesn't, think distal humeral fracture
Distinguishing between an empyema and a peripherally located pulmonary abscess is essential.
Lung abscesses are usually managed with prolonged antibiotics and physiotherapy with postural drainage whereas an empyema usually requires percutaneous or surgical drainage.
Getting a film with endometrial polyp in the exam is one of the many exam set-pieces that can be prepared for.
Transabdominal and transvaginal pelvic ultrasound images in a lady with post-menopausal bleeding show an anteverted uterus with focal increased endometrial thickness to 1...
Endoscopic ultrasound (EUS) is a procedure combining the range of endoscopy with the diagnostic abilities of ultrasound. The procedure has applications in both the respiratory system as well as the digestive system.
Endoscopic ultrasound can be used fo...
Enlargement of the cardiac silhouette on chest x-ray can be due to a number of causes 1:
cardiomegaly (most common cause by far)
anterior mediastinal mass
prominent epicardial fat pad
Recognising enlargement relies upon an understanding of the nor...
Enteroclysis is a gastrointestinal technique designed to provide improved evaluation of the small bowel. The conventional fluoroscopic technique is not widely used since it is somewhat invasive, time and labour intensive, and often unpleasant for the patient. The exam also requires a degree of s...
Epistaxis (nosebleed) is very common and has a broad differential diagnosis in clinical practice. In clinical practice, anterior epistaxis are mainly located in Kiesselbach's plexus and posterior epistaxis (5% of all epistaxis) in Woodruff's plexus.
Epistaxis is very common, with ...
Errors in diagnostic radiology occur for a variety of reasons related to human error, technical factors and system faults.
This classification was proposed by Renfrew et al5 in 1992, and at the time of writing (July 2016) remains the most widely accepted...
Evacuation proctography (defecography) is a fluoroscopic technique to evaluate pelvic floor disorders. The technique traditionally involves fluoroscopy and barium, but an analogous MRI technique has also been developed (see: MR dynamic pelvis imaging).
incomplete defecation / const...
Recurrent bone tumours are a common complication post currettage or resection.
Radiographs taken pre- and post-operatively are sufficient for evaluation of recurrence based on following features:
matrix mineralization (characteristic of a particular tumor)...
Exam set-pieces refer to those cases that can be considered likely to turn up in the exam setting and can be prepared for. In the oral exam, having a prepared "speech" for these set-pieces allows the candidate to focus less on the stress of describing what is in front of them and more ...
Expiratory HRCT is an useful method for detecting small airway obstructive disease in which the air remain trapped in the small airways even after the expiration and appear as mosaic attenuation.
Ideally, an expiratory HRCT scan should be performed in all obstructive airway diseases...