11-13 week antenatal scan is considered a routine investigation advised for the fetal well being as well as for early screening in pregnancy (see antenatal screening).
It includes multiple components and is highly dependant on the operator. Traditionally three factors are used to calculate the ...
Three-dimensional (3D) ultrasound is a technique that converts standard 2D grayscale ultrasound images into a volumetric dataset. The 3D image can then be reviewed retrospectively. The technique was developed for problem-solving (particularly in obstetric/gynecologic exams) and to potentially re...
ABC/2 is a fast and simple method for estimating the volume of intracerebral haemorrhage (or any other ellipsoid lesion for that matter) which does not require volumetric 3D analysis or software. Intracerebral haemorrhage volume is an important predictor of morbidity and mortality (and thus tria...
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 b...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review:
A: air - where it should and shouldn't be
B: bowel - position, size and wall thickness
D: dense st...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where A refers to the assessment of the presence and location of air.
This is a s...
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...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where X refers to the assessment of external objects and artifacts.
This is a sum...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where B refers to the assessment of the bowel loops.
This is a summary article; w...
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where D refers to the assessment of dense structures such as the bones and areas of calcification.
Abdominal x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using ABDO X is a helpful and systematic method for abdominal x-ray review, where O refers to the assessment of the intra-abdominal organs and soft tissues.
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...
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...
Achondrogenesis type Ib, also known as Parenti-Fraccaro subtype, is a subtype of achondrogenesis and is an extremely rare skeletal dysplasia (chondrodysplasia).
Undersulphation has a pronounced effect on the composition of the extracellular matrix of cartilage, and this has been sh...
Acromiohumeral interval is a useful and reliable measurement on AP shoulder radiographs and when narrowed is indicative of rotator cuff tear or tendinopathy.
Measurements of the acromiohumeral interval in the following intervals are suggestive of pathology 1-2:
>12 mm: shoulder dis...
ACR TI-RADS is a reporting system for thyroid nodules on ultrasound proposed by the American College of Radiology (ACR) 1.
This uses a standardised scoring system for reports providing users with recommendations for when to use fine needle aspiration (FNA) or ultrasound follow-up of suspicious ...
Acute pelvic pain is a common presenting symptom to the emergency department and radiologist. Pelvic ultrasound with transabdominal and endovaginal approaches is usually the first line imaging modality.
pain of <3 months duration
Patients also often pres...
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 favourites 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 can be 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 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 at least 25 m...
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 Down...
Antenatal screening and diagnosis are currently available for a few selected genetic conditions, including trisomy 21 (Down syndrome), trisomy 18 (Edward syndrome), trisomy 13 (Patau syndrome) and neural tube defects.
For an overview of the conditions and their manifestations, please refer to t...
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 the posterior third.
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 as the left superior intercostal vein serves as a collateral path...
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.
Artifacts that mimic breast calcification can arise from a number of sources. These include:
deodorants on skin: most practices recommend that clients for mammography do not use deodorant or perfume on the day of the study for this reason. The residue from deodorant is a very fine, dense, misty...
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...
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 reconstructed CT image.
The bimastoid line is drawn between the inferior tips of the of mastoid processes bilaterally. The tip of the odontoid process of C2 normally projects ...
Blumensaat line is the line drawn along the roof of the 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 a...
Böhler angle, also written as Bohler angle or Boehler angle, is also called the calcaneal angle or tuber joint angle 1, and 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 calca...
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:
Breast MRI is the most sensitive method for detection of breast cancer. Depending on international health regulations, it is either applied for screening of women at high risk for developing breast cancer (e.g. BRCA-1 and BRCA-2 carriers), as an additional diagnostic test in pretherapeutic breas...
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 2015 for the management of pulmonary nodules seen on CT. In the United Kingdom, they supersede the Fleischner Society guidelines.
They are based initially on identifying whether the nodule is solid or sub-solid a...
The Brock model, also known as the PanCan model, is a multivariable model that estimates the risk that a pulmonary nodule on CT scan is a lung cancer.
The model was developed from participants enrolled in the Pan-Canadian Early Detection of Lung Cancer Study 1, has been validated in lung cancer...
Bronchogenic cysts and oesophageal duplication cysts are embryological foregut duplication cysts and are also differential diagnoses for a cystic mediastinal mass.
asymptomatic bronchogenic cyst
symptomatic oesophageal cyst in the case of peptic ulceration
Canadian C-spine rules are a set of guidelines that help a clinician decide if cervical spine imaging is not appropriate for a trauma patient in the emergency department. The patient must be alert and stable.
There are three rules:
is there any high-risk factor present that requires cervical s...
The Canadian CT head rule (CCTHR) is a validated clinical decision rule to determine the need for CT head in adult emergency department patients with minor head injuries.
Patient has suffered minor head trauma with resultant:
loss of consciousness
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, physiology and pathology.
The main advantages of cardiac MRI in comparison with other techniques are:
better definition of soft tissues
use of different types of sequences improves diagnostic accuracy
no 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...
Catheter-directed thrombolysis is an endovascular approach to the treatment of acute iliofemoral deep vein thrombosis. It involves the administration of a lytic agent directly into a thrombus.
precise diagnosis of iliofemoral deep vein thrombosis
first episode of acute iliofemor...
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 obstetric ultrasound tool used as a predictor of adverse pregnancy outcome in both small for gestational age (SGA) and appropriate for gestational age (AGA) fetuses. An abnormal CPR reflects redistribution of cardiac output to the cerebral circulation, and has ...
ABCDEFGHI can be used to guide a systematic interpretation of chest x-rays.
Assessment of quality / Airway
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 wi...
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...
Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using A, B, C, D, E is a helpful and systematic method for chest x-ray review:
B: breathing (the lungs and pleural spaces)
C: circulation (cardiomediastinal contour)
Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using A, B, C, D, E is a helpful and systematic method for chest x-ray review where A refers to the assessment of the airways.
This is a summary article; we do n...
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 conditions, as well as acting as a tool for follow-up.
Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using A, B, C, D, E is a helpful and systematic method for chest x-ray review where C refers to circulation and assessment of the heart and cardiomediastinal contour.
Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using A, B, C, D, E is a helpful and systematic method for chest x-ray review where D refers to disability and specifically fractures and dislocations.
This is a...
Chest x-ray ET (endotracheal tube) position should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we do not have a more in-depth reference article.
tip 5 cm above carina
width 2/3 tracheal diameter
Chest x-ray review is a key competency for medical students, junior doctors and other allied health professionals. Using A, B, C, D, E is a helpful and systematic method for chest x-ray review where E refers to "everything else".
This is a summary article; we do not have a mo...
Chest x-ray lines and tubes can be easily assessed and should be the first thing that you look at when reviewing a chest x-ray. Assessment of their position is important, but they also give you an idea about how sick the patient is and narrow down the differential diagnosis.
Chest x-ray PICC (peripherally inserted central catheter) position should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we do not have a more in-depth reference article.
usually inserted via the antecubi...
Computed tomographic (CT) colonography, also called CTC, virtual colonoscopy (VC) or CT pneumocolon, is a powerful minimally invasive technique for colorectal cancer screening.
screening test for colorectal carcinoma
colon evaluation after incomplete or unsuccessful conventional c...
Computed tomographic (CT) gastrography, also called virtual gastroscopy (VG), is a noninvasive procedure for the detection of gastric abnormalities.
rapid and noninvasive exam
offers information about local tumor invasion, lymph node and distant metastasis in cases of gastric cance...
Computed tomography (CT) of the chest is a cross-sectional evaluation of the heart, airways, lungs, mediastinum, and associated bones and soft tissues.
Two key methods of image acquisition include:
standard CT with 5 mm slice thickness for mediastinum and gross evaluation of lungs
Computed tomography texture analysis (or CTTA) is a new useful biomarker that provides an objective and quantitative assessment of tumour heterogeneity by analysing the differences in the pixel values of an image.
Gray-level frequency distribution: pixel intensity histogra...
Concurrent suprasellar and pineal region lesions have a relatively short differential to be considered, including:
other germ cell tumours
embryonal cell carcinoma
yolk sac tumour (endodermal sinus tumour)
primary CNS lymphoma
The nipple areolar complex is a major anatomic 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 inversion
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...
Coronary Artery Disease - Reporting and Data System (CAD-RADSTM) classification is proposed by the Society for Cardiovascular Computed Tomography (SCCT), the American College of Radiology (ACR), and the North American Society for Cardiovascular Imaging (NASCI), last updated in 2016.
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 angiography of the cerebral arteries is a noninvasive technique allows visualization of the internal and external carotid arteries and vertebral arteries and can include just the intracranial compartment or also extend down to the arch of the aorta.
By using multidetector CT after intravenou...
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...
The approach taken to interpreting a CT scan of the head is no doubt different depending on the circumstances and the reading clinician, however, most radiologists will go through the same steps. What follows is merely a suggested approach to interpreting a CT of the head.
An important aspect ...
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 unenhanced CT brain imaging.
It enables differentiation of salvageable ischaemic brain tissue (the penumbra) from irrevocably d...
Below is an approach used for the "primary survey" of a CT polytrauma/multitrauma (also called trauma CT), often performed at the CT console with the patient still on the CT table. It allows rapid communication of significant findings to the trauma team as well as the decision to perform additi...
Chest x-ray CVC (central venous catheter) position should be assessed following initial placement and on subsequent radiographs.
This is a summary article; we do not have a more in-depth reference article.
may be inserted via
internal jugular vein (left ...
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