Articles

Articles are a collaborative effort to provide a single canonical page on all topics relevant to the practice of radiology. As such, articles are written and edited by countless contributing members over a period of time. A global group of dedicated editors oversee accuracy, consulting with expert advisers, and constantly reviewing additions.

523 results found
Article

Amniotic fluid volume

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. Physiology Change in volume through gestation The AFV undergoes characteristic changes with gestation. It progressively ri...
Article

Reticular and linear pulmonary opacification

In chest radiology, reticular and linear opacification refers to a broad subgroup of pulmonary opacification caused by a decrease in the gas to soft tissue ratio due to a pathological process centered in or around the pulmonary interstitium. This includes thickening of any of the interstitial co...
Article

Right paratracheal stripe

The right paratracheal stripe is a normal finding on the frontal chest x-ray and represents the right tracheal wall, adjacent pleural surfaces and any mediastinal fat between them. It is visible because of the silhouette sign created by air within the trachea medially and air within the lung lat...
Article

Breast MRI enhancement curves

Following administration of gadolinium, there can be three possible enhancement (time intensity) 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 or persiste...
Article

Umbilical arterial Doppler assessment

Umbilical arterial (UA) Doppler assessment is used in surveillance of fetal well-being in the third trimester of pregnancy. Abnormal umbilical artery Doppler is a marker of placental insufficiency and consequent intrauterine growth restriction (IUGR) or suspected pre-eclampsia.  Umbilical arter...
Article

Umbilical venous flow assessment

Umbilical venous flow in the physiological situation comprises of a monophasic non-pulsatile flow pattern in the umbilical vein with a mean velocity of 10-15 cm/s. Since a normal umbilical vein supplies a continuous forward flow of oxygenated blood to the fetal heart, the presence of pulsatility...
Article

Abnormal ductus venosus waveforms

Abnormal ductus venosus waveforms can arise in a number of conditions ranging from aneuploidy to vascular malformations and fetal tumors. "A wave" reversal can be seen in 5% of euploid fetuses 9. Pathology Abnormal waveforms in fetal ductus venosus flow assessment can occur in a number of situ...
Article

Fetal middle cerebral arterial Doppler assessment

Fetal middle cerebral arterial (MCA) Doppler assessment is an important part of assessing fetal cardiovascular distress, fetal anemia or fetal hypoxia. In the appropriate situation it is a very useful adjunct to umbilical artery Doppler assessment. It is also used in the additional work up of: ...
Article

Ravitch procedure

The Ravitch procedure is one of the corrective surgical treatments for pectus excavatum and pectus carinatum. The costal cartilage is removed and the sternum detached before inserting a small bar underneath the sternum to hold it in the desired position. The bar is left implanted until the carti...
Article

Reversal of umbilical arterial end diastolic flow

Reversal of umbilical artery end-diastolic flow (REDF) or velocity is often an ominous finding if detected after 16 weeks. It is classified as Class III in severity in abnormal umbilical arterial Dopplers 6. Epidemiology The estimated incidence is at ~0.5% of all pregnancies with a much higher...
Article

Apical zone

The apical zone (a.k.a. lung apex) 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 "review areas". It is sometimes thought of as a subdivision of the upper zone.  Radiographic features Pl...
Article

Chest radiograph zones

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 oriented obliquely, it is often not possible to determine which lobe pathology...
Article

Mesenteric lymph nodes

In the premultidetector CT era, mesenteric lymph nodes (often shortened to mesenteric nodes) were only really appreciated when enlarged. Following the advent of routine volume acquisition CT (and especially coronal reformats) lymph nodes in the mesentery are commonly seen in normal individuals, ...
Article

Amniotic fluid index

The amniotic fluid index (AFI) is an estimate of the amniotic fluid volume in a pregnant uterus. It is part of the fetal biophysical profile.  Technique the uterus is divided into four imaginary quadrants with the linea nigra and a mediolateral line running through the umbilicus acting as the ...
Article

Fleischner Society pulmonary nodule recommendations

The Fleischner Society pulmonary nodule recommendations pertain to the follow-up and management of indeterminate pulmonary nodules detected incidentally on CT and are published by the Fleischner Society. The guideline does not apply to lung cancer screening, patients younger than 35 years, or pa...
Article

Antenatal features of Down syndrome

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...
Article

Viva technique

Viva technique is hugely important when sitting oral examinations. You must remember that the examiners may well have been examining for several days and for hours at a time. They will have shown their films many times and will know them backwards! Moreover, their films will be beloved, so do no...
Article

Exam set-pieces

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 on conside...
Article

Antenatal screening

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...
Article

Gunshot injuries

Gunshot injuries often require imaging assessment, and this evaluation has both clinical relevance (assessment of organ damage, surgical planning, and prognostication), and often also forensic implications. Epidemiology Incidence of gunshot injuries to the head is increasing in some countries,...
Article

Left atrial enlargement

Left atrial enlargement (LAE) may result from many conditions, either congenital or acquired. It has some characteristic findings on a frontal chest radiograph. CT or MRI may also be used for diagnosis. Clinical presentation An enlarged left atrium can have many clinical implications, such as:...
Article

Breast density

Breast density refers to the amount of fibroglandular tissue in a breast relative to fat. It can significantly vary between individuals and within individuals over a lifetime. Classification There are four descriptors for breast density on mammography in the 5th edition of BI-RADS 1,2: a: the...
Article

Revised PIOPED criteria for diagnosis of pulmonary embolus

The revised PIOPED criteria for the diagnosis of pulmonary embolus indicate the probability of pulmonary emboli based on findings on V/Q scan (ventilation-perfusion scintigraphy). The following article reflects the revised interpretation criteria promulgated in 1993 1 based on retrospective anal...
Article

Breast MRI

Breast MRI is the most sensitive method (>90%) for the detection of breast cancer, its role in diagnosis and management continues to evolve 13. Terminology Dynamic contrast-enhanced (DCE)-MRI provides information about the morphology and function of a lesion with high sensitivity but moderate ...
Article

Hysterosalpingogram

Hysterosalpingogram (HSG) is a fluoroscopic examination of the uterus and the Fallopian tubes, most commonly used in the investigation of infertility or recurrent spontaneous abortions. Indications Infertility to assess uterine morphology and tubal patency. Contraindications pregnancy activ...
Article

Polydactyly

Polydactyly (less commonly called hyperdactyly) refers to the situation where there are more than the usual number of digits (five) in a hand or foot. It can be broadly classified as: preaxial polydactyly: extra digit(s) towards the thumb/hallux (radially) postaxial polydactyly: extra digit(s)...
Article

Joint effusion

A joint effusion is defined as an increased amount of fluid within the synovial compartment of a joint. There is normally only a small amount of physiological intra-articular fluid. Abnormal fluid accumulation can result from inflammation, infection (i.e. pus) or trauma and might be exudate, tr...
Article

Pulmonary nodule

Pulmonary nodules are small, rounded opacities within the pulmonary interstitium. Pulmonary nodules are common and, as the spatial resolution of CT scanners has increased, detection of smaller and smaller nodules has occurred, which are more often an incidental finding. Classification Pulmonar...
Article

Reactive vs malignant lymph nodes (ultrasound features)

A number of sonographic features are helpful in distinguishing reactive versus malignant lymph nodes. Grey scale features Features that favor reactive/infective nodes over malignancy include: nodal matting surrounding soft tissue edema Doppler features Doppler examination is particularly u...
Article

Ultrasound assessment of carotid arterial atherosclerotic disease

Ultrasound assessment of carotid arterial atherosclerotic disease has become the first choice for carotid artery stenosis screening, permitting the evaluation of both the macroscopic appearance of plaques as well as flow characteristics in the carotid artery. This article focus on internal caro...
Article

Causes of perfusion defects on a VQ scan

There are several causes leading to a perfusion defect on a VQ scan with an acute pulmonary embolus being only one of them: Vascular causes acute pulmonary embolus previous pulmonary embolus (including fat embolism, thromboembolism, air embolism, tumor) vasculitides affecting the pulmonary v...
Article

Increased retrosternal airspace

Increased retrosternal airspace is an indicator of hyperinflation of the lungs and is usually due to emphysema. The thickness of the space between the ascending aorta and the posterior margin of the sternum (3 cm inferior to the sternomanubrial joint) and is normally no more than 2.5 cm 1 altho...
Article

Flattening of the diaphragm

Flattening of the diaphragm is the most sensitive sign on chest radiographs for the presence of hyperinflation of the lungs, usually due to emphysema 1,2. On a lateral chest radiograph, the normal dome of each hemidiaphragm should rise at least 1.5 cm above a line connecting the costophrenic an...
Article

Ultrasound evaluation of breast cysts

Ultrasound evaluation of breast cysts is the modality of choice. Obstruction of the ducts, often appearing as the result of epithelial hyperplastic processes or stromal fibrosis, or both processes lead to the formation of cysts, disabling the drainage of the terminal ducts of the lobules. In al...
Article

CT head (an approach)

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, although order may vary. What follows is merely a suggested approach to interpreting a CT of the hea...
Article

Standardized reports

Standardized reports may be a helpful starting point for reporting examinations. However, with practice and confidence, breaking away from the standard report is possible and, in many cases, desirable. On the other hand in some instances standardized reports facilitate the creation of automated ...
Article

Reporting tips for aortic aneurysms

When issuing an MRI or CT report on a patient with an aortic aneurysm, whether it be thoracic or abdominal, a number of features should be mentioned to aid the referring clinician in managing the patient. Reporting tips for aortic aneurysms include 1,2: size and shape sac dimensions (outer su...
Article

Empyema vs pulmonary abscess

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. Radiographic features Plai...
Article

Congenital heart disease chest x-ray (an approach)

With the advent of echocardiography, and cardiac CT and MRI, the role of chest x-rays in evaluating congenital heart disease has been largely relegated to one of historical and academic interest. However, they continue to crop up in radiology exams. In most instances a definite diagnosis cannot ...
Article

Caudate–right lobe ratio

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 line 1...
Article

Tentorial angle

The tentorial angle is measured between a line connecting the nasion with the tuberculum sellae and the angle of the straight sinus. Normally it should measure between 27° and 52°. Abnormalities of the posterior fossa or base of skull can alter this. For example, this angle is elevated in achon...
Article

Chest radiograph assessment using ABCDEFGHI

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...
Article

Crohn disease vs ulcerative colitis

Due to the overlap in the clinical presentation of Crohn disease (CD) and ulcerative colitis (UC), imaging often has a role to play in distinguishing the two. Distinguishing features include: bowel involved CD: small bowel 70-80%, only 15-20% have only colonic involvement UC: rectal involveme...
Article

Hemorrhage on MRI

Hemorrhage on MRI has highly variable imaging characteristics that depend on: the age of the blood the type of hemoglobin present: oxy-, deoxy- or met- whether or not the red blood cell walls are intact: i.e. intra- vs extracellular the MRI sequence Although MRI is often regarded as being i...
Article

Enchondroma vs low grade chondrosarcoma

Distinguishing between enchondromas and low-grade conventional chondrosarcomas is a frequent difficulty as the lesions are both histologically and radiographically very similar. It is important to remember, though, that differentiating between them may be a moot point since both can either be c...
Article

Sonographic features of malignant lymph nodes

Lymphadenopathy is quite common, and it can be very difficult to differentiate malignant lymphadenopathy from reactive nodal enlargement. Several gray scale and color Doppler features favor malignancy in a lymph node. Gray scale parameters that favor malignancy size: larger - more likely mali...
Article

Intervertebral disc disease nomenclature

Intervertebral disc disease nomenclature has changed over the years, and a familiarity with current definitions is essential if clear communication is to be achieved via radiology reports or referrals, especially as lumbar disc disease is a common problem and a source of a great deal of imaging....
Article

Unilateral hypertranslucent hemithorax

Unilateral hypertranslucent hemithorax has many potential causes. It may be the result of rotation away from an optimal position or because of pathology. Rotation A unilateral hypertranslucent hemithorax may be caused by the positioning of the patient. Rotation away from the radiation beam alt...
Article

Solitary pulmonary nodules

Solitary pulmonary nodule (SPN) is defined as a relatively well defined round or oval pulmonary parenchymal lesion equal to or smaller than 30 mm in diameter. It is surrounded by pulmonary parenchyma and/or visceral pleura and is not associated with lymphadenopathy, atelectasis, or pneumonia 9. ...
Article

Pneumothorax

Pneumothorax, sometimes abbreviated to PTX, (plural: pneumothoraces) refers to the presence of gas (often air) in the pleural space. When this collection of gas is constantly enlarging with resulting compression of mediastinal structures, it can be life-threatening and is known as a tension pneu...
Article

Renal artery stenosis

Renal artery stenosis (RAS) (plural: stenoses) refers to a narrowing of a renal artery. When the process occurs slowly, it leads to secondary hypertension. Acute renal artery stenosis does not lead to hypersecretion of renin. Pathology When the stenosis occurs slowly, collateral vessels form a...
Article

Uteroplacental blood flow assessment

Uteroplacental blood flow assessment is an important part of fetal well-being assessment and evaluates Doppler flow in the uterine arteries and rarely the ovarian arteries. Pathology In a non-gravid state and at the very start of pregnancy the flow in the uterine artery is of high pulsatility ...
Article

Ultrasound of the shoulder

Ultrasound of the shoulder is a fast, relatively cheap, and dynamic way to examine the rotator cuff and is particularly useful in diagnosing: shoulder impingement shoulder instability rotator cuff disorders The examination requires attention to technique and appropriate patient positioning. ...
Article

Subfalcine herniation

Subfalcine herniation, also known as midline shift or cingulate hernia, is the most common cerebral herniation pattern. It is generally caused by unilateral frontal, parietal or temporal lobe disease that creates a mass effect with medial direction of the ipsilateral cingulate gyrus beneath the ...
Article

Situs inversus

Situs inversus, (rare plural: sitūs inversi) short form of the Latin “situs inversus viscerum”, is a term used to describe the inverted position of chest and abdominal organs. Terminology The condition is called situs inversus totalis when there is a total transposition of abdominal and thorac...
Article

Mammography

Mammography is a dedicated radiographic technique for imaging the breast, and the resultant images are known as mammograms. Types of mammography In general terms, there are two types of mammography: screening and diagnostic. Mammography differs significantly in many respects from the rest of ...
Article

Ground-glass opacification

Ground-glass opacification/opacity (GGO) is a descriptive term referring to an area of increased attenuation in the lung on computed tomography (CT) with preserved bronchial and vascular markings. It is a non-specific sign with a wide etiology including infection, chronic interstitial disease an...
Article

Böhler angle

The Böhler angle, also written as Bohler angle or Boehler angle, is also called the calcaneal angle or tuber joint angle. It is used in the assessment of intra-articular calcaneal fractures. Measurement The Böhler angle is the angle on a lateral foot radiograph between a line joining the highe...

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.