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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 continuously improved upon by countless contributing members. Our dedicated editors oversee each edit for accuracy and style. Find out more about articles.

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Liver lesions (pediatric)

Pediatric liver lesions are a heterogeneous group that includes infiltrative lesions and those that demonstrate mass-effect. Moreover, they may be solitary or multiple, benign or malignant: benign liver tumors malignant liver tumors Epidemiology There are differing frequencies of both benign...

Tibial tuberosity to posterior cruciate ligament distance (TT-PCL distance)

The tibial tuberosity to posterior cruciate ligament (TT-PCL) distance is an alternative measure to the TT-TG distance for determining tibial tuberosity lateralization, which has a role in patellofemoral instability, without the effect of femoral rotation 1. Usage TT-PCL and TT-TG have simila...

Aortofemoral bypass

Aortofemoral bypass surgery is a type of vascular surgery that is performed to treat aortoiliac occlusive diseases, commonly known as Leriche syndrome, by inserting an artificial tube (graft) from the end of the body's main artery (aorta) to the artery that supply blood to the legs (femoral arte...

Viva preparation

Viva preparation is key to successful completion of professional exams. It is really important to think about the types of cases that you will be shown in the viva and prepare orally for them. So, rather than learning sitting with your books, get a set of films or use the Radiopaedia quiz mode ...

Localization of parotid lesions

Localization of parotid lesions to the superficial and/or deep parotid gland is an essential aspect of imaging and vital information which needs to be conveyed to the surgeon. Measurement The following lines are proposed for differentiating superficial from deep lobe: Conn's arc (CA): drawn w...

Sonographic features of malignant lymph nodes

Lymphadenopathy is quite common, and it can be challenging to differentiate malignant lymphadenopathy from reactive nodal enlargement. Several gray scale and color Doppler features favor malignancy in a lymph node 1,7-9. Gray scale parameters that favor malignancy size: larger - more likely m...

Atlantodental interval

The atlantodental interval is used in the diagnosis of atlanto-occipital dissociation injuries and injuries of the atlas and axis. Measurement The anterior atlantodental interval is the horizontal distance between the posterior cortex of the anterior arch of the atlas (C1) and the anterior cor...

Bronchogenic cyst vs esophageal duplication cyst

Bronchogenic cysts and esophageal duplication cysts are embryological foregut duplication cysts and are also differential diagnoses for a cystic mediastinal mass. Differences Symptoms bronchogenic cysts asymptomatic unless infected esophageal duplication cysts can present with hemorrhage or ...

Assessment of thyroid lesions (ultrasound)

Ultrasound is the first-line imaging modality for assessment of thyroid nodules found on clinical examination or incidentally on another imaging modality. This article is an overview of ultrasonographic features of thyroid nodules, which are used to determine the need for biopsy with fine needle...

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...

Prosthetic cardiac valves on chest x-ray (an approach)

Prosthetic cardiac valves are a routine finding on chest X-ray. The frequency and degree of exposure is greatest in larger hospitals with cardiothoracic centers; however, prosthetic valves are commonplace universally. Recognition of which valve has been replaced, any other related cardiothoraci...

Extrusion index

The extrusion index, also known as the (Reimers) hip migration index, is a radiographic measurement of femoral head bony coverage by the acetabulum. It is useful in assessing for developmental dysplasia of the hip, femoroacetabular impingement, and assessment of hip subluxation in cerebral palsy...

CT colonography (protocol)

Computed tomographic (CT) colonography, also called CTC, virtual colonoscopy (VC) or CT pneumocolon, is a powerful minimally invasive technique for colorectal cancer screening. Indications screening test for colorectal carcinoma colon evaluation after incomplete or unsuccessful optical (conv...

Fetal urinary bladder

The fetal urinary bladder, also known as the bladder bubble, is visible as an anechoic cyst on ultrasound in most fetuses from 12-13 weeks of gestation 1. The size of the bladder is denoted by measuring the longitudinal bladder diameter from superiorly to inferiorly in the sagittal plane. Age-r...

Testicular and scrotal ultrasound

Testicular and scrotal ultrasound is the primary modality for imaging most of the male reproductive system. It is relatively quick, relatively inexpensive, can be correlated quickly with the patient's signs and symptoms, and, most importantly, does not employ ionizing radiation. MRI is occasion...

Medial clear space (ankle)

The medial clear space is a radiographic measurement that may be useful in the diagnosis of ankle instability, syndesmotic injuries and ankle fractures 5. Usage The medial clear space is used in the prediction of deltoid ligament injury 1 and in conjunction with the tibiofibular clear space th...

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...

On-track and off-track shoulder lesions

Bipolar shoulder lesions of anterior glenohumeral dislocations (i.e. combined bony Bankart lesions and Hill-Sachs defects) put patients at increased risk of Hill-Sachs engagement or recurrent instability. Determining if the Hill-Sachs defects are on-track or off-track can help guide management, ...

Satisfaction of search error

Satisfaction of search (SOS) error is a common error in diagnostic radiology. It occurs when the reporting radiologist fails to continue to search for subsequent abnormalities after identifying an initial one. This initial detection of an abnormality satisfies the "search for meaning" and the re...

CT peritoneography

CT peritoneography is an examination used to assess difficulties with peritoneal dialysis. Indications Recurrent peritonitis with difficulty with fluid exchange, abdominal wall or genital soft tissue edema, localized bulging of the abdomen, and poor ultrafiltration. Technique Before perform...

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