Articles

Hounsfield units (HU) are a dimensionless unit universally used in computed tomography (CT) scanning to express CT numbers in a standardized and convenient form. Hounsfield units are obtained from a linear transformation of the measured attenuation coefficients 1. This transformation (figure 1) ...

Flocculation refers to the breakdown of a barium suspension during a fluoroscopic study. The small bowel environment eventually separates out a barium suspension, and this can occur during the normal course of a barium study (15 minutes to three hours) or as a feature of certain pathological en...

Esophageal-pleural stripe is a soft tissue interface formed between the right wall of the esophagus and the medial wall of the right pleura, projecting from the level of clavicles downwards until the gastro-esophageal junction 1. Although the esophageal-pleural stripe can be used in most patien...

Probability is the likelihood of a random outcome (called an “event”) and is written as P(event)= x, where x is a number ≥0 and ≤1. Using this notation, the probability of rolling a 2 with a fair 6-sided die is written as P(2)=1/6. A probability of 0 means that an event is impossible while a pro...

Buckle rib fractures are incomplete fractures involving only the inner cortex. They typically occur due to an anterior compressive force to the chest, most commonly during external cardiac massage, but can be seen following any such traumatic injury. Pathology Buckle rib fractures occur in all...

The thyroid gland is a single midline endocrine organ in the anterior neck responsible for thyroid hormone production which lies in the visceral space completely enveloped by pretracheal fascia (middle layer of the deep cervical fascia). Gross anatomy The thyroid extends from C5 to T1 and lies...

Unclassified cerebellar dysplasia is defined as focal or diffuse dysplasia of cerebellar hemispheres or vermis not associated with other known malformations or syndromes. Clinical presentation Can present with hypotonia, microcephaly or speech delay. Radiographic features MRI asymmetry or f...

This article contains a list of commonly used medical abbreviations and acronyms that start with the letter L and may be encountered in medicine and radiology (please keep the main list and any sublists in alphabetic order). A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - Q - R ...

External auditory canal exostoses, also known as surfer's ear, are benign bony overgrowths of the bony external auditory canal brought about by exposure to cold wind and water combined. Epidemiology The estimated prevalence in cold-water surfers is thought to range between 70-80% 5,6,8. Clini...

This is a basic article for medical students and other non-radiologists 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 pa...

Heel fat pad syndrome, also known as plantar fat pad syndrome or heel fat pad atrophy is a common but not well-known cause of heel pain in the adult population. Epidemiology Heel fat pad syndrome is common. It is the second most common cause of plantar heel pain after plantar fasciitis. It is ...

Portal venous flow is normally towards the liver (hepatopetal), with the normal main portal vein peak systolic velocities usually measuring 20-40 cm/s. In pathological situations, the flow velocity may decrease or even invert resulting in hepatofugal flow. The flow waveform is usually smooth b...

The basilar transverse fissure, also known as Saucer's fissure, is a potential channel through the clivus in the basilar part of the occipital bone. It is considered a normal anatomical variant and should not be confused with clival clefts that can be seen with certain syndromes such CHARGE synd...

Splenic epithelial cysts, also known as splenic epidermoid cysts or primary splenic cysts, are unilocular fluid lesions with thin and smooth walls and no enhancement. They represent ~20% of cysts found in the spleen, and are usually an innocuous incidental imaging finding. Note that most (~80%)...

Splenic pseudocysts, also known as secondary splenic cysts, are acquired cystic lesions not delineated by a true epithelial wall. They represent the majority of the splenic cystic lesions, corresponding to approximately 80% of them (cf. splenic epithelial cysts). The main causes are:  splenic t...

Doppler shift or Doppler effect is defined as the change in frequency of sound wave due to a reflector moving towards or away from an object, which in the case of ultrasound is the transducer. Terminology When sound of a given frequency is discharged and subsequently reflected from a source th...

Modified Choi classification of common bile duct duplication is a widely used system for classifying the rare duplication of the extrahepatic biliary tree. 1-3: type I: distal septum splitting the bile duct lumen type II: bifurcation of the distal bile duct with each lumen draining independent...

Dual-energy CT has a number of clinical applications in the assessment of the musculoskeletal system particularly in the realm of artefact reduction and material composition. Detection of bone marrow edema Similar to the concept of using virtual non-contrast imaging, virtual non-calcium images...

The amplitude and intensity of ultrasound waves decrease as they travel through tissue, a phenomenon known as attenuation. Given a fixed propagation distance, attenuation affects high frequency ultrasound waves to a greater degree than lower frequency waves. This dictates the use of lower freque...

Refraction of a sound wave occurs if it travels between tissues with different propagation speeds. As the incident pulse or returning echo strikes an interface of different density or elasticity and therefore a different propagation speed, the direction of the wave changes according to Snell’s l...