Items tagged “snippet”

A dichorionic twin pregnancy is a type of twin pregnancy characterized by two chorions. They are always dichorionic-diamniotic but can be either monozygotic (~11%) or dizygotic (~88%) ref.

The default mode network (DMN), is a group of specific brain regions that are functionally-connected. The regions become active in the resting state (not doing any active task), and inactive when someone is engaged in any attention-demanding tasks 1; this phenomenon has been termed task-induced ...

The lateral marginal vein (also known as the vein of Servelle or the Klippel-Trenaunay vein) is one of two known persisting embryonic veins of the leg, the persistent sciatic vein being the other.  Development As an embryonic vein it usually undergoes regression before birth. It is part of the...

The talonavicular coverage angle reflects the degree of, if any, talonavicular lateral subluxation. On DP weight-bearing foot radiographs, it is the angle between: articular surface of the talar head articular surface of the proximal navicular Interpreting the talonavicular coverage angle: n...

Turret exostoses are a benign osteocartilagenous lesion. Pathology It is believed to arise from reactive periosteum following relatively mild trauma. It is usually seen a smooth dome-shaped parosteal bone proliferation.  Location  Often seen in the phalanges but can also present in rare site...

The salted pretzel sign is an uncommon sign of the presence of numerous small (<3 mm) calcific foci in the distal branches of a cerebral artery on non-contrast CT head that represent a shower of calcified cerebral emboli 1. Cerebral calcified emboli may be the initial manifestation of significan...

An early structural scan is a first-trimester obstetric scan performed around 12-16 weeks gestation. It can have some similarity to the 11-13 week antenatal scan and assess limited fetal anatomy. A formal assessment of nuchal translucency is, however, not part of this scan.

Bridging of the sella turcica is the fusion of the anterior and posterior clinoid processes. Epidemiology The prevalence of a sella turcica bridge in a healthy population is estimated to be ~4% (range 1.75-6 %) in anatomical and radiographic studies. Pathology It has been reported to occur i...

The tadpole sign, also known as the lollipop sign, refers to a characteristic morphology of post-traumatic bridging vein thrombosis with a rounded "head" and a tapering "tail". The finding demonstrates a high specificity for abusive head trauma, a sub-type of non-accidental injury, and should wa...

The modified Lodwick-Madewell classification is a system for describing the radiographic appearance of a lytic bone lesion. It was proposed in 2016 as a successor to the Lodwick classification and better reflects the risk of malignancy with increasing grade 1. Classification 1A: well-defined,...

Fluoroscopy is an imaging modality that allows real-time x-ray viewing of a patient with high temporal resolution. It is based on an x-ray image intensifier coupled to a still/video camera. In recent years flat panel detectors (which are similar to the digital radiography used in projection radi...

Fluoroscopy and fluorography are very similar imaging techniques and, in many instances, can be performed on the same equipment. Fluoroscopy vs fluorography Fluoroscopy low current (0.5-5 mA), continuous or near-continuous x-ray exposures relatively low signal to noise ratio (SNR) prioritis...

The marching cleft sign is a finding on sagittal MR images, which is useful in characterizing the configuration of meniscal tears. It is present when a meniscal tear is oriented obliquely in relation to both coronal and sagittal plane, which results in the tear cleft moving towards or away from ...

Vertebral artery hypoplasia is a congenital anatomical variation characterized by underdevelopment of the vertebral artery. Epidemiology The prevalence of hypoplastic vertebral arteries is reported to be 2-6% from autopsy and angiograms 1. Clinical presentation These are an asymptomatic anat...

CT liver volumetry is an essential imaging study in preoperative assessment for living donor liver transplantation. NB: This article is intended to outline some general principles of protocol design. The specifics will vary depending on CT hardware and software, radiologists' and referrers' pre...

A non-mass finding on breast ultrasound refers to a discrete region of altered breast parenchymal echotexture that does make a mass shape (i.e. non-identifiable in two planes). "Non-mass finding" is not a current BI-RADS descriptor.  Terminology Non-mass findings are described in numerous ways...

Hildreth sign describes pain relief with application of a proximal tourniquet in patients with a glomus tumor 1. The rationale is that ischemia will decrease the size of the tumor, as these tumors are highly vascular. The sign is reportedly very sensitive and specific for glomus tumor, with a se...

The footprint of the rotator cuff is referred to as the insertional anatomy of the rotator cuff. It is an integral part of the stability of the glenohumeral joint. Gross anatomy The rotator cuff footprint involves the convergence of the four rotator cuff muscle tendons, which form a multi-laye...

Rotating envelope x-ray tubes (RET), are a relatively novel type of high-performance x-ray tube developed in the early 2000s. Their two main features are the direct contact of the anode plate with the cooling oil, and rotation of the entire envelope around the axis of the anode.  In rotating en...

The meningo-ophthalmic artery is a variant arterial anatomy in which the entire supply to the ophthalmic artery derives from the middle meningeal artery. This variation represents one extreme of a spectrum of the persistence of the embryologic stapedial artery. Gross anatomy The meningo-ophtha...