Iraqi Board Radiology flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Hounsfield unit formula

HU = 1000 × (μ_tissue − μ_water) / μ_water. Water is 0 HU, air is approximately −1000 HU, and dense bone ranges from +1000 to +3000 HU.

ALARA principle

As Low As Reasonably Achievable: minimize radiation dose by reducing exposure time, increasing distance, and using shielding, while maintaining diagnostic image quality.

CT dose index volume

CTDIvol = CTDIw / pitch, where pitch is table feed per rotation divided by beam collimation. It estimates radiation dose per unit volume in CT.

Gadolinium safety

Macrocyclic gadolinium agents are more stable than linear agents. Avoid gadolinium in patients with eGFR below 30 mL/min/1.73 m² due to nephrogenic systemic fibrosis risk.

Couinaud liver segments

The liver is divided into eight segments based on portal vein branches and hepatic veins. Segment I is the caudate lobe; segments II–IV form the left lobe; V–VIII the right lobe.

Circle of Willis

An arterial anastomotic ring at the brain base formed by anterior communicating, paired anterior cerebral, internal carotid, posterior communicating, and posterior cerebral arteries; common site of berry aneurysms.

Conus medullaris level

The spinal cord ends at the conus medullaris, typically at L1–L2 in adults and L3 in neonates. Below this, the cauda equina consists of nerve roots.

Hounsfield unit of hemorrhage

Acute hemorrhage typically measures 50–90 HU on non-contrast CT, appearing hyperdense relative to normal brain parenchyma, which helps identify acute intracranial bleeding.

Restricted diffusion in abscess

An abscess shows central restricted diffusion with high signal on DWI and low ADC, plus rim enhancement. This helps differentiate abscess from cystic tumor or edema.

NF2 hallmark

Neurofibromatosis type 2 is characterized by bilateral vestibular schwannomas, often with meningiomas and ependymomas. It results from a mutation on chromosome 22.

Silhouette sign

Loss of the normal border between a lesion and an adjacent structure of similar density indicates they are in contact, such as right middle lobe opacity obscuring the right heart border.

Air bronchogram

Air-filled bronchi outlined by consolidated lung, indicating an alveolar filling process such as pneumonia, edema, or hemorrhage, rather than atelectasis or pleural disease.

Hampton hump

A wedge-shaped peripheral opacity on chest imaging representing pulmonary infarction, classically associated with pulmonary embolism. CTPA is the first-line diagnostic test.

Appendicitis CT criteria

Appendix diameter greater than 6 mm, periappendiceal fat stranding, wall enhancement, and appendicolith. Ultrasound shows a non-compressible blind-ending tubular structure.

Hepatocellular carcinoma enhancement

Hepatocellular carcinoma typically shows arterial hyperenhancement followed by portal venous or delayed washout. This pattern is used for non-invasive diagnosis in at-risk patients.

Diverticulitis CT findings

Colonic diverticula with wall thickening and pericolic fat stranding. Complications include abscess, fistula, and perforation. CT is the preferred imaging modality.

PI-RADS score

Prostate Imaging Reporting and Data System version 2.1 uses multiparametric MRI (T2, DWI, DCE) and assigns scores 1–5. Scores 4–5 indicate clinically significant cancer and warrant targeted biopsy.

Ectopic pregnancy discriminatory hCG

A transvaginal ultrasound should visualize an intrauterine gestational sac when hCG is above approximately 1500–2000 mIU/mL. An empty uterus with an adnexal mass suggests ectopic pregnancy.

Placenta previa

Placenta covering the internal cervical os, diagnosed by transvaginal ultrasound. It carries a risk of severe hemorrhage and usually requires cesarean delivery.

Osteosarcoma radiographic signs

Aggressive bone tumor with sunburst periosteal reaction, Codman triangle, and bone destruction, typically in the metaphysis of long bones in adolescents and young adults.

Osteoporosis DXA threshold

A T-score of −2.5 or lower on dual-energy X-ray absorptiometry defines osteoporosis. T-scores between −1.0 and −2.5 indicate osteopenia.

Anterior shoulder dislocation

The most common shoulder dislocation, with the humeral head displaced inferiorly and medially to the glenoid. An axillary view is needed to exclude associated fractures.

Dawson fingers

Ovoid periventricular lesions perpendicular to the ventricles on sagittal MRI, characteristic of multiple sclerosis. They reflect demyelination along medullary veins.

Glioblastoma imaging

Intra-axial brain tumor with irregular ring enhancement, central necrosis, and surrounding edema, often crossing the corpus callosum (butterfly pattern). It is the most common primary malignant brain tumor in adults.

BI-RADS category 3

Probably benign finding with less than 2% risk of malignancy. Short-interval follow-up (usually 6 months) is recommended rather than immediate biopsy.

Suspicious breast calcifications

Fine, linear, branching, or clustered pleomorphic calcifications on mammography are suspicious for malignancy and typically warrant biopsy (BI-RADS 4 or 5).

Intussusception ultrasound sign

Target sign or pseudokidney appearance on ultrasound. Air or contrast enema is both diagnostic and therapeutic, unless perforation or peritonitis is present.

Pyloric stenosis ultrasound

Thickened pyloric muscle greater than 3 mm and elongated canal greater than 15 mm in an infant with projectile vomiting at 3–6 weeks of age.

Salter-Harris classification

A five-type classification of physeal fractures in children: I through physis, II through physis and metaphysis, III through physis and epiphysis, IV through all, V crush injury.

Abdominal aortic aneurysm repair threshold

Repair is generally indicated when the abdominal aortic diameter exceeds 5.5 cm or grows rapidly. Options include endovascular aneurysm repair and open surgical repair.

FAST exam

Focused Assessment with Sonography for Trauma detects free fluid in pericardial, perihepatic, perisplenic, and pelvic spaces. It guides urgent management in hemodynamically unstable trauma patients.

FDG-PET uptake

Fluorodeoxyglucose uptake reflects metabolic activity. Normal high uptake occurs in brain, myocardium, kidneys, and bladder; malignancies, infection, and inflammation also show increased uptake.