SPEX Radiology and Imaging Flashcards

A 68-year-old patient with known multiple myeloma presents with acute back pain. Plain radiographs show vertebral compression fractures. MRI reveals multiple lesions with low T1 and high T2 signal. Which imaging finding would most strongly suggest superimposed pathological fracture rather than osteoporotic fracture?

Answer: Paraspinal soft tissue mass extending beyond the vertebral endplate

A paraspinal soft tissue mass extending beyond the vertebral endplate is the most specific MRI finding distinguishing pathological (malignant) fracture from osteoporotic fracture. While posterior cortex convexity, diffuse marrow signal change, and multi-level involvement can all occur in myeloma, an epidural or paraspinal soft tissue component that crosses anatomical boundaries strongly implies tumor extension and is not a feature of benign osteoporotic collapse.

During fluoroscopic-guided lumbar puncture, a patient develops sudden severe headache, photophobia, and neck stiffness 30 minutes after the procedure despite uneventful needle placement confirmed by CSF flow. Non-contrast CT head is normal. The MOST appropriate next imaging step is:

Answer: CT angiography of the head and neck to exclude subarachnoid hemorrhage

Sudden severe headache ('thunderclap') with meningismus following lumbar puncture raises concern for subarachnoid hemorrhage (SAH), which can occur as a complication of dural puncture causing venous or arterial bleeding. When non-contrast CT is negative for SAH but clinical suspicion is high, CT angiography (CTA) is the appropriate next step to rule out an underlying aneurysm or vascular malformation as the cause. MRI with gadolinium is useful for chronic meningitis but not acute SAH evaluation. Repeat CT at 6 hours is a strategy for delayed hemorrhage detection but not the priority here.

A radiologist reviews a bone scan in a patient with prostate cancer showing a 'superscan' pattern. Which of the following additional findings on the same study would MOST strongly support a superscan rather than a technical artifact or metabolic bone disease?

Answer: Absent renal activity with faint bladder activity

A superscan in metastatic prostate cancer is characterized by diffusely intense skeletal uptake that causes absent or markedly diminished renal and soft tissue activity — because nearly all injected tracer is taken up by the skeleton, leaving little to be excreted renally. Absent renal visualization with faint or absent bladder activity is the most specific ancillary sign confirming a true superscan. Symmetric axial uptake, calvarial uptake, and costochondral junction activity can be seen in metabolic bone disease (e.g., renal osteodystrophy) without representing a malignant superscan.

On a gadolinium-enhanced brain MRI, a 45-year-old with HIV (CD4 count 40 cells/µL) has a ring-enhancing lesion in the right basal ganglia with surrounding edema. MR spectroscopy shows an elevated lipid/lactate peak with markedly reduced NAA and choline. Thallium-201 SPECT is negative. Which diagnosis does this constellation MOST favor?

Answer: Toxoplasma encephalitis

In an HIV patient with CD4 < 50, a ring-enhancing basal ganglia lesion is classically either toxoplasmosis or primary CNS lymphoma (PCNSL). The key discriminator here is Thallium-201 SPECT: PCNSL is Thallium-avid (positive scan) due to its high metabolic activity, while toxoplasmosis is Thallium-negative. The MRS pattern with elevated lipid/lactate and reduced NAA and choline also favors an infectious/necrotic process (toxoplasmosis) over lymphoma, which typically shows elevated choline. Tuberculoma can ring-enhance but is less common at this CD4 level, and PML does not typically enhance or produce ring-enhancing lesions.

A trauma patient undergoes CT angiography of the chest. Imaging reveals a focal outpouching at the isthmus of the aorta with a smooth contour, surrounding periaortic hematoma, and no intimal flap. There is also an incidental finding of a rounded, smooth-walled outpouching at the lesser curvature of the aortic arch between the left subclavian and ligamentum arteriosum, with NO surrounding hematoma and imperceptible neck. The MOST accurate characterization of the incidental outpouching is:

Answer: Ductus diverticulum, a normal variant

A ductus diverticulum is a normal anatomical variant representing the remnant of the ductus arteriosus at the aortic isthmus on the lesser curvature. Its distinguishing features from traumatic pseudoaneurysm include: smooth contour, no surrounding hematoma, obtuse margins with the aortic wall, location on the anteromedial aspect (lesser curvature), and an imperceptible or wide neck. Traumatic pseudoaneurysms occur at the isthmus on the anterolateral (greater curve) aspect, have acute margins, and are associated with periaortic hematoma. Misidentifying a ductus diverticulum as a pseudoaneurysm leads to unnecessary invasive intervention.

A 72-year-old woman with a 30-pack-year history presents with an incidentally found 8 mm solid pulmonary nodule in the right upper lobe on CT. Per Lung-RADS 2022 guidelines, this nodule would be categorized as Lung-RADS 3 and recommended for 6-month follow-up CT. If on the 6-month follow-up CT the same nodule has grown to 10 mm and now shows subtle internal ground-glass opacity, what is the REVISED Lung-RADS category and next recommended management?

Answer: Lung-RADS 4X — recommend PET/CT or tissue sampling, with category upgraded due to additional suspicious features

Under Lung-RADS 2022, a solid nodule growing from 8 mm to 10 mm in 6 months represents significant interval growth (>1.5 mm increase), which on its own would place it in Lung-RADS 4A (≥8 mm new or growing solid component). However, the additional suspicious morphologic feature — new internal ground-glass opacity suggesting a mixed solid/subsolid component — triggers an upgrade to Lung-RADS 4X. Lung-RADS 4X is used when a nodule has additional features that increase the suspicion of malignancy beyond what its size alone would suggest, such as spiculation, part-solid morphology with growth, or PET avidity. The recommended management for 4X is PET/CT or tissue sampling.