Different facets of intracranial central nervous system lymphoma and its imaging mimics.

Lymphomas of the central nervous system (CNS) are broadly classified into primary CNS lymphoma (PCNSL) and secondary CNS lymphoma (SCNSL). PCNSL refers to lymphoma restricted to the brain, leptomeninges, spinal cord, or eyes without evidence of it outside the CNS at primary diagnosis, while SCNSL refers to secondary CNS involvement by systemic lymphoma. The brain is the most common site of involvement and intracranial CNS lymphoma has a highly variable imaging appearance and varies according to the patient's clinical profile and immunity. This pictorial essay aims to illustrate the different facets of intracranial CNS lymphomas on neuroimaging. This enables radiologists to be familiarized with their key diagnostic features and differentiate from their differential diagnoses, leading to early diagnosis, and treatment.

Gallium-67 Scan with Single Photon Emission Computed Tomography for the Evaluation and Monitoring of Infected Abdominal Aortic Aneurysms: A 10-Year Case Series.

PURPOSE: This study aimed to evaluate the role of gallium-67 single photon emission computed tomography (SPECT) with contrast computed tomography (CT) in the evaluation and monitoring of infected abdominal aortic aneurysms (IAAA). MATERIALS AND METHODS: A retrospective cohort analysis was performed using prospectively collected data of consecutive patients with IAAA in Princess Margaret Hospital in Hong Kong between January 2010 and December 2020. The patients were identified using the Radiology Information System. RESULTS: All five patients had proven IAAA on CT and/or metabolic imaging. Among them, three were further supported by positive blood culture results. Gallium- 67 SPECT with contrast CT was useful in the detection of residual disease, monitoring, and detection of recurrence. CONCLUSION: Gallium-67 SPECT with contrast CT is helpful for evaluating IAAA. It serves an important role in guiding management, especially during long-term follow-up.

US findings of melamine-related renal disorders in Hong Kong children.

BACKGROUND: The melamine-tainted milk incident has caused renal disorders in more than 290,000 children from mainland China since the start of the outbreak in 2008. Since then, more than 27,000 children in Hong Kong have undergone renal US screening. OBJECTIVE: To present and discuss the US features of melamine-related renal abnormalities in Hong Kong children. MATERIALS AND METHODS: Between September 2008 and February 2009, 3,835 children attended the Department of Radiology of Princess Margaret Hospital for renal US examination. CT or plain abdominal radiography was performed in those with inconclusive findings. The US findings of detected melamine-related renal disorders were analysed. RESULTS: Echogenic foci in the kidneys were found in 22 children (0.6%). These were located in the renal pelvicalyceal system (in 12 children) and in the renal medulla (in 10 children). The echogenic foci measured 0.1-0.7 cm, with 6 children showing posterior acoustic shadowing, 14 showing comet-tail artefacts, and 2 showing echogenic dots. CONCLUSION: The incidence of renal disorders amongst Hong Kong children exposed to melamine was lower than in their mainland China counterparts. The renal stones detected were also relatively small, with most demonstrating comet-tail artefacts instead of posterior acoustic shadowing.

Hybrid method in severe pulmonary embolism not suitable for systemic fibrinolysis.

Acute massive pulmonary embolism is known to be associated with high mortality, and treatment options may be limited if systemic fibrinolysis is contraindicated. We report the exciting results of a novel mechanical-pharmacological hybrid approach in 3 patients with life-threatening massive pulmonary embolism, in whom systemic fibrinolysis was contraindicated.

Early Enlargement of Aneurysmal Sac and Separation of EndoBags of Nellix Endovascular Aneurysm Sealing System as Signs of Increased Risk of Later Aneurysm Rupture.

Nellix Endovascular Aneurysm Sealing (EVAS) system is a new concept and technology of abdominal aortic aneurysm (AAA) repair. Elective EVAS using Nellix device was performed for a 83-year-old man with AAA. 2-month post-EVAS CTA surveillance demonstrated mild enlargement of aneurysmal sac and separation of the EndoBags, but without detectable endoleak. The patient developed sudden AAA rupture with retroperitoneal hematoma at about 4 months after EVAS. We postulated that early enlargement of aneurysmal sac and separation of EndoBags of Nellix devices after EVAS, even without detectable endoleak, might indicate significant aneurysmal wall weakening with increased risk of later AAA rupture. To the best of the authors' knowledge, this was the first reported case of aortic rupture after EVAS without detectable endoleak during and after the procedure.

Medications as causes of intraluminal hyperdensities: what radiologists need to know.

In computed tomography (CT) angiogram or some dedicated CT studies of the abdomen, the use of positive enteric contrast should be avoided as its presence could decrease the sensitivity of the test. There are, however, cases of CT scans with unexpected hyperdense intraluminal contents detected due to the use of certain oral or rectal medications. Reports on medications as causes of intraluminal hyperdensities are sparse in the English literature. We have studied several commonly used medications and revealed that many drugs appear hyperdense in CT scans. The presence of unexpected intraluminal hyperdensities can potentially cause erroneous interpretation of images and in some cases decrease the sensitivity of the test. The hyperdense bowel contents may be mistaken as acute hemorrhage in CT angiogram for detection of GI bleeding. Active GI bleeding, presented as intraluminal extravasation of contrast material, can also be obscured. Certain intra-abdominal pathologies could be masked, for example, in plain CT scan for detection of urinary tract stones or in contrast CT study for suspected bowel ischaemia. It is important for radiologists and clinicians to be aware of this situation in order to prevent misinterpretation of images and to select the most appropriate imaging modality when such unexpected intraluminal hyperdensities are encountered.