Kelvin Yap

Magnetic resonance features of primary central nervous system lymphoma in the immunocompetent patient: a pictorial essay.

Primary central nervous system lymphoma (PCNSL) is an uncommon but important variant of non‐Hodgkin lymphoma and represents up to 6% of all primary central nervous system (CNS) malignancies. Recognition of this entity by radiologist on MRI may avoid unnecessary neurosurgical resection and redirect to biopsy. The pretreatment MRI of patients with biopsy proven PCNSL from the last 5 years at our institution was reviewed. Selected examples were used to construct a pictorial essay to illustrate some of the typical and atypical MR features of PCNSL. MRI of other CNS conditions with imaging similarities to PCNSL was included to demonstrate possible mimics. The typical features of PCNSL lymphoma are intra‐axial homogenous single or multiple contrast enhancing lesions, with marked surrounding oedema and restricted diffusion, usually contacting a cerebrospinal fluid (CSF) surface. Necrosis, peripheral enhancement, haemorrhage or calcification are unusual and other diagnoses should be considered if any of these features are present. Potential mimics include high grade glioma, infarcts, metastatic disease, demyelination, abscess and secondary lymphoma. Careful assessment of the MR features and correlation with the clinical findings should enable the radiologists to raise the possibility of PCNSL and minimise the risk of unnecessary resection.

Combined Proximal Endografting With Distal Bare-Metal Stenting for Management of Aortic Dissection

BACKGROUND Established endovascular treatments for aortic dissection often result in incomplete aortic repair, potentially leading to late complications involving the distal aorta. To address the problems of incomplete true lumen reconstitution and late aneurysmal change, we report the midterm results of combined proximal endografting with distal true lumen bare-metal stenting (STABLE: Staged Total Aortic and Branch vesseL Endovascular reconstruction) in Stanford type A and B aortic dissection. METHODS Between January 2003 and January 2010, 31 patients underwent staged total aortic and branch vessel endovascular reconstruction for management of acute (type A, 13; type B, 11) and chronic (type B, 7) aortic dissection. Proximal endografting was combined with bare-metal Z stent implantation in the distal true lumen. Patients with type A dissection underwent adjunctive treatment at operation. Computed tomography angiography was performed at baseline, 1 year, and annually thereafter to assess aortic remodelling. RESULTS Primary technical success was 97%. Thirty-day rates of death, stroke, and permanent paraplegia/paresis were 3% (n=1), 0%, and 0%, respectively. Mean follow-up was 57.3 months (range, 5 to 100 months). Overall survival was 60% at 100 months. Aortic-specific survival was 93%. Four patients (13%) underwent device-related reintervention. One (3%) late aortic-related death occurred. Thoracic (p=0.64) and abdominal (p=0.14) aortic dimensions were stable. The true lumen index increased significantly at follow-up. CONCLUSIONS Staged total aortic and branch vessel endovascular reconstruction is a feasible ancillary endovascular technique to address the problems of distal true lumen collapse, incomplete aortic remodelling, and late aneurysm formation in aortic dissection.

Primary central nervous system lymphoma in immunocompetent patients: a retrospective review of MRI features.

Introduction: To define the features of primary central nervous system lymphoma (PCNSL) on MRI in immunocompetent patients.

Solid focal liver lesion characterisation with apparent diffusion coefficient ratios

Non‐invasive characterisation of focal liver lesions using diffusion‐weighted imaging (DWI) has been heavily investigated and has shown substantial overlap between benign and malignant lesions. We have calculated a ratio of lesion to normal liver to determine if it improves accuracy for correct categorisation.

Part 1: MRI features of focal nodular hyperplasia with an emphasis on hepatobiliary contrast agents

Focal nodular hyperplasia (FNH) is the second most common benign liver tumour and typically do not require any treatment. An accurate non‐invasive diagnosis is therefore vital to avoid unnecessary intervention and to reassure patients. This article discusses the demographics and pathology of FNH and reviews the appearance of FNH at MRI using liver‐specific contrast agents.

Prevalence of incidental or unexpected findings on low-dose CT performed during routine SPECT/CT nuclear medicine studies.

In nuclear medicine, single‐photon‐emission computed tomography (SPECT) is often combined with ‘simultaneous’ low‐dose CT (LDCT) to provide complementary anatomical and functional correlation. As a consequence, numerous incidental and unexpected findings may be detected on LDCT. Recognition of these findings and appropriate determination of their relevance can add to the utility of SPECT/CT. We aimed to evaluate the prevalence and categorise the relevance of incidental and unexpected findings on LDCT scans performed as part of routine SPECT/CT studies.

Part 2: MRI of hypervascular focal liver lesions using liver specific contrast agents

Hypervascular liver lesions are frequently encountered and can be characterised by using hepatobiliary contrast agents at MRI examinations. The imaging characteristics of a variety of hypervascular liver lesions are presented with an emphasis on differentiating features.

Prevalence of non 18F‐fluorodeoxyglucose‐avid incidental findings of clinical significance on whole body positron emission tomography/computed tomography: A review of 500 consecutive cases

The prevalence of incidental 18F‐fluorodeoxyglucose (FDG)‐avid findings on positron emission tomography–computed tomography (PET/CT) has been extensively described. Few studies, however, have assessed the prevalence and significance of non‐FDG‐avid findings; pathology that is identified on review of the low‐dose, non‐contrast CT. The aim of this study was to determine the overall prevalence of non FDG‐avid incidental findings on PET/CT and the prevalence of ‘clinically significant’ non FDG‐avid pathology.

Intraventricular CNS lesions: A pictorial essay

Intraventricular lesions of the central nervous system (CNS) can present a diagnostic challenge due to a range of differential diagnoses and radiological appearances. Both CT and MRI imaging findings, in combination with location and patients age, can help limit the differentials. This pictorial essay presents the salient radiological features, location and demographics of the more common intraventricular lesions of the brain.