Cher Heng Tan

CT volumetry of the liver: Where does it stand in clinical practice?

Imaging-based volumetry has been increasingly utilised in current clinical practice to obtain accurate measurements of the liver volume. This is particularly useful prior to major hepatic resection and living donor liver transplantation where the size of the remnant liver and liver graft, respectively, affects procedural success and postoperative mortality and morbidity. The use of imaging-based volumetry, with emphasis on computed tomography, will be reviewed. We will explore the various technical factors that contribute to accurate volumetric measurements, and demonstrate how the accuracies of these techniques are influenced by their methodologies. The strengths and limitations of using anatomical imaging to estimate liver volume will be discussed, in relation to laboratory and functional imaging methods of assessment.

Diffusion-weighted MRI of adult male pelvic cancers

Magnetic resonance imaging (MRI), with its superior soft-tissue delineation, plays a pivotal role in the staging and surveillance of cancers affecting adult males, in particular, rectal, urinary bladder, and prostate cancers. There has been much recent interest in the complementary roles of diffusion-weighted imaging (DWI) for imaging of pelvic cancers. DWI measures the diffusivity of water molecules in biological tissue. Cancer, with its high cellular density and nuclear:cytoplasmic ratio, and extracellular disorganization, typically shows significant restricted diffusivity compared with surrounding normal tissue. In theory, diffusivity of water molecules may vary according to degree of tumour aggressiveness and changes in cell density and extracellular fluid content after treatment. Information regarding these variations may be used to study the histological grades of cancers and their response to treatment. In this article, we present the currently available evidence on the potential roles of DWI for the assessment of pelvic cancers in men, and demonstrate with imaging examples how this knowledge may be applied to daily clinical practice.

Use of positive oral contrast agents in abdominopelvic computed tomography for blunt abdominal injury: meta-analysis and systematic review

AbstractObjectivesTo determine whether positive oral contrast agents improve accuracy of abdominopelvic CT compared with no, neutral or negative oral contrast agent.MethodsLiterature was searched for studies evaluating the diagnostic performance of abdominopelvic CT with positive oral contrast agents against imaging with no, neutral or negative oral contrast agent. Meta-analysis reviewed studies correlating CT findings of blunt abdominal injury with positive and without oral contrast agents against surgical, autopsy or clinical outcome allowing derivation of pooled sensitivity and specificity. Systematic review was performed on studies with common design and reference standard.ResultsThirty-two studies were divided into two groups. Group 1 comprised 15 studies comparing CT with positive and without oral contrast agents. Meta-analysis of five studies from group 1 provided no difference in sensitivity or specificity between CT with positive or without oral contrast agents. Group 2 comprised 17 studies comparing CT with positive and neutral or negative oral contrast agents. Systematic review of 12 studies from group 2 indicated that neutral or negative oral contrasts were as effective as positive oral contrast agents for bowel visualisation.ConclusionsThere is no difference in accuracy between CT performed with positive oral contrast agents or with no, neutral or negative oral contrast agent.Key Points• There is no difference in the accuracy of CT with or without oral contrast agent. • There is no difference in the accuracy of CT with Gastrografin or water. •Omission of oral contrast, utilising neutral or negative oral contrast agent saves time, costs and decreases risk of aspiration.

Emergency computed tomography for acute pelvic trauma: Where is the bleeder?

Contrast medium extravasation at computed tomography (CT) is an accurate indicator of active haemorrhage in pelvic trauma. When this is present, potentially lifesaving surgical or endovascular treatment should be considered. Identification of the site or territory of haemorrhage is helpful for the interventional radiologist as it allows for focused angiographic evaluation and expedites haemostatic angio-embolisation. Even with thin-section arterial phase CT, tracing the bleeding vessel is not always possible and is often time consuming. We introduce a technique for predicting the bleeding vessel based on knowledge of the cross-sectional anatomical territory of the vessel as an alternative to tracing the vessels course. Several case examples with digital subtraction angiography (DSA) correlation will be provided.

Revisiting renovascular imaging for renal sympathetic denervation: current techniques and applications

AbstractRenal sympathetic denervation (RDN) is an emerging technique in the treatment of resistant hypertension, most commonly performed using an endovascular approach. Clinical and anatomical criteria for RDN are well established and imaging plays an integral role in selecting patients with suitable anatomy, procedural planning and device selection. Nevertheless, the current body of literature surrounding imaging related to RDN remains limited. The purpose of this article is to illustrate the expectations and limitations of various imaging techniques, including Doppler ultrasound, CT angiography, MR angiography and newer techniques such as non-contrast MR angiography, in the context of RDN.Key Points• To understand the role of imaging in renal denervation • To understand strengths and weaknesses of current imaging techniques • To understand the relevant imaging findings in the context of renal denervation

Validity of estimating muscle and fat volume from a single MRI section in older adults with sarcopenia and sarcopenic obesity

AIM To determine if there is a correlation between the cross-sectional areas (CSAs) in a single section and the volumes of muscles and fat in the thigh of sarcopenic and sarcopenic obesity (SO) populations using magnetic resonance imaging (MRI), and to assess the correlation between thigh MRI data and patient health status, i.e., normal, obese, sarcopenia, and SO. MATERIALS AND METHODS One hundred and ninety community-dwelling older adults were recruited and categorised into four subgroups based on Asian established criteria: normal, obese, sarcopenia, and SO. MRI images were acquired and muscles, subcutaneous fat (SF), and intermuscular fat (IMF) were automatically segmented in the thighs. Volumes of muscles and fat were calculated for the middle third of the thigh, while CSAs were assessed using a single section at 50% femur length. RESULTS Correlation between CSA and volume were significantly high (p<0.001) for all components of muscle (0.907), SF (0.963), and IMF (0.939). Thigh CSA and volume both correlated significantly with a clinical diagnosis of normal, obesity, sarcopenia, and SO (p<0.03). CONCLUSIONS A single CSA at 50% of femur length yields good estimation of muscle and fat volume in the thighs of older adults and correlates closely with the clinical criteria for sarcopenia and SO. This has the potential to greatly reduce costs, scan time, and post-processing time in clinical practice for the prediction of these conditions.

Multidetector row CT diagnosis of an infected right atrial thrombus following repeated dialysis catheter placement

Right atrial thrombus formation is a known complication of dialysis catheter placements. We describe the case of a 61-year-old woman with end-stage renal failure who presented with gram-negative septicaemia. A gas-containing filling defect was noted incidentally in the right atrium during a CT scan of the abdomen and pelvis, indicative of a thrombus infected by a gas-forming organism. The finding correlated with a positive blood culture of Klebsiella pneumoniae and the two-dimensional echocardiography finding of an echogenic atrial thrombus.

Mesenteric desmoid tumour masquerading as a fat-containing cystic mass.

Mesenteric desmoid tumour (MDT) is an uncommon neoplasm that typically presents as a solid soft-tissue mass on cross-sectional imaging. MDT manifesting as a fat-containing cystic mass on CT has not been described in the literature. We report such an unusual case with clinicopathological correlation.

The role of multidetector computed tomography versus digital subtraction angiography in triaging care and management in abdominopelvic trauma.

INTRODUCTION This study aimed to assess the ability of contrast-enhanced computed tomography (CECT) to detect active abdominopelvic haemorrhage in patients with blunt trauma, as compared to digital subtraction angiography (DSA). METHODS In this retrospective study, patients who underwent DSA within 24 hours following CECT for blunt abdominal and/or pelvic trauma were identified. The computed tomography (CT) trauma protocol consisted of a portal venous phase scan without CT angiography; delayed phase study was performed if appropriate. All selected CECT studies were independently reviewed for the presence of active extravasation of contrast by two radiologists, who were blinded to the DSA results. Fishers exact test was used to correlate the presence of extravasation on CT with subsequent confirmed haemorrhage on DSA. RESULTS During the eight-year study period, 51 patients underwent CECT prior to emergent DSA for abdominal or pelvic trauma. Evidence of active extravasation of contrast on CECT was observed in 35 patients and active haemorrhage was confirmed on DSA in 31 of these patients; embolisation was performed in all 31 patients. Two patients who were negative for active extravasation of contrast on CECT but positive for active haemorrhage on DSA had extensive bilateral pelvic fractures and haematomas. The sensitivity, specificity, and positive and negative predictive values of CECT in detecting active abdominopelvic haemorrhage, as compared to DSA, were 93.9%, 77.8%, 88.6% and 87.5%, respectively. CONCLUSION When compared with DSA, dual-phase CECT without CT angiography shows high sensitivity and positive predictive value for the detection of active haemorrhage in patients with blunt abdominopelvic trauma.