Bertrand Ang - Academia.edu (original) (raw)

Papers by Bertrand Ang

Research paper thumbnail of How many adenocarcinoma lung cancers come from bronchioloalveolar carcinoma?

Thoracic Cancer, 2011

Results: The median patient age was 63, and the majority were of Chinese descent (75.4%). Women c... more Results: The median patient age was 63, and the majority were of Chinese descent (75.4%). Women comprised 43.5% of the patients (30 patients) and never-smokers comprised 47.8% (33 patients). Only 15 patients (21.7%) had surgical specimens. The presence of BAC ...

Research paper thumbnail of Non-ionic radiologic contrast (iohexol) interferes with laboratory measurements of endocrine hormones

Research paper thumbnail of Magnetic resonance elastography of liver in healthy asians: Normal liver stiffness quantification and reproducibility assessment

Journal of Magnetic Resonance Imaging, 2014

Purpose: To determine normal liver stiffness values evaluated with magnetic resonance elastograph... more Purpose: To determine normal liver stiffness values evaluated with magnetic resonance elastography (MRE) in healthy normal Asian volunteers and assess its reproducibility.

Research paper thumbnail of Imaging paradigms in assessment of rectal carcinoma: loco-regional and distant staging

Cancer Imaging, 2012

The role of imaging in the management of rectal malignancy has progressively evolved and undergon... more The role of imaging in the management of rectal malignancy has progressively evolved and undergone several paradigm shifts. Unlike a few decades ago when the role of a radiologist was restricted at defining the longitudinal extent of the tumour with barium enema, recent advances in imaging techniques permit highly accurate locoregional and distant staging of the disease as well as prognostication on those who are likely to have a postoperative recurrence. Computed tomography (CT) has always been the mainstay of imaging when evaluating for distant metastasis, with the advent of positron emission tomography/CT improving its specificity. In rectal malignancy, it is the local extent of the disease that often influences the surgical decision making and need for neoadjuvant therapy. Although endoscopic ultrasound has been the traditional technique for determining the depth of tumour invasion, over the last decade magnetic resonance imaging (MRI) has emerged as a very effective tool for accurate T-staging. This review intends to address the status of various imaging modalities and their advantages and limitations in detection, pretreatment staging, and assessment of therapeutic efficacy in rectal cancer, with emphasis on MRI of high spatial resolution.

Research paper thumbnail of Readout-segmented Echo-planar Imaging for Diffusion-weighted Imaging in the Pelvis at 3T—A Feasibility Study

Academic Radiology, 2014

Diffusion-weighted imaging (DWI) of the pelvis at 3T is prone to artifacts that diminish the imag... more Diffusion-weighted imaging (DWI) of the pelvis at 3T is prone to artifacts that diminish the image quality. Readout-segmented echo-planar imaging (RS-EPI) is a new DWI technique that can reduce the artifacts associated with standard single-shot echo-planar imaging (SS-EPI) DWI. The purpose of this study was to evaluate the feasibility and image quality of RS-EPI in pelvic DWI compared to SS-EPI on a 3T imaging system. Thirty patients underwent pelvic DWI on a 3T scanner with SS-EPI and RS-EPI techniques. Two blinded readers independently assessed each set of images for geometric distortion, image blurring, ghosting artifacts, lesion conspicuity, and overall image quality on a 7-point scale. Qualitative image scores were compared using paired Wilcoxon signed rank test. Interreader correlation was assessed by Spearman rank correlation. Geometric distortion, imaging blurring, ghosting artifacts, lesion conspicuity, and overall image quality were rated significantly better by both readers for RS-EPI technique (P < .01 for all parameters). There was moderate-high correlation between the readers (r = 0.649-0.752) for all parameters apart from lesion conspicuity (r = 0.351). Both readers preferred the RS-EPI set of DWI images in most of the cases (reader 1: 0.87, 95% CI 0.74-0.99; reader 2: 0.77, 95% CI 0.61-0.93). Mean difference and limits of agreement between apparent diffusion coefficient (ADC) values obtained from the two methods were 0.01 (-0.08, 0.10) × 10(-3) mm(2)/s. RS-EPI DWI images showed improved image quality compared to SS-EPI technique at 3T. RS-EPI is a feasible technique in the pelvis for producing high-resolution DWI.

Research paper thumbnail of Common bile duct obstruction by intraluminal colorectal metastasis without evidence of liver or intraabdominal nodal metastasis

International Journal of Colorectal Disease, 2012

The mechanism of jaundice in metastatic colorectal cancer with biliary tract obstruction is most ... more The mechanism of jaundice in metastatic colorectal cancer with biliary tract obstruction is most often due to direct invasion or extrinsic compression of the biliary system, either by metastasis to the liver or porta hepatis lymph nodes. The colon directly drains into the porta hepatis lymph nodes, and the incidence of right-sided colon cancer metastasizing to the peri-portal lymph nodes is more common than the left. Colorectal cancer frequently meta-stasizes to the liver because of the direct vasculature linking the colon to the liver via the portal vein, and fenestrations in the sinusoidal endothelium allow a foothold into the space of Disse for the tumor cells. Surgical series have shown that 40% of patients who undergo liver metastectomy from colorectal cancer have microscopic invasion into the bile ducts. However, biliary metastasis without liver or porta hepatis metastasis from colorectal adenocarcinoma is rare and we herein report a case and the management.

Research paper thumbnail of How many adenocarcinoma lung cancers come from bronchioloalveolar carcinoma?

Thoracic Cancer, 2011

Results: The median patient age was 63, and the majority were of Chinese descent (75.4%). Women c... more Results: The median patient age was 63, and the majority were of Chinese descent (75.4%). Women comprised 43.5% of the patients (30 patients) and never-smokers comprised 47.8% (33 patients). Only 15 patients (21.7%) had surgical specimens. The presence of BAC ...

Research paper thumbnail of Non-ionic radiologic contrast (iohexol) interferes with laboratory measurements of endocrine hormones

Research paper thumbnail of Magnetic resonance elastography of liver in healthy asians: Normal liver stiffness quantification and reproducibility assessment

Journal of Magnetic Resonance Imaging, 2014

Purpose: To determine normal liver stiffness values evaluated with magnetic resonance elastograph... more Purpose: To determine normal liver stiffness values evaluated with magnetic resonance elastography (MRE) in healthy normal Asian volunteers and assess its reproducibility.

Research paper thumbnail of Imaging paradigms in assessment of rectal carcinoma: loco-regional and distant staging

Cancer Imaging, 2012

The role of imaging in the management of rectal malignancy has progressively evolved and undergon... more The role of imaging in the management of rectal malignancy has progressively evolved and undergone several paradigm shifts. Unlike a few decades ago when the role of a radiologist was restricted at defining the longitudinal extent of the tumour with barium enema, recent advances in imaging techniques permit highly accurate locoregional and distant staging of the disease as well as prognostication on those who are likely to have a postoperative recurrence. Computed tomography (CT) has always been the mainstay of imaging when evaluating for distant metastasis, with the advent of positron emission tomography/CT improving its specificity. In rectal malignancy, it is the local extent of the disease that often influences the surgical decision making and need for neoadjuvant therapy. Although endoscopic ultrasound has been the traditional technique for determining the depth of tumour invasion, over the last decade magnetic resonance imaging (MRI) has emerged as a very effective tool for accurate T-staging. This review intends to address the status of various imaging modalities and their advantages and limitations in detection, pretreatment staging, and assessment of therapeutic efficacy in rectal cancer, with emphasis on MRI of high spatial resolution.

Research paper thumbnail of Readout-segmented Echo-planar Imaging for Diffusion-weighted Imaging in the Pelvis at 3T—A Feasibility Study

Academic Radiology, 2014

Diffusion-weighted imaging (DWI) of the pelvis at 3T is prone to artifacts that diminish the imag... more Diffusion-weighted imaging (DWI) of the pelvis at 3T is prone to artifacts that diminish the image quality. Readout-segmented echo-planar imaging (RS-EPI) is a new DWI technique that can reduce the artifacts associated with standard single-shot echo-planar imaging (SS-EPI) DWI. The purpose of this study was to evaluate the feasibility and image quality of RS-EPI in pelvic DWI compared to SS-EPI on a 3T imaging system. Thirty patients underwent pelvic DWI on a 3T scanner with SS-EPI and RS-EPI techniques. Two blinded readers independently assessed each set of images for geometric distortion, image blurring, ghosting artifacts, lesion conspicuity, and overall image quality on a 7-point scale. Qualitative image scores were compared using paired Wilcoxon signed rank test. Interreader correlation was assessed by Spearman rank correlation. Geometric distortion, imaging blurring, ghosting artifacts, lesion conspicuity, and overall image quality were rated significantly better by both readers for RS-EPI technique (P < .01 for all parameters). There was moderate-high correlation between the readers (r = 0.649-0.752) for all parameters apart from lesion conspicuity (r = 0.351). Both readers preferred the RS-EPI set of DWI images in most of the cases (reader 1: 0.87, 95% CI 0.74-0.99; reader 2: 0.77, 95% CI 0.61-0.93). Mean difference and limits of agreement between apparent diffusion coefficient (ADC) values obtained from the two methods were 0.01 (-0.08, 0.10) × 10(-3) mm(2)/s. RS-EPI DWI images showed improved image quality compared to SS-EPI technique at 3T. RS-EPI is a feasible technique in the pelvis for producing high-resolution DWI.

Research paper thumbnail of Common bile duct obstruction by intraluminal colorectal metastasis without evidence of liver or intraabdominal nodal metastasis

International Journal of Colorectal Disease, 2012

The mechanism of jaundice in metastatic colorectal cancer with biliary tract obstruction is most ... more The mechanism of jaundice in metastatic colorectal cancer with biliary tract obstruction is most often due to direct invasion or extrinsic compression of the biliary system, either by metastasis to the liver or porta hepatis lymph nodes. The colon directly drains into the porta hepatis lymph nodes, and the incidence of right-sided colon cancer metastasizing to the peri-portal lymph nodes is more common than the left. Colorectal cancer frequently meta-stasizes to the liver because of the direct vasculature linking the colon to the liver via the portal vein, and fenestrations in the sinusoidal endothelium allow a foothold into the space of Disse for the tumor cells. Surgical series have shown that 40% of patients who undergo liver metastectomy from colorectal cancer have microscopic invasion into the bile ducts. However, biliary metastasis without liver or porta hepatis metastasis from colorectal adenocarcinoma is rare and we herein report a case and the management.