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Biomedical subjects

G Brown

Publications and source records attributed to G Brown.

At least 19 recordsLinked to original sources
PubMed2007

High-resolution MRI in evaluation of the surgical anatomy of the esophagus and posterior mediastinum.

OBJECTIVE: The purpose of this study was to use high-resolution MRI to evaluate the surgical anatomy of the posterior mediastinum, in particular the esophagus and its relation to the surrounding structures. The aim was to familiarize radiologists with the appearance of structures considered important in planning surgical resection of the esophagus. MATERIALS AND METHODS: The thoraces of two cadavers were imaged with a 1.5-T magnet using a high-resolution T2-weighted sequence. Axial cadaveric sections of the posterior mediastinum were cut with a band saw at levels determined from the MR images, and histologic whole-mount sections of the esophagus and surrounding tissue were prepared from the cadaveric sections. The appearance of structures identified on the MR images was compared with the findings on corresponding gross anatomic and histologic whole-mount sections. RESULTS: The MR images depicted the esophagus and structures in close anatomic relation: the pleural reflections and pericardium. The technique enabled visualization of structures to our knowledge not previously described on cross-sectional imaging: the individual layers of the esophageal wall, the thoracic duct, a connective tissue layer attaching the esophagus to the anterior wall of the aorta, and a fascial plane passing between layers of the right and left parietal pleura posterior to the esophagus. CONCLUSION: High-resolution MRI of the posterior mediastinum provides detailed anatomic information, delineating structures not visible on other forms of cross-sectional imaging. It can provide important information for planning surgical intervention.

Aged↗
PubMed2006

Predictive poor prognostic factors in colonic carcinoma.

INTRODUCTION: Five-year survival in rectal cancer has been steadily improving since the introduction of neoadjuvant chemoradiation and total mesorectal excision surgery. In contrast, 5-year survival rates and management of colonic carcinoma remain relatively unchanged. This study aims to identify poor prognostic factors in colonic cancer patients that could potentially be predicted pre-operatively to identify a subset of patients amenable to neoadjuvant treatment strategies. METHODS: Database compilation of all operable rectal and colonic cancer patients presenting to a single district general hospital over 5 years. Data were documented on presentation and site of tumour, TNM staging, differentiation and extramural venous invasion. RESULTS: There was no significant difference in 4-year survival between rectal (57.5%) and right (57%) or left sided (52.5%) colonic cancers (p=0.4689). On multivariate analysis, N2-stage, T4-stage and emergency presentation were identified as independent prognostic factors. On univariate analysis, in addition to the above factors, presence of venous invasion (p=0.001) and poor differentiation (p=0.0003) of tumour also predicted for poor 5-year survival. CONCLUSION: T4-stage and N2-stage and extramural venous invasion are poor prognostic factors that could be identified pre-operatively with suitably accurate imaging. Such patients could then be considered for a pre-operative treatment strategy.

Adult↗
PubMed2006

The appearances of oesophageal carcinoma demonstrated on high-resolution, T2-weighted MRI, with histopathological correlation.

This paper describes the spectrum of imaging features of oesophageal adenocarcinoma seen using high-resolution T2-weighted (T2W) magnetic resonance imaging (MRI). Thirty-nine patients with biopsy-proven oesophageal adenocarcinoma were scanned using an external surface coil. A sagittal T2W sequence was used to localise the tumour and to plan axial images perpendicular to the tumour. Fast spin-echo (FSE) T2W axial sequence parameters were: TR/TE, 3,300-5,000 ms/120-80 ms; field of view (FOV) 225 mm, matrix 176x512(reconstructed) mm to 256x224 mm, giving an in-plane resolution of between 1.28x0.44 mm and 0.88x1.00 mm, with 3-mm slice thickness. Thirty-three patients underwent resection and the MR images were compared with the histological whole-mount sections. There were four T1, 12 T2, and 17 T3 tumours. The T2W high-resolution MRI sequences produced detailed images of the oesophageal wall and surrounding structures. Analysis of the imaging appearances for different tumour T stages enabled the development of imaging criteria for local staging of oesophageal cancer using high-resolution MRI. Our study illustrates the spectrum of appearances of oesophageal cancer on T2W high-resolution MRI, and using the criteria established in this study, demonstrates the potential of this technique as an alternative non-invasive method for local staging for oesophageal cancer.

Adenocarcinoma↗
PubMed2006

Colorectal hepatic metastases: quantitative measurements using single-shot echo-planar diffusion-weighted MR imaging.

The purpose of this study was to obtain quantitative measurements of the apparent diffusion coefficient (ADC1), flow insensitive apparent diffusion coefficient (ADC2) and perfusion fraction (F) of colorectal hepatic metastases using DWI and to compare these measurements with those obtained in liver parenchyma. Forty patients with 66 hepatic metastases from colorectal carcinoma were prospectively evaluated using DWI with three b values. Quantitative maps of the ADC1 (using b = 0, 150, 500 s/mm2 images), ADC2 (using b = 150, 500 s/mm2 images) and fractional variation (F) between ADC1 and ADC2, which reflects perfusion fraction, were calculated. The ADC1, ADC2 and F derived from metastases and liver parenchyma were compared. The mean ADC1 values of liver parenchyma and metastases were significantly higher than the mean ADC2 values (P < 0.0001, paired t-test). Colorectal metastases were found to have higher mean ADC1 and ADC2 values compared with liver (P < 0.0001, Mann-Whitney test). However, the estimated F was found to be lower in metastases compared to liver (P = 0.03, Mann-Whitney test). Colorectal hepatic metastases were characterised by higher ADC1 and ADC2 values, but lower F values compared to liver.

Adult↗
PubMed2006

MRI directed multidisciplinary team preoperative treatment strategy: the way to eliminate positive circumferential margins?

Histopathological audit of positive circumferential resection margins (CRMs) can be used as a surrogate measure of the success of rectal cancer treatment. We audited CRM involvement in rectal cancer patients and the impact of the multidisciplinary team (MDT) on implementing a magnetic resonance imaging (MRI)-based preoperative treatment strategy. Data were collected on all newly diagnosed rectal cancer patients treated in our network between January 1999 and December 2002. Data were analysed for MRI prediction and histopathological assessment of CRM together with the MDT meeting treatment decisions. The CRM+ve rate of those discussed at MDT vs those not discussed were compared. We re-audited the CRM+ve rates 1 year after introducing a policy of mandatory preoperative MRI-based MDT discussion. Of the 298 patients diagnosed with rectal cancer, 39 (13%) were deemed palliative, 178 underwent surgery alone and 81 underwent neoadjuvant therapy. Of these, 62 out of 178 patients underwent surgery alone without MRI-based MDT discussion resulting in positive CRM in 16 cases (26%) as compared to 1 out of 116 (1%) in those patients with MDT discussion of MRI. Overall CRM+ve rate in all nonpalliative patients with or without MDT discussion was 12.5% (32 out of 256), significantly lower than the <20% rate (P<0.001) quoted in national guidelines. Re-audit in 98 consecutive patients following a change of policy produced a lower CRM+ve rate of 3% (1 out of 37) for all surgery alone patients and an overall CRM+ve rate of 7% (5 out of 70). In conclusion, MDT discussion of MRI and implementation of a preoperative treatment strategy results in significantly reduced positive CRM in rectal cancer patients.

Adult↗
PubMed2006

Clarifying margins in the multidisciplinary management of rectal cancer: the MERCURY experience.

The Magnetic Resonance Imaging and Rectal Cancer European Equivalence Study (MERCURY) was an observational prospective study involving 11 European centres, to evaluate equivalence between magnetic resonance imaging and histopathology in measuring depth of tumour invasion beyond the bowel and involvement of the circumferential resection margin in rectal cancer specimens.

Adenocarcinoma↗
PubMed2006

Video capsule endoscopy in peutz-jeghers syndrome: a blinded comparison with barium follow-through for detection of small-bowel polyps.

BACKGROUND AND STUDY AIMS: Video capsule endoscopy has shown promise for the surveillance of significant small-bowel polyps in patients with Peutz-Jeghers syndrome. In this study the yield of significant small-bowel polyps by capsule endoscopy was compared to the yield of these polyps by barium follow-through in adults with Peutz-Jeghers syndrome. PATIENTS AND METHODS: A total of 19 adults with Peutz-Jeghers syndrome who were undergoing surveillance underwent both capsule endoscopy and barium follow-through examinations, and the number of small-bowel polyps of at least 1 cm in diameter that were detected was recorded for each method. The two methods were assessed in terms of comfort and convenience for the patients and their preferred future surveillance method, using a questionnaire. RESULTS: Capsule endoscopy detected a median of four significant small-bowel polyps while barium follow-through detected a median of one (P = 0.008). There was a trend towards more participants having at least one significant small-bowel polyp detected by capsule endoscopy than was the case with barium follow-through, though capsule endoscopy seemed to be less reliable for accurate sizing of polyps that were at the limit of clinical significance. Most participants expressed a preference for capsule endoscopy for future surveillance. CONCLUSIONS: Capsule endoscopy should replace barium follow-through for the surveillance of small-bowel polyps in adults with Peutz-Jeghers syndrome, but the findings of this study should be interpreted with caution until a more reliable means of sizing polyps by capsule endoscopy is available.

Administration, Oral↗
PubMed2006

Magnetic resonance imaging of the low rectum: defining the radiological anatomy.

Low rectal cancer provides a particular surgical challenge of local tumour control and sphincter preservation. Histopathological studies have shown that an involved circumferential resection margin (CRM) and depth of extramural invasion are independent markers of poor prognosis and correlate with high local recurrence rates due to residual microscopic disease [1]. Recent data suggests that a CRM at risk of tumour involvement can be reliably seen on the pre-operative magnetic resonance imaging (MRI) scan with good correlation with the histological specimen [2-5]. In published series, low rectal cancers have a higher incidence of involved resection margins, with rates up to 30% for abdomino-perineal excision (APE) vs 10% for low anterior resection (LAR) [6-9]. This has been attributed to narrow surgical planes deep within the pelvis as the mesorectum becomes narrowed and tapered, forming a bare muscle tube at the level of the anal sphincter complex. The challenge for the surgeon is to undertake careful removal of a cylinder of tissue beyond the rectal wall without perforating the tumour. An overall local recurrence rate of 10% after APE for all stages of rectal cancer has been reported and this low rate was attributed to the surgical technique that included a wide peri-anal dissection and lateral division of the levator ani. The abdominal dissection was stopped above the tumour, taking care to avoid separation of the tumour from the levator ani to reduce the risk of inadvertent tumour cell spillage [8]. Therefore, rates of involved surgical margins from APE specimens may be reduced when a cuff of levators is taken compared with standard resection. In this review, we will discuss how MRI of the low rectum can aid in the staging and optimization of the best treatment strategy for low rectal cancer.

Anal Canal↗
PubMed2006

Magnetic resonance imaging pelvimetry in 186 patients with rectal cancer confirms an overlap in pelvic size between males and females.

INTRODUCTION: It has generally been considered that open pelvic surgery is almost always easier in female subjects because of anatomical differences facilitating surgical access. In contrast, the male pelvis has been considered to be narrower and deeper. The objective of this study was to assess magnetic resonance imaging (MRI) pelvimetry in patients with rectal cancer in whom any difference in pelvimetry may potentially affect operative management. Male and female pelvic bony dimensions were compared. METHOD: A cohort of 186 patients (112 males and 74 females) with rectal cancer who had been recruited prospectively to the Magnetic Resonance Imaging and Rectal Cancer European Equivalence Study (MERCURY Study) were assessed. Complete digital images were available on these patients. A comparison of the pelvic dimensions was made between the sexes using 16 dimensions measured on the MRI workstation using the mid-sagittal and axial images. RESULTS: There was no significant difference and considerable overlap between the sexes with respect to each of the 14 parameters measured from the preoperative sagittal MRI scan. However, there was a highly significant difference between the interspinous and intertuberous transverse diameter of the pelvis (P < 0.0001). CONCLUSION: Outcome after surgery may be influenced by the technical difficulty of the operation and this had been thought to be partly affected by the pelvic size. In this cohort of 186 patients, the only difference seen between the sexes, was in the transverse mid-inlet and pelvic outlet diameter.

Adult↗
PubMed2006

Lipid abnormalities in HIV/hepatitis C virus-coinfected patients.

BACKGROUND: Among HIV-infected patients, hepatitis C virus (HCV) coinfection is associated with increased rates of lipodystrophy and insulin resistance. Its impact on HIV-associated dyslipidaemia is less clear. METHODS: The lipid profiles of all HIV-infected patients and a subset of HCV-infected patients seen at the VA Medical Center in Dallas from January 2003 to March 2004 were analysed. Demographic data, HCV serostatus, and HIV treatment history were recorded. Lipid profiles of HIV/HCV-coinfected patients were compared with those of HIV-monoinfected and HCV-monoinfected patients. RESULTS: A total of 359 HIV-infected patients, 91 (25.3%) of whom were HCV coinfected, and 112 HCV-infected patients were included in the analysis. Among the HIV-infected patients, HCV coinfection was associated with a reduced risk of hypercholesterolaemia [9.9% vs 24.8%; relative risk (RR)=0.333; 95% confidence interval (CI)=0.158-0.699; P<0.001] and hypertriglyceridaemia (48.4% vs 60.3%; RR=0.616; 95% CI=0.382-0.994; P=0.031). After controlling for duration of protease inhibitor (PI) therapy, race, alanine aminotransferase (ALT) concentration and platelet count, HCV remained an independent predictor of hypercholesterolaemia (RR=0.369; P=0.01) and any dyslipidaemia (RR=0.531; P=0.019). In addition, the rate of dyslipidaemias was lower among HCV-monoinfected than HIV/HCV-coinfected patients (29.5% vs 50.5; P=0.002). White race was also an independent predictor of dyslipidaemia (73.8% vs 50.7%; RR=2.32; 95% CI=1.44-3.76; P=0.001). CONCLUSIONS: HCV coinfection independently predicted lower rates of dyslipidaemia among HIV-infected patients. An analysis of lipid kinetics among mono- and coinfected patients may elucidate the mechanisms of the apparent protective effect of HCV infection.

Adult↗
PubMed2006

Diagnosis of pulmonary embolism with CT pulmonary angiography: a systematic review.

OBJECTIVE: To appraise the evidence on the diagnostic accuracy of CT pulmonary angiography and the prognostic value of a negative CT pulmonary angiogram in the diagnosis of pulmonary embolism. METHODS: Medline, EMBASE, and grey literature were systematically searched by two researchers. Any study which compared CT pulmonary angiography to an acceptable reference standard or prospectively followed up a cohort of patients with a normal CT pulmonary angiogram was included. Study methods were appraised independently by two researchers, and data were extracted independently by three researchers. RESULTS: Thirteen diagnostic and 11 follow up studies were identified. Studies varied in prevalence of pulmonary embolism (19-79%), patient groups, and method quality. Few studies recruited unselected emergency department patients. There was heterogeneity in the analysis of sensitivity (53 to 100%), specificity (79 to 100%), and false negative rate (1.0 to 10.7%). The pooled false negative rate of combined negative CT pulmonary angiography and negative deep vein thrombosis testing was 1.5% (95% CI 1.0 to 1.9%). CONCLUSION: Diagnostic studies give conflicting results for the diagnostic accuracy of CT pulmonary angiography. Follow up studies show that CT pulmonary angiography can be used in combination with investigation for deep vein thrombosis to exclude pulmonary embolism.

Angiography↗
PubMed2006

The development and optimization of high spatial resolution MRI for imaging the oesophagus using an external surface coil.

This paper describes the development and optimization of an innovative technique using an external surface coil to obtain high resolution, thin section MR images of the oesophagus using volunteers. T2 weighted fast spin echo sequences were performed with and without cardiac gating. The field of view (FOV), matrix size, slice thickness, number of signal averages (NSA), and repetition time (TR)/echo time (TE) were altered to optimize signal to noise ratio (SNR) whilst maintaining spatial resolution. The effect of cardiac gating was also investigated. Workstation images were evaluated on the ability to visualize: individual oesophageal wall layers; perioesophageal fat; the azygos vein and wall of the descending aorta, giving qualitative assessment of image clarity. The optimum sequence enabled the layers of the oesophageal wall and perioesophageal tissues to be demonstrated in an acceptable scan time of 7.07 min. A FOV of less than 250 mm degraded image quality so that individual oesophageal wall layers could not be depicted and noise within the image impaired visualization of posterior mediastinal structures. The results indicate that high resolution imaging of the oesophagus using an external surface coil can depict anatomic structures clearly and that the use of cardiac gating improves image clarity. The technique offers an alternative, non-invasive method of detailed imaging of the oesophagus.

Esophageal Neoplasms↗
PubMed2005

Surface complexation studied via combined grazing-incidence EXAFS and surface diffraction: arsenate on hematite (0001) and (10-12).

X-ray diffraction [crystal-truncation-rod (CTR)] studies of the surface structure of moisture-equilibrated hematite reveal sites for complexation not present on the bulk oxygen-terminated surface, and impose constraints on the types of inner-sphere sorption topologies. We have used this improved model of the hematite surface to analyze grazing-incidence EXAFS results for arsenate sorption on the c (0001) and r (10-12) surfaces measured in two electric vector polarizations. This work shows that the reconfiguration of the surface under moist conditions is responsible for an increased adsorption density of arsenate complexes on the (0001) surface relative to predicted ideal termination, and an abundance of "edge-sharing" bidentate complexes on both studied surfaces. We consider possible limitations on combining the methods due to differing surface sensitivities, and discuss further analysis possibilities using both methods.

Adsorption↗
PubMed2005

Distribution of mesorectal lymph nodes in rectal cancer: in vivo MR imaging compared with histopathological examination. Initial observations.

The aim of this work was to determine the distribution of mesorectal lymph nodes using T2-weighted magnetic resonance (MR) imaging compared with histopathological findings in patients with rectal carcinoma. Sixteen patients with rectal carcinoma undergoing primary surgery without pre-operative neoadjuvant treatment were evaluated using 3-mm axial T2-weighted MR imaging. The position of each visible mesorectal node on imaging was localised by measuring its minimum distance from the mesorectal fascia (d(m)), its minimum distance from the rectal wall (d(r)) and its distance from the distal tumour margin (d(v)). Independent assessment of d(m), d(r) and d(v) was made at histopathological examination. Eighty-five mesorectal nodes on in vivo MR imaging were matched to histopathological findings. On imaging, 67/85 mesorectal nodes were found at the level of the tumour and 84/85 were identified at or within 5 cm proximal to the tumour. Only one out of 85 nodes was seen below the inferior tumour margin. The mean difference of d(m) and d(r) obtained on in vivo MR imaging and histopathological examination was 0.7 mm (95% confidence interval, CI, -0.12 to 1.42 mm) and -1.1 mm (95% CI -2.29 to 0.14 mm), respectively. Almost all mesorectal nodes visible on MR imaging were found at the level of tumour or within 5 cm proximal to the tumour. This has implications for the planning of MR imaging and the level of mesorectal transection at surgery.

Adenocarcinoma↗
PubMed2005

Preoperative staging of rectal cancer: the MERCURY research project.

The development of a surgical technique that removes the tumour and all local draining nodes in an intact package, namely total mesorectal excision (TME) surgery, has provided the impetus for a more selective approach to the administration of preoperative therapy. One of the most important factors that governs the success of TME surgery is the relationship of tumour to the circumferential resection margin (CRM). Tumour involves the CRM in up to 20% of patients undergoing TME surgery, and results in both poor survival and local recurrence. It is therefore clear that the importance of the decision regarding the use of pre-operative therapy lies with the relationship of the tumour to the mesorectal fascia. In addition, a high-spatial-resolution MRI technique will identify tumours exhibiting other poor prognostic features, namely, extramural spread >5 mm, extramural venous invasion by tumour, nodal involvement, and peritoneal infiltration. The potential benefits of a selective approach using MRI-based selection criteria are evident. That is, over 50% of patients can be treated successfully with primary surgery alone without significant risk of local recurrence or systemic failure. Of the remainder, potentially dramatic improvements may be achieved through the use of intensive and targeted preoperative therapy aimed not only at reducing the size of the primary tumour and rendering potentially irresectable tumour resectable with tumour-free circumferential margins, but also at enabling patients at high risk of systemic failure to benefit from intensive combined modality therapy aimed at eliminating micrometastatic disease.

Endosonography↗
PubMed2005

What else has to happen for nitric oxide to induce cell death?

Nitric oxide (NO) can induce cell death; however, NO-induced cell death may be dependent/conditional on factors other than NO itself. Whether NO kills a particular cell depends on the amount of NO, source of NO, time of exposure to NO, cell type and the levels of other factors including, particularly oxygen, superoxide, H2O2, antioxidants, thiols and glycolysis.

Animals↗