Biomedical subjects

Andrew Slater

Publications and source records attributed to Andrew Slater.

10 recordsLinked to original sources

PubMed2006

CT colonography: automated measurement of colonic polyps compared with manual techniques--human in vitro study.

PURPOSE: To prospectively investigate the relative accuracy and reproducibility of manual and automated computer software measurements by using polyps of known size in a human colectomy specimen. MATERIALS AND METHODS: Institutional review board approval was obtained for the study; written consent for use of the surgical specimen was obtained. A colectomy specimen containing 27 polyps from a 16-year-old male patient with familial adenomatous polyposis was insufflated, submerged in a container with solution, and scanned at four-section multi-detector row computed tomography (CT). A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were produced to aid CT-histologic measurement correlation. A novice (radiographic technician) and an experienced (radiologist) observer independently estimated polyp diameter with three methods: manual two-dimensional (2D) and manual three-dimensional (3D) measurement with software calipers and automated measurement with software (automatic). Data were analyzed with paired t tests and Bland-Altman limits of agreement. RESULTS: Seven polyps (<or=6-mm diameter) could not be extracted by using the software; 20 polyps (5-15-mm diameter) remained for analysis. Automated measurement was not significantly different from histologic size for the experienced reader (mean difference, 0.63 mm; P=.06) or novice reader (mean difference, 0.58 mm; P=.12). With manual 2D measurement and manual 3D measurement, the experienced reader (1.21-mm mean difference, P<.001, and 0.68-mm mean difference, P=.03, respectively) and novice reader (1.54-mm mean difference, P<.001, and 0.84-mm mean difference, P=.002, respectively) significantly underestimated polyp size. Interobserver agreement was good and similar for all three methods (95% limits of agreement span, approximately 2.5 mm). Intraobserver agreement was related to reader experience, with differences of up to 2.5 mm within expected limits of agreement. CONCLUSION: For polyps smaller than 1 cm, measurement differences of up to 2.5 mm are within the expected limits of inter- and intraobserver agreement for all measurement techniques. Automated and manual 3D polyp measurements are more accurate than manual 2D measurements.

Adolescent↗

PubMed2006

Reader error during CT colonography: causes and implications for training.

This study investigated the variability in baseline computed tomography colonography (CTC) performance using untrained readers by documenting sources of error to guide future training requirements. Twenty CTC endoscopically validated data sets containing 32 polyps were consensus read by three unblinded radiologists experienced in CTC, creating a reference standard. Six readers without prior CTC training [four residents and two board-certified subspecialty gastrointestinal (GI) radiologists] read the 20 cases. Readers drew a region of interest (ROI) around every area they considered a potential colonic lesion, even if subsequently dismissed, before creating a final report. Using this final report, reader ROIs were classified as true positive detections, true negatives correctly dismissed, true detections incorrectly dismissed (i.e., classification error), or perceptual errors. Detection of polyps 1-5 mm, 6-9 mm, and > or =10 mm ranged from 7.1% to 28.6%, 16.7% to 41.7%, and 16.7% to 83.3%, respectively. There was no significant difference between polyp detection or false positives for the GI radiologists compared with residents (p=0.67, p=0.4 respectively). Most missed polyps were due to failure of detection rather than characterization (range 82-95%). Untrained reader performance is variable but generally poor. Most missed polyps are due perceptual error rather than characterization, suggesting basic training should focus heavily on lesion detection.

Clinical Competence↗

PubMed2006

Potentially serious adverse events at CT colonography in symptomatic patients: national survey of the United Kingdom.

PURPOSE: To retrospectively determine the incidence of potentially serious adverse events associated with computed tomographic (CT) colonography performed in patients with symptoms of colorectal cancer. MATERIALS AND METHODS: Ethical approval and informed consent were waived, since the study was deemed a clinical audit and patients would not be approached. With a national survey in the United Kingdom, all departments offering CT colonography in everyday practice were identified. The lead gastrointestinal radiologist from all responding departments was interviewed, and the frequency of potentially serious adverse events associated with CT colonography performed in patients with symptoms of colorectal cancer, the total number of examinations performed, and technical factors possibly related to perforation were determined. Where a potentially serious adverse event was encountered, it was explored in detail. Responses were collated, and raw frequencies were determined. Fisher exact test was used to determine differences in event rates between groups. RESULTS: At 50 centers, 17 067 CT colonographic examinations (mean number per center, 359; range, 10-3000) were performed. No deaths were reported. Thirteen patients (one [0.08%] of 1313) had had a potentially serious adverse event related to the procedure. There were nine perforations: Four (44%) were asymptomatic and five (56%) were symptomatic, and perforation had an attributable cause, with a symptomatic perforation rate of 0.03% (one in 3413 patients). One patient required laparotomy. An inflated rectal balloon was used to perform 9378 examinations. There was no significant difference between the proportion of perforations associated with rectal balloon inflation (n = 6) and the proportion of those that were not (n = 2) (P = .3). CONCLUSION: Potentially serious adverse events related to CT colonography occurred in 0.08% of symptomatic patients.

Colonography, Computed Tomographic↗

PubMed2006

Polyp detection with CT colonography: primary 3D endoluminal analysis versus primary 2D transverse analysis with computer-assisted reader software.

PURPOSE: To retrospectively compare primary three-dimensional (3D) endoluminal analysis with primary two-dimensional (2D) transverse analysis supplemented by computer-assisted reader (CAR) software for computed tomographic (CT) polyp detection and reader reporting times. MATERIALS AND METHODS: Ethical permission and patient consent were obtained from all donor institutions for use of CT colonography data sets. Twenty CT colonography data sets from 14 men (median age, 61 years; age range, 52-78 years) with 48 endoscopically proved polyps were selected. Polyp coordinates were documented in consensus by three unblinded radiologists to create a reference standard. Two radiologists read the data sets, which were randomized between primary 3D endoluminal views with 2D problem solving and 2D views supplemented by CAR software. Reading times and diagnostic confidence were documented. The CAR software highlighted possible polyps by superimposing circles on the 2D transverse images. Data sets were reread after 1 month by using the opposing analysis method. Detection rates were compared by using the McNemar test. Reporting times and diagnostic confidence were compared by using the paired t test and Mann-Whitney U test, respectively. RESULTS: Mean sensitivity values for polyps measuring 1-5, 6-9, and 10 mm or larger were 14%, 53%, and 83%, respectively, for 2D CAR analysis and 16%, 53%, and 67%, respectively, for primary 3D analysis. Overall sensitivity values were 41% for 2D CAR analysis and 39% for primary 3D analysis (P=.77). Reader 1 detected more polyps than reader 2, particularly when using the 3D fly-through method (P=.002). Mean reading times were significantly longer with the 3D method (P=.001). Mean false-positive findings were 1.5 for 2D analysis and 5.5 for 3D analysis. Reader confidence was not significantly different between analysis methods (P=.42). CONCLUSION: Two-dimensional CAR analysis is quicker and at least matches the sensitivity of primary 3D endoluminal analysis, with fewer false-positive findings.

Aged↗

PubMed2006

CT colonography: effect of colonic distension on polyp measurement accuracy and agreement-in vitro study.

RATIONAL AND OBJECTIVES: To investigate the effect of colonic distension on polyp measurement accuracy and reader agreement. MATERIALS AND METHODS: Institutional review board permission was obtained. A sealed colectomy specimen from a patient with familial adenomatous polyposis was scanned using a four-detector-row computed tomography (CT) after half and full air distension. A histopathologist measured the maximum dimension of all polyps in the opened specimen. Digital photographs and line drawings were used to individually match polyps visible in the CT datasets. Two observers (radiologist, technician) independently estimated the maximum polyp diameter using both two-dimensional (2D) and three-dimensional (3D) surface rendering. Full-distension measurements were repeated 1 week later. Accuracy was analyzed using paired t-test. Observer agreement was assessed using Bland Altman limits of agreement. RESULTS: Twenty-three polyps (4-15 mm) were identified. 2D measurements were significantly smaller than histologic size at both half distension (radiologist first): mean difference [md] -1.1 mm, md -1.7 mm, and full distension md -1.1 mm, md 1.4 mm (all P < .001). 3D measurements were not significantly different from true size other than after half distension for the technician (md -0.7 mm, P = .01). 95% Bland Altman limits for interobserver agreement were narrower after full distension, and better using 2D (half-distension span of agreement approximately 4.7 mm and 6 mm for 2D and 3D, respectively). 2D intraobserver span of agreement between half and full distension was approximately 3.8 mm and 3.2 mm for the radiologist and technician, respectively, compared with 6.2 mm and 5.5 mm using 3D. CONCLUSION: 3D polyp measurement is more accurate than 2D. However, in the presence of suboptimal distension, inter- and intraobserver agreement is superior using 2D.

Adenomatous Polyposis Coli↗

PubMed2006

Colonic polyps: effect of attenuation of tagged fluid and viewing window on conspicuity and measurement--in vitro experiment with porcine colonic specimen.

PURPOSE: To investigate effect of attenuation of tagged fluid and viewing window on polyp conspicuity and measurement with porcine colonic specimen. MATERIALS AND METHODS: Eleven (3-10-mm-diameter) polyps were created in porcine colon and the specimen submerged in saline. Four-detector row CT was performed after gas distension and after filling with six barium sulfate suspensions (attenuation, 100-1000 HU). Two readers independently measured maximal two-dimensional polyp diameter on each data set with the following four viewing windows and window levels and window widths, respectively: colon (-150 HU, 1500 HU), lung (-500 HU, 1500 HU), bone (500 HU, 2500 HU), and abdomen (40 HU, 400 HU). In consensus, polyp conspicuity (compared with air data set) was assigned a grade of 1-4 for each viewing window (grade 1, not seen or barely visible; grade 4, optimally seen). For statistical analysis, conspicuity grades were collapsed to a two-point scale. Data were analyzed with Mann-Whitney, Kruskal-Wallis, and chi2 tests. RESULTS: Accuracy of polyp measurement was independent of viewing window for attenuation of tagged fluid of 100-300 HU but differed significantly for 500-1000 HU (P < .001); that for colonic and bone viewing windows was superior (median size difference, 1.0 mm; interquartile range, 0.5-1.5). Conspicuity differed significantly according to viewing window at all attenuation values (P < .001). For 100-300 HU with abdominal viewing window, 83% (24 of 29) of observations were assigned grade 3 or 4 (best). For 500-1000 HU with bone viewing window, 94% (30 of 32) of observations were assigned grade 3 or 4 (superior). Overall conspicuity was best with bone viewing windows at 700 HU. CONCLUSION: Polyp conspicuity and measurement in tagged data sets were optimized at 700 HU with bone viewing windows. At less than 300 HU, conspicuity improved with abdominal viewing windows.

Animals↗

PubMed2006

COPD can mimic the appearance of pneumothorax on thoracic ultrasound.

PURPOSES: To determine the diagnostic accuracy of ultrasound in the diagnosis of pneumothorax in patients with COPD with particular regard to false-positive diagnoses. MATERIALS AND METHODS: This was a single-center, prospective, blinded study. Nine patients with pneumothorax, 9 patients with cystic fibrosis, 17 patients with COPD, and 6 control subjects were studied. Ultrasound clips were recorded at three positions in both hemithoraces of each patient and then reviewed by two observers blinded to patient status. Each clip was scored for the presence or absence of pneumothorax and the degree of observer confidence. RESULTS: The sensitivity and specificity for a pneumothorax were 100% and 84% for the experienced observer and 78% and 81% for the inexperienced observer, respectively. In the COPD patient group, specificity was 71% for the experienced observer and 65% for the inexperienced observer. There were no false-positive diagnoses in the cystic fibrosis or the control group. CONCLUSION: Patients with COPD commonly show signs on ultrasound mimicking a pneumothorax, but this was not seen in patients with cystic fibrosis. In patients with COPD, ultrasound may be used to exclude the presence of a pneumothorax, but it cannot be used to confidently diagnose pneumothorax without using other imaging modalities.

Adult↗

PubMed2005

Increased sensitivity and confidence of SPECT over planar imaging in dual-phase sestamibi for parathyroid adenoma detection.

UNLABELLED: PURPOSE OF REPORT: To determine the usefulness of SPECT imaging over planar imaging for the detection of parathyroid adenomas using dual-phase Tc-99m sestamibi. MATERIALS AND METHODS: The records of patients referred for dual-phase sestamibi scintigraphy for detection of parathyroid adenomas were reviewed retrospectively. The images were reviewed blindly and planar images were compared with SPECT. The imaging results were compared with the operative results to determine the sensitivity, accuracy of localization, and confidence of the reporting radiologist. RESULTS: The records of 37 patients were reviewed. Sensitivity was 62% for planar imaging and 73% for SPECT. There was one false positive. The side of the adenoma was correctly identified in all other patients. Confidence of detection was higher for SPECT than for planar imaging. CONCLUSION: SPECT imaging increased the sensitivity and confidence of the detection of parathyroid adenomas. The results indicate that SPECT should be used for all preoperative parathyroid localization.

Adenoma↗

PubMed2003

The natural history of cerebellar hemangioblastomas in von Hippel-Lindau disease.

BACKGROUND AND PURPOSE: Cerebellar hemangioblastomas (HBs) are traditionally classified into different morphologic types: cystic and solid. We have observed the progression from solid to cystic and have reviewed the cases seen at the regional von Hippel-Lindau (VHL) clinic to document the frequency of this progression. METHODS: A retrospective review of the notes and images of all patients with VHL disease seen at a regional referral clinic since its inception in 1991. Sporadic HBs were not included in this study. RESULTS: In eight patients, a total of 28 tumors were detected. Fourteen of these had or developed cysts. Of the 14 cystic tumors, eight increased in size over the follow-up period. Of the 14 solid tumors, only one increased in size without cystic change. In four patients, the tumor progressed from a cerebellar nodule to an enlarging cyst with a nodule, with the subsequent development of symptoms requiring surgical excision. CONCLUSION: We have demonstrated that, in VHL, cerebellar HBs begin as nodules, and some subsequently develop enlarging cysts that cause pressure symptoms. In our patient population, tumors that remained solid were asymptomatic and well tolerated in the cerebellum.

Adult↗

PubMedDate not supplied

Staging rectal cancer: MRI compared to MDCT.

PURPOSE: To audit the accuracy with which pre-operative MRI and multi-detector row CT determine the relationship between rectal tumour and the circumferential resection margin (CRM). MATERIALS AND METHODS: The MR and CT scans of 72 patients with rectal adenocarcinoma were retrieved. The relationship between tumour and the mesorectal fascia was determined by two observers, who classified appearances into three categories: no tumour within 5 mm of the mesorectal fascia; tumour within 5 mm of the mesorectal fascia ('threatened' margin); tumour at the mesorectal fascia ('involved' margin). Agreement with post-operative histopathology was assessed by Kappa statistics. RESULTS: There was poor agreement between both MRI and CT, and post-operative histology, both in all 72 patients and in the 42 who had received no pre-operative therapy or short-course radiotherapy only. Both imaging modalities had a tendency to overstage patients whose CRM was uninvolved subsequently. However, the negative predictive value for an uninvolved margin was 81.8% by MRI and 84.6% by CT. There was no patient with an involved margin by histopathology whose imaging had suggested the margin was uninvolved. CONCLUSION: Both pre-operative MRI and multi-detector row CT have high negative predictive values for a subsequently uninvolved resection margin.

Adenocarcinoma↗