Minimal preparation computed tomography instead of barium enema/colonoscopy for suspected colon cancer in frail elderly patients: an outcome analysis study.

AIM: To evaluate the efficacy of minimal preparation computed tomography (MPCT) in diagnosing clinically significant colonic tumours in frail, elderly patients. MATERIALS AND METHODS: A prospective study was performed in a group of consecutively referred, frail, elderly patients with symptoms or signs of anaemia, pain, rectal bleeding or weight loss. The MPCT protocol consisted of 1.5 l Gastrografin 1% diluted with sterile water administered during the 48 h before the procedure with no bowel preparation or administration of intravenous contrast medium. Eight millimetre contiguous scans through the abdomen and pelvis were performed. The scans were double-reported by two gastrointestinal radiologists as showing definite (>90% certain), probable (50-90% certain), possible (<50% certain) neoplasm or normal. Where observers disagreed the more pessimistic of the two reports was accepted. The gold standard was clinical outcome at 1 year with positive end-points defined as (1) histological confirmation of CRC, (2) clinical presentation consistent with CRC without histological confirmation if the patient was too unwell for biopsy/surgery, and (3) death directly attributable to colorectal carcinoma (CRC) with/without post-mortem confirmation. Negative end-points were defined as patients with no clinical, radiological or post-mortem findings of CRC. Patients were followed for 1 year or until one of the above end-points were met. RESULTS: Seventy-two patients were included (mean age 81; range 62-93). One-year follow-up was completed in 94.4% (n=68). Mortality from all causes was 33% (n=24). Five histologically proven tumours were diagnosed with CT and there were two probable false-negatives. Results were analysed twice: assuming all CT lesions test positive and considering "possible" lesions test negative [brackets] (95% confidence intervals): sensitivity 0.88 (0.47-1.0) [0.75 (0.35-0.97)], specificity 0.47 (0.34-0.6) [0.87 (0.75-0.94)], positive predictive value 0.18 [0.43], negative predictive value 0.97 [0.96], positive likelihood ratio result 1.6 [5.63], negative likelihood ratio result 0.27 [0.29], kappa 0.31 [0.43]. Tumour prevalence was 12%. A graph of conditional probabilities was generated and analysed. A variety of unsuspected pathology was also found in this series of patients. CONCLUSIONS: MPCT should be double-reported, at least initially. "Possible" lesions should be ignored. Analysis of the graph of conditional probability applied to a group of frail, elderly patients with a high mortality from all causes (33% in our study) suggests: (1) if MPCT suggests definite or probable carcinoma, regardless of the pre-test probability, the post-test probability is high enough to warrant further action, (2) frail, elderly patients with a low pre-test probability for CRC and a negative MPCT should not have further investigation, (3) frail, elderly patients with a higher pre-test probability of CRC (such as those presenting with rectal bleeding) and a negative MPCT should have either double contrast barium enema (DCBE) or colonoscopy as further investigations or be followed clinically for 3-6 months. MPCT was acceptable to patients and clinicians and may reveal significant extra-colonic pathology.

Automated segmentation of colonic walls for computerized detection of polyps in CT colonography.

PURPOSE: A new method for fully automated segmentation of the colonic walls in volumetric CT data was developed for limitation of the search space in computerized detection of polyps. METHOD: For reliable segmentation, an anatomy-oriented approach was used, in which several anatomical structures are segmented in addition to the colon for utilization of their properties. RESULTS: The segmentation method was validated by use of 14 data sets, consisting of cases positive for colonic polyps. We found that the segmented colonic walls included all of the polyps. A subjective rating of the results was performed based on several criteria for visualization of anatomic detail of the colonic wall and mucosal surface. Except for a few cases in which insufflation of the colon was insufficient, all of the results included >95% of the colonic walls. CONCLUSION: This method for colonic wall segmentation is reliable and the segmentation results are applicable in both visualization of the colon and computer-aided diagnosis in the detection of polyps in CT colonography.

Tumor size on computed tomography scans: is one measurement enough?

BACKGROUND: Bidimensional tumor measurements are used routinely as surrogates for tumor volume. The purpose this study was to determine whether there is any added benefit in bidimensional or tridimensional measurements over a unidimensional measurement. METHODS: Sixty-nine colorectal hepatic metastases on 19 computed tomography scans (1-8 lesions per scan) from 9 patients were analyzed. Five patients contributed 2-4 scans each (mean, 3 scans). The standard volume of these lesions was determined by the "summation of areas" technique. The maximum axial dimension, the product of the greatest axial dimensions, and several volume estimates (based on the volumes of a sphere, an ellipsoid, and a cube) each were correlated with the standard volume. RESULTS: The maximum axial dimension and the product of the greatest axial dimensions correlated equally with tumor volume (correlation coefficient = 0.93). Surrogate measures based on the equations for a sphere and an ellipsoid underestimated tumor volume, whereas the equation for a cube overestimated volume. CONCLUSIONS: When reporting tumor size, there is no significant added benefit in reporting bidimensional or tridimensional measurements over the maximum axial dimension.

Applying 'technology assessment' and 'evidence based medicine' theory to interventional radiology. Part 1: Suggestions for the phased evaluation of new procedures.

AIM: To compare and contrast interventional radiology (IR) clinical and research practices with the technology assessment and evidence-based medicine (EBM) paradigms and make suggestions for the phased evaluation of new IR procedures. MATERIALS AND METHODS: Course literature of the Association of University Radiologists' 'Basic Technology Assessment for Radiologists' course and the McMaster University Health Information Research Unit's 'How to Teach Evidence-Based Medicine 1999' course were used to identify major publications in each discipline. A computer search was performed to seek other relevant literature. A model of traditional development of IR procedures was developed. Suggestions for the phased evaluation of IR procedures were derived. RESULTS: As in diagnostic radiology, several levels of progressively stronger IR study design can be described and related to EBM 'levels of evidence'. These range from case reports and case series through case-control and cohort studies to randomized controlled trials (RCTs). The major weakness in the existing IR literature is the predominance of small, uncontrolled, case series. Randomized controlled trials are likely to provide the best possible evidence of effectiveness. They are expensive and randomization is sometimes unethical or impractical. Case-control and cohort studies have been under-utilized. Evidence-based medicine indices of benefit and harm have not yet been applied in IR and may have clinical advantages over traditional statistical methods. A literature search (10 years) using MeSH terms 'radiology, interventional' and 'efficacy' yielded 30 papers. Combining 'radiology, interventional' and 'evidence-based medicine' yielded no papers. Comparative searches substituting the term 'diagnostic imaging' for 'radiology, interventional' yielded 4883 and 62 papers, respectively. CONCLUSION: Principles of technology assessment and EBM can be applied to the investigation of new IR procedures. A tool is needed to simplify the application of EBM analytic methods. Better education in research methods is needed to raise the levels of evidence provided by the bulk of IR research and allow new procedures to be introduced into practice appropriately. Malone, D. E. & MacEneaney, P. M. (2000). Clinical Radiology55, 929-937.

Applying 'evidence-based medicine' theory to interventional radiology. Part 2: a spreadsheet for swift assessment of procedural benefit and harm.

AIM: To design a spreadsheet program to analyse interventional radiology (IR) data rapidly produced in local research or reported in the literature using 'evidence-based medicine' (EBM) parameters of treatment benefit and harm. MATERIALS AND METHODS: Microsoft Excel(TM)was used. The spreadsheet consists of three worksheets. The first shows the 'Levels of Evidence and Grades of Recommendations' that can be assigned to therapeutic studies as defined by the Oxford Centre for EBM. The second and third worksheets facilitate the EBM assessment of therapeutic benefit and harm. Validity criteria are described. These include the assessment of the adequacy of sample size in the detection of possible procedural complications. A contingency (2 x 2) table for raw data on comparative outcomes in treated patients and controls has been incorporated. Formulae for EBM calculations are related to these numerators and denominators in the spreadsheet. The parameters calculated are benefit - relative risk reduction, absolute risk reduction, number needed to treat (NNT). Harm - relative risk, relative odds, number needed to harm (NNH). Ninety-five per cent confidence intervals are calculated for all these indices. The results change automatically when the data in the therapeutic outcome cells are changed. A final section allows the user to correct the NNT or NNH in their application to individual patients. RESULTS: This spreadsheet can be used on desktop and palmtop computers. The MS Excel(TM)version can be downloaded via the Internet from the URL ftp://radiography.com/pub/TxHarm00.xls. CONCLUSION: A spreadsheet is useful for the rapid analysis of the clinical benefit and harm from IR procedures.

The role of hepatic arterial Doppler ultrasound after liver transplantation: an 'audit cycle' evaluation.

AIMS: To compare the diagnostic performance of hepatic arterial (HA) Doppler ultrasound post-liver transplantation for hepatic artery thrombosis and stenosis in our unit with the literature. To evaluate the role of the technique in clinical practice. MATERIALS AND METHODS: In a two-phase 'audit cycle' study, adult OLT patients had Doppler studies comprising detection of HA flow and measurements of peak systolic velocity, resistive index and systolic acceleration time. In phase I, patients had Doppler examinations 'routinely' and for any hepatic biochemical abnormality. In phase II, Doppler ultrasound was performed early post-OLT and later only if a senior transplant clinician suspected graft ischaemia. In addition to HA measurements the waveform was visually assessed. Clinical outcome was the 'gold standard'. RESULTS: Phase 1: 38 patients, 40 OLT operations, 125 Doppler studies; 14 arteriograms. Phase 2: 35 patients, 42 OLT operations, two HA angioplasties, one HA revision, one non-occlusive thrombus, 140 studies; 17 arteriograms. Results; Phase 1 [Phase 2]: sensitivity 80% [100%]; specificity 71% [81%]; PPV 28% [56%]; NPV 96% [100%]; incidence of HA abnormality 12.5% [19. 5%]; likelihood ratio of negative result 0.28 [0]; of positive result 2.8 [5.3]. CONCLUSION: Previously reported results are reproducible. Normal HA waveform should also be a criterion of normality. The technique is very sensitive but relatively non-specific. Predictive values improve with discriminate use. MacEneaney, P. M. (2000). Clinical Radiology55, 517-524.

The meaning of diagnostic test results: a spreadsheet for swift data analysis.

AIMS: To design a spreadsheet program to: (a) analyse rapidly diagnostic test result data produced in local research or reported in the literature; (b) correct reported predictive values for disease prevalence in any population; (c) estimate the post-test probability of disease in individual patients. MATERIALS AND METHODS: Microsoft Excel(TM)was used. Section A: a contingency (2 x 2) table was incorporated into the spreadsheet. Formulae for standard calculations [sample size, disease prevalence, sensitivity and specificity with 95% confidence intervals, predictive values and likelihood ratios (LRs)] were linked to this table. The results change automatically when the data in the true or false negative and positive cells are changed. Section B: this estimates predictive values in any population, compensating for altered disease prevalence. Sections C-F: Bayes' theorem was incorporated to generate individual post-test probabilities. The spreadsheet generates 95% confidence intervals, LRs and a table and graph of conditional probabilities once the sensitivity and specificity of the test are entered. The latter shows the expected post-test probability of disease for any pre-test probability when a test of known sensitivity and specificity is positive or negative. RESULTS: This spreadsheet can be used on desktop and palmtop computers. The MS Excel(TM)version can be downloaded via the Internet from the URL ftp://radiography.com/pub/Rad-data99.xls CONCLUSION: A spreadsheet is useful for contingency table data analysis and assessment of the clinical meaning of diagnostic test results.