Biomedical subjects

Denis Tack

Publications and source records attributed to Denis Tack.

7 recordsLinked to original sources

PubMed2005

Suspected acute colon diverticulitis: imaging with low-dose unenhanced multi-detector row CT.

PURPOSE: To prospectively compare the sensitivity and specificity of unenhanced low-dose multi-detector row computed tomography (CT) with those of contrast material-enhanced standard-dose multi-detector row CT in patients suspected of having acute diverticulitis. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. One hundred ten consecutive patients (40 men, 70 women; age range, 30-82 years; mean, 57 years) suspected of having acute diverticulitis underwent unenhanced multi-detector row CT with 4 x 2.5-mm collimation, 120 kVp, and 30 effective mAs, as well as contrast-enhanced standard-dose multi-detector row CT with the same parameters but with 120 mAs. All scans were independently read by four readers. Intra- and interobserver agreements were calculated with the kappa statistic. Contrast-enhanced standard-dose scans read by three other experts and considered together with results from colonoscopy, surgery, and pathologic evaluation were used as reference. Differences in sensitivity and specificity between readers, radiation doses, and reading sessions were investigated. Pearson exact test and logistic regression models were used. RESULTS: Colon diverticulitis was present in 39 patients (34%) and was graded as mild in 22 patients (56%) and severe in 17 (44%). Agreement within and between readers was good to excellent. No significant difference was observed in sensitivity (P ranging from .081 to >.99) or in specificity (P ranging from .326 to >.99) for any sign or overall diagnosis between radiation doses by all readers, except wall thickening, which for one reader had a higher specificity at low dose than at standard dose (P = .025). No significant difference in misclassification was detected between doses, regardless of the reader (P ranging from .481 to >.99). At both doses, the most predictive sign for acute diverticulitis was retroperitoneal fat stranding (P < .001). CONCLUSION: Low-dose unenhanced multi-detector row CT has a diagnostic performance similar to that of contrast-enhanced standard-dose multi-detector row CT in patients suspected of having acute diverticulitis.

Acute Disease↗

PubMed2005

Multi-detector row CT pulmonary angiography: comparison of standard-dose and simulated low-dose techniques.

PURPOSE: To compare standard-dose and simulated low-dose multi-detector row computed tomography (CT) pulmonary angiography. MATERIALS AND METHODS: The institutional review board approved the study protocol and waived patient informed consent because the study was based on existing data. Raw data from 21 CT scans obtained at 90 mAs (effective) in 11 women and 10 men aged 25-74 years (mean, 52 years) that showed at least one filling defect within a pulmonary artery were used to simulate CT pulmonary angiography with reduced radiation doses, at 60, 40, 20, and 10 mAs. Three independent readers coded each central and segmental pulmonary artery twice as positive, negative, or inconclusive for presence of a filling defect. The second reading of images obtained with 90 mAs was considered the reference standard. The potential dependence of results on reader, radiation dose, and/or pulmonary artery segment was investigated with analysis of variance. Positive and negative consistent values were calculated for standard-dose scans and simulated low-dose scans in the first reading session. The branching order of the artery with the most distal filling defect was recorded. The quality of intravascular contrast at each tube current-time product setting was scored on a five-point scale. Interreader agreement was investigated with kappa statistics. RESULTS: The frequencies of positive and inconclusive results (P = .21 and .08, respectively), positive and negative consistent values (P = .19 and .34, respectively), and branching order of the most distal artery with a filling defect (P = .41) did not depend on the radiation dose. Values for inter- and intrareader agreement were higher for central arterial segments than for branch arteries but were not influenced by dose reduction, regardless of arterial segment. The quality of intravascular contrast was not significantly changed when the tube current-time product was reduced from 90 to 40 mAs (P = .10 to >.99). CONCLUSION: The evaluated parameters remained stable when tube current-time product was reduced from 90 (effective) to 10 (simulated) mAs at multi-detector row CT pulmonary angiography.

Adult↗

PubMed2005

Paracardiac opacity following inferior- and middle-lobe resection for bronchogenic carcinoma: unsuspected diagnosis.

We report the case of a patient who had benefited initially from a right middle and lower lobectomy for bronchogenic carcinoma and who had an extensive radiologic workup in an outside hospital in the early postoperative period. Based on CT scan findings, this patient was referred back with a diagnosis that conveys both medical and medicolegal issues: a gossypiboma (or retained surgical sponge). We describe herein the unexpected operative findings that highlight the difficulty in accurately diagnosing intrathoracic foreign bodies.

Aged↗

PubMed2004

Acute appendicitis: comparison of low-dose and standard-dose unenhanced multi-detector row CT.

PURPOSE: To prospectively compare low- and standard-dose unenhanced multi-detector row computed tomography (CT) in patients suspected of having acute appendicitis. MATERIALS AND METHODS: Ninety-five consecutive patients underwent two unenhanced multi-detector row CT examinations with 4 x 2.5-mm collimation, 120 kVp, and 30 and 100 effective mAs. Two radiologists independently read the images obtained at each dose during two sessions. Readers recorded visualization of the appendix and presence of gas in its lumen, appendicolith, periappendiceal fat stranding, cecal wall thickening, and abscess or phlegmon to measure the diameter of the appendix and to propose diagnosis (appendicitis or alternative). Data were compared according to dose and reader, with definite diagnosis established on basis of surgical findings (n = 37) or clinical follow-up. chi(2) tests and logistic regression were used. Measurement agreements were assessed with Cohen kappa statistics. RESULTS: Twenty-nine patients had a definite diagnosis of appendicitis. No difference was observed between the frequency of visualization of the appendix (P =.874) neither in its mean diameter (P =.101-.696, according to readers and sessions) nor in the readers' overall diagnosis (P =.788) at each dose. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of each sign were not different between doses. Fat stranding, appendicolith, and diameter were the most predictive signs, regardless of dose, yielding approximately 90% of correct diagnoses. The ability to propose a correct alternative diagnosis was not influenced by the dose. CONCLUSION: Low-dose unenhanced multi-detector row CT has similar diagnostic performance as standard-dose unenhanced multi-detector row CT for the diagnosis of acute appendicitis.

Acute Disease↗

PubMed2003

Low-dose unenhanced multidetector CT of patients with suspected renal colic.

OBJECTIVE: This study is designed to assess the intraobserver and interobserver agreements and the diagnostic performances of low-dose unenhanced multidetector CT (MDCT) in patients with suspected renal colic. SUBJECTS AND METHODS: The study included 106 patients who underwent unenhanced MDCT with 4 x 2.5 mm collimation, 120 kVp, 30 mAs, and, if necessary, additional focused acquisitions at 60 or 120 mAs on areas with an equivocal ureteral stone or with significant image noise. The effective radiation dose was computer-simulated with software based on the Monte Carlo model and International Commission on Radiological Protection recommendations. CT scans were archived and independently reviewed by three radiologists during two interpretation sessions on a workstation with three dimensions functions. Intraobserver and interobserver agreements were calculated with the kappa statistics. Accuracy for detection of ureteral stone on low-dose MDCT was calculated by comparison with combined clinical (stone passage), surgical (stone retrieval, extracorporeal shock wave lithotripsy), biologic (urinalysis, urine culture), and other imaging (excretory urography, standard-dose MDCT, follow-up sonography, and abdominal radiography) findings or by evidence for an alternative diagnosis. RESULTS: Ureteral stones were present in 38 (36%) of 106 patients. Thirty-six of 38 ureteral stones were detected by low-dose MDCT. From reviewer to reviewer, the number of true-positive, false-positive, true-negative, and false-negative findings ranged, respectively, from 34 to 36, 1 to 4, 64 to 68, and 2 to 4. The corresponding sensitivity, specificity, and accuracy ranged from 89.5% to 94.7%, from 94.1% to 100%, and from 93.4% to 98.1%, respectively. The intraobserver and interobserver agreements were excellent, with kappa values ranging from 0.87 to 0.98. In 13 patients, an alternative diagnosis explaining the patient's symptoms was proposed by all reviewers using images obtained at 30 mAs. No additional or alternative diagnosis was found at standard dose. At 30 mAs, the mean effective dose was 1.2 mSv in men and 1.9 mSv in women. Additional acquisitions at 60 mAs, all focused on the lower pelvis, were acquired in 20 patients, but the corresponding images were needed by the reviewers for only six of them. The acquisitions at 60 mAs were responsible for an additional mean effective dose of 0.5 in men and 0.8 mSv in women. CONCLUSION: Our study shows that low-dose unenhanced MDCT is appropriate for the diagnosis of ureteral stones, and that it provides excellent intraobserver and interobserver agreements and does not obscure alternative diagnoses.

Adolescent↗

PubMed2003

Dose reduction in multidetector CT using attenuation-based online tube current modulation.

OBJECTIVE: This study was designed to quantify the radiation dose saved by attenuation-based online tube current modulation applied to multidetector CT (MDCT) of the adult trunk as a function of effective milliampere-second (mAs) presets, sex, and body habitus. SUBJECTS AND METHODS. One hundred twenty patients underwent MDCT of the trunk (60 thoracic, 60 abdominal) with an attenuation-based online tube current modulation. Consecutive acquisitions at standard and two lower effective mAs presets were obtained in each patient. Mean percentage effective mAs reductions were compared for each effective mAs preset, taking into account sex and body mass index. RESULTS: Mean effective mAs reduction was 16.9% and 20.0% for the chest and the abdomen, respectively. Mean percentage effective mAs reductions were found to be significantly different for sex (chest, p = 0.003; abdomen, p = 0.002) but not significantly different for the different effective mAs presets or body mass index. CONCLUSION: Attenuation-based online tube current modulation used with MDCT should be considered as a secondary tool of radiation dose reduction because it saves as much as 20% of the radiation dose on the adult trunk, regardless of initial mAs preset. However, initial decreases of mAs presets by the physician should be considered the primary tool for radiation dose reduction.

Adult↗

PubMed2003

Comparison between low-dose and standard-dose multidetector CT in patients with suspected chronic sinusitis.

OBJECTIVE: This study was designed to compare low- and standard-dose multidetector CT (MDCT) findings in patients with suspected chronic sinusitis. SUBJECTS AND METHODS. Fifty patients underwent MDCT at 10 and 150 effective mAs. The low-dose MDCT protocol delivered a radiation dose of 0.047 mSv in men and 0.051 mSv in women, whereas the standard-dose MDCT protocol delivered a radiation dose of 0.70 mSv in men and 0.76 mSv in women. Scans of the right and left sides of sinonasal cavities were reviewed by three radiologists, with each physician reviewing a scan twice over an interval of more than 2 weeks. The reviewers were asked to evaluate the scans for eight mucosal and two bone abnormalities. We calculated the number of discrepancies in observed abnormalities between pairs of reviewers, among all three reviewers, and between findings on scans acquired with the two radiation doses. RESULTS: The mean number of discrepancies in observed abnormalities on scans acquired with different radiation doses ranged from 0 to 5.2. Discrepancies between pairs of reviewers ranged from 1.0 to 12.8 for low-dose scans and from 1.0 to 13.0 for standard-dose scans. Discrepancies among all reviewers ranged from 1.0 to 10.3 for low-dose scans and from 1.0 to 8.7 for standard-dose scans. In analyzing cases of significant discrepancies in observations, we found greater variation between pairs of reviewers and among all three reviewers than between findings obtained with different dose levels. CONCLUSION: Dose reduction played a far less important role in discrepancies of detected abnormalities than did the human element of reviewer observation. Given this finding and the fact that low-dose MDCT delivers a radiation dose that is no higher than that delivered by a four-view radiographic examination, low-dose MDCT should be considered the imaging method of choice in patients with suspected chronic sinusitis.

Adolescent↗