Biomedical subjects

Richard H Cohan

Publications and source records attributed to Richard H Cohan.

7 recordsLinked to original sources

PubMed2003

Helical computed tomography for identification of crossing vessels in ureteropelvic junction obstruction-comparison with operative findings.

OBJECTIVES: To evaluate the use of contrast-enhanced helical computed tomography (HCT) scanning with three-dimensional reconstructions as a possible identifier of crossing vessels in ureteropelvic junction (UPJ) obstruction. Endoscopic treatment of UPJ obstruction has a success rate that approaches 90%. These results drop to 40% in the presence of crossing vessels. Unrecognized crossing vessels can also result in significant hemorrhage during endopyelotomy. The presence of crossing vessels is, for many, an indication for open or laparoscopic UPJ repair. Therefore, accurate preoperative imaging is crucial for appropriate treatment planning. METHODS: Our study population consisted of 18 patients evaluated and treated for UPJ obstruction at the University of Michigan Health System. These patients underwent routine contrast-enhanced preoperative HCT scanning before UPJ repair. A prior history of failed endoscopic treatment, patient preference, and HCT findings of crossing vessels were indications for open or laparoscopic repair. The imaging findings were compared with open findings during laparoscopic or open pyeloplasty. RESULTS: An HCT finding of the presence of crossing vessels was a significant positive predictor, with a value of 100%. The sensitivity in this population was 91% and the specificity was 100%. No difference was noted between the detection of arterial or venous crossing vessels. The positive predictive value was 100%, and the negative predictive value was 88%. CONCLUSIONS: HCT is an accurate predictor of the presence of crossing vessels in UPJ obstruction. Because crossing vessels may have a profound impact on treatment outcome, HCT can serve as an effective, noninvasive, preoperative screening tool.

Adult↗

PubMed2003

Multidetector CT of the liver and hepatic neoplasms: effect of multiphasic imaging on tumor conspicuity and vascular enhancement.

OBJECTIVE: Our aim was to determine which of three contrast-enhanced phases (early arterial, late arterial, or portal venous) was optimal for achieving maximal enhancement of the celiac artery, portal vein, and hepatic parenchyma. We also wanted to learn which phase provided the maximal tumor-to-parenchyma difference when using multidetector CT (MDCT) with fixed timing delays. MATERIALS AND METHODS: Fifty-two patients with suspected or known hepatic tumors underwent multiphasic contrast-enhanced MDCT using double arterial (early and late arterial) and venous phase acquisitions with fixed timing delays. All patients were administered 150 mL of IV contrast material at an injection rate of 4 mL/sec. Images were acquired at 20 sec for the early arterial phase, 35 sec for the late arterial phase, and 60 sec for the portal venous phase. Attenuation measurements of the celiac artery, portal vein, normal hepatic parenchyma, and the hepatic tumor were compared. Three reviewers independently and subjectively rated tumor conspicuity for each of the three phases. Ratings were compared using kappa statistics. RESULTS: Late arterial phase images showed maximal celiac axis attenuation, whereas portal venous phase images revealed the highest portal vein and normal hepatic parenchymal attenuation. Maximal tumor-to-parenchyma differences for hypovascular tumors was superior in the portal venous phase, but we found no significant differences in maximal tumor-to-parenchyma differences for hypervascular tumors among the evaluated phases. On subjective analysis, interobserver agreement was moderate to very good for the three phases. All three reviewers graded both hypovascular and hypervascular tumor conspicuity as superior in either the late arterial phase or the portal venous phase in most patients. In only one patient was the early arterial phase graded as superior to the late arterial and portal venous phases (by two of the three reviewers). CONCLUSION: When MDCT of the liver is performed using fixed timing delays, maximal vascular and hepatic parenchymal enhancement is achieved on either late arterial phase or portal venous phase imaging. In most patients, early arterial phase imaging does not improve tumor conspicuity by either quantitative or subjective analysis.

Adult↗

PubMed2002

Is past academic productivity predictive of radiology resident academic productivity?

RATIONALE AND OBJECTIVES: The authors performed this study to determine whether academic productivity in college and medical school is predictive of the number of publications produced during radiology residency. MATERIALS AND METHODS: The authors reviewed the records of 73 radiology residents who completed their residency from 1990 to 2000. Academic productivity during college, medical school, and radiology residency, other postgraduate degrees, and past careers other than radiology were tabulated. The personal essay attached to the residency application was reviewed for any stated academic interest. Residents were classified as being either previously productive or previously unproductive. Publication rates during residency and immediately after residency were compared for the two groups. For the productive residents, a correlation analysis was used to examine the relationship between past frequency of publication and type of previous activity. Least-squares regression analysis was used to investigate the relationship between preresidency academic productivity, advanced degrees, stated interest in academics, and other careers and radiology residency publications. RESULTS: There was no statistically significant difference in the number of articles published by those residents who were active and those who were not active before residency (P = .21). Only authorship of papers as an undergraduate was weakly predictive of residency publication. CONCLUSION: These selected measures of academic productivity as an undergraduate and during medical school are not helpful for predicting publication during residency. There was no difference in publication potential between those residents who were academically productive in the past and those who were not.

Achievement↗

PubMed2002

Does medical school performance predict radiology resident performance?

RATIONALE AND OBJECTIVES: The authors performed this study to examine the relationship, if any, of a large number of measures of medical school performance with radiology residency performance. MATERIALS AND METHODS: Applications of 77 radiology residents enrolled from 1991 to 2000 were reviewed. Medical school grades, dean's letter summary statements, letters of recommendation, selection to Alpha Omega Alpha (AOA), and National Board of Medical Examiners (NBME) and U.S. Medical Licensing Examination (USMLE) Step 1 scores were recorded. Student t tests, analysis of variance, and correlation coefficients were used to examine the relationship between these measures of medical school performance and subsequent performance during radiology residency as determined by rotation evaluations, retrospective faculty recall scores, and American College of Radiology (ACR) and American Board of Radiology (ABR) examination scores. Resident performance was also correlated with prestige of the medical school attended. RESULTS: Preclinical grades of Honors or A; clinical grades of Honors or A in medicine, surgery, and pediatrics; and high NBME/USMLE scores strongly predicted success on the ABR written clinical examination but did not predict rotation performance. Most other measures of medical school performance, including outstanding Dean's letters and letters of recommendation, AOA selection during the senior year, and high medical school prestige did not predict high examination scores or superior rotation performance during residency. CONCLUSION: Success on the ABR examination can be predicted by medical school success in preclinical courses, some clinical courses, and USMLE examination scores. Dean's letters, letters of recommendation, AOA selection during the senior year, and medical school prestige do not appear to predict future resident performance as reliably.

Educational Measurement↗

PubMed2002

Detection and characterization of renal masses and staging of renal cancers: new considerations in the era of helical computed tomography.

With the introduction of helical CT and its ability to acquire images very rapidly, new problems are being encountered, which can profoundly affect the quality of CT examinations performed for evaluation of known or suspected renal masses. In this article, these problems are summarized and recommendations made for CT techniques that will maximize sensitivity and specificity in renal mass detection, accuracy in renal mass characterization, and accuracy in staging of renal cancer.

Contrast Media↗

PubMed2002

Urinary tract abnormalities: initial experience with multi-detector row CT urography.

PURPOSE: To evaluate multi-detector row computed tomographic (CT) urography for detection of urinary tract abnormalities. MATERIALS AND METHODS: Sixty-five patients referred from the urology service, in whom urinary tract abnormalities were strongly suspected, underwent multi-detector row CT urography. The technique included unenhanced, nephrographic, compression, and excretory-phase images through the abdomen and pelvis. Transverse images and three-dimensional reformations were reviewed by one of two radiologists. Findings were retrospectively compared with results of urinalysis, cystoscopy and/or ureteroscopy, and/or surgery. RESULTS: Multi-detector row CT urography depicted many clinically diagnosed urinary tract abnormalities, including 15 of 16 uroepithelial malignancies, five congenital anomalies, five urinary tract calculi, and 18 calyceal and/or papillary, 30 renal pelvic and/or ureteral, and 25 bladder abnormalities. All abnormalities were detected on transverse images. These abnormalities included diffuse urothelial wall thickening in four patients (three of whom had transitional cell carcinoma), a renal abscess, a colovesical fistula, and incidentally detected extrarenal disease (a liver mass, hepatic metastases, lymph node metastases, an aortic dissection, and a pheochromocytoma; each of these findings was seen in one patient). CONCLUSION: Multi-detector row CT urography is a useful method for detecting urinary tract abnormalities.

Adult↗

PubMed2002

Adrenal masses: characterization with combined unenhanced and delayed enhanced CT.

PURPOSE: To assess the accuracy of a dedicated adrenal computed tomographic (CT) protocol. MATERIALS AND METHODS: One hundred sixty-six adrenal masses were evaluated with a protocol consisting of unenhanced CT, and, for those with attenuation values greater than 10 HU, contrast material-enhanced and delayed enhanced CT. Attenuation values and enhancement washout calculations were obtained. An adenoma was diagnosed if a mass had an attenuation value of 10 HU or less at unenhanced CT or a percentage enhancement washout value of 60% or higher. RESULTS: The final diagnosis was adenoma in 127 masses and non-adenoma in 39. Masses measuring more than 10 HU on unenhanced CT scans were confirmed at biopsy (n = 28) or were examined for stability or change in size at follow-up CT performed at a minimum interval of 6 months (n = 33). Thirty-six (92%) of 39 non-adenomas and 124 (98%) of 127 adenomas were correctly characterized. The sensitivity and specificity of this protocol were 98% and 92%, respectively. This protocol correctly characterized 160 (96%) of 166 masses. CONCLUSION: With a combination of unenhanced and delayed enhanced CT, nearly all adrenal masses can be correctly categorized as adenomas or non-adenomas.

Adenoma↗