Faculty Bibliography

PURPOSE: The purpose of this work was to determine the costs of computed tomography (CT) procedures in a large academic radiology department, including both professional (PC) and technical (TC) components, by analyzing actual resource consumption using an activity-based costing (ABC) method and comparing them with Medicare payments. METHOD: Over a 12 month period from July 1, 1996, to June 30, 1997, 1,011 CT procedures, representing 16 Physicians' Current Procedural Terminology (CPT) codes and 98.3% of CT studies performed, were carefully observed by a research assistant trained in ABC methodology. Information collected during these time and motion studies included personnel/machine time and direct materials used. Actual resource units used during the different activities in each CT procedure were valued using appropriate cost drivers. Unit values for both direct and overhead costs were calculated: the cost of an individual procedure equaled the sum of component costs. Costs were compared with PC and TC payments according to the 1997 Medicare Fee Schedule. RESULTS: Total costs of CPT codes 70450 (CT Head unenhanced), 71260 (CT Chest enhanced), and 74160 (CT Abdomen enhanced), which represented 71.2% of CT studies performed, were $189.19, $273.53, and $343.20, respectively. For all 16 nonmodified CPT codes analyzed, Medicare's professional reimbursement was less than the professional cost, whereas its technical reimbursement exceeded respective cost in 14 of the 16 codes. CONCLUSION: In the setting and time period studied, Medicare underreimbursed professional costs while overreimbursing technical costs

Acute appendicitis is a common clinical problem. Accurate and prompt diagnosis is essential to minimize morbidity. While the clinical diagnosis may be straightforward in patients who present with classic signs and symptoms, atypical presentations may result in diagnostic confusion and delay in treatment. Helical computed tomography (CT) and graded compression color Doppler ultrasonography (US) are highly accurate means of establishing the diagnosis. These imaging modalities have now assumed critical roles in the treatment of patients suspected to have appendicitis. The purpose of this article is threefold: to provide an update on new information regarding the pathophysiology, clinical diagnosis, and laparoscopic treatment of acute appendicitis; to describe the state-of-the art use of CT and US in diagnosing this disease entity; and to address the role of medical imaging in this patient population

Colonic ischemia isolated to the cecum is a rare entity. The authors evaluated two patients who underwent computed tomography (CT) because appendicitis was suspected at clinical examination. CT findings were suggestive of isolated cecal ischemia or infarction. Surgical-histopathologic findings helped confirm the presumptive CT diagnoses. Isolated cecal infarction should be included in the differential diagnosis of acute right lower quadrant pain

PURPOSE: To determine if simple renal cysts may be accurately characterized with helical computed tomography (CT) during peak levels of renal enhancement. MATERIALS AND METHODS: Water-filled 'cysts' were suspended in varying concentrations of iodine solution, meant to simulate varying levels of renal enhancement, within an abdominal phantom. Volume-averaging effects were minimized by scanning cylindric 5-30-mm cysts with a helical technique (collimation, 5 mm; pitch, 1:1). Axial and helical techniques were then compared, and volume-averaging effects were evaluated by scanning 10- and 20-mm round cysts with 3-, 5-, and 7-mm collimation at background attenuation levels of 100 and 200 HU. RESULTS: Cylindric cyst attenuation increased consistently with increasing background attenuation. As background attenuation increased by 90 HU, attenuation increased by 11-17 HU in small (5- or 10-mm) cysts, and by 7-9 HU in large (15-30-mm) cysts. As background attenuation increased by 180 HU, attenuation increased by 18-28 HU in small cysts and by 10-15 HU in large cysts. Spherical cyst attenuation differences were maximized when smaller cysts were imaged with larger collimation, which is when volume-averaging effects became apparent. Axial and helical CT numbers did not differ substantially. Computer simulation studies showed that the observed effect could not be explained by beam hardening alone. CONCLUSION: Pseudoenhancement of renal cysts may occur if helical CT is performed during peak renal enhancement. CT algorithm modification may be necessary to correct for this effect, which is likely related to an inadequate algorithmic correction for beam hardening

PURPOSE: To assess the ability of an extravasation detection accessory (EDA) to detect clinically important (> or = 10 mL) extravascular injection of iodinated contrast material delivered with an automated power injector. MATERIALS AND METHODS: Five hundred patients referred for contrast material-enhanced body computed tomography (CT) participated in a prospective, multi-institutional, observational study in which the EDA was used to identify and interrupt any injection associated with clinically important extravasation. The presence or absence of extravasation was definitively established with helical CT at the injection site (injection rate, from 1.0 to 5.0 mL/sec; mean, 2.9 mL/sec; median, 3.0 mL/sec). RESULTS: There were four true-positive (extravasation volumes, 13-18 mL), 484 true-negative, 12 false-positive, and no false-negative cases. The prevalence of overall and clinically important (> or = 10 mL) extravasation was 3.6% (18 of 500 cases) and 0.8% (four of 500 cases), respectively. The EDA had a sensitivity of 100% (four of four cases; 95% CI: 51%, 100%) and a specificity of 98% (484 of 496 cases; 95% CI: 96%, 99%) in the detection of clinically important extravasation. CONCLUSION: The EDA is easy to use, safe, and accurate in the monitoring of intravenous injections for extravasation, which could prove especially useful in high-flow-rate CT applications

We report a patient found to have a hypertrophied antral-pyloric fold on barium study, in whom CT demonstrated a smooth soft tissue mass on the anterior wall of the pre-pyloric antrum. When this finding is encountered on CT, a double-contrast upper GI study should be performed as the next diagnostic test. Endoscopy can probably be avoided if the barium study shows the typical findings of a hypertrophied antral-pyloric fold

PURPOSE: To evaluate a bolus-tracking technique in helical computed tomography (CT) for identifying the onset of the nephrographic phase and to determine the effect of varying the volume and injection rate of contrast material on nephrographic phase onset. MATERIALS AND METHODS: Seventy-five patients underwent bolus tracking of contrast material followed by helical renal CT. In 50 patients, 150 mL of 60% iodinated contrast material (iohexol or iothalamate meglumine) was injected at either 2 mL/sec (25 patients [group 1]) or 3 mL/sec (25 patients [group 2]). In 25 patients who had previously undergone nephrectomy, 100 mL of 60% iodinated contrast material was injected at 3 mL/sec (group 3). Nephrographic phase onset was determined by visually assessing the transition to a homogeneous nephrogram during a monitoring scan series starting 40 seconds after injection. RESULTS: Nephrographic phase onset ranged from 60 to 136 seconds (mean, 89 seconds +/- 17 [+/- SD]). Statistically significant differences in mean onset times were observed among groups 1 (103 seconds +/- 12), 2 (91 seconds +/- 16), and 3 (75 seconds +/- 9) (P < .001). Multiple regression analysis showed patient age, contrast material volume, and injection rate to be independent predictors of nephrographic phase onset. Contrast material volume, patient age, and patient weight were independent predictors of the degree of renal enhancement. CONCLUSION: Nephrographic phase onset is highly dependent on methods of contrast material administration and patient characteristics

To detect extravasation of contrast media during mechanical power injection at dynamic computed tomography, a 5 x 8-cm pliable adhesive patch was applied to the skin over the intravenous cannula and connected to the power injector with a cable to monitor electrical skin impedance. If the rate of change or the slope of impedance over time indicated an extravasation event, the power injector was set into a pause mode. In animal and human studies, monitoring with the device was successful. Extravasation of ionic contrast agents decreased impedance and that of nonionic agents increased impedance