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Rendon C Nelson

Publications and source records attributed to Rendon C Nelson.

At least 19 recordsLinked to original sources
PubMed2007

Abdominal pain: coronal reformations from isotropic voxels with 16-section CT--reader lesion detection and interpretation time.

PURPOSE: To retrospectively assess if reader detection of intraabdominal pathologic findings on coronal reformations from isotropic voxels at 16-section computed tomography (CT) was similar to reader detection on transverse scans. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant study, and a waiver of informed consent was obtained. Twenty-nine consecutive patients (12 men, 17 women; mean age, 48 years; age range, 21-93 years) with abdominal pain underwent 16-section CT with coronal reformations. Eight independent readers reviewed randomized scans (transverse and coronal) and identified pathologic findings in multiple organ systems. Timing for each interpretation was recorded. One month later, readers reviewed the scan reformatted in the other imaging plane. Agreement between transverse and coronal scans was measured by using Cohen kappa coefficients. RESULTS: Agreement was moderate to near perfect between transverse and coronal interpretations for intraabdominal anatomic and pathologic findings (kappa=0.59-1.00). For transverse interpretations, more thoracic pathologic findings were noted than for coronal interpretations; for coronal interpretations, more lymph nodes were noted than for transverse interpretations. Mean transverse interpretation time was 4.9 minutes+/-1.1 (standard deviation) (range, 2.9-6.5 minutes); mean coronal interpretation time was 5.1 minutes+/-0.8 (range, 3.3-6.7 minutes). For each reader, there was no statistically significant difference in interpretation time between transverse and coronal scans (P=.06). CONCLUSION: With regard to the presence of intraabdominal pathologic findings, coronal reformations from isotropic voxels are similar to transverse scans in terms of interpretation time and reader agreement.

Abdominal Neoplasms↗
PubMed2006

Abdominal magnetic resonance imaging at 3.0 T what is the ultimate gain in signal-to-noise ratio?

RATIONALE AND OBJECTIVES: The purpose of this study was to calculate the gain in signal-to-noise ratio (SNR) of four human abdominal tissues at 3.0 Tesla (T) compared with standard 1.5 T and to validate this calculation in vivo. MATERIALS AND METHODS: The expected gain in SNR at 3.0 T in the liver, pancreas, spleen, and kidney compared with standard 1.5 T was approximated theoretically for a T2-weighted HASTE (half-Fourier acquisition single-shot turbo spin-echo) and a T1-weighted gradient-echo in- and opposed-phase sequence. Fifteen healthy male subjects underwent abdominal MR imaging using a 1.5 T and 3.0 T scanner. Coronal T2-weighted HASTE images and axial T1-weighted gradient-echo in- and opposed-phase images were acquired using the sequence parameters optimized by the vendor. RESULTS: Except for opposed-phased imaging of pancreatic tissue, in vivo adjusted SNR values of all abdominal tissues were significantly higher at 3.0 T for all sequences (P < .05). The highest overall gain in SNR was achieved with the HASTE sequence ranging from 3.8-fold for renal imaging to 7.4-fold for hepatic imaging. The theoretical calculation of SNR gain was in good agreement with the experimentally measured gain in SNR for the HASTE and the in-phase sequence. CONCLUSION: High-field abdominal MR imaging at 3.0 T offers significantly higher SNR compared with standard 1.5 T MR imaging.

Abdomen↗
PubMed2006

Intrahepatic tumor recurrence after partial hepatectomy: value of percutaneous radiofrequency ablation.

PURPOSE: To determine the risks and benefits of percutaneous radiofrequency (RF) ablation of recurrent hepatic tumors in patients who have undergone hepatic resection. MATERIALS AND METHODS: Retrospective review of the institutional RF ablation database yielded 35 patients with recurrent hepatic tumor after hepatectomy. Sixty-one recurrent hepatic tumors (mean diameter +/- SD, 1.7 +/- 1.1 cm; range, 0.5-5.3 cm) were ablated percutaneously under sonographic guidance or combined guidance with sonographic and fluoroscopic computed tomography (CT). Follow-up CT, magnetic resonance imaging, or both were used for assessment of the primary and secondary therapeutic effectiveness rate and failure of RF ablation. Patients' survival status was determined by contacting the primary care physician or searching the Social Security Death Index. RESULTS: Complete ablation was accomplished in 54 of 61 hepatic tumors (primary therapeutic effectiveness rate, 88.5%). During a mean follow-up time of 18 months (range, 1-65 months), 14.8% of the tumors (n = 9) were incompletely ablated. Three of the nine incompletely ablated tumors were treated with a second RF ablation, all three of which failed (secondary therapeutic effectiveness rate, 0%). Distant intrahepatic tumor progression appeared in 23 of 35 patients (65.7%). One major complication (2.1%, one of 48 sessions) and eight minor complications (16.7%, eight of 48 sessions) were reported. The major complication was hepatic abscess formation. The overall survival rates for all patients at 1, 2, and 3 years were 76%, 68%, and 45%, respectively. For patients with metastases from colorectal cancer (n = 14), the overall survival rates were 72%, 60%, and 60% at 1, 2, and 3 years, respectively; and for patients with hepatocellular carcinoma (n = 8), the overall survival rates were 72%, 58%, and 44% at 1, 2, and 3 years, respectively. CONCLUSION: Percutaneous RF ablation offers a safe and effective treatment option for recurrent hepatic tumors after previous partial hepatectomy.

Catheter Ablation↗
PubMed2006

Optimization of multiplanar reformations from isotropic data sets acquired with 16-detector row helical CT scanner.

Institutional review board approval and waiver of consent were obtained for the patient component of this retrospective HIPAA-compliant study. By using an anthropomorphic phantom and metal oxide semiconductor field effect transistor detectors, radiation dose was determined for one eight-detector row and two 16-detector row computed tomographic (CT) protocols. A custom phantom was scanned by using the three protocols to identify isotropy. Contrast-to-noise ratios (CNRs) were determined for the same protocols by using a third phantom. Seven patients had undergone isotropic 16-detector row CT of the abdomen and pelvis. Anonymized coronal reformations at various thicknesses were ranked qualitatively by three radiologists. Effective dose equivalents were similar for the eight- and 16-detector row protocols. When transverse and coronal reformations of data acquired in the custom phantom were compared, coronal reformations obtained with the 16-detector row and 0.625-mm section thickness protocol were found to be nearly identical to the transverse image for all sets of line pairs. CNRs were consistently highest on 5-mm-thick coronal reformations (CNR range, 1.2-3.3). For qualitative assessment, 2- and 3-mm-thick coronal reformations were consistently preferred.

Adult↗
PubMed2006

Pigtail catheters used for percutaneous fluid drainage: comparison of performance characteristics.

PURPOSE: To compare the performance characteristics of various single-lumen all-purpose pigtail drainage catheters. MATERIALS AND METHODS: The following parameters were compared: flow rates between catheters of the same size, whether changing the fluid viscosity has any effect on catheter comparisons, the effect on flow of leaving an open three-way stopcock in the drainage pathway, the tendency of the catheters to kink, and catheter patency after kinking, as measured according to flow. All-purpose 8.0-, 8.3-, and 8.5-F (collectively referred to as 8-F); 10.0-, 10.2-, and 10.3-F (collectively referred to as 10-F); and 12.0-F pigtail drainage catheters from three manufacturers were evaluated. Data were compared by using two-tailed t tests after normal distributions were confirmed. P < .05 was considered to represent a significant difference. RESULTS: At comparison of the 8-F catheters, the C.R. Bard catheters demonstrated better flow rates than the Cook and Boston Scientific devices. Among the 10-F catheters, there were no significant differences in the flow rates of fluid with viscosity equivalent to that of water between the C.R. Bard and Boston Scientific catheters; however, both these catheter types demonstrated significantly (P < .05) better flow rates than the Cook devices. Among the 12-F catheters, the C.R. Bard catheters demonstrated significantly (P < .05) better flow rates than the other two catheter types. Changing the fluid viscosity caused no changes in comparison results. In all catheter groups, the presence of a stopcock significantly (P < .05) impaired flow. None of the evaluated catheters demonstrated a clear advantage in terms of patency or susceptibility to kinking. CONCLUSION: At comparison of the in vitro performances of catheters from different manufacturers, the C.R. Bard 8.0-F and Cook 10.2-F catheters had comparable flow rates, and flow rates through the C.R. Bard and Boston Scientific 10.0-F catheters were comparable to flow rates through the Cook and Boston Scientific 12.0-F catheters. Varying viscosity had no effect on comparisons of catheter flow rates; however, a stopcock between the vacuum source and the catheter was noted to impair flow rates in all brands and sizes of evaluated catheters.

Catheterization↗
PubMed2006

Postprocedure sepsis in imaging-guided percutaneous hepatic abscess drainage: how often does it occur?

OBJECTIVE: This retrospective study was conducted to determine the incidence of sepsis at our institution after percutaneous drainage of a hepatic abscess. MATERIALS AND METHODS: Thirty-three patients with a hepatic abscess treated using percutaneous aspiration and drainage from 1995 to 2000 were identified from a search of the interventional database. The patients' charts and CT images were reviewed independently by two radiologists for clinical presentation, relevant medical history, pre- and postprocedure antibiotic regimens, and clinical course after percutaneous aspiration and drainage. The preprocedure images were reviewed for the location and morphology of the abscess. The procedure details including percutaneous approach, guidance technique, catheter size, and immediate postprocedure complications were reviewed. RESULTS: Of the 33 patients, 14 patients underwent only needle aspiration of the abscess. In six (43%) of these 14 patients, the abscesses resolved with aspiration and appropriate antibiotic treatment alone. Eight (57%) of the patients who had aspiration of the abscess initially went on to have drainage catheters placed within a 72-hr period. Nineteen patients had drainage catheters placed from the onset. Of these, 17 patients (89%) had abscess resolution. Of the 27 patients who had catheters placed, a total of seven patients (26%) developed clinical symptoms of septicemia after catheter placement, but all patients, at least initially, responded to supportive treatment. Two patients died from septicemia 3-6 weeks after the procedure. None of the patients who underwent aspiration only developed postprocedure septicemia. CONCLUSION: After placement of a percutaneous drainage catheter in a hepatic abscess, there is a significant risk (26%) of postprocedure sepsis. Although it appears to be a random and unpredictable event in our small series, interventional radiologists and referring physicians should be aware of the risk of sepsis after percutaneous drainage of hepatic abscess.

Adult↗
PubMed2005

Acute appendicitis: added diagnostic value of coronal reformations from isotropic voxels at multi-detector row CT.

PURPOSE: To assess retrospectively the added value of coronal reformations from isotropic voxels obtained with 16-section multi-detector row computed tomography (CT) of the abdomen and pelvis in patients with suspected acute appendicitis. MATERIALS AND METHODS: This study was approved by the institutional review board, and informed consent was waived. One hundred consecutive patients (21 men, 79 women; mean age, 38 years) with suspected appendicitis underwent 16-section multi-detector row CT (section thickness, 0.625 mm; pitch, 1.75; table speed, 35 mm/sec [17.5 mm per rotation, two rotations]; and gantry speed, 0.5 second per rotation), with coronal reformations. Twenty-four patients had appendicitis; 76 did not. Protocol included 150 mL oral iopamidol administered at 3 mL/sec. Transverse scans were reconstructed with 5-mm-thick sections at 5-mm intervals and 0.625-mm-thick sections at 0.625-mm intervals. The second data set was reformatted coronally, with 3-mm-thick sections at 5-mm intervals. Three independent blinded readers interpreted transverse scans alone and then coronal scans; confidence in visualization of any portion of appendix, entire appendix, wall thickening, distention, inflammation, fluid, and appendicitis was scored with 1-5 scale. Sensitivity and specificity were determined for each reader and compared by means of signed rank test. Agreement between readers was determined with kappa statistic. Differences in mean confidence ratings for each finding were determined with Wilcoxon signed rank test. RESULTS: Mean sensitivity and specificity for all three readers together were 96% and 95% for transverse reformations alone and 95% and 94% for combined transverse and coronal reformations (not significant), respectively. Visualization rates for portion or all of appendix were higher for combined transverse and coronal reformations than for transverse reformations alone (higher mean confidence scores: 0.23 higher [P < .009] and 0.51 higher [P < .001], respectively). In patients without appendicitis, transverse and coronal reformations together enhanced confidence in exclusion of wall thickening, distention, and fluid (lower confidence scores: 0.21 lower [P < .001], 0.17 lower [P < .01], 1.00 lower [P < .001], respectively). Combined transverse and coronal reformations enhanced confidence in identification of appendix in mean of 57 patients. Combined transverse and coronal scans helped exclude appendicitis in mean of 38 patients and aided diagnosis of it in 15. CONCLUSION: Sixteen-section multi-detector row CT transverse and coronal reformations are equally sensitive and specific for diagnosis of appendicitis. Coronal reformations improve confidence in visualization of appendix (whether diseased or normal) and in diagnosis or exclusion of appendicitis.

Acute Disease↗
PubMed2005

Acoustic radiation force impulse imaging of the abdomen: demonstration of feasibility and utility.

The feasibility of utilizing acoustic radiation force impulse (ARFI) imaging to assess the mechanical properties of abdominal tissues was investigated. The thermal safety of the technique was also evaluated through the use of finite element method models. ARFI imaging was shown to be capable of imaging abdominal tissues at clinically realistic depths. Correspondence between anatomical structures in B-mode and ARFI images was observed. ARFI images showed similar tumor contrast when compared with B-mode images of ex vivo abdominal cancers. Finite element method models and in vitro measurements confirmed the thermal safety of ARFI imaging at depth. ARFI imaging is inexpensive, safe and convenient and is a promising modality for use in abdominal imaging.

Abdomen↗
PubMed2005

Complications after percutaneous radiofrequency ablation of renal tumors.

OBJECTIVES: To evaluate our experience with percutaneous radiofrequency ablation (pRFA) to determine common characteristics of patients with complications, to elucidate possible relative contraindications to therapy. METHODS: Medical records of all patients undergoing pRFA were reviewed for demographic data, medical and surgical history, indication, tumor characteristics, and treatment information (complications and management). The group of patients with complications was analyzed for common characteristics. RESULTS: From January 2000 to September 2003, 24 patients (mean age 61 years, 5:1 male/female) with 32 renal tumors were treated with pRFA. Indications for pRFA included prior renal surgery and/or chronic renal insufficiency, significant medical disease, patient choice, von Hippel-Lindau disease, and treatment of a metastasis. Average pretreatment tumor size was 2.4 cm (range 0.5-8.6 cm). Of the 5 patients experiencing complications from pRFA treatment, 2 developed perinephric hematomas, 1 had a persistent urinoma and proximal ureteral stricture, and 2 had colonic injuries. Among patients with complications, 3 of 5 had undergone prior partial nephrectomy on the pRFA-treated kidney. Two of four patients treated for multiple tumors and 57% of patients (4 of 7) with anteriorly located tumors experienced complications. CONCLUSIONS: Early experience with pRFA for renal tumor seems promising, but patient selection criteria are evolving. On the basis of our limited experience, we recommend caution when using renal pRFA in patients with prior partial nephrectomy, multiple tumors treated in the same setting, and tumors located anteriorly or centrally. Further clinical experience will help establish guidelines for the use of this powerful technology in the management of renal tumors.

Aged↗
PubMed2005

Pancreatic FNA in 1000 cases: a comparison of imaging modalities.

BACKGROUND: Image-guided FNA is a popular method for evaluating pancreatic lesions, but few large studies on pancreatic FNA exist. METHODS: Cytologic material, imaging reports, and clinical follow-up information were reviewed from pancreatic FNA cases performed over a 5-year period. RESULTS: A total of 1050 pancreatic FNAs were obtained by EUS (n = 843), US (n = 140), and CT (n = 67). On-site assessment was performed in 89.2% (n = 937) of cases. Findings were as follows: positive for neoplasm 48.9% (n = 503), negative 29.1% (n = 306), descriptive 10% (n = 105), suspicious 5.9% (n = 62), atypical/inconclusive 4.6% (n = 48), and nondiagnostic/inadequate 1.5% (n = 26). Follow-up in the form of histology or at least 6 months of clinical observation was available for 61.2% (n = 643). There was an overall false-positive rate of 0.3% and a false-negative rate of 14.3%. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were as follows: 79.4, 99.0, 99.4, 67.9, 84.5 for the total series, respectively; 79.9, 98.8, 99.2, 72.5, 86.5 for EUS, respectively; 77.9, 100, 100, 48.6, 81.7 for US, respectively; and 78.6, 100, 100, 47.1, 82.0 for CT, respectively. In general, accuracy was not influenced by lesion size or site, number of FNA passes, or number of procedures per patient. After controlling for lesion size, EUS resulted in greater accuracy than US or CT when evaluating lesions <3 cm ( p = 0.015). CONCLUSIONS: All imaging modalities showed moderate to high sensitivity, specificity, and accuracy. Logistic regression analysis showed that for lesions <3 cm, the EUS method had higher accuracy than US or CT. No statistically significant difference was seen for larger lesions or for the number of FNA passes.

Adenocarcinoma↗
PubMed2004

Practice patterns in percutaneous image-guided intraabdominal abscess drainage: survey of academic and private practice centers.

PURPOSE: To evaluate current practice patterns of percutaneous image-guided abdominal and pelvic abscess drainage in academic and private practice centers. MATERIALS AND METHODS: The institutional review board did not require approval for this study. In a survey conducted between November 2002 and February 2003, 493 questionnaires were sent to 193 academic and 300 private practice radiology departments in the United States. All recipients were informed of the study purpose. The survey included questions about departmental demographics, patient selection criteria for percutaneous abscess drainage (eg, abscess diameter at imaging, laboratory parameters such as white blood cell count, and clinical indications such as fever), use of analgesia or conscious sedation, drainage method, and imaging technique. The statistical significance of differences between respondent subgroups was analyzed with a Pearson or Mantel-Haenszel chi(2) test. RESULTS: Academic centers returned 95 questionnaires (49%), and private practice centers, 72 (24%). Percutaneous abscess drainage is performed by a fellowship-trained radiologist at 92 (97%) of 95 academic centers and 41 (79%) of 52 private practice centers (P < .001). Among 95 academic respondents and 52 private practice respondents, respectively, 56 (59%) and 33 (63%) do not perform drainage if an abscess has a diameter of less than 3 cm; 30 (32%) and nine (17%), if the white blood cell count is normal; and 16 (17%) and six (12%), if the patient is afebrile. Most (90 [95%] of 95 academic, 45 [87%] of 52 private practice) respondents use conscious sedation. A transabdominal approach and 8-12-F catheters are most frequently used by both groups. Academic respondents more frequently use transvaginal and transrectal approaches (54 [57%] and 51 [54%] of 95, vs 16 [31%] and 15 [29%] of 52 private practice respondents; P = .003) and 14-F catheters (69 [73%] of 95 vs 18 [35%] of 52; P < .001). CONCLUSION: Percutaneous drainage is usually performed by fellowship-trained radiologists in abscesses of more than 3 cm in diameter, for appropriate clinical indications (multiple parameters above the established threshold), by using conscious sedation and 8-12-F catheters.

Abdominal Abscess↗
PubMed2004

Multidetector helical computed tomography of the liver: comparison of hepatic enhancement using two different contrast media strategies.

RATIONALE AND OBJECTIVES: The purpose of this study was to compare hepatic enhancement characteristics using two different contrast media injection protocols with multidetector helical computed tomography. MATERIALS AND METHODS: Twenty-three patients with known or suspected liver lesions scheduled to undergo biphasic hepatic multidetector helical computed tomography were randomized into one of two groups: (1) 150 mL of iopamidol (300 mgI/mL) at 5 mL/second, or (2) 100 mL of iopamidol (370 mgI/mL) at 4 mL/second. Unenhanced images were acquired initially, followed by both hepatic arterial phase (scan delay, 33 seconds) and portal venous phase (PVP; scan delay, 65 seconds) imaging. Three abdominal radiologists independently graded the images on a scale from 1-5 for enhancement and overall scan quality. Time-attenuation curves were generated from operator-defined region-of-interest measurements of liver parenchyma and aorta. RESULTS: Qualitatively, the three reviewers found no significant difference between the two study groups in terms of overall scan quality (P = .23) or aortic enhancement (hepatic arterial phase, P = .9; PVP, P = .24). However, liver enhancement during the PVP was considered to be less in the Isovue 370 group (P = .04). Quantitatively, during the hepatic arterial phase, there was no statistically significant difference between the two injection protocols comparing either aortic or hepatic parenchymal enhancement (P = .62 and .80, respectively). During the PVP, these differences were statistically significant, with both aortic and hepatic parenchymal enhancement lower in the Isovue 370 group (P < .01 and P = .04, respectively). CONCLUSION: It is important to consider the amount of iodine injected per second and the duration of the injection when setting up protocols to achieve target organ enhancement. 100 mL of iopamidol 370 at 4 mL/second can be used to obtain images of the liver with good diagnostic quality compared to more conventional protocols using 150 mL of iopamidol 300 at 5 mL/second. However, the degree of liver parenchymal enhancement during the PVP using the latter injection scheme is lower, which in turn could potentially reduce hepatic lesion conspicuity.

Adult↗
PubMed2004

Abdominal aortic aneurysms at multi-detector row helical CT: optimization with interactive determination of scanning delay and contrast medium dose.

PURPOSE: To prospectively evaluate a technique for optimizing aortoiliac enhancement at multi-detector row helical computed tomography (CT) with both the scanning delay and contrast medium dose determined by using an interactive method. MATERIALS AND METHODS: Forty-five patients with abdominal aortic aneurysm were randomized to undergo multi-detector row helical CT with either an interactive protocol (n = 23) or a standard protocol (n = 22). Scanning delays in all patients were determined with automated triggering. Patients in the standard protocol group received 150 mL of contrast medium intravenously at 4 mL/sec. The same injection rate was used for the interactive protocol group, but the dose was reduced with discontinuation of injection at start of scanning. Quantities of contrast medium used and contrast-enhanced aortic attenuation achieved were compared. Aortoiliac enhancement was evaluated qualitatively by using a five-point scale (1 = poor, 5 = excellent). Quantitative and qualitative data were analyzed with the two-tailed t test and Wilcoxon rank sum test, respectively, to determine significance of differences (P <.05). RESULTS: Data from six patients were excluded because of technical errors. Data were analyzed from 20 patients in the interactive protocol group and 19 in the standard protocol group. Mean contrast medium volume was 107 mL +/- 20 (standard deviation) in the interactive protocol group and 148 mL +/- 3 in the standard protocol group (P <.001). Mean contrast-enhanced attenuation at initial, peak, and final measurements was 257 HU +/- 38, 285 HU +/- 46, and 269 HU +/- 54, respectively, for the interactive protocol group, and 261 HU +/- 65, 288 HU +/- 66, and 269 HU +/- 61 for the standard protocol group (P >.05). Mean qualitative enhancement scores for interactive and standard protocol groups were 4.47 and 4.44, respectively (P =.47). CONCLUSION: The interactive method is a simple, efficient, and reproducible way to optimize aortoiliac enhancement while reducing contrast medium dose.

Aged↗
PubMed2004

Real-time 3D color flow Doppler for guidance of vibrating interventional devices.

The goal of this investigation was to examine the feasibility of guiding interventional devices using piezoelectric buzzers to create velocity sources, which were imaged and tracked with real-time 3D color flow Doppler. The interventional devices examined in this study included a pacemaker lead, Brockenbrough needle for cardiac septal puncture, cardiac guidewire and radiofrequency ablation needles for cancer therapy. Each was mechanically coupled to a piezoelectric buzzer and was imaged using a commercial real-time 3D ultrasound system with either a 2.5 MHz matrix array transducer or a 5 MHz, 22 F catheter transducer equipped with a tool port. In vitro images acquired in tissue phantoms, excised liver with a 'tumor' target and an excised sheep heart show strong vibration signals in 3D color flow Doppler, enabling real-time tracking and guidance of all the devices in three dimensions. In a sheep model, in vivo tracking of the pacing lead was performed in the superior vena cava as well as the right atrium using RT3D color flow Doppler images. The vibrating rf ablation needles were guided through the liver toward "tumor" targets in vivo with real-time 3D color flow Doppler images.

Animals↗
PubMed2004

Dual-phase 3D MDCT angiography for evaluation of the liver before hepatic resection.

OBJECTIVE: We sought to evaluate the accuracy of dual-phase MDCT angiography for assessing the liver before hepatic resection and to compare 2D and 3D images for quality and arterial branch visualization. MATERIALS AND METHODS: Sixty-three patients with colorectal metastases (n = 30), hepatocellular carcinomas (n = 13), giant hemangiomas (n = 5), and other lesions (n = 15) underwent dual-phase MDCT using either a LightSpeed QX/i 4-MDCT (n = 31) or LightSpeed QX/i Ultra 8-MDCT (n = 32) scanner. Contrast material (150 mL of Isovue 370 [iopamidol]) was injected at a rate of 5 mL/sec. The arterial phase images were rendered on a workstation to obtain 3D MDCT angiograms that were assessed by two reviewers who were blinded to the surgical findings. Arterial anatomy was categorized according to the Michels classification. The reviewers assessed the 2D and 3D images for quality, arterial branch visualization, and differences between the 4- and 8-MDCT images. In the 43 patients who underwent resection, imaging findings were correlated with intraoperative findings. RESULTS: The anatomy of hepatic arteries in the 63 patients was classified as follows: Michels type I, 51 patients (80.9%); type III, four patients (6.3%); type V, five patients (7.9%); and types VII, VIII, and IX, one patient (1.6%) each. In 40 (93%) of 43 patients, the surgical findings concurred with MDCT findings. Three discrepancies were due to failure to identify small accessory left hepatic arteries. Branch visualization and image quality of the 2D images were superior to those of the 3D images. No significant difference was found between the 4- and 8-MDCT images in branch visualization and image quality. CONCLUSION: Three-dimensional MDCT angiography is accurate for classification of hepatic arterial anatomy before hepatic resection. Although 2D data sets show small arteries to better advantage than 3D MDCT angiograms, the 3D MDCT angiograms provide a useful overview of hepatic anatomy.

Adult↗
PubMed2003

Helical CT for nephrolithiasis and ureterolithiasis: comparison of conventional and reduced radiation-dose techniques.

PURPOSE: To determine the accuracy of unenhanced helical computed tomography (CT) performed at reduced milliampere-second, and therefore at a reduced patient radiation dose, by using conventional unenhanced helical CT as the standard. MATERIALS AND METHODS: Fifty patients with acute flank pain who weighed less than 200 lb (90 kg) were prospectively recruited for this study. Conventional helical CT scans were obtained with patients in the prone position by using 5-mm-thick sections, 140 kVp, 135-208 mAs (mean, 160 mAs), and a pitch of 1.5 (single-detector row CT) or 0.75 (multi-detector row CT, 4 x 5-mm detector configuration). Conventional CT was immediately followed by low-dose scanning, whereby the tube current was reduced to 100 mA (mean, 76 mAs). All other technical parameters and anatomic coverage remained constant. Three independent readers who were blinded to patient identity interpreted the scans in random order. The observers noted the location, size, and number of calculi; secondary signs of obstruction; and other clinically relevant findings. High- and low-dose scans were compared by using paired t tests and the signed rank test. RESULTS: Calculi were found in 33 (66%) patients; 25 (50%) had renal calculi and 19 (38%) had an obstructing ureteral calculus. The accuracy rates (averaged over the three readers) for determining the various findings on the low-dose scan compared with the high-dose scan were as follows: nephrolithiasis, 91%; ureterolithiasis, 94%; obstruction, 91%; and normal findings, 92%. When interpretations between readers were compared, agreement rates were 90%-95% for standard-dose scans and 90%-92% for reduced-dose scans (P >.5). Uncomplicated mild diverticulitis was found in three patients. No other clinically important abnormality was identified. A reduction in the tube current to 100 mA resulted in a dose reduction of 25% for multi-detector row CT and 42% for single-detector row CT. CONCLUSION: In patients who weighed less than 200 lb, unenhanced helical CT performed at a reduced tube current of 100 mA, and therefore at a reduced patient dose, resulted in scans of high accuracy.

Adolescent↗
PubMed2003

Optimization of eight-element multi-detector row helical CT technology for evaluation of the abdomen.

PURPOSE: To evaluate protocols for abdominal imaging with an eight-element multi-detector row computed tomographic (CT) scanner. MATERIALS AND METHODS: An eight-element helical CT scanner was used to acquire data in two phantoms with four-element (pitch, 0.75 and 1.5; section thickness, 1.25, 2.5, and 5.0 mm) and eight-element (pitch, 0.625, 0.875, 1.35 and 1.675; section thickness, 1.25 and 2.5 mm) protocols. One phantom was used for low-contrast detectability and streak artifact; the other, for high-contrast performance. Protocols included near constant radiation dose (140 kV and varied tube current, confirmed by using the above protocols to scan a dedicated radiation dose phantom). Data were analyzed by three blinded readers for streak artifacts, contrast-to-noise ratio, and z-axis resolution (contrast-transfer function). Statistical analysis included studentized range tests. RESULTS: Contrast-to-noise ratios for four and eight elements were not consistently different. Qualitative evaluation for streak artifacts revealed fewer artifacts for all eight-element 1.25-mm-thick section protocols, as compared with eight-element 2.5-mm protocols. All eight-element 2.5-mm protocols except that with 27.0 mm per rotation had fewer streak artifacts than did four-element protocols (P =.02-.04). Contrast-transfer functions along the z axis for eight-element protocols were better than those for four-element protocols, demonstrating improved z-axis resolution (P <.05). CONCLUSION: Images acquired at eight sections per rotation demonstrated no sacrifice of contrast-to-noise ratio, improved z-axis resolution, and fewer streak artifacts, even when radiation dose was similar to that for four-element CT.

Artifacts↗