Multidetector CT urography: experimental analysis of radiation dose reduction in an animal model.

The purpose of this study was to evaluate the possibility of reducing X-ray exposure during multidetector CT urography (MDCTU) considering image quality using a porcine model. MDCTU was performed in eight healthy pigs. Scanning was conducted using a gradual reduction of the tube current-time product at 120 kV [200-20 mAs (eff.) in ten steps]. Three blinded observers independently evaluated the image data for anatomic detail, subjective image quality, and subjective image noise. Overall image quality was compared to milliampere-second settings and radiation dose. Objective noise measurements were assessed. Noise measurements in patients were also performed to verify the comparabilty of the animal model. Adequate image quality allowing for detailed visualization of the upper urinary tract was obtained when the tube current-time product was decreased to 70 eff. mAs at 120 kV. Image noise did not impair image quality to a relevant degree using these parameters. There was high agreement among the observers (ICC = 0.95). In the animal experiments, reduced-dose MDCTU produced good image quality. A maximum current-time product reduction to 70 eff. mAs at 120 kV (CTDI(vol) = 5.3 mGy) proved to be feasible, thereby offering an advantageous dosage reduction. The study provides a basis for the development of reduced-dose MDCTU protocols in humans.

Value of T2-weighted, first-pass and delayed enhancement, and cine CMR to differentiate between acute and chronic myocardial infarction.

The aim of this study was to analyze the diagnostic accuracy of edema on T2-weighted (T2w) cardiac magnetic resonance imaging (CMR), presence of microvascular obstruction (MO) on first-pass enhancement (FPE) or on delayed enhancement (DE) CMR, and wall thinning on cine CMR to differentiate between acute (AMI) and chronic myocardial infarction (CMI) in patients with infarction on DE-CMR. Fifty patients were imaged 5 +/- 3 days (baseline) and 8 +/- 3 months (follow-up) after AMI at 1.5 T. Imaging findings were graded as present or absent in a blinded consensus reading. Edema was present at baseline in 48 (96%) patients and absent at follow-up in 49 (98%) patients. At baseline, MO was present in 29 (58%) patients on FPE-CMR and in 24 (48%) patients on DE-CMR (P = ns). At follow-up, persisting hypoenhancement was observed in ten (20%) patients on FPE-CMR, whereas two (4%) patients showed persisting hypoenhancement on DE-CMR (P<0.05). Wall thinning was present in 4 (8%) patients at baseline and in 20 (40%) patients at follow-up. Edema had high sensitivity (96%), specificity (98%), and accuracy (97%) to differentiate between AMI and CMI. Accuracy of all other imaging findings was lower compared to that of edema (P<0.001). In the presence of infarction on DE-CMR, T2w-CMR reliably differentiates between AMI and CMI.

Improved visualization of the urinary tract in multidetector CT urography (MDCTU): analysis of individual acquisition delay and opacification using furosemide and low-dose test images.

PURPOSE: To retrospectively analyze the reliability of opacification and image quality of a modified MDCTU examination protocol using furosemide and an individual acquisition delay by low-dose test images MATERIALS AND METHODS: Excretory phase images obtained from 4-row and 16-row MSCTU examinations in 103 patients (69 men, 34 women) were independently reviewed by two radiologists. MDCTUs were performed by using a low-dose furosemide iv injection. No fixed delay for urographic image acquisition was applied. Urographic timing was individually adjusted by performing low-dose test images of the distal ureters to display their current opacification. Image analysis included grading of opacification and image quality of the segmented collecting system. Average urographic delay was calculated. Stratified comparisons of mean scores were assessed. Interobserver kappa values were calculated. RESULTS: Calculated median scan delay for patients with normal creatine levels (n = 92) was 420 sec (mean 453 sec; SD, 121 sec). The median number of acquired test images was 2 (range 1-6 images). The analysis of opacification demonstrated that 97% of the ICS, 89% of the proximal, 86% of the middle, and 81% of the distal ureter segments showed opacification greater than 90%. 7.8% of the distal ureteral segments could not be visualized. Statistics did not show significant differences of opacification between proximal, middle, and distal ureteral segments (P > 0.05). Overall image quality of MSCTU showed to be high when latest test images indicated homogeneous bilateral contrasted ureters (Pearson correlation coefficient r= 0.81). Interobserver kappa values were 0.8 and 0.78. CONCLUSION: Furosemide and scan delay timing by means of test images for MDCTU proved to be a reliable procedure to reach improved opacification of the upper urinary tract. It features the individual adaption of MDCTU to the excretory rate of the kidneys.

Characterization of the peri-infarction zone using T2-weighted MRI and delayed-enhancement MRI in patients with acute myocardial infarction.

To characterize the peri-infarction zone using T2-weighted (T2w) magnetic resonance imaging (MRI) and infarct size on delayed enhancement (DE) MRI in patients with acute myocardial infarction (AMI). In 65 patients, short-axis T2w and DE MRI images were acquired 5 +/- 3 d after AMI. The MRI was analyzed using a threshold method defining infarct size on DE MRI and edema on T2w MRI as areas with signal intensity larger than +2 SD above remote normal myocardium. The peri-infarction zone was calculated as the difference between the size of edema and the infarct size. The size of edema on T2w MRI (31.3 +/- 13.4% of LV area) was larger than the infarct size on DE MRI (20.3 +/- 10.4% of LV area, p< 0.0001). The size of the peri-infarction zone was 11.0 +/- 10.0% of the LV area. Good correlation was found between infarct size on DE MRI and peak creatine kinase (CK) isoenzyme MB (r = 0.65, p< 0.0001), but there was no correlation between the size of the peri-infarction zone and CK MB (r = 0.05, p = 0.67). The peri-infarction zone was larger in patients with an infarct size <28% of the LV area (12.6 +/- 10.0% LV area) compared with patients with an infarct size > or =28% of the LV area (6.7 +/- 9.0% of the LV area, p< 0.05). The peri-infarction zone does not correlate with enzymatic parameters of infarct size and is substantially larger in small infarcts, indicating viable myocardium.

Multislice computed tomography-urography: intraindividual comparison of different preparation techniques for optimized depiction of the upper urinary tract in an animal model.

OBJECTIVES: We sought to evaluate intraindividually 3 different preparation protocols for achieving improved opacification and anatomic depiction of the upper urinary tract in multisclice computed tomography urography (MSCTU) using a porcine model. MATERIAL AND METHODS: MSCTU was performed in 8 healthy pigs. Each animal underwent 3 MSCT urographies using 3 different preparations before the injection of contrast material: A, intravenous (iv) saline (250 mL); B, iv low-dose furosemide (0.1 mg/kg); and C, iv saline (250 mL) plus iv low-dose furosemide (0.1 mg/kg). Image analysis was performed blinded to the applied protocols and included the evaluation of the opacification and anatomic depiction of the upper urinary tract by means of graded scales. Ureteral distension was determined and density was measured within the collecting system. RESULTS: Furosemide significantly improved both mean opacification scores and mean scores of anatomic depiction compared with the exclusive infusion of saline for MSCTU. There was no significant difference between the application of furosemide and the combination of furosemide plus saline. A significant increase of 25-26% for ureteral distension was found when furosemide was applied. Significant lower mean attenuation values (Hounsfield units) and standard deviation were found within the opacified urine for diuretic-enhanced MSCTU. CONCLUSIONS: Low-dose furosemide injection is superior to saline infusion for achieving optimal enhancement in MSCTU. It is not necessary to combine furosemide and saline infusion. In MSCTU, low-dose furosemide is a simple add-on simplifying image acquisition timing and removing the need for abdominal compression devices.

MR evaluation of dural ectasia in Marfan syndrome: reassessment of the established criteria in children, adolescents, and young adults.

PURPOSE: To retrospectively evaluate known criteria for assessment of dural ectasia by using magnetic resonance (MR) imaging in children, adolescents, and young adults with and those without Marfan syndrome. MATERIALS AND METHODS: Local ethics committee approval and informed consent were obtained. MR images of the lumbar spine in 28 patients with clinically proved Marfan syndrome (group A; 17 male, 11 female; age range, 4-21 years; mean, 12.1 years), seven patients with suspicion of Marfan syndrome (group B; six male, one female; age range, 6-18 years; mean, 10.4 years), and 55 patients without Marfan syndrome (group C; 26 male, 29 female; age range, 4-20 years; mean, 10.7 years) were evaluated retrospectively for dural ectasia criteria (scalloping, dural sac ratio, nerve root sleeve diameter, sagittal dural sac width at S1 greater than that at L4) and according to classifications by Ahn et al and Fattori et al. For statistical comparison of results, one-way analysis of variance with Scheffe post hoc comparisons was used, with an overall two-tailed significance at alpha = .05. RESULTS: No significant differences in scalloping and nerve root sleeve diameter were shown between groups. A significant difference was measured for dural sac ratios at L5 and S1 (F test, P = .003 and P < .001 at L5 and S1, respectively; post hoc t test for groups A vs C, P = .004 and P < .001 at L5 and S1, respectively). Significant differences were also obtained between groups A and C for sagittal dural sac width at S1 greater than that at L4 according to the calculated mean difference (for both F test and post hoc t test, P < .001 and P = .003 at S1 and L4, respectively). The Ahn et al and Fattori et al classifications were of limited value. CONCLUSION: The data suggest that only dural sac ratio at L5 and S1 and a sagittal dural sac width at S1 greater than that at L4 are statistically significant criteria for the assessment of dural ectasia in children, adolescents, and young adults.