Post-biopsy arteriovenous fistula in transplant kidney: treatment with superselective transcatheter embolisation.

PURPOSE: To evaluate the technical success and therapeutic effect of superselective embolisation of arteriovenous fistulas in renal allografts. MATERIALS AND METHODS: Between 2000 and 2009, 20 patients underwent angiography of 24 AV fistulas (AVF) following percutanous biopsy of the transplanted kidney. Indications for angiography were the diagnosis of AVF by ultrasound and in addition persistent or worsening transplant renal function, or haematuria. Superselective catheterisation of the fistula was performed with a coaxial microcatheter and microcoils were used to occlude the fistula. To assess the short-term effect of embolisation, serum creatinine values were evaluated before embolisation, in the first week after embolisation and after a period of minimum 42 days after the procedure. RESULTS: Angiography identified a single AVF in 16 patients and two AVFs in 4 patients. In 19 patients, successful embolisation was achieved without complications. In one patient, a second session was needed to embolise the AVF completely. The mean serum creatinine level of all patients with embolisation dropped significantly (p=0.0014) from 4.4 mg/dl (range: 1.4-11.6 mg/dl, standard deviation: 3.0) before embolisation to 2.7 mg/dl after embolisation (range: 1.0-7.0mg, standard deviation: 1.8). No patient showed an increase in serum creatinine. Long-term outcomes of the renal allograft revealed a well-functioning allograft in 19/20 patients. One patient returned to haemodialysis due to acute rejection. CONCLUSION: Superselective transcatheter embolisation is a safe and highly effective treatment for AVFs in renal allografts. Renal function was improved in the majority of patients.

Intraindividual comparison of image quality in MR urography at 1.5 and 3 tesla in an animal model.

PURPOSE: Experimental evaluation of image quality of the upper urinary tract in MR urography (MRU) at 1.5 and 3 Tesla in a porcine model. MATERIALS AND METHODS: In this study four healthy domestic pigs, weighing between 71 and 80 kg (mean 73.6 kg), were examined with a standard T1w 3D-GRE and a high-resolution (HR) T1w 3D-GRE sequence at 1.5 and 3 Tesla. Additionally, at 3 Tesla both sequences were performed with parallel imaging (SENSE factor 2). The MR urographic scans were performed after intravenous injection of gadolinium-DTPA (0.1 mmol/kg body weight (bw)) and low-dose furosemide (0.1 mg/kg bw). Image evaluation was performed by two independent radiologists blinded to sequence parameters and field strength. Image analysis included grading of image quality of the segmented collecting system based on a five-point grading scale regarding anatomical depiction and artifacts observed (1: the majority of the segment (>50%) was not depicted or was obscured by major artifacts; 5: the segment was visualized without artifacts and had sharply defined borders). Signal-to-noise (SNR) and contrast-to-noise (CNR) ratios were determined. Statistical analysis included kappa-statistics, Wilcoxon and paired student t-test. RESULTS: The mean scores for MR urographies at 1.5 Tesla were 2.83 for the 3D-GRE and 3.48 for the HR3D-GRE sequence. Significantly higher values were determined using the corresponding sequences at 3 Tesla, averaging 3.19 for the 3D-GRE (p = 0.047) and 3.92 for the HR3D-GRE (p = 0,023) sequence. Delineation of the pelvicaliceal system was rated significantly higher at 3 Tesla compared to 1.5 Tesla (3D-GRE: p = 0.015; HR3D-GRE: p = 0.006). At 3 Tesla the mean SNR and CNR were significantly higher (p < 0.05). A kappa of 0.67 indicated good interobserver agreement. CONCLUSION: In an experimental setup, MR urography at 3 Tesla allowed for significantly higher image quality and SNR compared to 1.5 Tesla, particularly for the visualization of the pelvicaliceal system.

[Magnetic resonance imaging of single SPIO labeled mesenchymal stem cells at 3 Tesla]. / Magnetresonanz-Bildgebung von einzelnen SPIO-markierten mesenchymalen Stammzellen bei 3 Tesla.

PURPOSE: To assess the detectability of single magnetically labeled mesenchymal stem cells (MSC) in-vitro on a clinical 3T MR scanner using a small animal volume coil. MATERIALS AND METHODS: GFP-transfected MSC were magnetically labeled with superparamagnetic iron oxide particles (SPIO) while applying different dosages of iron (56 vs. 560 microg Fe/ml). The cellular iron content was determined with atomic absorption spectrometry (AAS). Single labeled MSC were displayed in a culture flask using MR imaging and microscopy. Special cell phantoms were designed to examine the detection of labeled MSC with MR imaging in a spatial model. A T2*-weighted 3D gradient echo sequence with isotropic spatial resolution of 150 to 500 microm (3) was used for image acquisition. The detection of labeled MSC in the cell phantoms was quantitatively evaluated using an automated image analysis. Statistical analysis was performed with a significance level of p < 0.05. RESULTS: The labeling of MSC yielded a mean cellular iron content of 1.5 +/- 0.17 pg Fe/cell (56 microg Fe/ml) and 8.3 +/- 1.85 pg Fe/cell (560 microg Fe/ml). Examination of the culture flasks showed single magnetically labeled MSC centered in much larger MR signal voids. The detection and quantification of single MSC in cell phantoms were feasible for spatial resolutions of 150 microm and 200 microm. Cells with a lower SPIO content (1.5 +/- 0.17 pg Fe/cell) were detected in 14.2 +/- 4.2 % (150 microm) and 7.7 +/- 3.8 % (200 microm). MSC with a higher cellular SPIO content (8.3 +/- 1.85 pg Fe/cell) revealed significantly higher occurrences at both spatial resolutions with 81.4 +/- 5.8 % (150 microm) and 59.9 +/- 12.4 % (200 microm), respectively. Regarding the spatial resolution (150 vs. 200 microm), significantly different detection rates were determined only for MSC with the higher SPIO content (8.3 +/- 1.85 pg Fe/cell). CONCLUSION: Detection of single magnetically labeled MSC is feasible on a clinical 3T MR scanner with a small animal volume coil at isotropic spatial resolutions of 150 microm and 200 microm. The number of detected cells is influenced by the cellular iron content and the spatial resolution.

Detection of small pulmonary nodules in high-field MR at 3 T: evaluation of different pulse sequences using porcine lung explants.

To evaluate two MR imaging sequences for the detection of artificial pulmonary nodules inside porcine lung explants. 67 agarose nodules ranging 3-20 mm were injected into ten porcine lungs within a dedicated chest phantom. The signal on T1-weighted images and radiopacity were adjusted by adding 0.125 mmol/l Gd-DTPA and 1.5 g/l of iodine. A T1-weighted three-dimensional gradient-echo (T1-3D-GRE; TR/TE:3.3/1.1 ms, slice:8 mm, flip-angle:10 degrees ) and a T2-weighted half-Fourier fast-spin echo sequence (T2-HF-FSE; TR/TE:2000/66 ms, slice:7 mm, flip-angle:90 degrees ) were applied in axial orientation using a 3-T system (Intera, Philips Medical Systems, Best, The Netherlands), followed by CT (16x0.5 mm) as reference. Nodule sizes and locations were assessed by three blinded observers. In nodules of >10 mm, sensitivity was 100% using 3D-GRE-MRI and 94% using the HF-FSE sequence. For nodules 6-10 mm, the sensitivity of MRI was lower than with CT (3D-GRE:92%; T2-HF-FSE:83%). In lesions smaller than 5 mm, the sensitivity declined to 80% (3D-GRE) and 53% (HF-FSE). Small lesion diameters were overestimated with both sequences, particularly with HF-FSE. This study confirms the feasibility of 3 T-MRI for lung nodule detection. In lesions greater than 5 mm, the sensitivity of the 3D-GRE sequence approximated CT (>90%), while sensitivity and PPV with the HF-FSE sequence were slightly inferior.

[Modern diagnostic assessment of the upper urinary tract using multislice CT urography]. / Moderne Diagnostik des oberen Harntraktes mittels Mehrschicht-CT-Urographie.

The advent of Multislice Computed Tomography (MSCT) has made evaluation of the entire urinary tract with high-resolution sections during a single breath-hold a reality. Acquisition of multiple thin overlapping slices provides excellent two-dimensional (2D) and three-dimensional (3D) reformations of the urinary tract. The concept of "Multislice CT Urography (MSCTU)" has emerged from this technical improvement. As a result, a wide range of pathologies inside and outside the urinary tract can be identified. During the last several years, MSCTU has challenged intravenous urography (IVU) in the evaluation of urinary tract abnormalities. Compared with IVU, MSCT(U) is more sensitive and specific in the detection and characterization of a variety of urinary tract disorders, including renal masses and urolithiasis. The main advantage of IVU has been its ability to offer excellent delineation of pelvicalyceal and ureteral anatomy and to depict subtle uroepithelial abnormalities. MSCTU has already shown promising results for overcoming this challenge. Optimal opacification and distension appear to be an essential requirement for a thorough evaluation of the collecting system. Dedicated preparation strategies have been developed to meet these technical difficulties. The biggest disadvantage of MSCTU is the significant radiation exposure. For broad routine clinical application, there is still a need for dose reduction protocols despite the ongoing technical developments in MSCTU. In this article, we outline the different concepts of technical processing for MSCTU and summarize the current role of MSCTU in the evaluation of the upper urinary tract.

[16-Row multidetector CT of the pelvis after iliosacrally inserted osteosynthetic screws: experimental study of dose adjustment on preserved human cadaver specimens]. / 16-Zeilen-Spiral-CT des knöchernen Beckens nach Schraubenosteosynthese der iliosakralen Gelenke--Untersuchungen zur Dosisanpassung in einem Ex-vivo-Modell.

PURPOSE: The study was performed to assess the necessity of dose adjustment (kV or mAs (eff.)) in 16-slice CT (MDCT) in postoperative controls of iliosacrally inserted osteosynthetic screws (OS) on preserved human cadaver specimens. The minimal tube settings for diagnostic imaging of the pelvic bone were analyzed and the effective doses and important organ doses were calculated. MATERIALS AND METHODS: 16 preserved human cadaver specimens with transiliac osteosynthetic screws were scanned on a 16-slice CT (collimation 16 x 0.75 mm, pitch 0.7) with 10 different tube settings (35, 50, 75, 100, 150 mAs (eff.) and 120 and 140 kV). 32 datasets (blinded for name and scan parameters) with and without OS were independently evaluated by four observers. The 10 series were sorted by subjective image quality (image noise, contours, artifacts), and the series with the lowest but still diagnostic quality was selected. The statistical analysis included multi-rater-kappa-test and Wilcoxon test for paired samples. RESULTS: The multi-reader agreements for sorting the series were fair (kappa = 0.38). The agreements in comparing the lowest diagnostic image qualities were slight to fair (kappa = 0.08-0.23). The paired sample test comparing the lowest diagnostic image quality with and without OS showed no statistical significance (p = 0.29). 87.5 % of the readouts (n = 64 [16 examinations, 4 readers]) with OS and 78.1 % of those without OS could be adequately diagnosed using the three series with the lowest effective doses (0.9-1.4 mSv for men, 1.4-2.0 mSv for women; 120 kV-35 mAs (eff.), 120-50, 140-35). CONCLUSION: MSCT scans of the pelvic bone can be performed with very low effective doses. It is not necessary to adjust tube settings when imaging bones with osteosynthetic screws. If the concept for the control of the pelvic osteosynthetic screw position includes more than 2 conventional films (for example anterioposterior view with additional inlet and outlet views), a low dose CT is preferable to conventional radiography.

[Multislice CT urography (MSCTU): evaluation of a modified scan protocol for optimized opacification of the collecting system]. / Mehrschicht-CT-Urographie (MSCTU): Beurteilung eines modifizierten Untersuchungsprotokolls zur Optimierung der Kontrastierung des Harnwegsystems.

PURPOSE: To retrospectively quantify opacification of the urinary tract using a MSCTU protocol based on furosemide and individual adaptation of urographic acquisition delay. MATERIALS AND METHODS: MSCTU examinations obtained from 4-row and 16-row CT scanners in 53 patients (35 men, 18 women, average age 59) were independently reviewed by two radiologists. MSCTUs were performed using a low-dose injection of furosemide. No fixed scan delay for urographic image acquisition was applied. The urographic timing was individually adapted by performing low-dose test images of the distal ureters to display their current opacification. Image analysis included grading of the opacification of the segmented collecting system. The average urographic delay was calculated. Stratified comparisons of mean scores were assessed using the Friedman and Wilcoxon tests. The inter-observer kappa value was calculated. RESULTS: The calculated median scan delay for patients with normal serum-creatinine levels (n = 51) was 418 sec (mean 447 sec; SD, 118 sec). The median number of acquired test images was 2 (range 1 - 6 images). The opacification analysis demonstrated that 98 % of the ICS, 90 % of the proximal, 86 % of the middle, and 83 % of the distal ureteral segments showed opacification greater than 90 %. 9.5 % of the distal ureteral segments could not be visualized. Statistics did not show significant opacification differences between proximal, middle, and distal ureteral segments (p > 0.05). The two observers were largely in agreement (kappa coefficient r = 0.81). CONCLUSION: The analyzed MSCTU technique based on furosemide and scan delay timing by means of test images reliably lead to a homogenous opacification of the entire upper urinary tract. It features the individual adaptation of MSCTU to the excretory rate of the kidneys.

[Economic evaluation of angiographic interventions including a whole-radiology in- and outpatient care]. / Wirtschaftliche Evaluation angiographischer Interventionen einschliesslich einer radiologischen stationären und ambulanten Patientenbetreuung.

PURPOSE: To determine the economic efficiency of a whole-radiology in- and outpatient treatment with angiographic interventions performed as the main or sole therapy. MATERIALS AND METHODS: The calculations represent the data of a university radiology department, including the following angiographic interventions (neuroradiology not considered): Vascular intervention (PTA, stent implantation) of kidneys and extremities, recanalization of hemodialysis access, chemoembolization, diagnostic arterioportal liver CT, port implantation, varicocele embolization, PTCD, percutaneous implantation of biliary stent. First, the different angiographic interventions are categorized with reference to the German DRG system 2005. Considering the example of a university hospital, the individual cost of each intervention is calculated and correlated with reimbursements by G-DRG2005 and so-called "ambulant operation" (EBM200plus). With these data, profits and losses are calculated for both in- and outpatient care. RESULTS: Radiologic interventions of inpatients yield a profit in the majority of cases. With a base rate of 2900 euros, the profits in our university hospital range between - 872 euros and + 3411 euros (mean: + 1348 euros). On the other hand, those angiographic interventions suitable for "ambulant operation" generate average profits of + 372 euros, if only direct costs are considered. The data of outpatient radiological interventions average between 381 euros up to 1612 euros lower than compared with profits obtained from in patient care. CONCLUSION: Once an angiographic intervention represents the major or sole therapy, German radiologists are advised to operate out- and inpatient care by themselves. In Germany, the G-DRG-system and EBM enable radiology departments to generate considerable proceeds for their hospitals and, secondly, to yield a valuable add-on profit for their own department budget, which then is partly detached from the inflexible conventional reimbursement of radiological services.

[Labeling of mesenchymal stem cells with different superparamagnetic particles of iron oxide and detectability with MRI at 3T]. / Untersuchungen zur Markierung von mesenchymalen Stammzellen mit unterschiedlichen superparamagnetischen Eisenoxidpartikeln und Nachweisbarkeit in der MRT bei 3T.

PURPOSE: In vitro evaluation of labeling efficiency of human mesenchymal stem cells (hMSCs) with different types of superparamagnetic iron oxide nanoparticles as well as detection and quantification by MRI at 3T. MATERIAL AND METHODS: hMSCs were incubated for 24 hours with 5 ultrasmall superparamagnetic particles of iron oxide (USPIO) contrast agents (1 : 30 - 1 : 30,000) of different size, coating and core compound: Endorem, Resovist, citric acid coated magnetite cores of 3 nm (CMF3), 7 nm (CMF7) and 12 nm (CoF, core: cobalt ferrite). Iron uptake, intracellular retention, detection and quantification were evaluated with MRI up to 5 weeks after incubation by cytological analysis (Prussian blue), atomic absorption spectrometry and MR relaxometry measurements. RESULTS: An effective labeling of hMSCs was achieved using Resovist, CMF3 and CMF7 with mean iron concentrations of 5.1/1.8, 1.9/1.4 and 1.5/1.0 pg/cell (dilutions 1:30 [933, 2100, 2800 microg Fe/ml]/1 : 300 [93, 210, 280 microg Fe/ml]) compared with 0.58/0.34 and 0.43/0.30 pg/cell (Endorem, CoF, dilution 1 : 30 [400, 4200 microg Fe/ml]/1 : 300 [40, 420 microg Fe/ml] unlabelled control cells: 0.01 pg/cell). Particle uptake correlated with the concentration of USPIO in the incubation medium. Detection of 5 x 10 (4) labelled cells/ml with MRI was possible up to 5 weeks after incubation (Resovist, CMF7 and CMF3). MR relaxometry measurements showed a strong correlation between cellular iron load and R2* (1/T2*), r > 0.78. No changes in cell viability or toxic effects were found. CONCLUSION: Efficiency of labeling hMSCs with USPIOs depends on coating, size and core compound of used particles. Carboxydextran-coated, clinically approved SPIO (Resovist, 50 nm) or ultrasmall citrate-coated particles (< 10 nm) result in an improved cellular uptake. In principle, the long intracellular retention of particles offers the possibility of cell tracking and migration monitoring in MRI.

[Multislice CT urography Aspects for technical management and clinical application]. / Mehrschicht-CT-Urographie Aspekte zur Durchführung und klinischen Anwendung.

The introduction of multislice computed tomography with its well-known advantages has made it possible to visualize the entire urinary tract with thin collimation during a breath-holding phase. CT data acquisition during urographic contrast enhancement for contiguous imaging of the entire upper urinary tract is termed "multislice CT urography" (MSCTU). Multiplanar reconstructions, maximum intensity projections, and average intensity projections can be rendered from the volume datasets to view the urogenital tract. MSCTU will play an important role in the future of modern uroradiology. This article describes the technical aspects involved in the course of the MSCTU examination and identifies additional potential indications for clinical application.

Evaluation of spatial and temporal resolution for ECG-gated 16-row multidetector CT using a dynamic cardiac phantom.

Measurements of spatial and temporal resolution for ECG-gated scanning of a stationary and moving heart phantom with a 16-row MDCT were performed. A resolution phantom with cylindrical holes from 0.4 to 3.0 mm diameter was mounted to a cardiac phantom, which simulates the motion of a beating heart. Data acquisition was performed with 16x0.75 mm at various heart rates (HR, 60-120 bpm), pitches (0.15-0.30) and scanner rotation times (RT, 0.42 and 0.50 s). Raw data were reconstructed using a multi-cycle real cone-beam reconstruction algorithm at multiple phases of the RR interval. Multi-planar reformations (MPR) were generated and analyzed. Temporal resolution and cardiac cycles used for image reconstruction were calculated. In 97.2% (243/250) of data obtained with the stationary phantom, the complete row of holes with 0.6 mm was visible. These results were independent of heart rate, pitch, scanner rotation time and phase point of reconstruction. For the dynamic phantom, spatial resolution was determined during phases of minimal motion (116/250). In 40.5% (47/116), the resolution was 0.6 mm and in 37.1% (43/116) 0.7 mm. Temporal resolution varied between 63 and 205 ms, using 1.5-4.37 cardiac cycles for image reconstruction.

Evaluation of balanced steady-state free precession (TrueFISP) and K-space segmented gradient echo sequences for 3D coronary MR angiography with navigator gating at 3 Tesla.

PURPOSE: To test the feasibility of k-space segmented gradient-echo pulse sequences for free-breathing coronary magnetic resonance angiography (cMRA) on a clinical 3T system. MATERIALS AND METHODS: T2-prepared, fat-suppressed turbo field echo (TFE, turboFLASH, SFPGR) as well as balanced TFE (b-TFE, trueFISP, FIESTA, segmented SSFP) sequences with navigator gating for prospective motion correction were applied on a 3T system equipped with a six-element phased-array cardiac coil. In 15 healthy volunteers, the right coronary artery (RCA) was examined with TFE and b-TFE sequences. Due to examination time limitations, the left coronary artery (LM/LAD) was examined exclusively with the TFE sequence in ten volunteers. Image quality was graded on a five point scale (0 = not visualized to 4 = excellent). The length, diameter and sharpness of the vessels and the contrast-to-noise ratios (CNR) were measured. RESULTS: 98 % of all major segments (proximal/middle/distal) of the RCA could be seen with the TFE sequence and 82 % with the b-TFE sequence. The image quality for the three segments was graded higher for the TFE sequence (2.7/2.7/1.5) than for the b-TFE sequence (1.9/1.6/0.9) with P: (< or = 0.001/< or = 0.004/< or = 0.056). The kappa of the interobserver variability was 0.75 for the TFE sequence and 0.8 for the b-TFE sequence. The measured vessel lengths were longer for the TFE sequence (95 +/- 22 mm) than for the b-TFE sequence (80 +/- 40 mm; P < or = 0.115). No significant changes (P < or = 0.074, P < or = 0.145) in diameter and vessel sharpness of the RCAs were observed between the TFE (2.4 +/- 0.3 mm, 60 % +/- 5) and b-TFE sequences (2.4 +/- 0.3 mm, 62 % +/- 6). The CNR was higher for the TFE sequence (10.1 +/- 3.4) than for the b-TFE sequence (6.6 +/- 2.1; P < or = 0.014). All ten main and proximal segments of the LM/LAD, which were examined exclusively with the TFE sequence, were visible with grade 2.5 and 2.1. The middle segment was visible in seven cases with grade 1.3. In three cases, the distal segment was visible with grade 0.5. The vessel length was 78 +/- 27 mm and the CNR 11.9 +/- 2.4. CONCLUSION: The conventional TFE technique has demonstrated good feasibility for cMRA at 3T. In its operational availability at 3T, the b-TFE sequence is inferior to the TFE sequence.

[Image quality of thin- and thick-slice MSCT reconstructions in low-contrast objects (liver lesions) with equal doses]. / Dünn- und dickschichtige MSCT-Untersuchungen bei Niedrigkontrastobjekten (Leberläsionen): Vergleich der Bildqualität bei gleicher Dosis.

PURPOSE: To evaluate the image quality of thin-section MSCT examinations of low-contrast objects such as liver lesions, and to find out whether a thin slice technique requires an increase in radiation dose. MATERIALS AND METHODS: MSCT examinations of the liver were performed in the portal venous phase on a Volume Zoom Scanner (Siemens, Erlangen) with a collimation of 4 x 2.5 mm, 120 kV, 125 mAs and table speed of 12.5 mm. Forty small hypodense liver lesions with a mean size of 3 mm (1 to 8 mm) were reconstructed using a slice thickness of 3, 5, 7, and 10 mm. All lesions were evaluated for each slice thickness by 3 independent radiologists using a 5-point scale (excellent to poor) for the following 7 criteria: contrast, demarcation and contour of the lesion, image noise and quality, demarcation of liver veins and liver contour. The mean values of the reviewers' scores were calculated. The correlation of the three observers in the evaluation of the criteria was determined using the Kendall's Tau coefficient. RESULTS: The 3-mm thin sections were excellent in the evaluation of lesion detection, lesion contrast and lesion contour with a mean score of 1.4 compared to 4.1 for 10-mm sections. Concerning the criteria image quality and liver contour, thin sections achieved the best results in our series. Image noise was pronounced in thin sections but did not affect negatively the image analysis. Interrater agreement was 0.53 for the criterium image noise. CONCLUSION: Thin sections in MSCT examinations of low contrast objects such as liver lesions do not require an increase in radiation dose because the increase in image noise is compensated by improved lesion contrast.

MR elastography of the prostate: initial in-vivo application.

PURPOSE: To analyze the initial assessment of the technical feasibility of in-vivo MR elastography (MRE) of the prostate gland in healthy volunteers. MATERIALS AND METHODS: Dynamic sinusoidal MR elastography was performed in 7 healthy volunteers in prone position. The mechanical wave was induced via an external oscillator attached to the pubic bone. A 1.5 Tesla MR system (Philips Medical Systems, Netherland) was used with 4 combined surface coils for signal reception. MRE data acquisition was performed with a motion-sensitive spin-echo MR sequence that was phase-locked to the mechanical oscillation. Subsequently, these images were used to reconstruct the local distribution of elasticity inside the prostate gland. The applied reconstruction algorithm was tested by means of phantom measurements. RESULTS: Sufficient penetration of the mechanical wave into the prostate gland was achieved in all volunteers, allowing the acquisition of utilizable image data sets. The reconstructed distribution of elasticity (shear-modulus) inside the healthy prostate gland correlated with the zonal anatomy of the gland. The elasticity of the central portion (2.2 +/- 0.3 kPa) appeared to be lower than the peripheral prostatic portion (3.3 +/- 0.5 kPa). CONCLUSION: In-vivo MRE of the prostate gland is technically feasible. The proposed experimental set-up allows the efficient insertion of the mechanical wave into the prostate gland and provides a successful MR data acquisition.

[Multislice CT of the pelvis: dose reduction with regard to image quality]. / Mehrzeilen-Spiral CT (MSCT) des Beckenskelettes: Dosisoptimierung unter Berücksichtigung der Bildqualität.

PURPOSE: To optimize the examination protocols of multislice CT (MSCT) of the pelvis for dose reduction with regard to image quality. MATERIALS AND METHODS: MSCT of the pelvis was performed on 5 cadaver specimens with stepwise reduction of the tube current at 140 kV (250, 200, 150, 100, 75, 50, 35, 25 mAs) and 120 kV (50, 27 mAs). The remaining scan parameters like collimation (4 x 1 mm) and table speed of 4 mm per rotation remained unchanged. Axial sections and coronal reconstructions were used to evaluate cortex, trabecular structures, subjective image quality, image noise and detail detectability (pelvis and SI joint), with evaluation performed independently by four blinded experienced radiologists on a 5-point scale. Kappa coefficient, accuracy of the observers to sort the films with regard to dose reduction and mean scores of image evaluation were determined for statistical analysis. RESULTS: The deterioration of the image quality was most pronounced for all criteria between 75 mAs and 50 mAs at 140 kV. Good results with adequate image quality were obtained for detail detectability at 50 mAs and 140 kV (effective dose [E]: 3.3 mSv) and for the remaining four criteria at 75 mAs (E: 4.9 mSv). There was a moderate agreement between the four observers (kappa coefficient: 0.27). All observers were excellent in arranging the images according to the increasing dose reduction. CONCLUSIONS: Image quality of MSCT of the pelvis appears to be acceptable at 75 mAs and 140 kV with the dose reduced to 46% of the average value of the nation-wide survey of the German Roentgen Society in 1999 for this type of examination.

Aneurysmal bone cyst: value of MR imaging and conventional radiography.

Our objective was to investigate the accuracy and the diagnostic value of different imaging features of primary aneurysmal bone cysts (ABC) in conventional radiographs and MRI. Conventional radiographs and MR images of 34 patients with a suspected aneurysmal bone cyst were reevaluated by six independent radiologists in a blinded fashion. Morphological features, MR signal characteristics, and contrast enhancement patterns were assessed. Diagnoses were correlated with histology. Sensitivity and specificity of the different imaging findings for each imaging technique were calculated. In 24 patients ABC was histologically proven. In 10 cases diagnoses other than ABC were established. Conventional radiography and MRI each demonstrated a sensitivity of 76.4 and 77.8% with a specificity of 55.0 and 66.7%, respectively. With combined use of both imaging modalities sensitivity and specificity increased to 82.6 and 70%, respectively. The ABC was significantly more often seen as circumscribed lesion with bone expansion, lobulation, septa, and pathological cortical bone reaction than those cases with different diagnoses. Septal contrast enhancement proved to be a useful MR imaging finding in suspected ABC. The combined use of conventional radiographs and MRI revealed the highest sensitivity in the diagnosis of ABC in relation to histology. Magnetic resonance imaging provides improved diagnostic specificity and valuable information on soft tissue changes.

[MR-urography and CT-urography: principles, examination techniques, applications]. / MR-Urographie und CT-Urographie: Prinzipien, Untersuchungstechniken, Anwendungsmöglichkeiten.

MR-urography (MRU) and CT-urography (CTU) provide refined imaging of the upper urinary tract not achievable with conventional intravenous urography (IVU). The traditional MR-urographic technique utilizes unenhanced, heavily T2 -weighted turbo spin-echo sequences for obtaining static fluid images of the urinary tract independent of the excretory renal function. T2 -weighted MR-urograms have proved to be excellent in visualizing the dilated urinary tract, even in non-excreting kidneys. In contrast, T1 -weighted MRU reflects the excretory renal function and displays the urine flow through the upper tract after renal excretion of an intravenously administered gadolinium chelate. The gadolinium-enhanced urine is visualized with fast T1 -weighted 3D-gradient-echo sequences. The combination of gadolinium and low-dose furosemide (5 - 10 mg) is the key for achieving a uniform distribution of gadolinium in the collecting system and for avoiding susceptibility artifacts (T2*-effects) in the urine. T1 -weighted excretory MRU provides impressive urograms of both non-dilated and obstructed collecting systems in patients with normal or moderately impaired renal function. Multislice-CT-urography (MS-CTU) is also an excretory urography like T1 -weighted MRU. Furthermore, MS-CTU can be combined with low-dose furosemide for accelerated passage of excreted contrast material obviating the need for abdominal compression. CT-urography is limited by its radiation burden and the nephrotoxicity of radiographic contrast media. Combining MRU or MS-CTU with conventional MRI or CT offers several applications, e.g., diagnosis of intrinsic and extrinsic tumors. Meanwhile, MRU has replaced IVU in pediatric uroradiology and is also recommended for the assessment of renal transplants. MS-CTU may provide valuable information in chronic urolithiasis, especially if associated with a distorted urinary tract anatomy. Both MRU and MS-CTU will play an important role in modern uroradiology.

MR urography today.

Magnetic resonance (MR) urography is performed by pursuing two different imaging strategies. On the one hand, heavily T2-weighted turbo spin-echo sequences are employed for obtaining unenhanced static-water images of the urinary tract. On the other, the T(1)-weighted MR urographic technique imitates conventional intravenous pyelography and is, therefore, referred to as excretory MR urography. For this reason, a gadolinium contrast agent is injected intravenously and, after its renal excretion, the gadolinium-enhanced urine is imaged with fast T1-weighted gradient-echo sequences. Both MR urographic techniques can be combined for a comprehensive examination of the upper urinary tract. This article reviews the current technical principles, imaging capabilities, and clinical applications of T2- and T1-weighted MR urography in adult and pediatric patients.