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Zusammenfassung Hintergrund Orbitaverletzungen mit organischen Fremdkörpern sind eine klinische Herausforderung, da sie eine Vielzahl von Komplikationen verursachen können und manchmal zu irreversiblen Visuseinschränkungen führen. Material und Methoden Wir berichten über 5 konsekutive Fälle von Patienten mit organischen orbitalen Fremdkörpern, die zwischen 2012 und 2022 vorstellig wurden. Alter, Geschlecht, Zeitpunkt der Verletzung, Verletzungsmechanismus, bestkorrigierter Visus prä- und postoperativ, Vorhandensein von Schmerzen, Motilitätseinschränkungen, durchgeführte Bildgebung, Therapie sowie Komplikationen wurden ausgewertet. Ergebnisse Das mittlere Patientenalter betrug 62 ± 33 Jahre und das Geschlechterverhältnis war 4/1 (weiblich/männlich). In 4 Fällen war von einem Verletzungsgeschehen berichtet worden, welches im Mittel 4,6 (0/14 min/max) Tage zurücklag. Der bestkorrigierte Visus bei Erstvorstellung betrug 0,5 ± 0,2 dezimal und nach einem mittleren Follow-up von 12,7 (0,5/38 min/max) Monaten 0,67 ± 0,3 dezimal (p = 0,2). Der Grund der Erstvorstellung waren Schmerzen (n = 3) und/oder Doppelbilder (n = 2). Bei allen Patienten wurde eine Computertomographie (CT) durchgeführt. In allen 5 Fällen konnte das Fremdkörpermaterial chirurgisch vollständig entfernt werden, wobei eine Patientin wegen verbliebender Fremdkörper mehrmals operiert werden musste. Beim Fremdkörpermaterial handelte sich in 4 Fällen um Holz und einmal um Wachs. Schlussfolgerung Bei Orbitatraumata muss eine sorgfältige Wundexploration durchgeführt werden, insbesondere wenn der Unfallhergang anamnestisch nicht eindeutig zur klären und verbleibende Fremdkörper oder eine Perforationsverletzung nicht ausgeschlossen werden können. Die Bildgebung der Wahl ist die CT, die ggf. im postoperativen Verlauf erneut durchgeführt werden muss.

Orbital injuries with organic foreign bodies are a clinical challenge as they can cause a variety of complications and sometimes lead to irreversible visual impairment.We report five consecutive cases of patients with organic orbital foreign bodies who presented between 2012 and 2022. Documented parameters include age, gender, time of injury, mechanism of injury, best-corrected visual acuity (BCVA), presence of pain, restriction of motility, performed imaging, location and type of foreign body, treatment and complications.The mean patient age was 61.8 ± 32.3 years and the gender ratio was 4:1 (female:male). In 4 cases the injury had been reported on average 4.6 days (0/14 days min/max) previously. Best corrected visual acuity at first presentation was 0.5 ± 0.2 decimal and after a mean follow-up of 12.7 months (0.5/38 months min/max) at last presentation 0.67 ± 0.3 decimal (p = 0.2). The reason for initial presentation was pain (n = 3) and/or double vision (n = 2). All patients underwent computer tomography (CT). The diagnosis was confirmed in two cases by means of CT. In all five cases the foreign body material could be completely surgically removed, while one patient needed repeated surgery due to retained foreign body material. The organic foreign body material included wood (4) and wax (1). In two cases, a foreign body-induced infection was successfully treated with systemic antibiotics. There were no other complications.In orbital trauma a thorough wound exploration must be performed, especially if the mechanism of injury is uncertain and residual foreign bodies or a perforation injury cannot be excluded. The imaging of choice is CT, which may have to be performed again in the postoperative course.HINTERGRUND: Orbitaverletzungen mit organischen Fremdkörpern sind eine klinische Herausforderung, da sie eine Vielzahl von Komplikationen verursachen können und manchmal zu irreversiblen Visuseinschränkungen führen.Wir berichten über 5 konsekutive Fälle von Patienten mit organischen orbitalen Fremdkörpern, die zwischen 2012 und 2022 vorstellig wurden. Alter, Geschlecht, Zeitpunkt der Verletzung, Verletzungsmechanismus, bestkorrigierter Visus prä- und postoperativ, Vorhandensein von Schmerzen, Motilitätseinschränkungen, durchgeführte Bildgebung, Therapie sowie Komplikationen wurden ausgewertet.Das mittlere Patientenalter betrug 62 ± 33 Jahre und das Geschlechterverhältnis war 4/1 (weiblich/männlich). In 4 Fällen war von einem Verletzungsgeschehen berichtet worden, welches im Mittel 4,6 (0/14 min/max) Tage zurücklag. Der bestkorrigierte Visus bei Erstvorstellung betrug 0,5 ± 0,2 dezimal und nach einem mittleren Follow-up von 12,7 (0,5/38 min/max) Monaten 0,67 ± 0,3 dezimal (p = 0,2). Der Grund der Erstvorstellung waren Schmerzen (n = 3) und/oder Doppelbilder (n = 2). Bei allen Patienten wurde eine Computertomographie (CT) durchgeführt. In allen 5 Fällen konnte das Fremdkörpermaterial chirurgisch vollständig entfernt werden, wobei eine Patientin wegen verbliebender Fremdkörper mehrmals operiert werden musste. Beim Fremdkörpermaterial handelte sich in 4 Fällen um Holz und einmal um Wachs.Bei Orbitatraumata muss eine sorgfältige Wundexploration durchgeführt werden, insbesondere wenn der Unfallhergang anamnestisch nicht eindeutig zur klären und verbleibende Fremdkörper oder eine Perforationsverletzung nicht ausgeschlossen werden können. Die Bildgebung der Wahl ist die CT, die ggf. im postoperativen Verlauf erneut durchgeführt werden muss.

PURPOSE The aim of this study was to investigate potential effects of acute caffeine intake on J-difference-edited MRS measures of the primary inhibitory neurotransmitter γ-aminobutyric acid (GABA). METHODS J-difference-edited Mescher-Garwood PRESS (MEGA-PRESS) and conventional PRESS data were acquired at 3T from voxels in the anterior cingulate and occipital area of the brain in 15 healthy subjects, before and after oral intake of a 200-mg caffeine dose. MEGA-PRESS data were analyzed with the MATLAB-based Gannet tool to estimate GABA+ macromolecule (GABA+) levels, while PRESS data were analyzed with LCModel to estimate levels of glutamate, glutamate+glutamine, N-acetylaspartate, and myo-inositol. All metabolites were quantified with respect to the internal reference compounds creatine and tissue water, and compared between the pre- and post-caffeine intake condition. RESULTS For both MRS voxels, mean GABA+ estimates did not differ before and after caffeine intake. Slightly lower estimates of myo-inositol were observed after caffeine intake in both voxels. N-acetylaspartate, glutamate, and glutamate+glutamine did not show significant differences between conditions. CONCLUSION Mean GABA+ estimates from J-difference-edited MRS in two different brain regions are not altered by acute oral administration of caffeine. These findings may increase subject recruitment efficiency for MRS studies.

Purpose To evaluate the feasibility of renal diffusion quantification using the Pade exponent model (PEM) in healthy subjects. Materials and Methods Diffusion measurements were completed in 10 healthy subjects (mean age, 32.4 ± 8.9 years) on a 3T MRI scanner (Magnetom Trio, Siemens AG, Germany). A respiratory-triggered echo planar imaging sequence (15 slices with 6 mm thickness; 16 b-values [0–750 s/mm2]; three diffusion directions; field of view: 400 × 375 mm; Matrix 192 × 192; repetition time/echo time: 3000/74 ms) was acquired in the coronal direction. Parameter maps were calculated for the monoexponential, biexponential, kurtosis models, and the PEM. A regression analysis using an R2-test and corrected Akaike information criterion (AICc) was performed to identify the best mathematical fitting to the measured diffusion-weighted imaging signal decay. Results The mathematical accuracy of the PEM was significantly higher than for the other three-parameter and the monoexponential model (P

PURPOSE To evaluate the sensitivity of stimulated-echo acquisition mode (STEAM) and pulsed-gradient spin-echo (PGSE) diffusion tensor imaging (DTI) acquisitions with different diffusion times for measuring renal tissue anisotropy. METHODS Twelve healthy volunteers underwent an MRI examination at a 3T scanner including STEAM and PGSE DTI with variable diffusion times Δ (20.3, 37 and 125 ms). Three volunteers were scanned twice to test the reproducibility for repeated examinations. Diffusion parameters fractional anisotropy (FA) and apparent diffusion coefficient (ADC) in the automatically segmented cortical and medullary regions of interests in both kidneys were calculated and averaged over all subjects for further analysis. Moreover, 5-grade qualitative evaluation of the FA and ADC maps from each sequence was conducted by two experienced radiologists in a consensus. RESULTS The cortex-medulla difference in the STEAM sequence was significantly higher than that in PGSE with short ∆ = 20.3 ms (P

Purpose The study sought to assess the frequency and prognostic value of hyperattenuating adrenal glands on contrast-enhanced computed tomography (CT) scans of surgical intensive care unit (ICU) patients with acute clinical deterioration. Methods Eighty-eight consecutive ICU patients (63.2 ± 14.5 years of age) were included in this retrospective analysis. All patients underwent biphasic contrast-enhanced CT due to an acute clinical deterioration. Hyperattenuation of the adrenal glands was assessed subjectively and objectively. Subjective presence or absence of hyperattenuating adrenal glands was assessed by 2 blinded radiologists (J.B. and R.S.L.) in consensus. Hounsfield units (HU) were measured in the adrenal glands and in the inferior vena cava. Objective hyperattenuation was defined as HU (adrenal glands) > HU (inferior vena cava) with a 15-HU threshold. Death within 14 days following CT was set as endpoint and acquired from electronic patient data. Results Thirty-eight patients (43.2%, Group Asubj) exhibited hyperattenuation of the adrenal glands, whereas 50 patients (56.8%, Group Bsubj) did not. Concerning the objective analysis, 31 patients (35.2%, Group Aobj) exhibited hyperdense adrenal glands, whereas 53 patients (64.8%, Group Bobj) did not. Overall 27 of 88 patients (30.6%) died within 14 days following the CT examination. Lethal outcome was significantly more frequent among patients in Group Asubj and Aobj (19 of 38 patients [50.0%] and 15 of 31 patients [48.4%]) as compared with patients in Group Bsubj (8 of 50 patients [16.0%]) and Group Bobj (12 of 57 patients [21.1%]; P < .05). Subjective and objective analysis correlated significantly ( P < .05). Conclusions Hyperattenuation of adrenal glands on contrast-enhanced CT of ICU patients with acute clinical deterioration is associated with a high mortality and might serve as a prognostic marker for patients' outcome.

Rationale and Objectives There has been a trend toward lowering tube potential in computed tomography angiography (CTA) examinations to reduce radiation dose or contrast medium dose. The aim of this study was to evaluate the influence of tube potential on peripheral artery in-stent lumen visibility in CTA examinations. Materials and Methods Nine different peripheral artery stents were placed in a vessel phantom (inner diameter: 5 mm, surrounded by water) and scanned consecutively using a 128-row CT scanner with 70, 80, 100, 120, and 140 kV and two different concentrations of contrast medium to simulate contrast-enhanced blood. Medium-smooth and ultra-sharp reconstruction kernels with filtered back projection (B30f, B46f) and iterative reconstruction technique (I30f, I46f) were used. Visible in-stent lumen diameter and artifact width were evaluated using a semiautomatic software tool. All stents were scanned with digital angiography, which was regarded as the reference standard. Results Averaged over all stents, visible in-stent lumen diameter ranged from 1.30 ± 0.21 mm (CM2/70 kV/I30f) to 3.13 ± 0.32 mm (CM1/120 kV/I46f). In-stent lumen diameters were significantly higher for 120 and 140 kV compared to 70 kV (2.39 ± 0.73 and 2.39 ± 0.66 mm vs 1.99 ± 0.69 mm; P = 0.01 and P = 0.005). Ultra-sharp reconstruction kernels lead to significantly better in-stent lumen visibility than smooth reconstruction kernels (B46f: 2.74 ± 0.34 mm vs B30f: 1.57 ± 0.36 mm; P Conclusions Despite all known benefits of low kV CTA protocols, the use of a very low tube potential may hamper in-stent lumen visibility. A sharp kernel may be of value when evaluating the inner lumen of vascular stents.

Purpose To characterize the proton exchange in aqueous urea solutions using a modified version of the WEX II filter at high magnetic field, and to assess the feasibility of performing quantitative urea CEST MRI on a 3T clinical MR system. Methods In order to study the dependence of the exchange-rate constant k sw of urea as a function of pH and T, the WEX-spectra were acquired at 600 MHz from urea solutions in a pH range from 6.4 to 8.0 and a temperature range from T = 22 ∘ C to 37 ∘ C . The CEST experiments were performed on a 3T MRI scanner by applying a train of 50 Gaussian-shaped pulses, each 100-millisecond long with a spacing of 100 milliseconds, for saturation. Exchange rates of urea were calculated using the (extended) AREX metric. Results The results showed that proton exchange in aqueous urea solutions is acid and base catalyzed with the rate constants: k a = ( 9.95 ± 1.1 ) × 10 6 l/(mol·s) and k b = ( 6.21 ± 0.21 ) × 10 6 l/(mol·s), respectively. Since the urea protons undergo a slow exchange with water protons, the CEST effect of urea can be observed efficiently at 3T. However, in neutral solutions the exchange rate of urea is minimal and cannot be estimated using the quantitative CEST approach. Conclusions By means of the WEX-spectroscopy, the kinetic parameters of the proton exchange in urea solutions have been determined. It was also possible to estimate the exchange rates of urea in a broad range of pH values using the CEST method at a clinical scanner.

Object To assess changes diffusion properties of renal cortex over the entire cardiac cycle using electrocardiogram-gated respiratory-triggered dynamic diffusion-weighted imaging (DWI). Materials and methods 20 healthy volunteers were investigated on a 1.5 T MR scanner. Blood flow velocity within the renal arteries was determined by electrocardiogram-gated phase-contrast measurements. For dynamic renal DWI, an electrocardiogram-gated respiratory-triggered coronal single-slice EPI sequence was acquired at 14 times at 20, 70, 120, 170, …, 570, 620, 720 ms after the R-wave over the cardiac cycle. ROI measurements were performed by two authors in the renal cortex on apparent diffusion coefficient (ADC) maps. A pulsatility index was calculated for ADC as maximal percentage change. Five subjects were measured twice to assess scan-rescan reproducibility. Results Flow measurements exhibited a minimum velocity of 15.7 ± 4.3 cm/s during the R-wave and a maximum of 43.2 ± 10.4 cm/s at 182.5 ± 48.3 ms after the R-wave. A minimal mean ADC of 2.19 ± 0.09 × 10−3 mm2/s was observed during the R-wave. A maximum mean ADC of 2.85 ± 0.20 × 10−3 mm2/s was measured 193 ± 57 ms after the R-wave. The mean ADC pulsatility index in the renal cortex was 29.9 ± 5.8%. ADC variation exhibited a significant correlation with pulsatile blood flow velocity. The scan-rescan reproducibility in this study had a low deviation of 0.3 ± 0.1%. The inter-reader reproducibility was 2.9 ± 0.6%. Conclusion Renal ADCs exhibit pulsatile characteristics. Due to the significant difference of systolic and diastolic ADCs, the pulsatility index can be calculated.

Renal transplantation is the therapy of choice for patients with end-stage renal diseases. Improvement of immunosuppressive therapy has significantly increased the half-life of renal allografts over the past decade. Nevertheless, complications can still arise. An early detection of allograft dysfunction is mandatory for a good outcome. New advances in magnetic resonance imaging (MRI) have enabled the noninvasive assessment of different functional renal parameters in addition to anatomic imaging. Most of these techniques were widely tested on renal allografts in past decades and a lot of clinical data are available. The following review summarizes the comprehensive, functional MRI techniques for the noninvasive assessment of renal allograft function and highlights their potential for the investigations of different etiologies of graft dysfunction.

Introduction The objective of this study was to evaluate image quality and radiation dose of a CT angiography (CTA) protocol using 80 kVp in combination with iterative reconstruction and automated tube current modulation. Methods Ninety-five aortic CTA examinations were included in this study. A novel 80 kVp aortic CTA-protocol with iterative reconstruction was introduced in our department in March 2012 for patients with a body mass index (BMI) below 32 kg/m2. The first 72 consecutive examinations were retrospectively assigned to group A (56 patients, 42 men, 14 women, mean age 69.6 ± 10.7years, BMI range 19.7–31.1 kg/m2). For comparison, the last 23 consecutive examinations performed with the old protocol (100 kVp) were assigned to group B (21 patients, 13 men, 8 women, mean age 67.4 ± 11.1years, BMI range 19.7–31.9 kg/m2). Thoracic and abdominal contrast-to-noise ratio (CNR), signal-to-noise ratio (SNR) and aortic attenuation were assessed. Subjective image quality was rated on a 5-point scale (1 = non diagnostic; 5 = excellent). Furthermore, dose length product (DLP) and volumetric computed tomography dose index (CTDIvol) were analysed. Results All examinations achieved diagnostic image quality. Attenuation of the aorta was significantly higher in group A compared with B (thoracic: 443.5 ± 90.5 Hounsfield units (HU) vs. 296.0 ± 61.0 HU; abdominal: 426.3 ± 94.2 HU vs. 283.6 ± 60.5 HU; P 0.05, respectively). CTDIvol and DLP were significantly lower in group A (1.9 ± 0.5 mGy; 139.2 ± 41.1 mGy × cm) as compared with group B (4.2 ± 1.4 mGy; 292.1 ± 91.5 mGy × cm; P

Purpose To analyze age-dependency of glycosaminoglycan content using gagCEST (glycosaminoglycan chemical exchange saturation transfer) imaging in lumbar intervertebral discs of healthy volunteers. Materials and Methods In all, 70 volunteers without low back pain (mean age 44 ± 14 years, range: 21–69 years) were examined with T2-weighted and gagCEST imaging with a 3T MR scanner, with approval of the local Ethics Committee after written informed consent was obtained. Pfirrmann grading and classification into discs without bulging and herniation, discs with bulging, and discs with herniation were performed. Only intervertebral discs without bulging and herniation were analyzed. A region-of-interest-based gagCEST analysis of nucleus pulposus (NP) and annulus fibrosus (AF) was performed. Correlation between age and gagCEST was tested within groups of equal Pfirrmann score. Results GagCEST effects decreased significantly from 3.09 ± 1.12% in 20–29 years old volunteers to −0.24 ± 1.36% in 50–59 years old volunteers (P

Seit der Einfuhrung der Magnetresonanztomographie (MRT), fruher auch Kernspintomographie oder bildgebende „Nuclear Magnetic Resonance“ (NMR) genannt, Anfang der 1980er-Jahre, hat sich diese Untersuchungstechnik zu einer weitverbreiteten medizinischen Bildgebungsmethode entwickelt, die unterschiedlichste anatomische Regionen abbildet und verschiedenste morphologische und funktionelle Fragestellungen beantwortet. Dieses Kapitel soll einen Einblick in diese vielseitige diagnostische Technologie und ihre Moglichkeiten geben. Zunachst wird ein kurzer Uberblick uber die geschichtliche Entwicklung der Methode gegeben, im Folgenden werden nahere Details zur Entstehung des MR-Signals und dessen Verarbeitung erlautert. Es wird erklart, welche Hardware-Voraussetzungen erforderlich sind, um Bilder anzufertigen. Dann wird erlautert, wie Bildkontraste entstehen und welche kernphysikalischen Eigenschaften die MRT-Schnittbilder eigentlich abbilden.

PURPOSE: To investigate potential effects of acute caffeine intake on J-difference edited MR spectroscopy (MRS) measures of the primary inhibitory neurotransmitter γ-aminobutyric acid (GABA). METHODS: J-difference-edited MEGA-PRESS and conventional PRESS data were acquired at 3T from voxels in the anterior cingulate (ACC) and occipital area (OCC) of the brain in 15 healthy subjects, prior to and after oral intake of a 200-mg caffeine dose. MEGA-PRESS data were analysed with the MATLAB-based Gannet tool to estimate GABA + macromolecule (GABA+) levels, while PRESS data were analysed with LCModel to estimate levels of glutamate (Glu), glutamate+glutamine (Glx), N-acetylaspartate (NAA), and myo-inositol (mI). All metabolites were quantified with respect to the internal reference compounds creatine (Cr) and tissue water, and compared between the pre- and post-caffeine intake condition. RESULTS: For both MRS voxels, mean GABA+ estimates did not differ before and after caffeine intake. Slightly lower estimates of mI were observed after caffeine intake in both voxels. NAA, Glu and Glx did not show significant differences between conditions. CONCLUSION: Mean GABA+ estimates from J-difference edited MRS in two different brain regions are not altered by acute oral administration of caffeine. These findings may increase subject recruitment efficiency for MRS studies.

To analyse technical success, complications, and short- and intermediate-term outcomes after heparin-bonded stent graft implantation for the treatment of major abdominal vessel injury after upper abdominal surgery. This retrospective, IRB-approved analysis included 29 consecutive patients (female: n = 6, male: n = 23, mean age 65.9 ± 11.2 years). All patients underwent angiography and attempted heparin-bonded stent-graft implantation because of a major visceral arterial injury after upper abdominal surgery. Electronic clinical records, angiographic reports and imaging datasets were reviewed to assess technical success and complications. Telephone interviews were performed to obtain follow-up information and to estimate short- (> 30 days) and intermediate-term (> 90 days) outcomes. Successful stent graft placement was achieved in 82.8% (24/29). Peri-interventional complications were observed in 20.7% (6/29) and delayed, angiography-associated complications were observed in 34.5% (10/29) of the patients. Symptomatic re-bleeding occurred in 24.1% (7/29). Short-term survival (> 30 days) was 72.4% (21/29). Intermediate survival (> 90 days) was 37.9% (11/29). Treatment of major vascular injuries with heparin-bonded stent grafts is feasible with a high technical success rate. However, survival depends on the underlying surgical condition, making interdisciplinary patient management mandatory. • Stent graft implantation is challenging, but has a high technical success rate. • Complications are frequent but surgical conversion is rarely necessary. • Survival depends on the underlying surgical condition causing the vascular injury. • Interdisciplinary management is crucial for the survival of these patients.

Purpose To assess the feasibility and to optimize imaging parameters of diffusion kurtosis imaging (DKI) in human kidneys. Methods The kidneys of ten healthy volunteers were examined on a clinical 3 T MR scanner. For DKI, respiratory triggered EPI sequences were acquired in the coronal plane (3 b-values: 0, 300, 600 s/mm 2 , 30 diffusion directions). A goodness of fit analysis was performed and the influence of the signal-to-noise ratio (SNR) on the DKI results was evaluated. Region-of-interest (ROI) measurements were performed to determine apparent diffusion coefficient (ADC), fractional anisotropy (FA) and mean kurtosis (MK) of the cortex and the medulla of the kidneys. Intra-observer and inter-observer reproducibility using Bland-Altman plots as well as subjective image quality of DKI were examined and ADC, FA, and MK parameters were compared. Results The DKI model fitted better to the experimental data (r = 0.99) with p Calculation of reliable kurtosis parameters in human kidneys requires a minimum SNR of 8.31 on b = 0 s/mm 2 images. Corticomedullary differentiation was possible on FA and MK maps. ADC, FA and MK revealed significant differences in medulla (ADC = 2.82 × 10 − 3 mm 2 /s ± 0.25, FA = 0.42 ± 0. 05, MK = 0.78 ± 0.07) and cortex (ADC = 3.60 × 10 − 3 mm 2 /s ± 0.28, FA = 0.18 ± 0.04, MK = 0.94 ± 0.07) with p Conclusion Our initial results indicate the feasibility of DKI in the human kidney presuming an adequate SNR. Future studies in patients with kidney diseases are required to determine the value of DKI for functional kidney imaging.

Organ-specific dose reduction significantly reduces the radiation exposure of radiosensitive organs. The purpose of this study was to assess the impact of a novel organ-specific dose reduction algorithm on image quality of pediatric chest CT. We included 28 children (mean age 10.9 ± 4.8 years, range 3–18 years) who had contrast-enhanced chest CT on a 128-row scanner. CT was performed at 100 kV using automated tube current modulation and a novel organ-specific dose-reduction algorithm (XCare™; Siemens, Forchheim, Germany). Seven children had a previous chest CT performed on a 64-row scanner at 100 kV without organ-specific dose reduction. Subjective image quality was assessed using a five-point scale (1-not diagnostic; 5-excellent). Contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) were assessed in the descending aorta. Overall mean subjective image quality was 4.1 ± 0.6. In the subgroup of the seven children examined both with and without organ-specific dose reduction, subjective image quality was comparable (score 4.4 ± 0.5 with organ-specific dose reduction vs. 4.4 ± 0.7 without it; P > 0.05). There was no significant difference in mean signal-to-noise ratio and contrast-to-noise ratio with organ-specific dose reduction (38.3 ± 10.1 and 28.5 ± 8.7, respectively) and without the reduction (35.5 ± 8.5 and 26.5 ± 7.8, respectively) (P > 0.05). Volume computed tomography dose index (CTDIvol) and size-specific dose estimates did not differ significantly between acquisitions with the organ-specific dose reduction (1.7 ± 0.8 mGy) and without the reduction (1.7 ± 0.8 mGy) (P > 0.05). Organ-specific dose reduction does not have an impact on image quality of pediatric chest CT and can therefore be used in clinical practice to reduce radiation dose of radiosensitive organs such as breast and thyroid gland.

Purpose To assess the feasibility of non-Gaussian DWI as part of a FDG-PET/MRI protocol in patients with histologically proven non-small cell lung cancer. Material and methods 15 consecutive patients with histologically proven NSCLC (mean age 61 ± 11 years) were included in this study and underwent whole-body FDG-PET/MRI following whole-body FDG-PET/CT. As part of the whole-body FDG-PET/MRI protocol, an EPI-sequence with 5 b-values (0, 100, 500, 1000 and 2000 s/mm2) was acquired for DWI of the thorax during free-breathing. Volume of interest (VOI) measurements were performed to determine the maximum and mean standardized uptake value (SUVmax; SUVmean). A region of interest (ROI) was manually drawn around the tumor on b = 0 images and then transferred to the corresponding parameter maps to assess ADCmono, Dapp and Kapp. To assess the goodness of the mathematical fit R2 was calculated for monoexponential and non-Gaussian analysis. Spearman's correlation coefficients were calculated to compare SUV values and diffusion coefficients. A Student's t-test was performed to compare the monoexponential and non-Gaussian diffusion fitting (R2). Results T staging was equal between FDG-PET/CT and FDG-PET/MRI in 12 of 15 patients. For NSCLC, mean ADCmono was 2.11 ± 1.24 × 10−3 mm2/s, Dapp was 2.46 ± 1.29 × 10−3 mm2/s and mean Kapp was 0.70 ± 0.21. The non-Gaussian diffusion analysis (R2 = 0.98) provided a significantly better mathematical fitting to the DWI signal decay than the monoexponetial analysis (R2 = 0.96) (p Conclusion Simultaneous PET and non-Gaussian diffusion acquisitions are feasible. Non-Gaussian diffusion parameters show a good correlation with SUV and might provide additional information beyond monoexponential ADC, especially as non-Gaussian diffusion exhibits better mathematical fitting to the decay of the diffusion signal than monoexponential DWI.

Purpose To investigate non–contrast-enhanced arterial spin labeling (ASL) MRI for functional assessment of transplanted kidneys at 1.5 Tesla (T) and 3T. Materials and Methods This study was approved by the local ethics committee, and written informed consent was obtained from all participants. Ninety eight renal allograft recipients (mean age, 51.5 ± 14.6 years) were prospectively included in this study. ASL MRI was performed at 1.5T (n = 65) and 3T (n = 33) using a single-slice flow-sensitive alternating inversion recovery true–fast imaging with steady-state precession (FAIR True-FISP) sequence in the paracoronal plane. ASL perfusion was regional analyzed for the renal cortex on parameter maps. ASL was compared between patients with good or moderate allograft function (Group a; estimated glomerular filtration rate [eGFR] > 30 mL/min/1.73 m2) and patients with heavily impaired allograft function (Group b; eGFR ≤ 30 mL/min/1.73 m2) and correlated to renal function as determined by eGFR. Results ASL perfusion and eGFR were comparable at 1.5T (246.9 ± 66.8 mL/100 g/min and 41.9 ± 22.7 mL/min/1.73 m2) and 3T (236.5 ± 102.3 mL/100 g/min and 35.9 ± 22.9 mL/min/1.73 m2). ASL perfusion was significantly higher in group a (282.7 ± 60.8 mL/100 g/min) as compared to group b (178.2 ± 63.3 mL/100 g/min) (P < 0.0001). ASL perfusion values exhibited a significant correlation with renal function as determined by eGFR (r = 0.59; P < 0.0001). Conclusion Cortical ASL perfusion values differ between patients with good or moderate allograft function and poor allograft function and correlate significantly with allograft function. Our results highlight the potential of ASL MRI for functional evaluation of renal allografts. J. Magn. Reson. Imaging 2014;40:84–89. © 2013 Wiley Periodicals, Inc.

The goal of this study was to quantify CEST related parameters such as chemical exchange rate and fractional concentration of exchanging protons at a clinical 3T scanner. For this purpose, two CEST quantification approaches—the AREX metric (for ‘apparent exchange dependent relaxation’), and the AREX-based Ω-plot method were used. In addition, two different pulsed RF irradiation schemes, using Gaussian-shaped and spin-lock pulses, were compared. Numerical simulations as well as MRI measurements in phantoms were performed. For simulations, the Bloch–McConnell equations were solved using a two-pool exchange model. MR experiments were performed on a clinical 3T MRI scanner using a cylindrical phantom filled with creatine solution at different pH values and different concentrations. The validity of the Ω-plot method and the AREX approach using spin-lock preparation for determination of the quantitative CEST parameters was demonstrated. Especially promising results were achieved for the Ω-plot method when the spin-lock preparation was employed. Pulsed CEST at 3T could be used to quantify parameters such as exchange rate constants and concentrations of protons exchanging with free water. In the future this technique might be used to estimate the exchange rates and concentrations of biochemical substances in human tissues in vivo.

To evaluate the feasibility of diffusion-tensor (DT) imaging at 3 T for functional assessment of transplanted kidneys.This study was approved by the local ethics committee; written informed consent was obtained. Between August 2009 and October 2010, 40 renal transplant recipients were prospectively included in this study and examined with a clinical 3-T magnetic resonance (MR) imager. An echo-planar DT imaging sequence was performed in coronal orientation by using five b values (0, 200, 400, 600, 800 sec/mm(2)) and 20 diffusion directions. The fractional anisotropy (FA) and apparent diffusion coefficient (ADC) were determined for the cortex and medulla of the transplanted kidney. Relationships between FA, ADC, and allograft function, determined by the estimated glomerular filtration rate (eGFR), were assessed by using Pearson correlation coefficient. ADC and FA were compared between patients with good or moderate allograft function (group A; eGFR30 mL/min/1.73 m(2)) and patients with impaired function (group B; eGFR ≤ 30 mL/min/1.73 m(2)) by using a student t test. P.05 indicated a statistically significant difference.Mean FA of the renal medulla and cortex was significantly higher in group A (0.39 ± 0.06 and 0.17 ± 0.4) compared with group B (0.27 ± 0.05 and 0.14 ± 0.03) (P.001 and P = .009, respectively). Mean ADCs of renal cortex and medulla were significantly higher in group A than in group B (P = .007 and P = .01, respectively). In group B, mean medullary FA was significantly lower in patients whose renal function did not recover (0.22 ± 0.02) compared with those with stable allograft function at 6 months (0.29 ± 0.05, P.001). There was significant correlation between eGFR and medullary FA (r = 0.65, P.001), cortical ADC (r = 0.43, P = .003), and medullary ADC (r = 0.35, P = .01).DT imaging is a promising noninvasive technique for functional assessment of renal allografts. FA values in the renal medulla exhibit a good correlation with renal function.

Das Internet hat langst Einzug in den Arbeitsalltag von Radiologen gehalten. Nicht mehr der Zugang zu radiologisch relevanter Information stellt dabei die Herausforderung dar, sondern die kritische Wertung bei der Fulle der Informationen. Der Artikel bietet eine Hilfestellung, indem konkrete Internetangebote fur Radiologen erlautert werden. Angebote, die Entscheidungshilfen in der taglichen Praxis darstellen, werden ebenso vorgestellt wie Internetressourcen fur technische Belange in der Radiologie. Die aufgefuhrten Falldatenbanken und radiologisch orientierten Internetsuchmaschinen sind fur die Internetrecherche ein hilfreicher erster Schritt. Onlinenachschlagewerke der menschlichen Anatomie sind erhebliche Erleichterungen bei der Befundung. Eine Auswahl davon wird hier vorgestellt. Das Schreiben und Publizieren von wissenschaftlichen Artikeln in der Radiologie ist ohne ein breit gefachertes Angebot von Internetdiensten nicht mehr denkbar. Zusatzlich steht im Internet eine breite Auswahl teils kostenfreier Softwarelosungen zur Verfugung, die erheblich zur Bewaltigung radiologischer Aufgaben beitragen kann.

To evaluate the feasibility of renal diffusion quantification using the Padé exponent model (PEM) in healthy subjects.Diffusion measurements were completed in 10 healthy subjects (mean age, 32.4 ± 8.9 years) on a 3T MRI scanner (Magnetom Trio, Siemens AG, Germany). A respiratory-triggered echo planar imaging sequence (15 slices with 6 mm thickness; 16 b-values [0-750 s/mmThe mathematical accuracy of the PEM was significantly higher than for the other three-parameter and the monoexponential model (P 0.05), which enables more precise information about the deviation of the Gaussian behavior of the diffusion signal by the PEM. The biexponential model showed better fitting to the diffusion signal (medullar Rbi2 0.989 ± 0.008, AICcThe PEM is a novel promising approach to quantify diffusion properties in the human kidney and might further improve functional renal MR imaging.1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:160-167.

To evaluate which mathematical model (monoexponential, biexponential, statistical, kurtosis) fits best to the diffusion-weighted signal in prostate magnetic resonance imaging (MRI).24 prostate 3-T MRI examinations of young volunteers (YV, n=8), patients with biopsy proven prostate cancer (PC, n=8) and an aged matched control group (AC, n=8) were included. Diffusion-weighted imaging was performed using 11 b-values ranging from 0 to 800 s/mm(2).Monoexponential apparent diffusion coefficient (ADC) values were significantly (P.001) lower in the peripheral (PZ) zone (1.18±0.16 mm(2)/s) and the central (CZ) zone (0.73±0.13 mm(2)/s) of YV compared to AC (PZ 1.92±0.17 mm(2)/s; CZ 1.35±0.21 mm(2)/s). In PC ADC(mono) values (0.61±0.06 mm(2)/s) were significantly (P.001) lower than in the peripheral of central zone of AC. Using the statistical analysis (Akaike information criteria) in YV most pixels were best described by the biexponential model (82%), the statistical model, respectively kurtosis (93%) each compared to the monoexponential model. In PC the majority of pixels was best described by the monoexponential model (57%) compared to the biexponential model.Although a more complex model might provide a better fitting when multiple b-values are used, the monoexponential analyses for ADC calculation in prostate MRI is sufficient to discriminate prostate cancer from normal tissue using b-values ranging from 0 to 800 s/mm(2).

Von der zunehmenden Weiterentwicklung der Magnetresonanztomographie (MRT)-Technik in den letzen Jahrzehnten hat auch die Bildgebung bei Nieren- und Hochdruckkrankheiten profitiert. Die MRT bietet neben dem Fehlen von radioaktiver Strahlung die Moglichkeit einer exzellenten Abbildung pathologischer Prozesse in allen Raumebenen. MR-Angiographie und MR-Urographie sind bereits klinisch fest etablierte Spezialanwendungen der MRT, die in der Genauigkeit der Computertomographie (CT)-Untersuchung gleichzusetzen, in manchen Fragestellungen sogar exakter sind. Erweitert werden diese Verfahren durch spezielle, teils noch zu evaluierende, MRT-Untersuchungsmethoden, die eher funktionelle Aspekte messen bzw. ohne die Gabe von Kontrastmittel auskommen. Die MRT ist kostenintensiv, zeitaufwandig und nicht uberall verfugbar, sodass eine strenge Indikationsprufung auf Grundlage einer guten Kommunikation zwischen klinisch tatigen Arzten und Radiologen unabdingbar ist.

Purpose: To evaluate the impact of renal blood flow on apparent diffusion coefficients (ADC) and fractional anisotropy (FA) using time-resolved electrocardiogram (ECG)-triggered diffusion-tensor imaging (DTI) of the human kidneys. Materials and Methods: DTI was performed in eight healthy volunteers (mean age 29.1 ± 3.2) using a single slice coronal echoplanar imaging (EPI) sequence (3 b-values: 0, 50, and 300 s/mm2) at the timepoint of minimum (20 msec after R wave) and maximum renal blood flow (200 msec after R wave) at 3T. Following 2D motion correction, region of interest (ROI)-based analysis of cortical and medullary ADC- and FA-values was performed. Results: ADC-values of the renal cortex at maximum blood flow (2.6 ± 0.19 × 10−3 mm2/s) were significantly higher than at minimum blood flow (2.2 ± 0.11 × 10−3 mm2/s) (P < 0.001), while medullary ADC-values did not differ significantly (maximum blood flow: 2.2 ± 0.18 × 10−3 mm2/s; minimum blood flow: 2.15 ± 0.14 × 10−3 mm2/s). FA-values of the renal medulla were significantly greater at maximal blood (0.53 ± 0.05) than at minimal blood flow (0.47 ± 0.05) (P < 0.01). In contrast, cortical FA-values were comparable at different timepoints of the cardiac cycle. Conclusion: ADC-values in the renal cortex as well as FA-values in the renal medulla are influenced by renal blood flow. This impact has to be considered when interpreting renal ADC- and FA-values. J. Magn. Reson. Imaging 2013;37:233–236. © 2012 Wiley Periodicals, Inc.

This study was conducted to evaluate the mode of application, image quality (IQ), and radiation exposure resulting from introduction of a prospectively electrocardiogram-triggered high-pitch cardiac computed tomography angiography (CTA) acquisition mode into routine clinical practice.A total of 42 prospectively triggered cardiac CTAs were conducted on 34 patients (11 female, 23 male; mean age 56 ± 15 y) using a high-pitch mode (pitch 3.4) on a dual-source CT. In 8 of these patients with higher heart rates or occasional premature ventricular contractions, 2 immediately subsequent CTAs were performed ("double flash protocol"). Subjective IQ was assessed for coronary arteries using a 4-point scale (1=unevaluable to 4=excellent). Contrast-to-noise ratio (CNR) was measured in 9 locations. CT Dose Index and dose-length product were obtained, and the patients' effective dose was calculated.Mean effective doses were 2.6 ± 1.4 mSv (range: 1.1 to 6.4) for the entire cardiac examination and 1.4 ± 0.7 mSv (0.4 to 3.1) for individual high-pitch cardiac CTA. z-coverage ranged from 9.9 cm in a native coronary CTA to 31.4 cm in a bypass graft case. The overall subjective IQ was good to excellent (mean score: 3.5), with 1.5% unevaluable coronary segments. The "double flash protocol" resulted in a fully diagnostic CT study in all cases just after taking both scans into consideration. The mean CNR of all locations was 19.7 ± 2.6.Prospectively electrocardiograph-triggered high-pitch-mode cardiac CTA is a feasible and promising technique in clinical routine, allowing for evaluation of coronaries at good-to-excellent IQ and providing high CNR and minimal radiation doses. The "double flash protocol" might become a more robust tool in patients with elevated heart rates or premature ventricular contractions.

Aim To evaluate electrocardiogram (ECG)-gated quiescent-interval single-shot magnetic resonance angiography (QISS-MRA) for nonenhanced assessment of peripheral artery occlusive disease (PAOD) using contrast-enhanced MRA (CE-MRA) as the reference standard. Materials and methods Twenty-seven patients (mean age 66.6 ± 10.8 years) with PAOD were included in the study. QISS-MRA and CE-MRA of the lower extremity were performed using a 1.5 T MR scanner. In each patient, subjective image quality and the degree of stenosis were evaluated on a four-point scale for 15 predefined arterial segments. Results Twenty-five of the 27 patients were considered for analysis. Subjective image quality of QISS-MRA was significantly lower for the distal aorta, pelvic arteries, and femoral arteries as compared to CE-MRA (p < 0.01), while no significant difference was found for other vascular segments. The degree of stenosis was overestimated with QISS-MRA in 23 of 365 (6.3%) segments and underestimated in two of 365 (0.5%) segments. As compared to CE-MRA, QISS-MRA had a high sensitivity (98.6%), specificity (96%) as well as positive and negative predictive value (88.7 and 99.6%, respectively) for the detection of significant stenosis (≥50%). Conclusion ECG-gated QISS-MRA is a promising imaging technique for reliable assessment of PAOD without the use of contrast material.

Purpose To compare image quality of nonenhanced time-resolved 4D steady-state free precession MR angiography (4D SSFP MRA) of cerebral arteries at 1.5 T and 3 T. Materials and methods 12 healthy subjects (mean age 29.4 ± 6.9 years) were studied at both 1.5 T and 3 T. Two different positions of the acquisition slab were evaluated; in one acquisition the imaging slab included the carotid siphon (“Slow”), in the other acquisition the imaging slab was placed superior to the carotid siphon (“Shigh”). Subjective image quality of cerebral arteries was assessed independently by two readers on a 4-point scale. Relative Signal-to-Noise-Ratio (SNR) was determined for the M1 segment of the middle cerebral artery. Results Subjective image quality of the anterior cerebral artery (segments A1, A2) was significantly higher at 1.5 T as compared to 3 T, while 3 T provided significantly higher image quality for segment P3 of the posterior cerebral artery. For the middle cerebral artery (segments M1–M3), image quality was significantly higher at 1.5 T than at 3 T when the carotid siphon was included in the acquisition slab (“Slow”), while no significant difference was found between 1.5 T and 3 T with “Shigh”. Relative SNR was significantly higher at 1.5 T (23.1 ± 5.1) as compared to 3 T (12.1 ± 7.8) for “Slow” and significantly higher at 3 T (29.8 ± 5.9) than at 1.5 T (24.2 ± 3.6) for “Shigh”. Conclusion Our results indicate that 4D SSFP MRA should preferably be performed at 1.5 T with inclusion of the carotid siphon in the acquisition slab, which might be required for the assessment of intracranial collateral flow.

Zusammenfassung Einleitung Medizinische Curricula unterliegen derzeit einem Reformprozess mit einer Hinwendung zu interaktiven, fallbasierten Lehrkonzepten. In diesem Beitrag wird eine neuartige radiologische Lehrveranstaltung (CLICR-Kurs), die verschiedene innovative Ausbildungselemente vereint, beschrieben und erste Erfahrungen bei der praktischen Umsetzung sowie Evaluationsergebnisse vorgestellt. Methoden Es wurde ein neues Kursangebot fur das Fach Radiologie aufgebaut, in das Curriculum integriert und systematisch evaluiert. Inhaltlich wurden fur drei klinische Module themenbezogene, radiologische Fallvignetten erstellt, um durch den Einsatz von Computerarbeitsplatzen mit PACS-Nutzung, webbasierten Datenbanken und CASUS-Fallen das problemorientierte, fallbasierte und selbstbestimmte Lernen als erganzende Unterrichtsform zu den bestehenden radiologischen Kursen und Vorlesungen zu fordern. Ergebnisse Hinsichtlich der Evaluationsergebnisse schnitt der CLICR-Kurs im Vergleich zum Radiologischen Blockkurs bei allen vier gestellten Fragen deutlich besser ab. So beantworteten mehr als die Halfte der Studierenden die Frage nach der Gesamtzufriedenheit mit der Veranstaltung fur den CLICR-Kurs mit „trifft vollig zu“, wahrend dies fur den Radiologischen Blockkurs nur 3% taten. Eine ahnliche Tendenz ergab sich auch bei den ubrigen gestellten Fragen. Das neuartige, interaktive Kurskonzept und die Moglichkeit zur Nutzung einer webbasierten Datenbank wurde von den Studierenden gleichfalls positiv bewertet. Schlussfolgerungen Interaktive, fallbasierte Lehrkonzepte, wie der hier vorgestellte CLICR-Kurs, sowie webbasierte Datenbanken, sind nach Einschatzung der Studierenden eine sinnvolle Erweiterung des Lehrangebots fur das Fach Radiologie.

OBJECTIVE This study aimed to create a phantom, which allows reproducible computed tomography perfusion experiments, and to identify the influence of contrast bolus configuration, scan parameters, and scanner hardware on the calculation of perfusion parameters. METHODS A discoid perfusion phantom with centrifugally directed flow was constructed. Brain parenchyma was simulated by inert polyoxymethylene spheres. Repeated measurements were performed with variations of the above-mentioned factors, and their effects on perfusion results were analyzed. RESULTS Calculated flow values measured during experiments were reproducible and showed good correlation with the true flow (R = 0.995, P < 0.01). Tube voltage, injection rate of the contrast agent, the mathematical perfusion algorithm, and the hardware of the scanner hardware had a reproducible influence on calculated perfusion results. CONCLUSIONS In the long term, perfusion phantoms might be helpful in identifying hardware-specific and protocol-related factors of different computed tomography scanners to improve comparability of different scanners and scanning protocols.

Humanmedizinische Curricula unterliegen derzeit einem Reformprozess mit Etablierung ubergeordneter Lernziele, wie z. B. der diagnostischen, therapeutischen und praventiven Kompetenz. Damit verbunden sind eine Abkehr von traditionellen Lehrmethoden und die Hinwendung zu interaktiven, fallbasierten Ausbildungskonzepten. In diesem Beitrag werden die Konzeption, erste Erfahrungen sowie Evaluationsergebnisse eines neuen radiologischen Lehrkonzepts (Co-operative Learning In Clinical Radiology – CLICR) vorgestellt. Fur das Fach Radiologie wurde ein neues Kursangebot (CLICR-Kurs), das verschiedene innovative Ausbildungselemente vereint, erarbeitet und in das Curriculum integriert. Inhaltlich wurden fur 3 klinische Module themenbezogene radiologische Fallvignetten erstellt, um durch den Einsatz von Computerarbeitsplatzen mit PACS-Nutzung (PACS Picture Archiving and Communication System), webbasierten Datenbanken und der CASUS-Plattform das problemorientierte, fallbasierte und selbstbestimmte Lernen als erganzende Unterrichtsform zu den bestehenden radiologischen Kursen und Vorlesungen zu fordern. Die Evaluationsergebnisse des CLICR-Kurses und des radiologischen Blockkurses wurden miteinander verglichen. Der CLICR-Kurs schnitt im Vergleich zum radiologischen Blockkurs bei samtlichen gestellten Fragen signifikant besser ab. So beantworteten 52% der Studierenden die Frage nach der Gesamtzufriedenheit mit der Veranstaltung fur den CLICR-Kurs mit „trifft vollig zu“, wahrend dies fur den radiologischen Blockkurs nur 3% taten. Das interaktive Kurskonzept mit PACS-Anwendung und die Moglichkeit zur Nutzung einer webbasierten Datenbank wurden von den Studierenden gleichfalls positiv bewertet. So erachteten 95% der Studierenden das neue Kurskonzept insgesamt als Bereicherung fur das Medizinstudium und ebenfalls 95% befanden, dass speziell das interaktive Arbeiten im PACS sowie die Moglichkeit der Nutzung einer webbasierten Datenbank (82%) den Lernerfolg fordere. Interaktive fallbasierte Lehrkonzepte, wie der hier vorgestellte CLICR-Kurs, sind nach Einschatzung der Studierenden und Lehrenden eine sinnvolle Bereicherung des Lehrangebots fur das Fach Radiologie. In ihrer Grundkonzeption passen sie insbesondere in kompetenzorientierte Curricula.

Pacemakers and implantable cardioverter defibrillators (ICDs) are being increasingly employed in patients suffering from cardiac rhythm disturbances. The principal objective of this article is to familiarize radiologists with pacemakers and ICDs on chest radiographs and CT scans. Therefore, the preferred lead positions according to pacemaker types and anatomic variants are introduced in this study. Additionally, the imaging features of incorrect lead positions and defects, as well as complications subsequent to pacemaker implantation are demonstrated herein. Index terms: Pacemaker; ICD; Chest; Radiograph; CT

To evaluate multidetector CT volumetry in the assessment of bone defect healing in comparison to histopathological findings in an animal model.In 16 mini-pigs, a circumscribed tibial bone defect was created. Multidetector CT (MDCT) of the tibia was performed on a 64-row scanner 42 days after the operation. The extent of bone healing was estimated quantitatively by MDCT volumetry using a commercially available software programme (syngo Volume, Siemens, Germany).The volume of the entire defect (including all pixels from -100 to 3,000 HU), the nonconsolidated areas (-100 to 500 HU), and areas of osseous consolidation (500 to 3,000 HU) were assessed and the extent of consolidation was calculated. Histomorphometry served as the reference standard.The extent of osseous consolidation in MDCT volumetry ranged from 19 to 92% (mean 65.4 ± 18.5%). There was a significant correlation between histologically visible newly formed bone and the extent of osseous consolidation on MDCT volumetry (r = 0.82, P 0.0001). A significant negative correlation was detected between osseous consolidation on MDCT and histological areas of persisting defect (r = -0.9, P 0.0001).MDCT volumetry is a promising tool for noninvasive monitoring of bone healing, showing excellent correlation with histomorphometry.

Contrast-enhanced MRI is considered problematic in renal allograft recipients because of the development of nephrogenic systemic fibrosis. Therefore, we assessed the clinical value of a monoexponential model and a distribution function model of diffusion-weighted imaging (DWI) in renal allografts.A total of 23 patients were divided into three groups, as follows: group A, stable renal allograft function for at least 6 months; group B, transplantation within the past 30 days, with good renal allograft function; and group C, an acute deterioration or decrease in renal allograft function. T2-weighted axial, T1-weighted coronal, and a paracoronal DWI sequences with 16 b values (b = 0-750 s/mm(2)) were performed on a 1.5-T scanner. Region of interest-based analysis of the apparent diffusion coefficient (ADC) of the renal cortex was used.Monoexponential analysis showed mean (± SD) ADC values of 1932 ± 98, 2095 ± 246, and 1636 ± 200 10-(6) mm(2)/s for patient groups A, B, and C, respectively. The distribution function revealed a mean ADC of 2487 ± 185, 2850 ± 325, and 2142 ± 31410-(6) mm(2)/s for groups A, B, and C, respectively. The difference between groups A and B combined and group C (p0.005) was statistically significant for both models. R(2) yielded the best regression of mathematic fitting for the distribution function model (p0.0001).Unenhanced evaluation of renal allografts with DWI correlated well with renal function for both the monoexponential analysis and the distribution function model. There was no statistically significant difference in ADC values and renal allograft function between both types of analysis, but the distribution function showed the best regression.

Introduction: The purpose of the present study was to evaluate the feasibility of delayed gadolinium-enhanced magnetic resonance imaging of cartilage (dGEMRIC) in the detection of cartilage changes versus morphologic imaging in the long-term course of Legg–Calve–Perthes disease (LCPD). Methods: A total of 31 hips in 26 patients (mean age, 30.0 years; range, 18–54 years) who were diagnosed with LCPD in childhood were included. Twenty-one radiographically normal contralateral hips served as controls. dGEMRIC indices of femoral and acetabular cartilage in the weight-bearing zone. Cartilage morphology was classified on radial PD-weighted images according to the modified Outerbridge classification. Results: Mean dGEMRIC values of cartilage were significantly lower in hips after LCPD than in the radiographically normal contralateral hips (513 ± 100 ms vs. 579 ± 103 ms; P = 0.026). In 24 out of 31 LCPD hips and in 4 out of 21 radiographically normal contralateral hips, morphological cartilage changes were noted. Analysis of variance analysis revealed a significant influence of Outerbridge grading on decreased T1-values (P = 0.031). Conclusion: Our results suggest that dGEMRIC at 1.5 T is suitable to assess cartilage quality changes in the long-term follow-up after LCPD. The evaluation of biochemical cartilage quality with dGEMRIC may provide additional information about early cartilage changes occurring without visible alterations of cartilage morphology.

Background Periportal edema (PPE) can be seen in different clinical settings, including in patients following trauma. However, the underlying mechanisms and clinical significance in trauma patients still remain unclear. Purpose To determine the incidence of PPE in CT scans of trauma patients and to correlate PPE with trauma severity and different patterns of injury. Material and Methods We retrospectively analyzed contrast-enhanced spiral CT scans of 127 trauma patients that were referred to our Trauma Center Level I between January 2006 and June 2007. According to the Injury Severity Score (ISS), 70 patients with an ISS < 16 (minor trauma) were assigned to group 1 and 57 patients with an ISS ≥16 (major trauma) to group 2. Results The presence of PPE was significantly (p < 0.01) higher in group 2 (22 of 57 patients [38.6%]) than in group 1 (10 of 70 patients [14.3%]). In 29 patients PPE presented with a diffuse pattern and in three patients with a focal pattern, affecting only one liver lobe. In 14 patients PPE was found in absence of abdominal injuries. In addition, PPE was present in five patients with abdominal injuries but without liver injury. Conclusion PPE is seen significantly more often on abdominal CT scans following major traumas (ISS ≥ 16), but is not necessarily associated with liver injury.

Especially in regard to the potential risks for the development of nephrogenic systemic fibrosis (NSF) following the administration of Gadolinium-based contrast material, nonenhanced MR angiography (MRA) methods are becoming ever more important. Besides well-established time-of-flight (TOF) and phase-contrast (PC) MRA, alternative imaging techniques based on balanced steady-state free precession (bSSFP) and turbo-spin-echo (TSE) sequences are increasingly used in combination with or without arterial spin labeling (ASL) strategies. This article provides an overview of the principles and clinical values of different nonenhanced MRA techniques. In addition, recent nonenhanced MRA developments are presented.

To evaluate a nonenhanced time-resolved 4D SSFP MRA for dynamic visualization of intracranial collateral blood flow.22 patients (59.0 ± 11.8 years) with steno-occlusive disease of brain-supplying arteries were included in this study. 4D SSFP MRA of the intracranial arteries was acquired with 15 temporal phases and a temporal resolution of 115 ms using 1.5 T MR. Cerebral DSA served as the reference standard and was available in all patients.Nonenhanced 4D SSFP MRA allowed for detailed dynamic visualization of blood flow in the circle of Willis and its branches in 21 of 22 (95.5%) patients. Collateral flow was excluded with both 4D SSFP MRA and DSA in 4 patients. In 17 patients, DSA detected anterior collateral flow (n = 8), posterior collateral flow via the right (n = 8) and left (n = 7) posterior communicating artery as well as patent EC-IC bypasses (n = 8). 29 of 31 collateral flow pathways were visualized by 4D SSFP MRA. As compared to DSA, 4D SSFP MRA showed a high sensitivity (92.3%), specificity (100%), positive predictive value (100%) and negative predictive value (95.2%) for visualization of intracranial collateral flow.4D SSFP MRA is a promising non-invasive imaging technique for dynamic visualization of intracranial collateral flow.

To evaluate the feasibility of delayed gadolinium-enhanced magnetic resonance (MR) imaging of the cartilage of metacarpophalangeal (MCP) joints in patients with rheumatoid arthritis (RA) compared with that in control subjects.Institutional review board approval and informed consent were obtained. Thirty-one MCP joints in 10 patients with RA (mean age, 59 years; range, 35-77 years) and six healthy volunteers (mean age, 51 years; range, 30-71 years) were examined with delayed gadolinium-enhanced MR imaging of cartilage. Sagittal images of the second and third MCP joints (hereafter, MCP II and MCP III) were acquired with a three-dimensional dual-flip-angle gradient-echo sequence at 3.0 T. B(1) field inhomogeneity-corrected T1 maps were calculated, and delayed gadolinium-enhanced MR imaging of cartilage values for phalangeal and metacarpal cartilage were determined. In addition, cartilage thickness was measured. A nonparametric Mann-Whitney U test was used to assess differences between groups.Phalangeal and metacarpal delayed gadolinium-enhanced MR imaging of cartilage values in patients with RA (MCP II: 388 msec ± 105 [standard deviation] and 342 msec ± 79, respectively; MCP III: 409 msec ± 96 and 371 msec ± 89, respectively) were significantly lower than in control subjects (MCP II: 598 msec ± 62 and 560 msec ± 51, respectively; MCP III: 586 msec ± 57 and 561 msec ± 80, respectively). Cartilage thickness of both joints was comparable in patients with RA (MCP II: 1.28 mm ± 0.50, MCP III: 1.17 mm ± 0.24) and control subjects (MCP II: 1.42 mm ± 0.33, MCP III: 1.18 mm ± 0.26).Delayed gadolinium-enhanced MR imaging of cartilage of the MCP joints is feasible at 3.0 T. Delayed gadolinium-enhanced MR imaging of cartilage may help to assess cartilage degeneration in morphologically normal-appearing MCP II and III cartilage in patients with RA.

Ziel dieser Studie war es, die Pravalenz und klinische Bedeutung inzidenteller Herzbefunde im nicht EKG-getriggerten Thorax-CT ohne primar kardiale Fragestellung zu evaluieren. Dreihundert nicht EKG-getriggerte Thorax-CT-Untersuchungen wurden retrospektiv bzgl. inzidenteller Herzbefunde analysiert. Die klinische Bedeutung wurde von einem Kardiologen bewertet. Von 300 Patienten hatten 107 insgesamt 174 Herzbefunde: Koronarsklerose (90), Aorten-/Mitralklappenverkalkung (42), iatrogene Veranderungen (23), Perikarderguss (6), Herzvergroserung (4), Myokardpathologien (3), Perikardverkalkungen (2), Thrombus im linken Ventrikel (2) und Myxom (1). Im radiologischen Bericht wurden 51% aller Herzbefunde beschrieben. Bei 53 der 107 Patienten mit Herzbefund waren diese klinisch nicht bekannt. Als klinisch relevant wurden die bisher unbekannten Befunde von 8 Patienten eingestuft: Perikarderguss (4), Perikardverkalkung (1), Thrombus im linken Ventrikel (1), Vorhofmyxom (1) und Herzvergroserung (1). Inzidentelle Herzbefunde sind im nicht EKG-getriggerten Thorax-CT haufig und konnen in Einzelfallen von hoher klinischer Bedeutung sein.

Ziel: Beurteilung der Machbarkeit molekularer MR Knorpel-Bildgebung bei erstmaliger Anwendung an Fingergelenken. Material und Methoden: Mittels einer Variablen Flipwinkel-Methode (VFA) wurden delayed Gd(DTPA)2– enhanced MRI of the cartilage (dGEMRIC)-Untersuchungen vom Metacarpophalangealgelenk (MCP) II und MCP III an 18 Patienten mit rheumatoider Arthritis (RA) und 9 gesunden Probanden durchgefuhrt und die Knorpeldicke bestimmt. Zusatzlich wurden bei 2 Patienten mit Fingerpolyarthrose dGEMRIC-Untersuchungen der proximalen Interphalangealgelenken (PIP) angefertigt. Ergebnisse: Bei Patienten mit RA lagen im Vergleich zur Kontrollgruppe signifikant erniedrigte dGEMRIC-Indizes in allen untersuchten Knorpelarealen vor: Im MCP II betrug der dGEMRIC-Index im phalangealen Knorpel 389,6 ± 85,5 ms gegenuber 558,7 ± 74,4 ms in der Kontrollgruppe, im metacarpalen Knorpel 357,3 ± 97,1 ms gegenuber 490,0 ± 86,6 ms. Im MCP III wurden phalangeal 436,2 ± 113,6 ms bei RA, 558,8 ± 115,5 ms in der Kontrollgruppe, metacarpal 398,0 ± 97,6 ms bei RA und 529,6 ± 111,0 ms in der Kontrollgruppe gemessen. Signifikante Unterschiede von Alter und Knorpeldicke lagen nicht vor. An den PIP-Gelenken von Patienten mit Fingerpolyarthrose wurden im Vergleich zur Kontrollgruppe ebenfalls erniedrigte dGEMRIC-Indizes gefunden. Schlussfolgerung: Die dGEMRIC-Bildgebung an den Fingergelenken bei RA- und Fingerpolyarthrose-Patienten ist technisch moglich. Trotz morphologisch normalen Knorpels zeigen sich bei RA erniedrigte dGEMRIC-Indizes, was auf eine Schadigung des Knorpels auf molekularer Ebene hindeutet. Die klinische Bedeutung dieser Technik hinsichtlich Fruherkennung, Prognoseabschatzung und Monitoring muss durch weitere Studien gezeigt werden. Purpose: To evaluate the feasibility of molecular cartilage MRI in finger joints. Materials and Methods: Delayed Gd(DTPA)2-enhanced MRI of the cartilage (dGEMRIC) using a variable flip angle approach (VFA) was performed for the metacarpophalangeal (MCP) joints II and III in nine healthy volunteers and eighteen patients with rheumatoid arthritis (RA). The cartilage thickness was measured. Additionally, dGEMRIC was performed on proximal interphalangeal joints (PIP) in two patients with finger osteoarthritis (OA). Results: the dGEMRIC index of the four evaluated cartilage areas was significantly decreased in RA patients compared to healthy subjects. The dGEMRIC index of MCP II phalangeal cartilage was 389.6 ± 85.5 msec vs. 558.7 ± 74.4 msec in healthy subjects. The metacarpal MCP II cartilage dGEMRIC index was 357.3 msec ± 97.1 msec vs. 490.0 ± 86.6 msec. The dGEMRIC indices of MCP III were: phalangeal 436.2 ± 113.6 msec in RA, 558.8 ± 115.5 msec in healthy subjects and metacarpal 398.0 ± 97.6 msec in RA and 529.6 ± 111.0 msec in healthy subjects. Age and cartilage thickness were not significantly different. In PIP joints of finger osteoarthritis patients, low dGEMRIC indices were noted, compared to the controls. Conclusion: The dGEMRIC of finger joints is feasible in patients with RA and finger OA. Morphologically normal cartilage shows significantly decreased dGEMRIC values in RA, pointing towards cartilage degeneration on a molecular level. Further studies are needed to establish the usefulness of this technique for early diagnosis, prognosis and therapy monitoring.

Background Computed tomographic angiography has become the standard evaluating method of potential living renal donors in most centers. Although incidence of fibromuscular dysplasia is low (3.5–6%), this pathology may be relevant for success of renal transplantation. The incidence of FMD in our population of LRD and reliability of CTA for detecting vascular pathology were the aims of this study. Materials and methods 101 living renal donors, examined between 7/2004 and 9/2008 by CTA, were included in a retrospective evaluation. The examinations were carried out using a 64 Multi-detector CT (Siemens Medical Solutions, Erlangen). The presence or absence of the characteristic signs of fibromuscular dysplasia, as “string-of-beads” appearance, focal stenosis or aneurysms, were assessed and graded from mild (=1) to severe (=3). Furthermore, vascular anatomy and arterial stenosis were investigated in this study. Retrospective analysis of CTA and ultrasound were compared with operative and histological reports. Results Four cases of fibromuscular dysplasia (incidence 3.9%) in 101 renal donors were diagnosed by transplanting surgeons and histopathology, respectively. Three cases could be detected by CTA. In one donor even retrospective analysis of CTA was negative. Ten accessory arteries, 14 venous anomalies and 12 renal arteries stenosis due to atherosclerosis were diagnosed by CTA and could be confirmed by the operative report. Conclusion CTA is sufficient for detection of hemodynamic relevant stenosis and vascular anatomy. Only one patient with a mild form of FMD was under estimated. Therefore, if the CTA shows slightest irregularities which are not typical for atherosclerotic lesions, further diagnostic work up by DSA might still be necessary.

The signal of diffusion-weighted imaging of the human kidney differs from the signal in brain examinations due to the different microscopic structure of the tissue. In the kidney, the deviation of the signal behavior of monoexponential characteristics is pronounced. The aim of the study was to analyze whether a mono- or biexponential or a distribution function model fits best to describe diffusion characteristics in the kidney. To determine the best regression, different statistical parameters were utilized: correlation coefficient (R(2)), Akaike's information criterion, Schwarz criterion, and F-test (F(ratio)). Additionally, simulations were performed to analyze the relation between the different models and their dependency on signal noise. Statistical tests showed that the biexponential model describes the signal of diffusion-weighted imaging in the kidney better than the distribution function model. The monoexponential model fits the diffusion-weighted imaging data the least but is the most robust against signal noise. From a statistical point of view, diffusion-weighted imaging of the kidney should be modeled biexponentially under the precondition of sufficient signal to noise.

To quantify renal allograft perfusion in recipients with stable allograft function and acute decrease in allograft function using nonenhanced flow-sensitive alternating inversion recovery (FAIR)-TrueFISP arterial spin labeling (ASL) MR imaging.Following approval of the local ethics committee, 20 renal allograft recipients were included in this study. ASL perfusion measurement and an anatomical T2-weighted single-shot fast spin-echo (HASTE) sequence were performed on a 1.5-T scanner (Magnetom Avanto, Siemens, Erlangen, Germany). T2-weighted MR urography was performed in patients with suspected ureteral obstruction. Patients were assigned to three groups: group a, 6 patients with stable allograft function over the previous 4 months; group b, 7 patients with good allograft function who underwent transplantation during the previous 3 weeks; group c, 7 allograft recipients with an acute deterioration of renal function.Mean cortical perfusion values were 304.8 +/- 34.4, 296.5 +/- 44.1, and 181.9 +/- 53.4 mg/100 ml/min for groups a, b and c, respectively. Reduction in cortical perfusion in group c was statistically significant.Our results indicate that ASL is a promising technique for nonenhanced quantification of cortical perfusion of renal allografts. Further studies are required to determine the clinical value of ASL for monitoring renal allograft recipients.

PURPOSE: To evaluate the effects of a 2D non-linear adaptive post-processing filter (2D-NLAF) on image quality in dose-reduced multi-detector CT (MDCT) of the upper abdomen. MATERIALS AND METHODS: MDCT of the upper abdomen was simulated on a 64-slice scanner using a multi-modal anthropomorphic phantom (CIRS, Norfolk, USA). While keeping the collimation (64 × 0.6 mm) and pitch (p = 1) unchanged, the tube current (100 - 500 mAs) and tube potential (80 - 140 kVp) were varied to perform MDCT as high dose (CTDI > 20), middle dose (CTDI 10 - 20) and low dose (CTDI < 10) level protocols. Four independent blinded radiologists evaluated axial images with a thickness of 7 and 3 mm with respect to the presentation of ”mesenteric low contrast lesions”, ”liver veins”, ”liver cysts”, ”renal cysts” and ”big vessels”. The subjective image quality of original data and post-processed images using a 2D-NLAF (SharpViewCT, Linkoping, Sweden) was graded on a 5-point scale (from ”1” not visible to ”5” excellent) and statistically analyzed. The effective dose (E) was estimated using commercial software (CT-EXPO). RESULTS: For all protocol groups, 2D-NLAF led to a significant improvement in subjective image quality for all examined lesions (p < 0.01), particularly at the protocols of middle dose (E: 5 - 8 mSv) and low dose level (E: 1 - 5 mSv). A maximum effect was seen in middle dose protocols for ”low contrast lesions” (score ”3.3” with filter versus ”2.5” without) and ”liver veins” (”4.5” versus ”3.9”). CONCLUSION: The phantom study indicates a potential dose reduction of up to 50 % in MDCT of the upper abdomen by use of a 2D-NLAF, which should be further examined in clinical trails.

To evaluate high-resolution multi-pinhole single photon emission computed tomography (MPH-SPECT) for the detection of bony alterations in early rheumatoid arthritis (ERA), early osteoarthritis (EOA) of the fingers and healthy controls.The clinically dominant hands of 27 patients (13 ERA, nine EOA, five healthy controls) were examined by MPH-SPECT and bone scintigraphy. Additionally, magnetic resonance imaging (MRI) was performed in the ERA patients. Number of affected joints, localisation, pattern of tracer distribution and joint involvement were scored. Quantitative analysis was achieved by measurement of the region of interest (ROI) in all patients. The MPH-SPECT and MR images were fused in the ERA group.Bone scintigraphy detected fewer joints (26 joints,13/22 patients) with increased tracer uptake than did MPH-SPECT (80 joints, 21/22 patients). Bone scintigraphy did not show recognisable uptake patterns in any group of patients. With MPH-SPECT central tracer distribution was typical in ERA (10/13 patients, EOA 2/9). In contrast, an eccentric pattern was found predominantly in EOA (7/9, ERA 2/13). Normalised counts were 4.5 in unaffected joints and up to 222.7 in affected joints. The mean uptake values in affected joints were moderately higher in the EOA patients (78.75, and 62.16 in ERA). The mean tracer uptake in affected joints was approximately three-times higher than in unaffected joints in both groups (ERA 3.64-times higher, EOA 3.58). Correlation with MR images revealed that bone marrow oedema and erosions matched pathological tracer accumulation of MPH-SPECT in 11/13. MPH-SPECT demonstrated increased activity in 2/13 patients with normal bone marrow signal intensity and synovitis seen on MR images.MPH-SPECT is sensitive to early changes in ERA and EOA and permits them to be distinguished by their patterns of uptake.

PURPOSE Contrast-enhanced MRI is considered problematic in renal allograft recipients due to the association of gadolinium administration and the development of NSF. Therefore, we assessed the clinical value of mono- and biexponential analysis of diffusion-weighted imaging (DWI). MATERIALS AND METHODS A total of 32 patients were divided into four groups: (a) patients with stable function of renal allograft for at least 6 months, (b) patients with acute deterioration of allograft function, patients who recently underwent transplantation (< 14 days) with good (c) or decreased (d) renal function. T 2w ax. and T 1w cor. and a diffusion-weighted sequence with 16 b-values (b = 0 - 750 s/mm (2)) were performed on a 1.5 T scanner (Magnetom Avanto, Siemens Medical Solutions). ROI-based analysis of the renal cortex was analyzed using the software "Table Curve 2D". RESULTS Monoexponential analysis showed an ADC (mono) of 1961 +/- 104 1801 +/- 150, 2053 +/- 169 and 1720 +/- 191 10 (-6)mm (2) /sec for patient group a, b, c and d respectively. The difference in ADC (mono) between group (a) and (b) (p < 0.006) and between group (c) and (d) (p < 0.04) was statistically significant. Biexponential analysis revealed a mean perfusion fraction of 0.21, 0.23, 0.32 and 0.24 for group (a), (b), (c) and (d), respectively. Biexponential ADC showed a higher numerical accuracy. There were no statistically significant inter-group differences in diffusion (ADC (D)) and perfusion (ADC (P)). CONCLUSION Unenhanced evaluation of renal allografts with DWI is feasible. ADC (mono) of renal cortex correlates with renal function. The significance of the higher numerical accuracy of biexponential analysis in clinical settings requires further evaluation in larger-scale studies.