Guido M. Kukuk

Dual-Source Parallel Radiofrequency Excitation Body MR Imaging Compared with Standard MR Imaging at 3.0 T: Initial Clinical Experience

PURPOSE To prospectively compare the image quality and homogeneity of magnetic resonance (MR) images obtained by using a dual-source parallel radiofrequency (RF) excitation body MR imaging system with parallel transmission and independent RF shimming with the image quality and homogeneity of single-source MR images obtained by using standard sequences for routine clinical use in patients at 3.0 T. MATERIALS AND METHODS After institutional review board approval and informed patient consent were obtained, a dual-source parallel RF excitation 3.0-T MR system with independent RF shimming and parallel transmission technology was used to examine 28 patients and was compared with a standard 3.0-T MR system with single RF transmission. The RF power was distributed to the independent ports of the system body coil by using two RF transmission sources with full software control, enabling independent control of the phase and amplitude of the RF waveforms. Axial T2-weighted fast spin-echo (SE) and diffusion-weighted (DW) liver images, axial T2-weighted fast SE pelvic images, and sagittal T1- and T2-weighted fast SE spinal images were obtained by using dual- and single-source RF excitation. Two radiologists independently evaluated the images for homogeneity and image quality. Statistical significance was calculated by using the nonparametric Wilcoxon signed rank test. Interobserver agreement was determined by using Cohen kappa and Kendall tau-b tests. RESULTS Image quality comparisons revealed significantly better results with dual-source rather than single-source RF excitation at T2-weighted liver MR imaging (P = .001, kappa = 1.00) and better results at DW liver imaging at a statistical trend level (P = .066, tau-b > 0.7). Owing to reduced local energy deposition, fewer acquisitions and shorter repetition times could be implemented with dual-source RF excitation pelvic and spinal MR imaging, with image acquisition accelerating by 18%, 33%, and 50% compared with the acquisitions with single-source RF excitation. Image quality did not differ significantly between the two MR techniques (P > .05, tau-b > 0.5). CONCLUSION Dual-source parallel RF excitation body MR imaging enables reduced dielectric shading, improved homogeneity of the RF magnetic induction field, and accelerated imaging at 3.0 T.

Dual-source parallel RF transmission for clinical MR imaging of the spine at 3.0 T: intraindividual comparison with conventional single-source transmission.

PURPOSE To prospectively and intraindividually compare single-source radiofrequency (RF) excitation and dual-source parallel RF excitation in 3.0-T magnetic resonance (MR) imaging of the spine. MATERIALS AND METHODS Institutional review board approval and written informed patient consent were obtained. The RF power of a 3.0-T MR imaging system was distributed to two ports of the body coil of the system by using independent RF transmit channels. The maximum B(1) field strength for dual-source parallel RF excitation was maintained, as compared with single-source RF excitation. The repetition time was reduced according to the revised RF setup with dual-source parallel RF excitation while maintaining specific energy absorption limitations. Thirty patients were examined with and without dual-source parallel RF excitation. Diagnostic quality was assessed independently by two radiologists according to a four-point grading system. Image contrast ratios (CRs) were calculated between reference tissues and vertebrae for single-source RF excitation and dual-source parallel RF excitation. RESULTS The mean acceleration achieved with dual-source parallel RF excitation was 36% (range, 18%-50%). The total imaging duration of a three-station total spinal examination was reduced by one-third by using dual-source parallel RF transmission. For all cases investigated, diagnostic image quality without significant differences between the two methods and with a good interobserver agreement was achieved (Kendall tau-b, 0.50-0.84). The observed image contrast changes were predominantly small (<0.10 in 15 of 24 CRs), though they were significantly different (P < .05). CONCLUSION While shortening examination times by approximately one-third, the dual-source parallel RF transmission mode in MR imaging of the spine yielded diagnostic image quality comparable to that with the conventional single-source RF transmission mode.

Focal Liver Lesions at 3.0 T: Lesion Detectability and Image Quality with T2-weighted Imaging by Using Conventional and Dual-Source Parallel Radiofrequency Transmission

PURPOSE To prospectively compare T2-weighted single-shot turbo spin-echo (TSE) sequences performed with parallel and conventional radiofrequency (RF) transmission at 3.0 T for liver lesion detection, image quality, lesion conspicuity, and lesion contrast. MATERIALS AND METHODS After written informed consent and institutional review board approval, 52 consecutive patients (32 men, 20 women; mean age, 56.6 years ± 13.7 [standard deviation]) underwent routine magnetic resonance (MR) imaging with a clinical 3.0-T unit. Two independent readers reviewed images acquired with conventional and dual-source parallel RF transmission for detection of focal liver lesions, with separate reading of a third radiologist, including all available imaging findings, clinical history, and histopathologic findings, as reference. Image quality and lesion conspicuity were rated on five- and three-point evaluation scales, respectively. Contrast ratios between focal liver lesions and adjacent liver parenchyma were calculated. Significance was determined by using nonparametric Wilcoxon signed-rank and marginal homogeneity tests. RESULTS With the reference standard, 106 index lesions were identified in 22 patients. Detection rate significantly improved from 87% (92 of 106) to 97% (103 of 106) (reader 1) and from 85% (90 of 106) to 96% (102 of 106) (reader 2) with parallel RF transmission (reader 1, P = .0078; reader 2, P = .002). Quality of parallel RF transmission images was assigned scores significantly higher, compared with quality of conventional RF transmission images (mean for reader 1, 2.88 ± 0.73 vs 4.04 ± 0.44; mean for reader 2, 2.81 ± 0.72 vs 4.04 ± 0.39; P < .0001 for both). Lesion conspicuity scores were significantly higher on parallel RF transmission images, compared with conventional RF transmission images (mean for reader 1, 2.02 ± 0.64 vs 2.92 ± 0.27; mean for reader 2, 2.06 ± 0.67 vs 2.90 ± 0.30; P < .0001 for both). Contrast ratios were significantly higher with parallel RF transmission (P < .05). CONCLUSION Compared with conventional RF transmission, parallel RF transmission significantly improved liver lesion detection rate, image quality, lesion conspicuity, and lesion contrast. SUPPLEMENTAL MATERIAL http://radiology.rsna.org/lookup/suppl/doi:10.1148/radiol.11101429/-/DC1.

A gene for hypotrichosis simplex of the scalp maps to chromosome 6p21.3.

Hypotrichosis simplex of the scalp (HSS) is an autosomal dominant form of isolated alopecia causing almost complete loss of scalp hair, with onset in childhood. After exclusion of candidate regions previously associated with hair-loss disorders, we performed a genomewide linkage analysis in two Danish families and localized the gene to chromosome 6p21.3. This was confirmed in a Spanish family, with a total LOD score of 11.97 for marker D6S1701 in all families. The combined haplotype data identify a critical interval of 14.9 cM between markers D6S276 and D6S1607. Localization of the locus for HSS to 6p21.3 is a first step toward identification of the gene. The gene will give important insights into the molecular and cellular basis of hair growth on the scalp.

Cerebral arteriovenous malformations at 3.0 T: intraindividual comparative study of 4D-MRA in combination with selective arterial spin labeling and digital subtraction angiography.

Objective:Prospective intraindividual comparison of 4-dimensional contrast-enhanced MR angiography (4D-MRA) in combination with selective arterial spin labeling (ASL) at 3.0 Tesla and digital subtraction angiography (DSA) for anatomic and functional characterization of cerebral arteriovenous malformations (AVMs). Materials and Methods:In a prospective intraindividual comparative study, 16 patients diagnosed with symptomatic cerebral AVMs underwent 4D-MRA at an isotropic spatial resolution of 1.1 × 1.1 × 1.1 mm3 and a temporal resolution of 572 milliseconds, regional brain perfusion imaging using selective ASL and DSA. Selective ASL was performed for selective labeling of both carotid arteries and the vertebrobasilar complex. In a stepwise approach, all images were evaluated by 2 radiologists according to technical success rate, Spetzler-Martin classification, identification of arterial feeders, and existence of anatomic variants or functional cross-filling. Results:4D-MRA allowed for the same Spetzler-Martin classification as DSA in all patients. Of 28, 26 (93%) feeding arteries were correctly identified by both readers using 4D-MRA alone. Selective ASL provided additional functional or anatomic information in 4 of 16 cases (25%), enabling the detection of a cross-filling feeding artery that was not identified by 4D-MRA without selective ASL, thus improving the sensitivity of MRI in identification of arterial feeders from 26/28 (93%) to 27/28 (96%). The additional functional information regarding anatomic variants and cross-filling provided by selective ASL was confirmed by DSA in all cases. Conclusion:4D-MRA in combination with selective arterial spin labeling is a promising tool for the noninvasive assessment of cerebral AVMs providing functional information that so far has been gained only with DSA.

A distinct gene close to the hairless locus on chromosome 8p underlies hereditary Marie Unna type hypotrichosis in a German family.

Background Hypotrichosis of the Marie Unna type (HMU) is a rare autosomal dominant disorder characterized by male‐pattern hair loss with childhood onset and anomalies of the hair shaft.Objectives We aimed to evaluate a number of chromosomal loci as possible candidate regions for HMU. Methods A linkage analysis was performed in a large German family using microsatellite markers spanning candidate regions on chromosomes 8, 12 and 17.Results We found that the HMU locus maps to chromosomal region 8p21 in a 13·01‐cM interval between markers D8S1145 and D8S1771. This interval harbours the hairless gene (HR). Mutational analysis of HR on the genomic and transcript levels revealed no pathogenic mutation.Conclusions Our findings, together with a recent report of two unrelated families of Dutch and British origin, provide evidence for a hair growth regulatory gene distinct from HR in chromosomal region 8p21.

Contrast Material for Abdominal Dynamic Contrast-Enhanced 3D MR Angiography With Parallel Imaging: Intraindividual Equimolar Comparison of a Macrocyclic 1.0 M Gadolinium Chelate and a Linear Ionic 0.5 M Gadolinium Chelate

OBJECTIVE The purpose of this study was to compare a macrocyclic 1.0 M contrast agent with a linear ionic 0.5 M contrast agent at equimolar dosage in regard to image quality and number of vessel segments visualized at abdominal dynamic contrast-enhanced 3D MR angiography. SUBJECTS AND METHODS In an intraindividual comparative study, 15 patients (six women, nine men; mean age, 53 +/- 12.1 years; range, 25-72 years) underwent 32 1.5-T whole-body contrast-enhanced 3D MR angiographic examinations performed with parallel imaging technique. At random and in separate sessions, each patient was examined after IV injection of 0.1 mmol/kg body weight 1.0 M macrocyclic gadobutrol and 0.5 M linear ionic gadopentetate dimeglumine. Three-dimensional data sets were acquired in the arterial, portal venous, and venous phases with identical imaging protocols. Quantitative analysis included contrast measurements of vessels compared with adjacent background tissue (Students t test). Qualitative analysis was performed independently by two radiologists with regard to visualization of arterial and venous vessel segments and overall image quality (Wilcoxons test). RESULTS Visualization of individual vessel segments was rated significantly better after administration of 1.0 M macrocyclic gadobutrol compared with 0.5 M linear ionic gadopentetate dimeglumine (p < 0.001). Overall image quality was superior with 1.0 M macrocyclic gadobutrol, but the difference was not significant. Vessel-to-background contrast after injection of 1.0 M macrocyclic gadobutrol was significantly higher (arterial phase, 0.90, p = 0.02; portal venous phase, 0.78, p = 0.0002; venous phase, 0.74, p = 0.0002) compared with 0.5 M linear ionic gadopentetate dimeglumine (arterial phase, 0.89; portal venous phase, 0.73; venous phase, 0.67). CONCLUSION At abdominal contrast-enhanced 3D MR angiography, depiction of small abdominal vessels was significantly better and vessel-to-tissue contrast significantly higher with 1.0 M macrocyclic gadobutrol than with an equimolar dose of 0.5 M linear ionic gadopentetate dimeglumine.

Simultaneous MR arteriography and venography with blood pool contrast agent detects deep venous thrombosis in suspected arterial disease.

OBJECTIVE The purpose of this study was to investigate the prevalence of incidental deep venous thrombosis (DVT) in patients with clinically suspected peripheral arterial occlusive disease (PAOD) using contrast-enhanced MR angiography (MRA) with a blood pool contrast agent. SUBJECTS AND METHODS Two hundred fifty-nine MRA examinations with blood pool contrast agent in 245 consecutive patients (161 men; age range, 36-92 years), yielding a total of 4102 assessable arterial and venous vessel segments, were assessed with regard to the rate of incidentally observed acute and organized DVT and arterial stenosis grades. Incidental DVT was confirmed using duplex ultrasound. Contralateral nondiseased veins served as internal controls. The relationship between PAOD stages and acute and organized DVT was investigated using chi-square tests and a Mann-Whitney U test. RESULTS Arterial stenosis grading using MRA with blood pool contrast agent revealed less than 50% luminal stenosis in 78% of segments (3199/4102), 50% or greater stenosis in 8% of segments (317/4102), and occlusion in 14% of segments (586/4102). Incidental DVT was observed in 26 of 245 patients (11%) (acute DVT was seen in 10 patients and 26 segments; organized DVT was seen in 17 patients and 35 segments; and one patient had both acute and organized DVT). All incidentally diagnosed cases of DVT were confirmed by duplex ultrasound. Internal controls revealed no false-positive or -negative findings (26 patients and 172 segments). Incidental acute DVT was significantly more common among patients without arterial stenosis greater than 50% (p < 0.05). Otherwise, there was no significant relationship between Fontaine PAOD stages and the occurrence of acute (p = 0.688) or organized (p = 0.995) DVT. CONCLUSION Incidental DVT was prevalent in 11% of patients with clinically suspected PAOD. MRA with blood pool contrast agent has a potential role in the simultaneous assessment of arteries and veins and can detect concomitant venous disease affecting therapeutic management.

Hepatobiliary magnetic resonance imaging in patients with liver disease: correlation of liver enhancement with biochemical liver function tests.

ObjectivesTo evaluate hepatobiliary magnetic resonance imaging (MRI) using Gd-EOB-DTPA in relation to various liver function tests in patients with liver disorders.MethodsFifty-one patients with liver disease underwent Gd-EOB-DTPA-enhanced liver MRI. Based on region-of-interest (ROI) analysis, liver signal intensity was calculated using the spleen as reference tissue. Liver-spleen contrast ratio (LSCR) and relative liver enhancement (RLE) were calculated. Serum levels of total bilirubin, gamma glutamyl transpeptidase (GGT), aspartate aminotransferase (AST), alanine aminotransferase (ALT), glutamate dehydrogenase (GLDH), lactate dehydrogenase (LDH), serum albumin level (AL), prothrombin time (PT), creatinine (CR) as well as international normalised ratio (INR) and model for end-stage liver disease (MELD) score were tested for correlation with LSCR and RLE.ResultsPre-contrast LSCR values correlated with total bilirubin (r = -0.39; p = 0.005), GGT (r = -0.37; p = 0.009), AST (r = -0.38; p = 0.013), ALT (r = -0.29; p = 0.046), PT (r = 0.52; p < 0.001), GLDH (r = -0.55; p = 0.044), INR (r = -0.42; p = 0.003), and MELD Score (r = -0.53; p < 0.001). After administration of Gd-EOB-DTPA bilirubin (r = -0.45; p = 0.001), GGT (r = -0.40; p = 0.004), PT (r = 0.54; p < 0.001), AST (r = -0.46; p = 0.002), ALT (r = -0.31; p = 0.030), INR (r = -0.45; p = 0.001) and MELD Score (r = -0.56; p < 0.001) significantly correlated with LSCR. RLE correlated with bilirubin (r = -0.40; p = 0.004), AST (r = -0.38; p = 0.013), PT (r = 0.42; p = 0.003), GGT (r = -0.33; p = 0.020), INR (r = -0.36; p = 0.011) and MELD Score (r = -0.43; p = 0.003).ConclusionsLiver-spleen contrast ratio and relative liver enhancement using Gd-EOB-DTPA correlate with a number of routinely used biochemical liver function tests, suggesting that hepatobiliary MRI may serve as a valuable biomarker for liver function. The strongest correlation with liver enhancement was found for the MELD Score.Key Points• Relative enhancement (RLE) of Gd-EOB-DTPA is related to biochemical liver function tests.• Correlation of RLE with bilirubin, ALT, AST, GGT, INR and MELD Score is reverse.• The correlation of relative liver enhancement with prothrombin time is positive.• AST, ALT, GLDH, prothrombin time, INR and MELD Score correlate with pre-contrast liver-spleen contrast ratio.• Such biomarkers may help to evaluate liver function.

Diffusion-weighted whole-body MRI with background body signal suppression: Technical improvements at 3.0 T†

To improve image quality of diffusion‐weighted body magnetic resonance imaging (MRI) with background body signal suppression (DWIBS) at 3.0 T.