Ulrich Grosse

Perfusion measurements of the calf in patients with peripheral arterial occlusive disease before and after percutaneous transluminal angioplasty using Mr arterial spin labeling

To evaluate muscle perfusion in patients with peripheral arterial occlusive disease (PAOD) before and after percutaneous transluminal angioplasty (PTA) of the limb by means of MR arterial spin labeling (ASL) perfusion measurements during reactive hyperemia.

Ultrashort echo time MR imaging with off‐resonance saturation for characterization of pathologically altered Achilles tendons at 3 T

Off‐resonance radiofrequency saturation pulses applied prior to regular excitation in MR sequences can be used to modify signal contrast based on magnetization transfer and direct saturation effects. Clinical applicability and value of ultrashort echo time sequences combined with off‐resonance saturation pulses was tested in 16 healthy and 14 tendinopathic as well as paratendinopathic Achilles tendons in vivo at 3 T. A 3D ultrashort echo time sequence in combination with a gaussian off‐resonance saturation pulse (frequency offset: 1000–5000 Hz) was used to modify the detectable MR signal intensity from the Achilles tendon. Off‐resonance saturation ratio was calculated as the relative reduction in signal intensity under selective off‐resonance saturation in relation to a reference measurement without any saturation pulse. Off‐resonance saturation ratio in tendons of healthy volunteers ranged from 0.52 ± 0.06 (1000 Hz) to 0.24 ± 0.02 (5000 Hz), whereas symptomatic tendinopathic tendons (0.35 ± 0.04 to 0.17 ± 0.02) and asymptomatic tendinopathic tendons (0.41 ± 0.06 to 0.21 ± 0.02) showed significantly lower mean off‐resonance saturation ratio values. Off‐resonance saturation ratio values might provide a sensitive and quantitative marker for assessment of pathological microstructure alterations of the Achilles tendon. Magn Reson Med, 2013.

Humane metapneumovirus (HMPV) associated pulmonary infections in immunocompromised adults—Initial CT findings, disease course and comparison to respiratory-syncytial-virus (RSV) induced pulmonary infections

AIM To describe computed tomography (CT)-imaging findings in human metapneumovirus (HMPV)-related pulmonary infection as well as their temporal course and to analyze resemblances/differences to pulmonary infection induced by the closely related respiratory-syncytial-virus (RSV) in immunocompromised patients. MATERIALS AND METHODS Chest-CT-scans of 10 HMPV PCR-positive patients experiencing pulmonary symptoms were evaluated retrospectively with respect to imaging findings and their distribution and results were then compared with data acquired in 13 patients with RSV pulmonary infection. Subsequently, we analyzed the course of chest-findings in HMPV patients. RESULTS In HMPV, 8/10 patients showed asymmetric pulmonary findings, whereas 13/13 patients with RSV-pneumonia presented more symmetrical bilateral pulmonary infiltrates. Image analysis yielded in HMPV patients following results: ground-glass-opacity (GGO) (n=6), parenchymal airspace consolidations (n=5), ill-defined nodular-like centrilobular opacities (n=9), bronchial wall thickening (n=8). In comparison, results in RSV patients were: GGO (n=10), parenchymal airspace consolidations (n=9), ill-defined nodular-like centrilobular opacities (n=10), bronchial wall thickening (n=4). In the course of the disease, signs of acute HMPV interstitial pneumonia regressed transforming temporarily in part into findings compatible with bronchitis/bronchiolitis. CONCLUSIONS Early chest-CT findings in patients with HMPV-related pulmonary symptoms are compatible with asymmetric acute interstitial pneumonia accompanied by signs of bronchitis; the former transforming with time into bronchitis and bronchiolitis before they resolve. On the contrary, RSV-induced pulmonary infection exhibits mainly symmetric acute interstitial pneumonia.

Short-Term Exercise-Induced Changes in Hydration State of Healthy Achilles Tendons Can Be Visualized by Effects of Off-Resonant Radiofrequency Saturation in a Three-Dimensional Ultrashort Echo Time MRI Sequence Applied at 3 Tesla

Off‐resonant RF saturation influences signal intensity dependent on free and bound water fractions as well as the macromolecular content. The extent of interaction between these compartments can be evaluated by using the off‐resonance saturation ratio (OSR). Combined with UTE sequences quantification of OSR even in tendinous tissues with extremely fast signal decay is possible. The aim of this prospective study was to investigate short‐term exercise‐induced effects of hydration state of the Achilles tendon by means of OSR and tendon volume.

Diagnostic value of T1 and T2* relaxation times and off‐resonance saturation effects in the evaluation of achilles tendinopathy by MRI at 3T

To evaluate and compare the diagnostic value of T1, T2* relaxation times and off‐resonance saturation ratios (OSR) in healthy controls and patients with different clinical and morphological stages of Achilles tendinopathy.

Parenchymal Blood Volume Assessed by C-Arm-Based Computed Tomography in Immediate Posttreatment Evaluation of Drug-Eluting Bead Transarterial Chemoembolization in Hepatocellular Carcinoma.

ObjectivesThe aim of this study was to assess clinical utility of the quantitative perfusion parameter called parenchymal blood volume (PBV), as derived from C-arm–based computed tomography (CT), for immediate posttreatment assessment of drug-eluting bead (DEB) transarterial chemoembolization (TACE) in hepatocellular carcinoma (HCC). Materials and MethodsTwenty-four patients with early- or intermediate-stage HCC received DEB-TACE. A total of 52 HCC lesions were treated and assessed by C-arm CT before and after intervention. C-arm CT consisted of nonenhanced and contrast-enhanced acquisitions; from these, PBV maps were reconstructed. Lesion diameter, maximum PBV, and unenhanced parenchyma density were assessed before and after treatment. Diameter of visible contrast media deposits as well as residual vascularization was assessed after delivery of DEB. All patients underwent follow-up using cross-sectional imaging. All assessed lesions were evaluated concerning modified Response Evaluation Criteria in Solid Tumors for HCC. ResultsAll treated lesions showed significant decrease in PBV after DEB-TACE (mean difference, −15.61 mL/100 mL, P < 0.0001). Eleven lesions showed residual tumoral perfusion in PBV maps associated with an unfavorable outcome compared with completely treated lesions in terms of a lower tumor shrinkage over time (−0.02 ± 0.49 vs −0.76 ± 0.38; P < 0.0001). A contrast media deposit was seen in 78% of treated HCC lesions with a tendency toward better visibility in encapsulated lesions. Nonenhanced parenchyma density was significantly higher in all treated segments (149.69 ± 58.6 vs 68.42 ± 18.04, P < 0.0001). ConclusionsParenchymal blood volume values as derived from C-arm CT acquisitions in combination with nonenhanced and contrast-enhanced C-arm CT images are useful in posttreatment assessment of DEB-TACE in HCC. Residual tumor perfusion in PBV maps have predictive potential for mid-term tumor response in HCC and could allow a more individualized treatment schedule for DEB-TACE in HCC patients.

Automated volumetric assessment of the Achilles tendon (AVAT) using a 3D T2 weighted SPACE sequence at 3 T in healthy and pathologic cases

PURPOSE Achilles tendinopathy has been reported to be frequently associated with increasing volume of the tendon. This work aims at reliable and accurate volumetric quantification of the Achilles tendon using a newly developed contour detection algorithm applied on high resolution MRI data sets recorded at 3T. MATERIALS AND METHODS A total of 26 healthy tendons and 4 degenerated tendons were examined for this study. Automated identification (AI) of tendon boundaries was performed in transverse slices with isotropic resolution (0.8mm) gained with a T2-weighted SPACE sequence at 3T. For AI a snake algorithm was applied and compared to manual tracing (MT). RESULTS AI was feasible in all examined tendons without further correction. AI of both tendons was performed in each participant within 2 min (2 × 37 slices) compared to MT lasting 20 min. MT and AI showed excellent agreement and correlation (R(2) = 0.99, p<0.0001). AI provided a reduction of measurement error (0.4 cm(3) vs. 0.5 cm(3)) and coefficient of variation (1% vs. 2%). DISCUSSION Compared to MT the AI allows assessment of tendon volumes in highly resolved MRI data in a more accurate and reliable time-saving way. Therefore automated volume detection is seen as a helpful clinical tool for evaluation of small volumetric changes of the Achilles tendon.

Influence of Physical Activity on T1 and T2*Relaxation Times of Healthy Achilles Tendons at 3T

To evaluate longitudinal (T1) and transverse (T2*) relaxation times at different Achilles tendon locations (insertion, mid‐portion, and musculotendinous area) in a cohort of subjects with variable tendon straining activity, but without any signs of tendinopathy.

Diffusion-weighted imaging in musculoskeletal radiology—clinical applications and future directions

Diffusion-weighted imaging (DWI) is an established diagnostic tool with regards to the central nervous system (CNS) and research into its application in the musculoskeletal system has been growing. It has been shown that DWI has utility in differentiating vertebral compression fractures from malignant ones, assessing partial and complete tears of the anterior cruciate ligament (ACL), monitoring tumor response to therapy, and characterization of soft-tissue and bone tumors. DWI is however less useful in differentiating malignant vs. infectious processes. As of yet, no definitive qualitative or quantitative properties have been established due to reasons ranging from variability in acquisition protocols to overlapping imaging characteristics. Even with these limitations, DWI can still provide clinically useful information, increasing diagnostic accuracy and improving patient management when magnetic resonance imaging (MRI) findings are inconclusive. The purpose of this article is to summarize recent research into DWI applications in the musculoskeletal system.

Tendinopathy of the Achilles Tendon: Volume Assessed by Automated Contour Detection in Submillimeter Isotropic 3-Dimensional Magnetic Resonance Imaging Data Sets Recorded at a Field Strength of 3 T

Objective This prospective study assesses volume changes of the Achilles tendon in case of chronic tendinopathy (TEN), using an automated contour detection algorithm in submillimeter isotropic 3-dimensional magnetic resonance imaging data sets, recorded at 3 T. Methods Forty-one subjects (median age, 40 years; range, 19–68 years) were included in this prospective study and underwent nonenhanced magnetic resonance imaging of both Achilles tendons at 3 T, deploying a T2-weighted 3-dimensional Fast-Spin-Echo sequence with submillimeter resolution of 0.8 mm. Of the 41 subjects, 13 were classified as patients with TEN and 28 were healthy volunteers and served as control group. Of the 13 patients, 10 had unilateral TEN and 3 had bilateral TEN. Achilles tendons were automatically segmented in the T2-weighted magnetic resonance data sets for the evaluation of the tendon volume (0–3 cm proximal to the cranial border of the calcaneal bone). The total volume (length, 3 cm) was divided in 3 subvolumes of 1 cm length, named volume (0–1 cm), volume (1–2 cm), and volume (2–3 cm). Minimum and maximum tendon cross-sectional area within the total volume was processed. A standardized pain questionnaire was obtained from all patients. Results The automated contour detection algorithm worked reliably in all cases. The TEN group showed a significantly increased tendon volume compared to the control group (mean volume, 2.94 vs 2.43 mm3; P < 0.05). The difference was most obvious concerning volume (2–3 cm) (P < 0.0001). Evaluation of clinical severity revealed a moderate correlation between VISA-score and tendon volume (2–3 cm) as well as the maximum/minimum tendon area (&rgr; = −0.44, &rgr; = −0.48, and &rgr; = −0.41). In case of unilateral TEN, the symptomatic side showed an increased tendon volume (2–3 cm) and increased minimum area (P < 0.05). Conclusions Tendon volume and size are adequate surrogate parameters to differentiate patients with chronic TEN from healthy subjects, and may discriminate symptomatic TEN from asymptomatic “silent” TEN in patients with unilateral symptoms.