Adrian Ringelstein

Dual-energy-CT of hypervascular liver lesions in patients with HCC: investigation of image quality and sensitivity

ObjectiveTo investigate dual-energy CT of hypervascular liver lesions in patients with HCC.MethodsForty patients with hepatocellular carcinomas were investigated with abdominal dual-energy CT. In each patient unenhanced and contrast-enhanced imaging with arterial und portovenous delay were performed. Hypervascular lesions were documented on arterial phase 80-kVp images, 140-kVp images, and the averaged arterial images by two radiologists. Subjective image quality (5-point scale, from 5 [excellent] to 1 [not interpretable]) was rated on all images.ResultsThe mean number of hypervascular HCC lesions detected was 3.37 ± 1.28 on 80-kVp images (p < 0.05), 1.43 ± 1.13 on 140-kVp images (p < 0.05), and 2.57 ± 1.2 on averaged images. The image quality was 0.3 ± 0.5 for 80-kVp (p < 0.05), 1.6 ± 0.5 for 140-kVp (p < 0.05) and 3.2 ± 0.4 for the averaged images.ConclusionLow-kVp images of dual-energy datasets are more sensitive in detecting hypervascular liver lesions. However, this increase in sensitivity goes along with a decrease in the subjective image quality of low-kVp images.

Silent embolism after stent-assisted coiling of cerebral aneurysms: diffusion-weighted MRI study of 75 cases

Purpose New ischemic brain lesions are common findings after cerebral diagnostic angiography and endovascular therapy. Diffusion-weighted MRI (DWI) can be used for detection of these lesions. The aim of the present study was to investigate the incidence of DWI lesions after stent-assisted coiling and the evaluation of possible risk factors. Methods The study included a total of 75 consecutive patients treated with stent-assisted coiling. Post-procedural DWI of the brain was performed to detect ischemic lesions. Demographic data, aneurysm characteristics and angiographic parameters were correlated with properties of DWI lesions. Results In post-procedural DWI, 48 of the 75 patients (64%) had 163 DWI lesions in a pattern consistent with embolic events. The number of patients with DWI lesions was significantly increased in older patients (≥55 years) and longer intervention times (≥120 min). The ischemic brain volume was significantly increased in older patients (≥55 years) as well as in patients who were implanted with a shorter stent (<20 mm). Conclusions Thromboembolic events are common after stent-assisted coiling with an incidence comparable to DWI studies after coiling alone. Despite several devices and low operator experience, stent-assisted coiling for intracranial aneurysms has a very low risk of permanent neurologic disability. Further studies are necessary to improve the safety of stent-assisted coiling for patients in conditions with increased risk potential (age, procedure time, stent length).

Diffuse Axonal Injury at Ultra-High Field MRI

Objective Diffuse axonal injury (DAI) is a specific type of traumatic brain injury caused by shearing forces leading to widespread tearing of axons and small vessels. Traumatic microbleeds (TMBs) are regarded as a radiological marker for DAI. This study aims to compare DAI-associated TMBs at 3 Tesla (T) and 7 T susceptibility weighted imaging (SWI) to evaluate possible diagnostic benefits of ultra-high field (UHF) MRI. Material and Methods 10 study participants (4 male, 6 female, age range 20-74 years) with known DAI were included. All MR exams were performed with a 3 T MR system (Magnetom Skyra) and a 7 T MR research system (Magnetom 7 T, Siemens AG, Healthcare Sector, Erlangen, Germany) each in combination with a 32-channel-receive coil. The average time interval between trauma and imaging was 22 months. Location and count of TMBs were independently evaluated by two neuroradiologists on 3 T and 7 T SWI images with similar and additionally increased spatial resolution at 7 T. Inter- and intraobserver reliability was assessed using the interclass correlation coefficient (ICC). Count and diameter of TMB were evaluated with Wilcoxon signed rank test. Results Susceptibility weighted imaging revealed a total of 485 TMBs (range 1-190, median 25) at 3 T, 584 TMBs (plus 20%, range 1-262, median 30.5) at 7 T with similar spatial resolution, and 684 TMBs (plus 41%, range 1-288, median 39.5) at 7 T with 10-times higher spatial resolution. Hemorrhagic DAI appeared significantly larger at 7 T compared to 3 T (p = 0.005). Inter- and intraobserver correlation regarding the counted TMB was high and almost equal 3 T and 7 T. Conclusion 7 T SWI improves the depiction of small hemorrhagic DAI compared to 3 T and may be supplementary to lower field strengths for diagnostic in inconclusive or medicolegal cases.

Radiation exposure in perfusion CT of the brain.

Objective This study aimed to show the simulation of the radiation exposure of the brain during perfusion measurements multi-detector-CT. Material and Methods The effective dose and different organ doses were measured with thermoluminescent dosimeters in an Alderson-Rando phantom and compared with the data of a simulation program (CT-Expo V1.6) for varying scan protocols with different tube voltages (in kilovolts) and constant parameters for tube current (270 mAs), scan length (28.8 mm), scan time (40 seconds), slice thickness (24 × 1.2 mm), and number of scans (40) for multi-detector-CT perfusion measurements of the brain. Results The thermoluminescent dosimeter measurements yielded effective doses of 3.8 mSv (80 kV), 8.6 mSv (100 kV), 14.1 mSv (120 kV), and 22.2 mSv (140 kV). These values were in line with the data from the simulation program CT-Expo V1.6. The organ doses varied between 97 and 556 mGy (brain), 10.7 and 80.9 mGy (eye lens), 9.6 and 46 mGy (bone marrow), 1.2 and 6.7 mGy (thyroid gland), and 4.1 to 22.3 mGy (skin). The maximum local skin dose ranged from 355 mGy (80 kV) to 1855 mGy (140 kV) in the directly exposed part of the skin. Conclusions The radiation exposure during perfusion measurements of the brain is strongly dependent on the tube voltage and can vary widely even if the other exposure parameters remain constant. Maximum organ doses up to 556 mGy (brain) can be measured. Even if we never reached local organ doses that can cause a direct radiation injury, the review of the tube voltages implemented by the vendor is mandatory beside the limitation of the scanned area by clinical examination and the reduction of the number of scans. Simulation programs are a valuable tool for dose measurements.

Diagnostic value of 3D fluid attenuated inversion recovery sequence in multiple sclerosis

Background Magnetic resonance imaging (MRI) is an indispensable tool in the diagnostic work-up of multiple sclerosis (MS). To date, guidelines suggest MRI protocols containing axial dual-echo, unenhanced and post-contrast T1-weighted sequences. Especially the usage of dual-echo sequences has markedly improved the ability of MRI to detect cortical and infratentorial lesions. Newer 3D FLAIR sequences are supposed to provide even more positive imaging features such as improved detection of white matter lesions and a better resolution due to smaller slice thickness. Purpose To evaluate the diagnostic impact of 3D FLAIR sequences in comparison to conventional T2 and PD sequences. Material and Methods Examinations of 20 MS patients (10 women, 10 men) were reviewed retrospectively. All patients received MRI standard protocol containing PD and T2 sequences and a mid-sagittal T2 sequence. Additionally an isotropic 3D FLAIR sequence was performed. Whole-brain lesion load and number of lesions in juxtacortical, infratentorial, and midcallosal localizations were assessed by two observers independently and compared. Results Whole lesion load and the count of detectable lesions at the 3D FLAIR sequence were significantly higher in the juxtacortical and infratentorial regions compared to the PD/T2 sequence. Detection rate of midcallosal lesions did not differ significantly in sagittal T2 and 3D FLAIR sequence. Conclusion 3D FLAIR sequences can improve the detection of brain lesions in patients with MS and are even more sensitive in depicting lesions in cortical and infratentorial locations than current dual-echo sequences. The sequence can replace both PD/T2 sequences and mid-sagittal T2 sequences of the corpus callosum.

Efficacy of high-pitch CT protocols for radiation dose reduction

Various strategies have been developed to reduce radiation exposure of patients in CT examinations. The aim of this study was to evaluate the efficacy of high pitch in representative CT protocols examining lung embolism. We performed thermoluminescence measurements with an anthropomorphic phantom exposing it to CT algorithms for lung embolism in a 128-multislice, dual-source CT scanner: a standard CT protocol (sCT) and a CT protocol with a high pitch (+ F). Radiation doses for both CT algorithms were compared and the dose reduction potential of high pitch for individual organs was evaluated. As expected, the  +F mode reduced the effective dose and organ doses in the primary beam of radiation (namely, lung, bone marrow, heart, breast, skin and skeleton) compared with sCT by up to 52% for an equivalent image quality. On the contrary, for organs at the margin of the primary beam (thymus, thyroid, liver, pancreas, kidneys, colon and small intestine), the  +F mode reduced effective radiation doses by only 0-30%, compared with sCT. The dose reduction potential of the  +F mode greatly depends on the position of the organ in the scan field. While for organs in the primary beam  + F leads to a considerable dose reduction, it is less effective for tissues at the margin of the scanned area.

Spinal metastasis from malignant meningeal intracranial hemangiopericytoma: one-staged percutaneous Onyx™ embolization and resection - a technical innovation

BackgroundWe are the first to report one-staged resection of a spinal metastasis from malignant cranial hemangiopericytoma after preoperative Onyx™-20 embolization by direct percutaneous puncture.Spinal metastases from cranial hemangiopericytoma are extremely rare. Surgical morbidity of these highly vascularized tumours results mainly from excessive blood loss. Preoperative embolization of hyper vascular tumours has been used to reduce intraoperative blood loss for a long time. To avoid complications from arterial catheter intervention, direct percutaneous puncture has been advocated as a safe and effective alternative.MethodsA 46-year-old man with a history of malignant cranial hemangiopericytoma deriving from the left frontal skull base presented with a short history of lower back pain. A magnetic resonance imaging scan revealed an intra- and extra spinal mass lesion of the thoracic spine at Th 12. Indication for tumour resection was made and the patient’s written consent was obtained. Preoperatively, arterial catheter angiography was performed to reveal the tumour’s angioarchitecture, revealing high-flow arteriovenous shunts. In order to impede the expected perioperative blood loss, tumour embolization by direct percutaneous puncture and application of Onyx™-20 was performed prior to surgery.ResultsAfter percutaneous Onyx™-20 embolization, complete and safe resection of the lesion could be achieved. There was only minimal blood loss perioperatively. A pathohistological report confirmed malignant, anaplastic hemangiopericytoma.ConclusionsIn our case Onyx™-20 embolization via direct percutaneous puncture of a highly vascularized tumour was shown to be a safe and efficient tool prior to surgery. Despite high-flow arteriovenous shunts, direct percutaneous administration of non-adhesive ethanol liquid was an efficient alternative to transarterial catheter embolization. The perioperative blood loss could be substantially diminished.

Giant Intracranial Aneurysms at 7T MRI

Seven giant intracranial aneurysms were evaluated, and 2 aneurysms were available for histopathologic examination. Aneurysm walls were depicted as hypointense in TOF-MRA and SWI sequences with excellent contrast ratios to adjacent brain parenchyma. A triple-layered microstructure of the aneurysm walls was visualized in all aneurysms in TOF-MRA and SWI. This could be related to iron deposition in the wall, and similar findings were seen in 2 available histopathologic specimens. In vivo 7T TOF-MRA and SWI can delineate the aneurysm wall and the triple-layered wall microstructure in giant intracranial aneurysms. SUMMARY: Giant intracranial aneurysms are rare vascular pathologies associated with high morbidity and mortality. The purpose of this in vivo study was to assess giant intracranial aneurysms and their wall microstructure by 7T MR imaging, previously only visualized in histopathologic examinations. Seven giant intracranial aneurysms were evaluated, and 2 aneurysms were available for histopathologic examination. Six of 7 (85.7%) showed intraluminal thrombus of various sizes. Aneurysm walls were depicted as hypointense in TOF-MRA and SWI sequences with excellent contrast ratios to adjacent brain parenchyma (range, 0.01–0.60 and 0.58–0.96, respectively). The triple-layered microstructure of the aneurysm walls was visualized in all aneurysms in TOF-MRA and SWI. This could be related to iron deposition in the wall, similar to the findings in 2 available histopathologic specimens. In vivo 7T TOF-MRA and SWI can delineate the aneurysm wall and the triple-layered wall microstructure in giant intracranial aneurysms.

Value of DSA in the diagnostic workup of pulsatile tinnitus.

Objectives Pulsatile tinnitus (PT) is a rare complaint, but can be a symptom of life-threatening disease. It is often caused by vascular pathologies, e.g. dural arteriovenous fistula (dAVF), arteriovenous malformation (AVM) or vascularized tumors. The current diagnostic pathway includes clinical examination, cranial MRI and additional DSA. The aim of this study was to evaluate the diagnostic impact of DSA in the diagnostic workup of patients with PT in comparison to MRI alone. Methods Retrospectively, 54 consecutive patients with pulsatile tinnitus were evaluated. All patients had a diagnostic workup including cranial MRI and DSA. MRI examinations were blinded to the results of DSA and retrospectively analyzed in consensus by two experienced neuroradiologists. The MR-examinations were evaluated for each performed sequence separately: time-of-flight-angiography, ce-MRA, T2, ce-T1-sequence and ce-T1-sequence with fat saturation. Results 37 of the 54 patients revealed a pathology explaining PT on MRI, which was detected by the readers in 100% and proofed by means of DSA. 24 dAVF, four paraganglioma, two AVM and seven more pathologies were described. All patients without pathology on MRI did also not show any pathology in DSA. Conclusions MR imaging is sufficient to exclude pathology in patients with pulsatile tinnitus.

3-Jahres-Follow nach Aneurysmabehandlung mit dem Silk® Flow Diverter

PURPOSE Flow diverters may occlude aneurysms by endoluminal reconstruction of the parent artery and by reducing the blood flow into the aneurysm. The purpose of this study was to assess the rate of intervention-associated complications and a 3-year-follow-up. MATERIALS AND METHODS We retrospectively analyzed 18 patients treated with Silk® FD. Only patients with unruptured aneurysms were included. Treatment indications were fusiform, giant or recurrent aneurysms. We considered all aneurysms to have a high likelihood of failure and/or recurrence when treated with conventional endovascular techniques. RESULTS Silk FD could directly be placed in a proper position across the whole length of the aneurysm in 16/18 patients. In one case an additional PTA was necessary. In another case the first FD could not be properly deployed. 17 of 18 aneurysms (95 %) were occluded immediately, in the mid-term follow-up after 6 months or 3 years after treatment. The overall complication rate including technical (11.1 %), acute or delayed thromboembolic complication without (11.1 %) or with (16.6 %) severe complications was documented. CONCLUSION FD treatment is effective with a high occlusion rate of aneurysms also in long-term follow-up. In these complex aneurysms the complication rate is higher than in conventional stent-assisted coiling.