Graft versus self (GvS) against T-cell autoantigens is a mechanism of graft-host interaction.

Graft-versus-host disease (GVHD) represents the major nonrelapse complication of allogeneic hematopoietic cell transplantation. Although rare, the CNS and the eye can be affected. In this study, manifestation in the retina as part of the CNS and T-cell epitopes recognized by the allogeneic T cells were evaluated. In 2 of 6 patients with posttransplantation retina diseases and 6 of 22 patients without ocular symptoms, antigen-specific T-cell responses against retina-specific epitopes were observed. No genetic differences between donor and recipient could be identified indicating T-cell activation against self-antigens (graft versus self). Transplantation of a preexisting immunity and cross-reactivity with ubiquitous epitopes was excluded in family donors and healthy individuals. In summary, an immunological reaction against retina cells represents a mechanism of graft-versus-host interaction following hematopoietic cell transplantation.

Bilateral comparison of the vascular pattern of the superficial temporal artery based on digital subtraction angiography.

PURPOSE: This study was performed to investigate any bilateral differences in the vascular pattern and microsurgical relevant parameters of the superficial temporal artery (STA) in vivo. METHODS: Digital subtraction angiographies of the STA of 38 individuals were retrospectively analyzed. A bilateral comparison of the branching pattern as well as of surgically relevant diameters and lengths of the main branches of the STA was performed. Moreover, gender-specific differences were assessed. RESULTS: Only 10 cases (26%) demonstrated an identical type and subtype of the STA pattern bilaterally. The diameters of the STA at its origin and bifurcation level as well as of its parietal branch were statistically significant wider on the right than on the left side (p(o) = 0.0009, p(b) = 0.006, p(p) = 0.030). Moreover, the diameters of the STA at its origin level on the right side, at its bifurcation level on both sides and of the frontal branch on both sides were statistically significant wider in males than females. No statistically significant differences of the lengths of the STA and its main branches between the right and the left side were identified. CONCLUSION: The occurrence of the vascular pattern of the STA in vivo is random for each side of the same person and cannot be predicted by the vascular pattern of the opposite side. The calibers of the main branches of the STA are gender specific and commonly larger on the right than on the left side.

Dual-Source Dual-Energy CT Angiography of the Supra-Aortic Arteries with Tin Filter: Impact of Tube Voltage Selection.

RATIONALE AND OBJECTIVES: Automatic bone and plaque subtraction (BPS) in computed tomographic angiographic (CTA) examinations using dual-energy CT (DECT) remains challenging because of beam-hardening artifacts in the shoulder region and close proximity of the internal carotid artery to the base of the skull. The selection of the tube voltage combination in dual-source CT influences the spectral separation and the susceptibility for artifacts. The purpose of this study was to assess which tube voltage combination leads to an optimal image quality of head and neck DECT angiograms after bone subtraction. MATERIALS AND METHODS: Fifty-one patients received tin-filter-enhanced DECT angiograms of the supra-aortic arteries using two voltage protocols: 24 patients were studied using 80/Sn140 kV and 27 using a 100/Sn140 kV protocol, both protocols with an additional tin filter. A commercially available DE-CTA BPS algorithm was used. Artificial vessel erosions in BPS maximum intensity projections (four-level Likert scale with CTA source data as reference) and vessel signal-to-noise ratio (SNR) were assessed in the level of the shoulders and the base of the skull in each patient and compared. RESULTS: At the level of the shoulder, 100/Sn140 kV achieved higher SNR (23.4 ± 6.4 at 80/Sn140 kV vs. 35.1 ± 11.8 at 100/Sn140 kV; P < .0001) with less erosions (erosion score 3.9 ± 0.4 in 80/Sn140 kV vs. 2.1 ± 1.3 in 100/Sn140 kV; P < .0001) than 80/Sn140 kV. At the level of the skull base, erosion scores and objective image quality of arterial segments were comparable with both protocols (P = .14). CONCLUSIONS: The 100/Sn140 kV protocol achieved more favorable results for BPS of the supra-aortic arteries than the 80/Sn140 kV protocol.

In vivo analysis of the vascular pattern of the superficial temporal artery based on digital subtraction angiography.

BACKGROUND: Existing anatomic descriptions of the superficial temporal artery (STA) are mainly based on cadaver studies and do not accurately reflect the in vivo situation. In this study, the anatomical course and branching pattern of the STA were analyzed with digital subtraction angiographies (DSAs). METHODS: DSAs of 93 Caucasian individuals between 16- and 79-years old were retrospectively analyzed regarding the course and branching pattern of the STA as well as surgically relevant inner diameters and lengths of its main branches. RESULTS: In total, 11 variations in the branching pattern of the terminal STA were found. About 89% of the examined individuals demonstrated the classic variation in which the main trunk of the STA bifurcates into a single frontal and parietal branch. In 60% of cases with an existing bifurcation, the division of the main trunk of the STA was located above the zygoma. The mean inner diameters of the STA main trunk, the frontal branch and the parietal branch were 2.4 ± 0.6 mm, 1.3 ± 0.6 mm and 1.2 ± 0.4 mm, respectively. The surgically relevant "working lengths" of the frontal and parietal branches above the upper margin of the zygoma up to an inner diameter of 1 mm were 106.4 ± 62.1mm and 99.7 ± 40.9 mm, respectively. CONCLUSIONS: The common variations of the branching pattern of the STA are described in this study. Furthermore, surgically relevant inner diameters and lengths of the main branches of the STA are determined. These findings should improve our understanding of the suitability and usefulness of the STA for various surgical procedures.

Added value of integrated circuit detector in head CT: objective and subjective image quality in comparison to conventional detector design.

RATIONALE AND OBJECTIVES: A new computed tomography (CT) detector with integrated electric components and shorter conducting pathways has recently been introduced to decrease system inherent electronic noise. The purpose of this study was to assess the potential benefit of such integrated circuit detector (ICD) in head CT by comparing objective and subjective image quality in low-dose examinations with a conventional detector design. MATERIALS AND METHODS: Using a conventional detector, reduced-dose noncontrast head CT (255 mAs; effective dose, 1.7 mSv) was performed in 25 consecutive patients. Following transition to ICD, 25 consecutive patients were scanned using identical imaging parameters. Images in both groups were reconstructed with iterative reconstruction (IR) and filtered back projection (FBP) and assessed in terms of quantitative and qualitative image quality. RESULTS: Acquisition of head CT using ICD increased signal-to-noise ratio of gray and white matter by 14% (10.0 ± 1.6 vs. 11.4 ± 2.5; P = .02) and 17% (8.2 ± 0.8 vs. 9.6 ± 1.5; P = .000). The associated improvement in contrast-to-noise ratio was 12% (2.0 ± 0.5 vs. 2.2 ± 0.6; P = .121). In addition, there was a 51% increase in objective image sharpness (582 ± 85 vs. 884.5 ± 191; change in HU/Pixel; P < .000). Compared to standard acquisitions, subjective grading of noise and overall image quality scores were significantly improved with ICD (2.1 ± 0.3 vs. 1.6 ± 0.3; P < .000; 2.0 ± 0.5 vs. 1.6 ± 0.3; P = .001). Moreover, streak artifacts in the posterior fossa were substantially reduced (2.3 ± 0.7 vs. 1.7 ± 0.5; P = .004). CONCLUSIONS: At the same radiation level, acquisition of head CT with ICD achieves superior objective and subjective image quality and provides potential for significant dose reduction.

Diffusion restriction of the optic nerve in patients with acute visual deficit.

PURPOSE: Diffusion magnetic resonance imaging (MRI) is commonly used in acute stroke, but not considered diagnostic in ischemic optic neuropathy. This study evaluates the presence of diffusion restriction in patients with acute visual loss by analyzing diffusion-weighted images (DWI). MATERIALS AND METHODS: A retrospective study of all patients who clinically presented with acute visual loss and who underwent MRI with DWI between January 2011 and May 2012 were evaluated. Patients with suspected brainstem ischemia were used as a control group. Two neuroradiologists evaluated the DWI for the presence of diffusion restriction within the optic nerve. RESULTS: In all, 34 patients with acute visual deficit and 32 controls were evaluated. In all five cases of acute optic ischemia, diffusion restriction with reduced apparent diffusion coefficient was present. In 2/25 patients with clinically defined optic neuritis, a diffusion restriction was present. No diffusion restriction was seen in the control cases or in cases with other causes for an acute visual deficit. CONCLUSION: DWI can identify ischemic lesions of the optic nerve. As in acute multiple sclerosis lesions, optic neuritis can also present in rare circumstances with diffusion restriction and can therefore not be ruled out solely by DWI MRI.

Evaluation of a 3-dimensional voxel-based neuronavigation system with perspective image rendering for keyhole approaches to the skull base: an anatomical study.

BACKGROUND: Keeping track of the endoscope tip in 3 planes (axial, coronal, and sagittal) while performing skull base surgeries can be difficult because the surgeon is focused most on the live video images of the endoscope. For that reason, it was the aim of this anatomical cadaver study to evaluate the usefulness of a voxel-based neuronavigation system with 3-dimensional (3D) perspective image rendering for endoscopic procedures through keyhole approaches to the skull base. METHODS: On 5 whole-body fixed cadavers, frontolateral and retrosigmoid approaches were performed bilaterally using a neuronavigation system with 3D perspective image rendering (Cbyon, Med-Surgical Services Inc., Sunnyvale, California). Target points defined on the selected target structures were approached with the navigated ∅ 4-mm 0° endoscope (Storz, Tuttlingen, Germany). Using an Endocameleon 4-mm rigid endoscope capable of changing its angle of view while remaining stationary, the surgical field was checked for injuries before and after insertion of the navigated 0° endoscope. RESULTS: The median neuronavigation registration error was 0.95 mm (range 0.6 to 1.2 mm). Evaluation showed that 100% of the defined targets were reached and visualized. Neither a target structure nor neurovascular structures or surrounding brain tissue were injured by the navigated 0° endoscope. CONCLUSIONS: A neuronavigation system with 3D voxel-based perspective image rendering could potentially improve safety during complex skull base surgeries, and possibly also help to improve surgical results. Such a system, however, cannot replace a neurosurgeon's experience nor surgical skill or anatomical knowledge. It is an excellent teaching tool for young neurosurgeons, but it also has some limitations. Therefore, clinical studies will be necessary to further evaluate the benefits of this type of neuronavigation system in a clinical setting.

Clinical evaluation and potential radiation dose reduction of the novel sinogram-affirmed iterative reconstruction technique (SAFIRE) in abdominal computed tomography angiography.

RATIONALE AND OBJECTIVES: Computed tomographic angiography is the standard in routine follow-up after endovascular aneurysm repair, causing radiation exposure; thus, dose-saving strategies should be applied. The aim of this study was to evaluate the novel sinogram-affirmed iterative reconstruction (SAFIRE) algorithm in terms of clinical usability and potential reduction of radiation exposure. MATERIALS AND METHODS: Forty-six patients underwent computed tomographic angiographic follow-up after endovascular aneurysm repair. Data were acquired using a dual-source computed tomographic scanner running both x-ray tubes at the same voltage (120 kV). Raw data were reconstructed using projections of both tubes with filtered back projection (FBP) and of only one tube with FBP and SAFIRE, corresponding to synthetic acquisition with half the radiation dose of the clinical routine radiation dose. Image sets were objectively compared regarding signal-to-noise ratio and edge sharpness. Two radiologists independently assessed a set of subjective criteria, including diagnostic usability, depiction of contrasted vessels, and image noise. RESULTS: Half-dose (HD) SAFIRE images showed significantly higher signal-to-noise ratios compared to full-dose FBP images (P < .001), while having equal edge sharpness (P = .56). Most of the subjectively assessed parameters, such as diagnostic usability and depiction of contrasted vessels, were rated similar for HD SAFIRE and full-dose FBP images. Full-dose FBP images depicted fine anatomic structures more clearly (P < .05), while HD SAFIRE data sets showed less noise (P < .01). HD FBP images performed worse on all criteria (P < .001). Interrater agreement was good (κ = 0.74-0.80). CONCLUSIONS: Using the SAFIRE algorithm, the radiation dose of high-contrast abdominal computed tomographic angiography is reducible from routine clinical levels by up to 50% while maintaining good image quality and diagnostic accuracy.

Double Bolus Application in TWIST-MR-Angiography of the Cervical Arteries.

Purpose. The aim of the present work was to test the feasibility of the time-resolved MR-angiography (TWIST-MRA) of cervical arteries using double bolus injection. Material and Methods. TWIST-MRA with a temporal resolution of 8.4 seconds for each frame and a spatial resolution with a voxel size of 0.61 × 0.58 × 0.8 mm(3) was performed in 24 patients. A biphasic bolus injection protocol was used with the second injection being started 21 seconds after the first contrast dye bolus. Diagnostic image quality was rated according to a 4-point scale. Results. In 12 patients (50%) no clear separation between the cervical venous and arterial vessels was evident after the first bolus injection. Using TWIST-MRA data acquired after the second bolus a sufficient diagnostic image quality (rating ≥3, mean 3.5) could be obtained in 22 of 24 patients (92%). Discussion. The double bolus injection protocol using TWIST-MRA allows for very good separation of the cervical arteries.

High-pitch computed tomography coronary angiography-a new dose-saving algorithm: estimation of radiation exposure.

Purpose. To estimate effective dose and organ equivalent doses of prospective ECG-triggered high-pitch CTCA. Materials and Methods. For dose measurements, an Alderson-Rando phantom equipped with thermoluminescent dosimeters was used. The effective dose was calculated according to ICRP 103. Exposure was performed on a second-generation dual-source scanner (SOMATOM Definition Flash, Siemens Medical Solutions, Germany). The following scan parameters were used: 320 mAs per rotation, 100 and 120 kV, pitch 3.4 for prospectively ECG-triggered high-pitch CTCA, scan range of 13.5 cm, collimation 64 × 2 × 0.6 mm with z-flying focal spot, gantry rotation time 280 ms, and simulated heart rate of 60 beats per minute. Results. Depending on the applied tube potential, the effective whole-body dose of the cardiac scan ranged from 1.1 mSv to 1.6 mSv and from 1.2 to 1.8 mSv for males and females, respectively. The radiosensitive breast tissue in the range of the primary beam caused an increased female-specific effective dose of 8.6%±0.3% compared to males. Decreasing the tube potential, a significant reduction of the effective dose of 35.8% and 36.0% can be achieved for males and females, respectively (P < 0.001). Conclusion. The radiologist and the CT technician should be aware of this new dose-saving strategy to keep the radiation exposure as low as reasonablly achievable.

Primarily solid intraventricular brain tumors.

Solid intraventricular-neoplasms are readily seen on cross-sectional images, but the myriad of entities to be considered may make a focused differential diagnosis elusive. Clinical symptoms of patients with intraventricular-tumors are non-specific and are generally related to increased intracranial pressure or hydrocephalus. The objective of this article is to present the most relevant demographic, clinical and imaging features of solid intraventricular-tumors for the purpose of a more comprehensive differential-diagnosis.

Automatic lumen segmentation in calcified plaques: dual-energy CT versus standard reconstructions in comparison with digital subtraction angiography.

OBJECTIVE: Dual-energy CT has the potential to automatically remove calcified plaques from angiographic data sets. The objective of this study is to compare the accuracy of visual grading of stenoses after plaque removal with visual grading in standard reconstructions. Digital subtraction angiography (DSA) was used as a reference standard. SUBJECTS AND METHODS: Twenty-five patients underwent dual-energy CT (140 kV and 80 mAs; 80 kV and 234 mAs) angiography and DSA. Plaque and bone removal was performed. Twenty-nine calcified stenoses were quantified using standard reconstructions, plaque and bone removal maximum intensity projections after plaque and bone removal, and DSA images, according to the North American Symptomatic Carotid Endarterectomy Trial criteria. The accuracy of the detection of relevant stenoses (> 70%) and occlusions was assessed. Correlation coefficients of the grades of stenoses with DSA were calculated. The influence of vessel enhancement on the accuracy of plaque removal was analyzed. RESULTS: The average postprocessing time was 45 seconds. After plaque removal, all 25 relevant and four nonrelevant stenoses were correctly detected. Six relevant stenoses were overestimated as complete occlusions. With the standard reconstructions, two nonrelevant stenoses were overestimated as relevant. Correlation coefficients (r(2)) for the grading of stenoses after plaque removal and with standard reconstructions versus DSA were 0.7694 and 0.4329, respectively. Vessel contrast enhancement correlated weakly (r(2) = 0.2072) with the accuracy of plaque removal. CONCLUSION: Dual-energy CT with plaque removal automatically delivers CT luminograms with a high sensitivity for the detection of relevant stenoses and a higher correlation to DSA than standard reconstructions but frequently leads to an overestimation of high-grade stenoses as occlusions. Thus, dual-energy CT plaque and bone removal should be used complementary to standard reconstructions, and not exclusively.