Initial experience with a state-of-the-art mobile head CT scanner for use in neurointensive care units.

OBJECTIVE: Mobile head computed tomography (CT) scanners can reduce transport-related complications in neurointensive care unit (NICU) patients and decrease the burden on NICU staff; however, the initial investment cost and reduced image quality of early mobile scanners have prevented their widespread clinical use. Here, we report our initial experience with a novel 32-row mobile CT scanner for use in NICUs. METHODS: Over a 2-year period, 107 patients received a mobile head CT scan. The technical characteristics of the scanner and the organizational procedures are described in detail. Patient characteristics were retrospectively collected and image quality was subjectively evaluated on a Likert scale ranging from 0 to 5 and compared with a stationary CT scanner. RESULTS: Mobile head CT was used for follow-up of intracranial hemorrhage in 51%, routine postoperative imaging in 28%, evaluation of neurological deterioration in 14%, bedside monitoring after external ventricular drain placement in 4%, and follow-up of ischemic stroke in 3% of cases. Diagnostic imaging quality was achieved in all cases, eliminating the need for stationary CT scanning. The overall image quality of mobile CT (median 4 points) was inferior to that of conventional stationary CT (median 5 points, p < 0.01), but was rated with 4 or 5 points in the majority of cases. CONCLUSIONS: State-of-the-art mobile CT was found to be easy to use and maneuver and has the potential to expedite the diagnosis of NICU patients and reduce staff workload. Image quality was adequate for common NICU issues.

State-of-the-art mobile head CT scanner delivers nearly the same image quality as a conventional stationary CT scanner.

The use of mobile head CT scanners in the neurointensive care unit (NICU) saves time for patients and NICU staff and can reduce transport-related mishaps, but the reduced image quality of previous mobile scanners has prevented their widespread clinical use. This study compares the image quality of SOMATOM On.Site (Siemens Healthineers, Erlangen, Germany), a state-of-the-art mobile head CT scanner, and a conventional 64-slice stationary CT scanner. The study included 40 patients who underwent head scans with both mobile and stationary scanners. Gray and white matter signal and noise were measured at predefined locations on axial slices, and signal-to-noise ratios (SNRs) and contrast-to-noise ratios (CNRs) were calculated. Artifacts below the cranial calvaria and in the posterior fossa were also measured. In addition, image quality was subjectively assessed by two radiologists in terms of corticomedullary differentiation, subcalvarial space, skull artifacts, and image noise. Quantitative measurements showed significantly higher image quality of the stationary CT scanner in terms of noise, SNR and CNR of gray and white matter. Artifacts measured in the posterior fossa were higher with the mobile CT scanner, but subcalvarial artifacts were comparable. Subjective image quality was rated similarly by two radiologists for both scanners in all domains except image noise, which was better for stationary CT scans. The image quality of the SOMATOM On.Site for brain scans is inferior to that of the conventional stationary scanner, but appears to be adequate for daily use in a clinical setting based on subjective ratings.

Detecting Bone Marrow Edema of the Extremities on Spectral Computed Tomography Using a Three-Material Decomposition.

BACKGROUND: Detecting bone marrow edema (BME) as a sign of acute fractures is challenging on conventional computed tomography (CT). This study evaluated the diagnostic performance of a three-material decomposition (TMD) approach for detecting traumatic BME of the extremities on spectral computed tomography (SCT). METHODS: This retrospective diagnostic study included 81 bone compartments with and 80 without BME. A TMD application to visualize BME was developed in collaboration with Philips Healthcare. The following bone compartments were included: distal radius, proximal femur, proximal tibia, distal tibia and fibula, and long bone diaphysis. Two blinded radiologists reviewed each case independently in random order for the presence or absence of BME. RESULTS: The interrater reliability was 0.84 (p < 0.001). The different bone compartments showed sensitivities of 86.7% to 93.8%, specificities of 84.2% to 94.1%, positive predictive values of 82.4% to 94.7%, negative predictive values of 87.5% to 93.3%, and area under the curve (AUC) values of 85.7% to 93.1%. The distal radius showed the highest sensitivity and the proximal femur showed the lowest sensitivity, while the proximal femur presented the highest specificity and the distal tibia presented the lowest specificity. CONCLUSIONS: Our TMD approach provides high diagnostic performance for detecting BME of the extremities. Therefore, this approach could be used routinely in the emergency setting.

Clinical evaluation of white matter lesions on 3D inversion recovery ultrashort echo time MRI in multiple sclerosis.

Background: We clinically evaluated the quality of white matter lesions (WML) of the cerebrum on 3D inversion recovery ultrashort echo time (IR-UTE) magnetic resonance imaging (MRI) in multiple sclerosis (MS) patients. Methods: Forty-nine patients with MS were included in this study. A 3T MRI scanner was used. Two radiologists (readers) evaluated the quality of WML on IR-UTE images using a three-point Likert scale (1-good quality, 2-moderate quality, 3-insufficient quality). They also rated other WML-related factors potentially influencing WML quality using another three-point Likert scale (1-no/minor impact, 2-moderate impact, 3-high impact). Another reader rated the presence of WML on IR-UTE to evaluate the diagnostic value (right/false positive and false negative) of IR-UTE in detecting WML. Signal intensity ratios (SIRs) derived from WML signal intensities and WML sizes were also determined and analyzed. Results: Two hundred and seventy-five MS lesions were evaluated. 87% of the lesions were rated Likert 1 on IR-UTE (P<0.01). WML rated Likert 2 and 3 presented near the grey matter (GM) in 58% of the cases (n=21), with 14 lesions being ≤2 mm (P=0.03). 62.5% of the WML rated Likert 2/3 were in the temporal lobe (P=0.02). The mean SIR of WML on IR-UTE was 1.14±0.22, while the mean SIR on fluid-attenuated inversion recovery (FLAIR) was 6.97±1.88. There was no significant correlation of SIRs between IR-UTE and FLAIR (R=0.14, P=0.245). 92.4% of the WML were correctly detected on IR-UTE (n=254). 19 out of the 21 false positive/negative rated WML were located near the GM or in the temporal lobe. WML presented 7.7% smaller in mean on IR-UTE compared to FLAIR. Factors affecting WML quality with a moderate or high impact (Likert 2 and 3) were not found. Conclusions: Most WML are clearly detectable on IR-UTE sequences. The main limitations are WML in the temporal lobe and near the GM.

Long-term diagnostic value of MRI in detecting recurrent aggressive fibromatosis at two multidisciplinary sarcoma centers.

PURPOSE: To assess the diagnostic accuracy of MRI in detecting recurrent aggressive fibromatosis (AF) during long-term follow-up at two multidisciplinary sarcoma centers. METHODS: Seventy-nine patients from two sarcoma centers were included in this IRB-approved study and were examined postoperatively using 1.5-T MRI. MRI follow-up scans were reviewed for true-positive/-negative and false-positive/-negative results. Available pathological reports and MRI follow-ups were set as reference. RESULTS: The median age of the patients was 38.1 ±â€¯15.3 years. Of the patients 27.9 % showed recurrent AF lesions. The most common localizations of AF were the axilla/shoulder (n = 15) and the thigh (n = 11). From 498 postoperative MRI follow-ups, 24 true-positive, 16 false-positive, 6 false-negative, and 452 true-negative MRI follow-ups were identified. The overall sensitivity and specificity for detecting recurrent AF was 80 % and 97 %, respectively. There was no significant difference in the diagnostic accuracy at the two sarcoma centers. All false-negative results were found in small lesions. False-positive results mostly mimicked streaky (n = 10) and small ovoid/nodular (n = 5) lesions. The configuration of recurrent AF was significantly most often fascicular (50 %; p = 0.001-0.005). CONCLUSION: MRI shows a high long-term diagnostic value in detecting AF recurrences. Nevertheless, radiologists should pay close attention when lesions are small, as they may remain undetected. Although the configuration of recurrent AF is most often fascicular, recurrences may also appear in different shapes.

Configuration of Primary and Recurrent Aggressive Fibromatosis on Contrast-Enhanced MRI with an Evaluation of Potential Risk Factors for Recurrences in MRI Follow-Up.

PURPOSE: To analyze the appearance of primary and recurrent aggressive fibromatosis (AF) on MRI with a focus on configuration and to determine potential risk factors for recurrences detected on MRI follow-up scans. METHODS: From 79 consecutive patients with histologically proven diagnosis of AF, 39 patients underwent a minimum of four 1.5 T MRI follow-up scans after resection of primary AF between 2008 and 2018. The primary and recurrent tumors were radiographically examined for configuration, limitation and extent on MRI. Epidemiological data and loco-regional subcutaneous edema, muscle edema and post-operative seroma were included. RESULTS: The mean age of the patients was 39 ±â€Š2.6 years. Primary and recurrent AF most often occurred in the thigh. The main appearance of primary AF was significantly most often fascicular (p = 0.001-0.01) with heterogeneous and marked contrast enhancement. 21 % (n = 8) of the patients developed recurrences of AF. A fascicular configuration with homogeneous/heterogeneous contrast enhancement was the main appearance of recurrent AF, but recurrent AF appeared nodular, polycyclic, ovoid or streaky/flat as well. Recurrent AF significantly most often occurred within the first 9 months after primary tumor resection (p = 0.009), especially in patients up to 25 years of age (RR = 6.1; 95 % CI: 1.8-20.9; p = 0.004). The cases of recurrent AF were altogether significantly smaller than the primary tumors (p = 0.001). Post-treatment subcutaneous and muscle edema were present in 77 % and 56 %, respectively. Patients with muscle edema after primary tumor resection had a significantly higher risk for AF recurrences (relative risk ratio (RR) = 1.8; 95 % CI: 1.16-2.8; p = 0.0096). There was no significant difference detected in patients with complete or incomplete resection of the primary tumor. CONCLUSION: Primary and recurrent aggressive fibromatosis has a mostly fascicular configuration, but may appear ovoid, nodular, streaky/flat or polycyclic as well. High risks for tumor recurrences are detected for patients up to 25 years of age, patients within the first 9 post-operative months and patients with muscle edema after primary tumor resection. KEY POINTS: · Primary aggressive fibromatosis mostly has a fascicular configuration with heterogeneous contrast enhancement. · Recurrent aggressive fibromatosis usually has a fascicular configuration with heterogeneous/homogeneous contrast enhancement. · Patients within the first 9 post-operative months and up to 25 years of age have a significantly higher risk for recurrences. · Muscle edema after resection of primary aggressive fibromatosis is associated with a significantly higher risk for recurrences. CITATION FORMAT: · Sedaghat S, Surov A, Krohn S et al. Configuration of Primary and Recurrent Aggressive Fibromatosis on Contrast-Enhanced MRI with an Evaluation of Potential Risk Factors for Recurrences in MRI Follow-Up. Fortschr Röntgenstr 2020; 192: 448 - 457.

Coexisting patterns of population oscillations: the degenerate Neimark-Sacker bifurcation as a generic mechanism.

We investigate a population dynamics model that exhibits a Neimark-Sacker bifurcation with a period that is naturally close to 4. Beyond the bifurcation, the period soon becomes locked at 4 due to a strong resonance, and a second attractor of period 2 emerges, which coexists with the first attractor over a considerable parameter range. A linear stability analysis and a numerical investigation of the second attractor reveal that the bifurcations producing the second attractor occur naturally in this type of system.

Dynamic imaging of a model of intracranial saccular aneurysms using ultra-high-resolution flat-panel volumetric computed tomography. Laboratory investigation.

OBJECT: Imaging of intracranial aneurysms using conventional multidetector CT (MDCT) is limited because of nonvisualization of features such as perforating vessels, pulsatile blebs, and neck remnants after clip placement or coil embolization. In this study, a model of intracranial saccular aneurysms in rabbits was used to assess the ultra-high resolution and dynamic scanning capabilities of a prototype flat-panel volumetric CT (fpVCT) scanner in demonstrating these features. METHODS: Ten New Zealand white rabbits underwent imaging before and after clipping or coil embolization of surgically created aneurysms in the proximal right carotid artery. Imaging was performed using a prototype fpVCT scanner, a 64-slice MDCT scanner, and traditional catheter angiography. In addition to the slice data and 3D views, 4D dynamic views, a capability unique to fpVCT, were also created and reviewed. The images were subjectively compared on 1) 4 image quality metrics (spatial resolution, noise, motion artifacts, and aneurysm surface features); 2) 4 posttreatment features reflecting the metal artifact profile of the various imaging modalities (visualization of clip or coil placement, perianeurysmal clip/coil anatomy, neck remnant, and white-collar sign); and 3) 2 dynamic features (blood flow pattern and aneurysm pulsation). RESULTS: Flat-panel volumetric CT provided better image resolution than MDCT and was comparable to traditional catheter angiography. The surface features of aneurysms were demonstrated with much higher resolution, detail, and clarity by fpVCT compared with MDCT and angiography. Flat-panel volumetric CT was inferior to both MDCT and angiography in terms of image noise and motion artifacts. In fpVCT images, the metallic artifacts from clips and coils were significantly fewer than those in MDCT images. As a result, clinically important information about posttreatment aneurysm neck remnants could be derived from fpVCT images but not from MDCT images. Time-resolved dynamic sequences were judged slightly inferior to conventional angiography but superior to static MDCT images. CONCLUSIONS: The spatial resolution, surface anatomy visualization, metal artifact profile, and 4D dynamic images from fpVCT are superior to those from MDCT. Flat-panel volumetric CT demonstrates aneurysm surface features to better advantage than angiography and is comparable to angiography in metal artifact profile. Even though the temporal resolution of fpVCT is not quite as good as that of angiography, fpVCT images yield clinically important anatomical information about aneurysm surface features and posttreatment neck remnants not attainable with either angiography or MDCT images.

Musculoskeletal applications of flat-panel volume CT.

Flat-panel volume computed tomography (fpVCT) is a recent development in imaging. We discuss some of the musculoskeletal applications of a high-resolution flat-panel CT scanner. FpVCT has four main advantages over conventional multidetector computed tomography (MDCT): high-resolution imaging; volumetric coverage; dynamic imaging; omni-scanning. The overall effective dose of fpVCT is comparable to that of MDCT scanning. Although current fpVCT technology has higher spatial resolution, its contrast resolution is slightly lower than that of MDCT (5-10HU vs. 1-3HU respectively). We discuss the efficacy and potential utility of fpVCT in various applications related to musculoskeletal radiology and review some novel applications for pediatric bones, soft tissues, tumor perfusion, and imaging of tissue-engineered bone growth. We further discuss high-resolution CT and omni-scanning (combines fluoroscopic and tomographic imaging).