The purpose of this study was to assess the value of magnetic resonance imaging (MRI) in addition to computed tomography (CT) in gunshot wound cases with bullets or pellets lodged inside the head. In this context, the potential heating and movement of the lodged bullets were additionally investigated using animal models. Eleven forensic cases of penetrating gunshot wounds underwent CT and MRI. The data of each imaging modality were reviewed according to the following relevant characteristics: bony lesion at the entrance, intracranial bone fragments, intracranial metal fragments, gunshot residues, the wound channel and the severity of metal artifacts. Four-point Likert scales were used for the assessment. The heating of projectiles and their magnetic field interactions with the static magnetic field were assessed using animal models. MRI presented major advantages in cases with transversal trajectories and non-ferromagnetic bullets compared to CT. In general, MRI enabled a clear visualization of the wound channel and gunshot-related soft tissue injuries. An image fusion of CT and MRI datasets demonstrated the individual strengths of both modalities. Radio frequency (RF)-induced heating due to bullets lodged inside the brain tissue was invalidated. The likelihood of ferromagnetic projectile migration inside brain tissue is low. MRI of decedents with a bullet lodged inside their heads is viable and provides a valuable supplement to CT. The in situ, noninvasive depiction of the wound channel and gunshot-related soft tissue injuries on MRI can contribute to the knowledge of wound ballistics.

Background To assess changes of the craniocervical junction (CCJ), computed tomography (CT) is considered the reference standard. Recent advances in bone depiction on magnetic resonance imaging (MRI) enable high‐quality visualization of osseous structures. Consequently, MRI may serve as an alternative to CT, without the use of ionizing radiation. Purpose To compare two MRI sequences optimized for bone visualization to the CT reference standard in the assessment of the osseous CCJ. Study Type Prospective. Population/Subjects Twenty‐seven decedents and five healthy volunteers. Field Strength/Sequence 3T/ultrashort‐echo time gradient echo (UTE) and optimized 3D‐multiecho in‐phase gradient echo sequences (FRACTURE). Assessment All decedents were scanned with both MRI sequences and CT. Three observers rated degeneration to obtain a score for the upper (atlanto‐dental and left/right atlanto‐occipital joint) and for the lower part of the CCJ (left and right atlanto‐axial joint). Two reader rated the following quantitative parameters: basion‐axial‐interval, atlanto‐dental‐interval, atlanto‐occipital‐interval, Powers‐ratio, and signal/contrast‐to‐noise‐ratio. As a proof of concept, five healthy volunteers were scanned with both MRI sequences. Statistical Tests Degeneration was assessed on a Likert scale by three independent observers. Interrater and intermodality reliability were calculated using an intraclass correlation coefficient. To compare distance measurements between examination methods, a Friedman test, between‐degenerative ratings, and a Kruskal–Wallis test were performed. Results Degenerative ratings of the CCJ between MRI sequences and CT showed a good interrater and intermodality agreement. MRI sequences tended to underestimate the degree of degeneration compared to CT, and this became more marked with increasing degeneration severity. There were no significant relationships between distance measurements and the degree of degeneration (PCT = 0.62, PUTE = 0.64, PFRACTURE = 0.67). The in vivo examination proved the feasibility of both MRI methods in a clinical setting. Data Conclusion Quantitative and qualitative ratings on MR images were comparable to CT images; thus, MRI may be a valid alternative to CT assessing the CCJ. Level of Evidence 1. Technical Efficacy Stage 3.

Objectives To compare the image quality and diagnostic performance of conventional motion-corrected periodically rotated overlapping parallel line with enhanced reconstruction (PROPELLER) MRI sequences with post-processed PROPELLER MRI sequences using deep learning-based (DL) reconstructions. Methods In this prospective study of 30 patients, conventional (19 min 18 s) and accelerated MRI sequences (7 min 16 s) using the PROPELLER technique were acquired. Accelerated sequences were post-processed using DL. The image quality and diagnostic confidence were qualitatively assessed by 2 readers using a 5-point Likert scale. Analysis of the pathological findings of cartilage, rotator cuff tendons and muscles, glenoid labrum and subacromial bursa was performed. Inter-reader agreement was calculated using Cohen’s kappa statistic. Quantitative evaluation of image quality was measured using the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). Results Mean image quality and diagnostic confidence in evaluation of all shoulder structures were higher in DL sequences (p value = 0.01). Inter-reader agreement ranged between kappa values of 0.155 (assessment of the bursa) and 0.947 (assessment of the rotator cuff muscles). In 17 cases, thickening of the subacromial bursa of more than 2 mm was only visible in DL sequences. The pathologies of the other structures could be properly evaluated by conventional and DL sequences. Mean SNR (p value = 0.01) and CNR (p value = 0.02) were significantly higher for DL sequences. Conclusions The accelerated PROPELLER sequences with DL post-processing showed superior image quality and higher diagnostic confidence compared to the conventional PROPELLER sequences. Subacromial bursa can be thoroughly assessed in DL sequences, while the other structures of the shoulder joint can be assessed in conventional and DL sequences with a good agreement between sequences. Key Points • MRI of the shoulder requires long scan times and can be hampered by motion artifacts. • Deep learning–based convolutional neural networks are used to reduce image noise and scan time while maintaining optimal image quality. The radial k-space acquisition technique (PROPELLER) can reduce the scan time and has potential to reduce motion artifacts. • DL sequences show a higher diagnostic confidence than conventional sequences and therefore are preferred for assessment of the subacromial bursa, while conventional and DL sequences show comparable performance in the evaluation of the shoulder joint.