Achille Mileto

Purpose To evaluate the feasibility of use of dark borosilicate oral contrast media (DBOCM) in abdominopelvic CT in comparison with conventional oral contrast media (COCM) in a multi-institutional setting. Methods Patients with known or suspected inflammatory bowel disease (IBD) (Site A) or suspected peritoneal carcinomatosis (Site B), who had undergone initial standard-of-care CT using COCM (positive, n = 10; neutral n = 22), underwent research CT with DBOCM. Attenuation differences between bowel wall and lumen using COCM and DBOCM were measured. Three radiologists independently examined all examinations with COCM and DBOCM. Patient tolerance and safety were recorded. Bowel wall visualization, distention, distended bowel length, and radiologist preference for bowel visualization were rated. Imaging findings using both oral contrast media were recorded, and a final consensus evaluation was performed to evaluate whether additional findings detected with DBOCM were visible with COCM. Results Thirty-two patients (IBD, n = 15; suspected peritoneal carcinomatosis, n = 17) were included. No severe adverse effects were seen with DBOCM. Compared to COCM, DBOCM yielded significantly higher attenuation differences between bowel wall and lumen (P < .001). Bowel wall visualization, distention, and distended bowel length was significantly higher from the stomach to the ileum using DBOCM (P < .001). DBOCM was preferred by each reader over COCM for all intestinal segments, but significance was not achieved in pooled results. Additional imaging findings were found in seven patients (22% [7/32]; 95% CI 9–40%) using DBOCM. Conclusion Compared to COCM, DBOCM yielded improved bowel wall visualization and distention, also revealing additional imaging findings.

Precise and accurate staging of rectal cancer is critical for formulating an appropriate treatment plan, including determining the necessity for neoadjuvant therapy and establishing an adequate surgical approach. MRI is the gold standard for locoregional tumor staging, also playing a central role for patients selected for watchful waiting surveillance after total neoadjuvant therapy. Nevertheless, challenges exist from acquisition to interpretation of rectal MRI examinations and, despite societal guidelines, practices vary across institutions. In this paper, we review the optimal technique for acquisition of diagnostic quality rectal MRI and address its existing challenges and unmet needs, encompassing both acquisition and image interpretation.

Deep learning reconstruction CT algorithms can reduce image noise associated with lower radiation doses while preserving image texture and diagnostic performance, often overcoming the limitations of filtered backprojection and iterative reconstruction methods, and future DLR software developments combined with new CT hardware technologies such as photon-counting CT promise dramatically improved image quality.

T1-weighted (T1W) pulse sequences are an indispensable component of clinical protocols in abdominal MRI but usually require multiple breath holds (BHs) during the examination, which not all patients can sustain. Patient motion can affect the quality of T1W imaging so that key diagnostic information, such as intrinsic signal intensity and contrast enhancement image patterns, cannot be determined. Patient motion also has a negative impact on examination efficiency, as multiple acquisition attempts prolong the duration of the examination and often remain noncontributory. Techniques for mitigation of motion-related artifacts at T1W imaging include multiple arterial acquisitions within one BH; free breathing with respiratory gating or respiratory triggering; and radial imaging acquisition techniques, such as golden-angle radial k-space acquisition (stack-of-stars). While each of these techniques has inherent strengths and limitations, the selection of a specific motion-mitigation technique is based on several factors, including the clinical task under investigation, downstream technical ramifications, patient condition, and user preference. The authors review the technical principles of free-breathing motion mitigation techniques in abdominal MRI with T1W sequences, offer an overview of the established clinical applications, and outline the existing limitations of these techniques. In addition, practical guidance for abdominal MRI protocol strategies commonly encountered in clinical scenarios involving patients with limited BH abilities is rendered. Future prospects of free-breathing T1W imaging in abdominal MRI are also discussed. ^©RSNA, 2024 See the invited commentary by Fraum and An in this issue.

Photon counting detector CT (PCD-CT) is the newest major development in CT technology and has been commercially available since 2021. It offers major technological advantages over current standard-of-care energy integrating detector CT (EID-CT) including improved spatial resolution, improved iodine contrast to noise ratio, multi-energy imaging, and reduced noise. This article serves as a foundational basis to the technical approaches and concepts of PCD-CT technology with primary emphasis on detector technology in direct comparison to EID-CT. The article also addresses current technological challenges to PCD-CT with particular attention to cross talk and its causes (e.g., Compton scattering, fluorescence, charge sharing, K-escape) as well as pile-up.

For rectal cancer, MRI plays an important role in assessing extramural tumor spread and informs surgical planning. The contemporary standardized management of rectal cancer with total mesorectal excision guided by imaging-based risk stratification has dramatically improved patient outcomes. Colonoscopy and CT are utilized in surveillance after surgery to detect intraluminal and extramural recurrence, respectively; however, local recurrence of rectal cancer remains a challenge because postoperative changes such as fat necrosis and fibrosis can resemble tumor recurrence; additionally, mucinous adenocarcinoma recurrence may mimic fluid collection or abscess on CT. MRI and ¹⁸F-FDG PET are problem-resolving modalities for equivocal imaging findings on CT. Treatment options for recurrent rectal cancer include pelvic exenteration to achieve radical (R0 resection) resection and intraoperative radiation therapy. After pathologic diagnosis of recurrence, imaging plays an essential role for evaluating the feasibility and approach of salvage surgery. Patterns of recurrence can be divided into axial/central, anterior, lateral, and posterior. Some lateral and posterior recurrence patterns especially in patients with neurogenic pain are associated with perineural invasion. Cross-sectional imaging, especially MRI and ¹⁸F-FDG PET, permit direct visualization of perineural spread, and contribute to determining the extent of resection. Multidisciplinary discussion is essential for treatment planning of locally recurrent rectal cancer. This review article illustrates surveillance strategy after initial surgery, imaging patterns of rectal cancer recurrence based on anatomic classification, highlights imaging findings of perineural spread on each modality, and discusses how resectability and contemporary surgical approaches are determined based on imaging findings. Graphical abstract

MR defecating proctography provides temporally resolved multiplanar views of the pelvic floor musculature and pelvic organs, with images interpreted by using standard terms and definitions to guide... MR defecating proctography (MRDP) is a noninvasive examination that can be used for evaluating posterior compartment disorders. MRDP has several advantages over conventional fluoroscopic defecograp...

Esquivel A, et al. Korean J Radiol. 2022 Aug;23:e57. https://doi.org/10.3348/kjr.2022.0377