Radiographics最新文献

Large language models (LLMs) such as generative pretrained transformers (GPTs) have had a major impact on society, and there is increasing interest in using these models for applications in medicine and radiology. This article presents techniques to optimize these models and describes their known challenges and limitations. Specifically, the authors explore how to best craft natural language prompts, a process known as prompt engineering, for these models to elicit more accurate and desirable responses. The authors also explain how fine-tuning is conducted, in which a more general model, such as GPT-4, is further trained on a more specific use case, such as summarizing clinical notes, to further improve reliability and relevance. Despite the enormous potential of these models, substantial challenges limit their widespread implementation. These tools differ substantially from traditional health technology in their complexity and their probabilistic and nondeterministic nature, and these differences lead to issues such as "hallucinations," biases, lack of reliability, and security risks. Therefore, the authors provide radiologists with baseline knowledge of the technology underpinning these models and an understanding of how to use them, in addition to exploring best practices in prompt engineering and fine-tuning. Also discussed are current proof-of-concept use cases of LLMs in the radiology literature, such as in clinical decision support and report generation, and the limitations preventing their current adoption in medicine and radiology. ^©RSNA, 2025 See invited commentary by Chung and Mongan in this issue.

Anal cancer is a rare malignancy that is primarily treated with chemoradiation therapy (CRT). Clinical examination of the anal canal after CRT is often limited owing to the patient's discomfort. Therefore, radiologic surveillance plays a fundamental role in treatment response assessment. Currently recommended imaging modalities for posttreatment follow-up include pelvic MRI for local response evaluation and CT for evaluation of possible distant metastases. Patients who demonstrate a complete treatment response undergo regular clinical and imaging surveillance. Cases demonstrating an equivocal treatment response, an incomplete response, or disease progression should be streamlined for biopsy confirmation of the suspicious site and considered for salvage abdominoperineal resection. Radiologic differentiation of post-CRT inflammatory changes versus residual tumor, particularly in the early post-CRT period, can be challenging. However, careful interrogation of T2-weighted MR images correlated with matching diffusion-weighted and apparent diffusion coefficient images can increase reader confidence. The role of fluorine 18-fluorodeoxyglucose (FDG) PET/CT in assessing the response to anal cancer treatment is a debated topic. However, emerging research suggests that FDG PET/CT is complementary to pelvic MRI for accurate treatment response assessment, providing additional metabolic information. In this article, the authors provide a comprehensive review of the post-CRT imaging appearances of anal cancer, including examples from the spectrum of disease responses and therapy-related complications, and describe the strengths and limitations of pelvic MRI and FDG PET/CT. The authors also share the pearls and pitfalls in differentiating residual tumor from posttreatment inflammatory mimics. ^©RSNA, 2025 Supplemental material is available for this article.

Endometriosis involving the bowel is a severe form of the disease, and the bowel is the most common site of extragenital endometriosis. Surface lesions of the bowel are considered peritoneal disease. Bowel endometriosis (BE) is defined as endometriotic tissue infiltrating the muscularis propria layer of the bowel wall. BE is estimated to affect up to 37% of patients with known deep endometriosis, highlighting its coexistence with genital endometriosis. The rectosigmoid colon is the most common segment of the bowel involved, followed by the distal small bowel. US and MRI are the most common imaging modalities used to detect BE. Depending on which bowel segment is imaged, endometriosis protocols for transvaginal US after bowel preparation with a transabdominal component and MRI and MR enterography are most commonly used. The authors provide a systematic approach to the diagnosis of BE using these imaging modalities. Imaging protocols and techniques for optimization of visualization of the bowel are discussed, the normal bowel wall anatomy with both imaging modalities is described, and the varying degrees of bowel wall involvement in endometriosis are illustrated. The imaging features of infiltration of endometriosis in the bowel muscularis propria are described in detail, along with key imaging findings to be conveyed to surgical colleagues to optimize surgical treatment and decrease complications, thereby improving overall patient outcomes. ^©RSNA, 2025 Supplemental material is available for this article.

Craniovertebral junction (CVJ) instability, fixation, and stenosis in children are closely related conditions that are often challenging to diagnose and are associated with significant morbidity. Groups at higher risk for CVJ abnormalities include children with trisomy 21, juvenile idiopathic arthritis, upper respiratory infection or other inflammatory conditions of the head and neck, and certain skeletal dysplasias. Radiography, CT, and MRI play complementary roles in the evaluation of pathologic conditions of the CVJ. CVJ morphometry is helpful in characterizing osseous relationships and suggesting potential instability and/or neural compression. CT with multiplanar and three-dimensional volume-rendered reconstructions may be helpful in identifying (a) congenital anomalies associated with instability and/or neural canal narrowing; (b) disorders predisposing to atlantoaxial rotatory fixation (AARF), such as retropharyngeal inflammation in Grisel syndrome; and (c) acquired osseous abnormalities associated with irreducibility in children with chronic AARF (eg, facet deformity or new bone formation). Dynamic CT is particularly helpful for evaluating children with persistent torticollis that is refractory to initial conservative therapy. Early diagnosis and treatment of AARF are essential in reducing the likelihood of progression to chronic AARF. Performing CT angiography before C1-C2 fixation may help identify vascular variations that increase surgical risk and provide an opportunity for modification of the surgical plan. MRI is preferred for assessment of the hindbrain; upper cervical spinal cord; and nonossified structures such as cartilage, ligaments, and paravertebral soft tissues. The authors discuss normal development and anatomy, imaging evaluation, and disorders associated with CVJ instability, fixation, and stenosis in children. Imaging-related treatment considerations are also discussed. ^©RSNA, 2025 Supplemental material is available for this article.

MR urography (MRU) is an imaging technique that provides comprehensive evaluation of the kidneys, pelvicalyceal system, ureters, and urinary bladder. Although CT urography (CTU) remains the first-line imaging modality for the urinary tract, incremental improvements in MRU have allowed simultaneous imaging of the kidneys, collecting system, and urinary bladder with superior contrast resolution and tissue characterization, equivalent visualization of the upper tracts, and similar specificity for detection of noncalculous diseases of the collecting system compared with that of CTU. MRU has evolved into an alternative to CTU in the broader patient population and a first-line examination in specific patient populations for which CTU is less preferred. This subgroup includes pediatric patients, pregnant patients, patients needing recurring studies, and patients with poor renal function or severe allergies to iodinated contrast material. The most common techniques encompassing a conventional MRU examination include static-fluid T2-weighted imaging and gadolinium-enhanced urothelial and excretory phase imaging. The addition of dynamic contrast-enhanced MRI and diffusion-weighted imaging results in multiparametric MRU that increases diagnostic accuracy. Newer techniques, such as parallel imaging, compressed sensing, radial k-space sampling, and deep learning-based image reconstruction, can shorten examination times and improve image quality and patient compliance. Successful MRU interpretation relies on technique optimization, knowledge of various urinary tract pathologic conditions, and familiarity with different sequences, potential interpretive pitfalls, and artifacts. ^©RSNA, 2025 Supplemental material is available for this article.

Antineutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis (AAV) is a rare disease that manifests as necrotizing vasculitis involving small vessels without immune complex deposition. Granulomatosis with polyangiitis (GPA), eosinophilic granulomatosis with polyangiitis (EGPA), and microscopic polyangiitis (MPA) are included in this disease entity. Diagnosis and differentiation of AAV is challenging because of the diverse and overlapping clinical manifestations and lack of pathognomonic findings. Therefore, AAV classification criteria have been developed to increase the likelihood of diagnosis using multidisciplinary approaches, including clinical, radiologic, laboratory, and pathologic findings. The new American College of Rheumatology and European Alliance of Associations for Rheumatology classification criteria were released in 2022 to classify AAVs using weighted criteria and threshold scores. They are expected to make the classification of GPA, EGPA, and MPA more accurate in the setting of suspected small-vessel vasculitis. The criteria present key thoracic imaging discriminators of GPA as "pulmonary nodules, masses, or cavitation" and MPA as "interstitial fibrosis," whereas, radiologic criteria of EGPA are not present. ANCA positivity and eosinophil count are included as key laboratory discriminators. It is essential for radiologists to familiarize themselves with imaging findings of each AAV and know the key imaging discriminators to aid in the differential diagnosis of AAVs. By reviewing the radiologic findings of thoracic manifestations of each AAV and applying the new criteria in a series of cases, the authors aim to provide a practical and stepwise approach to AAV for radiologists. ^©RSNA, 2025 Supplemental material is available for this article.