PET/MRI: pictorial review of hepatobiliary and pancreatic applications.

PET and MRI both play valuable roles in the management of hepatobiliary and pancreatic (HBP) malignancies. Simultaneous PET/MRI combines the excellent soft-tissue resolution and anatomic details from MRI with functional information from PET in a single comprehensive examination. MRI is the main imaging modality in evaluating HCC, playing important roles in screening, characterization, local extent, and evaluating tumor response, whereas 18F-fluorodeoxyglucose (FDG) PET can help evaluate for lymph node involvement and metastatic disease. In cholangiocarcinoma and pancreatic malignancies, both PET and MRI have excellent utility in initial staging as well as assessing treatment response. In all HBP malignancies, FDG-PET/MRI is a unique problem-solving tool in complex cases and diagnostic challenges, especially after locoregional therapy and when differentiating residual or recurrent viable disease from inflammatory and other benign processes. In this manuscript, we review the role of PET/MRI in the diagnosis, staging, assessing treatment response, and characterizing post-treatment processes. With the introduction of multiple new tracers, the value of PET/MRI has not yet been fully realized, and more studies are needed to demonstrate the utility and efficacy of PET/MRI in improving patient care in hepatobiliary and pancreatic oncology.

Customization of Computed Tomography Radio-Opacity in 3D-Printed Contrast-Injectable Tumor Phantoms.

Medical Imaging Phantoms (MIPs) calibrate imaging devices, train medical professionals, and can help procedural planning. Traditional MIPs are costly and limited in customization. Additive manufacturing allows for customizable, patient-specific phantoms. This study examines the CT attenuation characteristics of contrast-injectable, chambered 3D-printed phantoms to optimize tissue-mimicking capabilities. A MIP was constructed from a CT of a complex pelvic tumor near the iliac bifurcation. A 3D reconstruction of these structures composed of three chambers (aorta, inferior vena cava, tumor) with ports for contrast injection was 3D printed. Desired attenuations were 200 HU (arterial I), 150 HU (venous I), 40 HU (tumor I), 150 HU (arterial II), 90 HU (venous II), and 400 HU (tumor II). Solutions of Optiray 350 and water were injected, and the phantom was scanned on CT. Attenuations were measured using ROIs. Mean attenuation for the six phases was as follows: 37.49 HU for tumor I, 200.50 HU for venous I, 227.92 HU for arterial I, 326.20 HU for tumor II, 91.32 HU for venous II, and 132.08 HU for arterial II. Although the percent differences between observed and goal attenuation were high, the observed relative HU differences between phases were similar to goal HU differences. The observed attenuations reflected the relative concentrations of contrast solutions used, exhibiting a strong positive correlation with contrast concentration. The contrast-injectable tumor phantom exhibited a useful physiologic range of attenuation values, enabling the modification of tissue-mimicking 3D-printed phantoms even after the manufacturing process.

The miR-29 family facilitates the activation of NK-cell immune responses by targeting the B7-H3 immune checkpoint in neuroblastoma.

Neuroblastoma (NB) is a highly aggressive pediatric cancer that originates from immature nerve cells, presenting significant treatment challenges due to therapy resistance. Despite intensive treatment, approximately 50% of high-risk NB cases exhibit therapy resistance or experience relapse, resulting in poor outcomes often associated with tumor immune evasion. B7-H3 is an immune checkpoint protein known to inhibit immune responses. MicroRNAs (miRNAs) are small non-coding RNAs involved in post-transcriptional gene regulation. Our study aims to explore the impact of miRNAs on B7-H3 regulation, the anti-tumor immune response, and tumorigenicity in NB. Analysis of NB patients and patient-derived xenograft tumors revealed a correlation between higher B7-H3 expression and poorer patient survival. Notably, deceased patients exhibited a depletion of miR-29 family members (miR-29a, miR-29b, and miR-29c), which displayed an inverse association with B7-H3 expression in NB patients. Overexpression and knockdown experiments demonstrated that these miRNAs degrade B7-H3 mRNA, resulting in enhanced NK cell activation and cytotoxicity. In vivo, experiments provided further evidence that miR-29 family members reduce tumorigenicity, macrophage infiltration, and microvessel density, promote infiltration and activation of NK cells, and induce tumor cell apoptosis. These findings offer a rationale for developing more effective combination treatments that leverage miRNAs to target B7-H3 in NB patients.

Off the wall: incidental paraspinal and pelvic muscle pathology on abdominopelvic imaging.

As the use of cross-sectional abdominal and pelvic imaging has increased exponentially in the past several decades, incidental musculoskeletal findings have become commonplace. These are often unrelated to the indication for the examination and are frequently referred to as the "radiologist's blind spot" on these studies. The differential diagnosis for abnormalities of the paraspinal and pelvic musculature is, in many cases, quite different from the anterior abdominal wall muscles. Furthermore, due to their relatively deep location, pathology involving the former muscle groups is more likely to be clinically occult, often presenting only incidentally when the patient undergoes cross-sectional imaging. Effective treatment of diseases of these muscles is dependent on adherence to a diverse set of diagnostic and treatment algorithms. The purpose of this review article is to familiarize the radiologist with the unique pathology of these often-overlooked muscles of the abdomen and pelvis.

Case 329.

HISTORY: A 45-year-old female patient who was previously healthy presented after several weeks of fullness in the right upper quadrant of the abdomen. The patient did not experience pain, nausea, vomiting, or jaundice, and had no contributory past medical or surgical history, including no history of malignancy. Upon examination, vital signs were within normal limits and the patient was appeared well with soft palpable fullness in the right upper quadrant. The abdomen was nontender and nondistended. Laboratory investigation revealed no abnormalities, with a normal complete blood cell count and normal serum tumor markers that included α-fetoprotein (<2.0 ng/mL; reference, <8.3 ng/mL), cancer antigen 19-9 (21.6 U/mL; reference, <35 U/mL), and carcinoembryonic antigen (1.3 ng/mL; reference, <5 ng/mL). CT of the abdomen and pelvis was performed with intravenous contrast material in the emergency department (Fig 1). Subsequently, combined MRI and MR cholangiopancreatography of the abdomen was performed with and without intravenous contrast material for further evaluation (Fig 2). CT of the chest performed during the same encounter was unremarkable.

SAP30, an oncogenic driver of progression, poor survival, and drug resistance in neuroblastoma.

Neuroblastoma is the most devastating extracranial solid malignancy in children. Despite an intense treatment regimen, the prognosis for high-risk neuroblastoma patients remains poor, with less than 40% survival. So far, MYCN amplification status is considered the most prognostic factor but corresponds to only ∼25% of neuroblastoma patients. Therefore, it is essential to identify a better prognosis and therapy response marker in neuroblastoma patients. We applied robust bioinformatic data mining tools, such as weighted gene co-expression network analysis, cisTarget, and single-cell regulatory network inference and clustering on two neuroblastoma patient datasets. We found Sin3A-associated protein 30 (SAP30), a driver transcription factor positively associated with high-risk, progression, stage 4, and poor survival in neuroblastoma patient cohorts. Tumors of high-risk neuroblastoma patients and relapse-specific patient-derived xenografts showed higher SAP30 levels. The advanced pharmacogenomic analysis and CRISPR-Cas9 screens indicated that SAP30 essentiality is associated with cisplatin resistance and further showed higher levels in cisplatin-resistant patient-derived xenograft tumor cell lines. Silencing of SAP30 induced cell death in vitro and led to a reduced tumor burden and size in vivo. Altogether, these results indicate that SAP30 is a better prognostic and cisplatin-resistance marker and thus a potential drug target in high-risk neuroblastoma.

Post-contrast abdominal magnetic resonance imaging of critically ill patients using compressed sensing free-breathing golden radial angle imaging.

Obtaining diagnostic-quality magnetic resonance imaging (MRI) of the abdomen in critically ill patients can be difficult due to challenges with breath-holding and the inability to follow technologist instructions. Protocols that harness advances in commercially available MRI techniques provide a potential solution, particularly using the golden radial angle sparse parallel (GRASP) technique for dynamic post-contrast T1-weighted imaging. The GRASP technique uses a combination of free-breathing, a stack-of-stars radial acquisition, and compressed sensing reconstruction acquired over several minutes to produce motion-free images at time points defined by the user; these include the non-contrast, arterial, venous, and delayed images, which are typical of abdominal MRI protocols. The three cases discussed herein illustrate the use of this technique in providing both exquisite image quality and diagnostic value in the care of critically ill patients with hepatopancreaticobiliary diseases. Our work aims to raise awareness of this technique and its utility in imaging patients who cannot hold their breath for dynamic T1-weighted post-contrast imaging.

The crosstalk between non-coding RNAs and cell-cycle events: A new frontier in cancer therapy.

The cell cycle comprises sequential events during which a cell duplicates its genome and divides it into two daughter cells. This process is tightly regulated to ensure that the daughter cell receives identical copied chromosomal DNA and that any errors in the DNA during replication are correctly repaired. Cyclins and their enzyme partners, cyclin-dependent kinases (CDKs), are critical regulators of G- to M-phase transitions during the cell cycle. Mitogenic signals induce the formation of the cyclin/CDK complexes, resulting in phosphorylation and activation of the CDKs. Once activated, cyclin/CDK complexes phosphorylate specific substrates that drive the cell cycle forward. The sequential activation and inactivation of cyclin-CDK complexes are tightly controlled by activating and inactivating phosphorylation events induced by cell-cycle proteins. The non-coding RNAs (ncRNAs), which do not code for proteins, regulate cell-cycle proteins at the transcriptional and translational levels, thereby controlling their expression at different cell-cycle phases. Deregulation of ncRNAs can cause abnormal expression patterns of cell-cycle-regulating proteins, resulting in abnormalities in cell-cycle regulation and cancer development. This review explores how ncRNA dysregulation can disrupt cell division balance and discusses potential therapeutic approaches targeting these ncRNAs to control cell-cycle events in cancer treatment.

Symptomatic Benign Prostatic Hyperplasia with Suppressed Epigenetic Regulator HOXB13 Shows a Lower Incidence of Prostate Cancer Development.

Our objective was to identify variations in gene expression that could help elucidate the pathways for the development of prostate cancer (PCa) in men with Benign Prostatic Hyperplasia (BPH). We included 98 men with BPH, a positive prostate MRI (Prostate Imaging Reporting and Data System; PIRADS ≥ 4), and a negative biopsy from November 2014 to January 2018. RNA sequencing (RNA-Seq) was performed on tissue cores from the MRI lesion and a geographically distant region (two regions per patient). All patients were followed for at least three years to identify who went on to develop PCa. We compared the gene expressions of those who did not develop PCa ("BPH-only") vs. those who did ("BPH/PCa"). Then, we identified the subset of men with BPH who had the highest American Urological Association (AUA) symptom scores ("symptomatic BPH") and compared their gene expression to the BPH/PCa group. At a median follow-up of 47.5 months, 15 men had developed PCa while 83 did not. We compared gene expressions of 14 men with symptomatic BPH (AUAss ≥ 18) vs. 15 with BPH/PCa. We found two clusters of genes, suggesting the two groups had distinctive molecular features. Differential analysis revealed genes that were upregulated in BPH-only and downregulated in BPH/PCa, and vice versa. Symptomatic BPH men had upregulation of T-cell activation markers (TCR, CD3, ZAP70, IL-2 and IFN-γ and chemokine receptors, CXCL9/10) expression. In contrast, men with BPH/PCa had upregulation of NKX3-1 and HOXB13 transcription factors associated with luminal epithelial progenitors but depleted of immune cells, suggesting a cell-autonomous role in immune evasion. Symptomatic BPH with immune-enriched landscapes may support anti-tumor immunity. RNA sequencing of benign prostate biopsy tissue showing upregulation of NKX3-1 and HOXB13 with the absence of T-cells might help in identifying men at higher risk of future PCa development, which may be useful in determining ongoing PCa screening.

Association between Bioimpedance Spectroscopy and Magnetic Resonance Lymphangiography in the Diagnosis and Assessment of Lymphedema.

BACKGROUND: This study assesses associations between bioimpedance spectroscopy (BIS) and magnetic resonance lymphangiography (MRL) in the staging and assessment of lymphedema. METHODS: Adults who received MRL and BIS between 2020 and 2022 were included. We collected fluid, fat, and lymphedema severity ratings, and measured fluid stripe thickness, subcutaneous fat width, and lymphatic diameter on MRL. BIS lymphedema index (L-Dex) scores were collected from patient charts. We assessed sensitivity and specificity of L-Dex scores to detect MRL-identified lymphedema, and examined associations between L-Dex scores and MRL imaging measures. RESULTS: Forty-eight limbs across 40 patients were included. L-Dex scores had 72.5% sensitivity and 87.5% specificity for detecting MRL-defined lymphedema, with a 96.7% estimated positive predictive value and 38.9% negative predictive value. L-Dex scores were associated with MRL fluid and fat content scores (p ≤ 0.05), and lymphedema severity (p = 0.01), with better discrimination between fluid than fat content levels on pairwise analysis, and poor discrimination between adjacent severity levels. L-Dex scores were correlated with distal and proximal limb fluid stripe thickness (distal: rho = 0.57, p < 0.01; proximal: rho = 0.58, p < 0.01), partially correlated with distal subcutaneous fat thickness when accounting for body mass index (rho = 0.34, p = 0.02), and were not correlated with lymphatic diameter (p = 0.25). CONCLUSION: L-Dex scores have high sensitivity, specificity, and positive predictive value for the identification of MRL-detected lymphedema. L-Dex has difficulty distinguishing between adjacent severity levels of lymphedema and a high false negative rate, explained in part by reduced discrimination between levels of fat accumulation.

Low-Field-Strength Body MRI: Challenges and Opportunities at 0.55 T.

Advances in MRI technology have led to the development of low-field-strength (hereafter, "low-field") (0.55 T) MRI systems with lower weight, fewer shielding requirements, and lower cost than those of traditional (1.5-3 T) systems. The trade-offs of lower signal-to-noise ratio (SNR) at 0.55 T are partially offset by patient safety and potential comfort advantages (eg, lower specific absorption rate and a more cost-effective larger bore diameter) and physical advantages (eg, decreased T2* decay, shorter T1 relaxation times). Image reconstruction advances leveraging developing technologies (such as deep learning-based denoising) can be paired with traditional techniques (such as increasing the number of signal averages) to improve SNR. The overall image quality produced by low-field MRI systems, although perhaps somewhat inferior to 1.5-3 T MRI systems in terms of SNR, is nevertheless diagnostic for a broad variety of body imaging applications. Effective low-field body MRI requires (a) an understanding of the trade-offs resulting from lower field strengths, (b) an approach to modifying routine sequences to overcome SNR challenges, and (c) a workflow for carefully selecting appropriate patients. The authors describe the rationale, opportunities, and challenges of low-field body MRI; discuss important considerations for low-field imaging with common body MRI sequences; and delineate a variety of use cases for low-field body MRI. The authors also include lessons learned from their preliminary experience with a new low-field MRI system at a tertiary care center. Finally, they explore the future of low-field MRI, summarizing current limitations and potential future developments that may enhance the clinical adoption of this technology. ©RSNA, 2023 Supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center. See the invited commentary by Venkatesh in this issue.

Computed Tomography Attenuation of Three-Dimensional (3D) Printing Materials-Depository to Aid in Constructing 3D-Printed Phantoms.

Three-dimensionally printed phantoms are increasingly used in medical imaging and research due to their cost-effectiveness and customizability, offering valuable alternatives to commercial phantoms. The purpose of this study was to assess the computed tomography (CT) attenuation characteristics of 27 resin materials from Formlabs, a 3D printing equipment and materials manufacturer. Cube phantoms (both solid and hollow constructions) produced with each resin were subjected to CT scanning under varying tube current-time products with attenuation measurements recorded in Hounsfield units (HU). The resins exhibited a wide range of attenuation values (-3.33 to 2666.27 HU), closely mimicking a range of human tissues, from fluids to dense bone structures. The resins also demonstrated consistent attenuation regardless of changes in the tube current. The CT attenuation analysis of FormLabs resins produced an archive of radiological imaging characteristics of photopolymers that can be utilized to construct more accurate tissue mimicking medical phantoms and improve the evaluation of imaging device performance.

Added Value of FDG PET/MRI in Gynecologic Oncology: A Pictorial Review.

Fluorine 18-fluorodeoxyglucose (FDG) PET and MRI independently play a valuable role in the management of patients with gynecologic malignancies, particularly endometrial and cervical cancer. The PET/MRI hybrid imaging technique combines the metabolic information obtained from PET with the excellent soft-tissue resolution and anatomic details provided by MRI in a single examination. MRI is the modality of choice for assessment of local tumor extent in the pelvis, whereas PET is used to assess for local-regional spread and distant metastases. The authors discuss the added value of FDG PET/MRI in imaging gynecologic malignancies of the pelvis, with a focus on the role of FDG PET/MRI in diagnosis, staging, assessing treatment response, and characterizing complications. PET/MRI allows better localization and demarcation of the extent of disease, characterization of lesions and involvement of adjacent organs and lymph nodes, and improved differentiation of benign from malignant tissues, as well as detection of the presence of distant metastasis. It also has the advantages of decreased radiation dose and a higher signal-to-noise ratio of a prolonged PET examination of the pelvis contemporaneous with MRI. The authors provide a brief technical overview of PET/MRI, highlight how simultaneously performed PET/MRI can improve stand-alone MRI and PET/CT in gynecologic malignancies, provide an image-rich review to illustrate practical and clinically relevant applications of this imaging technique, and review common pitfalls encountered in clinical practice. ©RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Renal Mass Imaging with MRI Clear Cell Likelihood Score: A User's Guide.

Small solid renal masses (SRMs) are frequently detected at imaging. Nearly 20% are benign, making careful evaluation with MRI an important consideration before deciding on management. Clear cell renal cell carcinoma (ccRCC) is the most common renal cell carcinoma subtype with potentially aggressive behavior. Thus, confident identification of ccRCC imaging features is a critical task for the radiologist. Imaging features distinguishing ccRCC from other benign and malignant renal masses are based on major features (T2 signal intensity, corticomedullary phase enhancement, and the presence of microscopic fat) and ancillary features (segmental enhancement inversion, arterial-to-delayed enhancement ratio, and diffusion restriction). The clear cell likelihood score (ccLS) system was recently devised to provide a standardized framework for categorizing SRMs, offering a Likert score of the likelihood of ccRCC ranging from 1 (very unlikely) to 5 (very likely). Alternative diagnoses based on imaging appearance are also suggested by the algorithm. Furthermore, the ccLS system aims to stratify which patients may or may not benefit from biopsy. The authors use case examples to guide the reader through the evaluation of major and ancillary MRI features of the ccLS algorithm for assigning a likelihood score to an SRM. The authors also discuss patient selection, imaging parameters, pitfalls, and areas for future development. The goal is for radiologists to be better equipped to guide management and improve shared decision making between the patient and treating physician. © RSNA, 2023 Quiz questions for this article are available in the supplemental material. See the invited commentary by Pedrosa in this issue.

Crosstalk between Noncoding RNAs and the Epigenetics Machinery in Pediatric Tumors and Their Microenvironment.

According to the World Health Organization, every year, an estimated 400,000+ new cancer cases affect children under the age of 20 worldwide. Unlike adult cancers, pediatric cancers develop very early in life due to alterations in signaling pathways that regulate embryonic development, and environmental factors do not contribute much to cancer development. The highly organized complex microenvironment controlled by synchronized gene expression patterns plays an essential role in the embryonic stages of development. Dysregulated development can lead to tumor initiation and growth. The low mutational burden in pediatric tumors suggests the predominant role of epigenetic changes in driving the cancer phenotype. However, one more upstream layer of regulation driven by ncRNAs regulates gene expression and signaling pathways involved in the development. Deregulation of ncRNAs can alter the epigenetic machinery of a cell, affecting the transcription and translation profiles of gene regulatory networks required for cellular proliferation and differentiation during embryonic development. Therefore, it is essential to understand the role of ncRNAs in pediatric tumor development to accelerate translational research to discover new treatments for childhood cancers. This review focuses on the role of ncRNA in regulating the epigenetics of pediatric tumors and their tumor microenvironment, the impact of their deregulation on driving pediatric tumor progress, and their potential as effective therapeutic targets.

Imaging of Vaginal and Vulvar Malignancy.

Vaginal and vulvar malignancies are rare gynecologic malignancies but can be associated with high morbidity and mortality if undiagnosed and untreated. Advanced imaging modalities such as MRI enable assessment of the local extent of disease and evaluation for regional or distant spread. Accurate identification and description of the primary lesion and sites of involvement as well as detection and localization of suspicious lymph nodes are critical in guiding appropriate management. Additionally, radiologists should be aware of potential mimickers on imaging and the differential diagnoses for vaginal and vulvar lesions.

Second-opinion interpretation of outside facility general ultrasound studies: rate of discrepancies and management change.

BACKGROUND: Second-opinion reads on imaging studies are common for CT and MRI, but many institutions are hesitant to implement a workflow for second read of ultrasound studies performed at other facilities due to quality considerations. OBJECTIVE: The purpose of this study was to assess discrepancy rates between initial and second-opinion general ultrasound reports METHODS: We reviewed all requests of second-opinion US studies referred to our tertiary care center between 02/01/2020 and 06/23/2022. We evaluated percentage of exams that were interpreted versus archived. Whenever the original report was available (n = 196 studies), we evaluated any discrepancy in findings, interpretation, and potential management change based on second report compared to the initial report as evaluated by consensus agreement of 3 subspecialized radiologists. RESULTS: A total of 586 ultrasound studies for 533 patients were nominated for consult. After excluding 58 studies for technical reasons (e.g., duplicate nomination, images for procedure guidance, modality is not ultrasound) and 282 studies that were archived by the reading radiologist due to various objective (e.g., studies such as echocardiography not interpreted by the abdominal imagers or more recent study available obviating need for consultation) and subjective (e.g., suboptimal image quality, lack of cine clips) reasons, a total of 246 studies were reinterpreted and were further analyzed. Only 21/246 patients (8.5%) got repeat ultrasound of the same body part within 3 months of original study date. The original (first-read) report was available for 196/246 studies, with discrepancy present between the first and second reads in 74/196 (37.8%) studies, with potential management change in 51/196 (26.0%) studies. CONCLUSION: Second-opinion interpretation of outside ultrasound examinations by subspecialized radiologists can result in recommended management change in 26% of studies indicating potential for added value to reinterpreting ultrasound studies despite the concerns for quality control.

Results of the 2020 Survey of the American Alliance of Academic Chief Residents in Radiology.

RATIONALE AND OBJECTIVES: An annual survey of chief residents in accredited North American radiology programs is conducted by the American Alliance of Academic Chief Residents in Radiology (A3CR2). The purpose of this study is to summarize the 2020 A3CR2 chief resident survey. MATERIALS AND METHODS: An online survey was distributed to chief residents from 194 Accreditation Council on Graduate Medical Education-accredited radiology residencies. Questions were designed to gather information about residency program practices, benefits, fellowship or advanced interventional radiology (IR) training choices, and the integration of IR training. Subsets of questions focused on the perception of corporatization, non-physician providers (NPPs), and artificial intelligence (AI) in radiology and their relationship to the radiology job market. RESULTS: 174 individual responses from 94 programs were provided, yielding a 48 % program response rate. Extended emergency department coverage has steadily decreased over the last 5 years (2016-2020), however only 52 % of programs have independent overnight call (without attending coverage). Regarding the impact of new integrated IR residencies on training, 42 % indicated there was no appreciable impact on their DR or IR training, while 20 % indicated DR training for IR residents suffered and 19 % indicated IR training for DR residents suffered. Corporatization in radiology was perceived as the biggest potential threat to the future job market. CONCLUSIONS: Integration of IR residency did not detrimentally affect DR or IR training in most programs. Radiology resident perception of corporatization, NPPs, and AI may help residency programs shape educational content.