How Imaging Advances Are Defining the Future of Precision Radiation Therapy.

Radiation therapy is fundamental in the treatment of cancer. Imaging has always played a central role in radiation oncology. Integrating imaging technology into irradiation devices has increased the precision and accuracy of dose delivery and decreased the toxic effects of the treatment. Although CT has become the standard imaging modality in radiation therapy, the development of recently introduced next-generation imaging techniques has improved diagnostic and therapeutic decision making in radiation oncology. Functional and molecular imaging techniques, as well as other advanced imaging modalities such as SPECT, yield information about the anatomic and biologic characteristics of tumors for the radiation therapy workflow. In clinical practice, they can be useful for characterizing tumor phenotypes, delineating volumes, planning treatment, determining patients' prognoses, predicting toxic effects, assessing responses to therapy, and detecting tumor relapse. Next-generation imaging can enable personalization of radiation therapy based on a greater understanding of tumor biologic factors. It can be used to map tumor characteristics, such as metabolic pathways, vascularity, cellular proliferation, and hypoxia, that are known to define tumor phenotype. It can also be used to consider tumor heterogeneity by highlighting areas at risk for radiation resistance for focused biologic dose escalation, which can impact the radiation planning process and patient outcomes. The authors review the possible contributions of next-generation imaging to the treatment of patients undergoing radiation therapy. In addition, the possible roles of radio(geno)mics in radiation therapy, the limitations of these techniques, and hurdles in introducing them into clinical practice are discussed. ©RSNA, 2024 Test Your Knowledge questions for this article are available in the supplemental material.

Current and Advanced Applications of Gadoxetic Acid-enhanced MRI in Hepatobiliary Disorders.

Gadoxetic acid is an MRI contrast agent that has specific applications in the study of hepatobiliary disease. After being distributed in the vascular and extravascular spaces during the dynamic phase, gadoxetic acid is progressively taken up by hepatocytes and excreted to the bile ducts during the hepatobiliary phase. The information derived from the enhancement characteristics during dynamic and hepatobiliary phases is particularly relevant in the detection and characterization of focal liver lesions and in the evaluation of the structure and function of the liver and biliary system. The use of new MRI sequences and advanced imaging techniques (eg, relaxometry, multiparametric imaging, and analysis of heterogeneity), the introduction of artificial intelligence, and the development of biomarkers and radiomic and radiogenomic tools based on gadoxetic acid-enhanced MRI findings will play an important role in the future in assessing liver function, chronic liver disease, and focal liver lesions; in studying biliary pathologic conditions; and in predicting treatment responses and prognosis. © RSNA, 2023 Quiz questions for this article are available in the supplemental material.

Usefulness of Computed Tomography Angiography in the Preoperative Workup of Patients With Colorectal Cancer.

OBJECTIVES: The objective of this study is to analyze the main patterns of branching of the inferior mesenteric artery (IMA) and to determine if your knowledge changes the surgical strategy in the colorectal cancer. METHODS: This retrospective study included 63 patients with cancer of the sigmoid or rectum. We assessed the patterns of IMA in 3 subtypes: type A (independent left colic artery [LCA]), type B (LCA and sigmoid artery arising in a common trunk) and type C (LCA, sigmoid artery, and superior rectal artery with a common origin). Colorectal surgeons evaluated how the vascular map changed the type of IMA ligation. RESULTS: Inferior mesenteric artery branching was classified as type A in 55.6% patients, type B in 23.8%, and type C in 20.6%. Knowledge of the vascular map changed the type of ligation from high to low in 20 of the 50 patients who were candidates for surgery. The change was possible in tumors located in the sigmoid colon and the rectosigmoid junction with the type A or B branching. CONCLUSIONS: Preoperative Multidetector Computed Tomography angiography can define the pattern of IMA branching. Based on this information, a low ligation can be performed in tumors located in sigmoid colon and rectosigmoid junction with IMA branching types A and B.

Assessing Immunotherapy with Functional and Molecular Imaging and Radiomics.

Immunotherapy is changing the treatment paradigm for cancer and has introduced new challenges in medical imaging. Because not all patients benefit from immunotherapy, pretreatment imaging should be performed to identify not only prognostic factors but also factors that allow prediction of response to immunotherapy. Follow-up studies must allow detection of nonresponders, without confusion of pseudoprogression with real progression to prevent premature discontinuation of treatment that can benefit the patient. Conventional imaging techniques and classic tumor response criteria are limited for the evaluation of the unusual patterns of response that arise from the specific mechanisms of action of immunotherapy, so advanced imaging methods must be developed to overcome these shortcomings. The authors present the fundamentals of the tumor immune microenvironment and immunotherapy and how they influence imaging findings. They also discuss advances in functional and molecular imaging techniques for the assessment of immunotherapy in clinical practice, including their use to characterize immune phenotypes, assess patient prognosis and response to therapy, and evaluate immune-related adverse events. Finally, the development of radiomics and radiogenomics in these therapies and the future role of imaging biomarkers for immunotherapy are discussed. Online supplemental material is available for this article. ©RSNA, 2020.

Radiologic Clues to Cerebral Venous Thrombosis.

Cerebral venous thrombosis (CVT) is uncommon, representing approximately 0.5% of all cases of cerebrovascular disease worldwide. Many factors, alone or combined, can cause CVT. Although CVT can occur at any age, it most commonly affects neonates and young adults. CVT is difficult to diagnose clinically because patients can present with a wide spectrum of nonspecific manifestations, the most common of which are headache in 89%-91%, focal deficits in 52%-68%, and seizures in 39%-44% of patients. Consequently, imaging is fundamental to its diagnosis. MRI is the most sensitive and specific technique for diagnosis of CVT. The different MRI sequences, with and without the use of contrast material, have variable strengths. Contrast material-enhanced MR venography has the highest accuracy compared with sequences without contrast enhancement.Online supplemental material is available for this article.©RSNA, 2019.

Update on Whole-body MRI in Musculoskeletal Applications.

Whole-body magnetic resonance imaging (WB-MRI) is a powerful tool increasingly used to assess oncologic and nononcologic diseases. WB-MRI provides information about diffuse multifocal pathologies with excellent anatomical definition through high soft tissue contrast and spatial resolution as well as valuable functional information from diffusion-weighted images. In addition to its roles in establishing the diagnosis and assessing the extent and severity of disease, WB-MRI is also useful for monitoring the response to treatment for malignant and benign systemic diseases affecting the musculoskeletal system. This article reviews and updates the applications of WB-MRI in current practice, discussing the role of this helpful tool in various conditions involving the musculoskeletal system including bone metastases, hematologic cancers, inflammatory processes, infections, and multisystemic-multifocal bone, nerve, vascular, and muscle/soft tissue disorders, as well as other idiopathic conditions.

Advanced Imaging Techniques in Evaluation of Colorectal Cancer.

Imaging techniques are clinical decision-making tools in the evaluation of patients with colorectal cancer (CRC). The aim of this article is to discuss the potential of recent advances in imaging for diagnosis, prognosis, therapy planning, and assessment of response to treatment of CRC. Recent developments and new clinical applications of conventional imaging techniques such as virtual colonoscopy, dual-energy spectral computed tomography, elastography, advanced computing techniques (including volumetric rendering techniques and machine learning), magnetic resonance (MR) imaging-based magnetization transfer, and new liver imaging techniques, which may offer additional clinical information in patients with CRC, are summarized. In addition, the clinical value of functional and molecular imaging techniques such as diffusion-weighted MR imaging, dynamic contrast material-enhanced imaging, blood oxygen level-dependent imaging, lymphography with contrast agents, positron emission tomography with different radiotracers, and MR spectroscopy is reviewed, and the advantages and disadvantages of these modalities are evaluated. Finally, the future role of imaging-based analysis of tumor heterogeneity and multiparametric imaging, the development of radiomics and radiogenomics, and future challenges for imaging of patients with CRC are discussed. Online supplemental material is available for this article. ©RSNA, 2018.

The morphological and functional diagnosis of a rare entity: lipomatous pseudohypertrophy of the pancreas.

Lipomatous pseudohypertrophy of the pancreas is a rare entity characterized by a replacement, focal or diffuse, of the normal pancreatic tissue by mature fatty tissue. Its definitive diagnosis is made based on histopathologic analysis. Nevertheless, typical imaging findings can allow a non-invasive diagnosis and help its clinical approach.

Splenosis: Non-invasive diagnosis of a great mimicker.

UNLABELLED: Splenosis is defined as the location of heterotopic splenic tissue implants in the abdominal cavity or other atypical location. This entity may mimic different benign and malignant processes, which may cause an inappropriate management of the patient. A previous history of splenic trauma or splenectomy should introduce this entity in the differential diagnosis in these patients. CLINICAL CASES: Clinical features and imaging findings of two cases of splenosis are presented and a review of the published literature on this entity is made. RESULTS: Based on the behavior of the lesions in different imaging techniques and taking into account the relevant history of previous splenectomy, it was possible to establish the final diagnosis of intraabdominal splenosis. CONCLUSIONS: Splenosis is an entity that should be considered in the differential diagnosis in patients with prior history of splenectomy and/or spleen trauma to avoid improper handling of them. Imaging techniques are key tools in non-invasive diagnosis of this entity.

IgG4-related Disease from Head to Toe.

Immunoglobulin G4 (IgG4)-related disease is a relatively recently proposed clinical-pathologic entity that is characterized by fibro-inflammatory lesions rich in IgG4-positive plasma cells and, often but not always, elevated serum IgG4 concentrations. IgG4-related disease was recognized as a systemic disease in 2003, when extrapancreatic manifestations were identified in patients with autoimmune pancreatitis. Since then, the disease has been reported as affecting virtually every organ system and has been identified in the biliary tree, salivary and lacrimal glands, periorbital tissues, lungs, lymph nodes, thyroid gland, kidneys, prostate gland, testicles, breasts, and pituitary gland. Its pathogenesis is poorly understood, but findings are consistent with both an autoimmune and an allergic disorder. Although definitive diagnosis requires histopathologic analysis, imaging plays an important role in demonstrating infiltration and enlargement of involved organs. Because of the systemic nature of the disease, imaging workup of IgG4-related disease should always include whole-body examinations to detect multiorgan involvement. Patients often present with subacute development of a mass in or diffuse enlargement of the affected organ, sometimes mimicking a neoplastic process. In every anatomic location, several inflammatory and neoplastic entities must be considered in the differential diagnosis. Because IgG4-related disease usually shows a marked response to corticosteroid therapy, radiologists should be familiar with its clinical and imaging manifestations to avoid a delay in diagnosis and unnecessary surgical interventions.

Retinal nerve fiber layer thickness, brain atrophy, and disability in multiple sclerosis patients.

OBJECTIVE: To study the relationship between retinal nerve fiber layer (RNFL) thickness and brain atrophy using magnetic resonance imaging (MRI) with bicaudate ratio (BCR) in patients with multiple sclerosis (MS) with different levels of disease severity. We also assessed whether RNFL thickness correlated with Expanded Disability Status Scale (EDSS) score. METHODS: The participants consisted of 88 patients with MS and 59 age- and sex-matched healthy control subjects. Eleven patients had clinically isolated syndrome (CIS), 68 patients had relapsing-remitting MS (RR-MS), and 9 patients had secondary progressive MS. Patients and controls were evaluated using optical coherence tomography (OCT, Cirrus) and scanning laser polarimetry with variable corneal compensation (GDx VCC). Patients underwent the same brain MRI scanning protocol. Disability was evaluated according to the EDSS. The BCR was calculated by dividing the minimum intercaudate distance by brain width along the same level. RESULTS: The BCR was higher in patients with MS (0.12 ± 0.03) than in controls (0.08 ± 0.009) (P < 0.001). OCT average RNFL thickness in patients with MS was significantly lower (84.51 ± 14.27 µm) than in control subjects (98.44 ± 6.83 µm). BCR was correlated with OCT average RNFL thickness (r = -0.48, P = 0.002) in patients with MS without optic neuritis. Significant correlations were found between average RNFL thickness and EDSS (r = -0.43, P = 0.003). Additionally, there were correlations between BCR with GDx parameters in patients with MS without optic neuritis. CONCLUSIONS: This study shows that RNFL thickness correlates with BCR and with MS subtypes. Additionally, our study indicates that OCT is better suited for MS assessment than GDx. We conclude that the damage of retinal axons appears related to brain damage in patients with MS.

Radiomics in CT and MR imaging of the liver and pancreas: tools with potential for clinical application.

Radiomics allows the extraction of quantitative imaging features from clinical magnetic resonance imaging (MRI) and computerized tomography (CT) studies. The advantages of radiomics have primarily been exploited in oncological applications, including better characterization and staging of oncological lesions and prediction of patient outcomes and treatment response. The potential introduction of radiomics in the clinical setting requires the establishment of a standardized radiomics pipeline and a quality assurance program. Radiomics and texture analysis of the liver have improved the differentiation of hypervascular lesions such as adenomas, focal nodular hyperplasia, and hepatocellular carcinoma (HCC) during the arterial phase, and in the pretreatment determination of HCC prognostic factors (e.g., tumor grade, microvascular invasion, Ki-67 proliferation index). Radiomics of pancreatic CT and MR images has enhanced pancreatic ductal adenocarcinoma detection and its differentiation from pancreatic neuroendocrine tumors, mass-forming chronic pancreatitis, or autoimmune pancreatitis. Radiomics can further help to better characterize incidental pancreatic cystic lesions, accurately discriminating benign from malignant intrapancreatic mucinous neoplasms. Nonetheless, despite their encouraging results and exciting potential, these tools have yet to be implemented in the clinical setting. This non-systematic review will describe the essential steps in the implementation of the radiomics and feature extraction workflow from liver and pancreas CT and MRI studies for their potential clinical application. A succinct overview of reported radiomics applications in the liver and pancreas and the challenges and limitations of their implementation in the clinical setting is also discussed, concluding with a brief exploration of the future perspectives of radiomics in the gastroenterology field.

CT perfusion in oncologic imaging: a useful tool?

OBJECTIVE: This article summarizes the current status of CT perfusion in oncologic imaging, including lesion characterization, staging, prediction of patient outcome or response to therapy, assessment of response to different therapies, and evaluation of tumor relapse. Technical limitations and drawbacks of CT perfusion are also discussed. CONCLUSION: Tumor angiogenesis is essential for cancer growth and provides an attractive target for oncologic therapies. CT perfusion is an emerging imaging tool that provides both qualitative and quantitative information regarding tumor angiogenesis.

Cholangitis and multiple liver abscesses after percutaneous ethanol injection (PEI) for recurrent hepatocellular carcinoma (HCC).

Percutaneous ablation procedures are minimally invasive treatments for unresectable early stage hepatocellular carcinoma (HCC). These techniques are usually safe, but rare and even fatal complications have been described. We present a fatal result after percutaneous ethanol injection (PEI) for the treatment of a recurrent HCC in a non-cirrhotic liver, with subsequent development of diffuse cholangitis and multiple liver abscesses. Although percutaneous drainage and intensive antibiotic treatment were employed, the patient finally died. We discuss about the etiology and the physiopathology of this rare complication in which the therapeutic options are limited and usually unsuccessful.

Testicular Evaluation Using Shear Wave Elastography (SWE) in Patients with Varicocele.

PURPOSE: To assess the possible influence of the presence of varicocele on the quantification of testicular stiffness. METHODS: Ultrasound with shear wave elastography (SWE) was performed on 48 consecutive patients (96 testicles) referred following urology consultation for different reasons. A total of 94 testes were studied and distributed in three groups: testes with varicocele (group A, n = 19), contralateral normal testes (group B; n = 13) and control group (group C, n = 62). Age, testicular volume and testicular parenchymal tissue stiffness values of the three groups were compared using the Kruskal-Wallis test. RESULTS: The mean age of the patients was 42.1 ± 11.1 years. The main reason for consultation was infertility (64.6%). The mean SWE value was 4 ± 0.4 kPa (kilopascal) in group A, 4 ± 0.5 kPa in group B and 4.2 ± 0.7 kPa in group C or control. The testicular volume was 15.8 ± 3.8 mL in group A, 16 ± 4.3 mL in group B and 16.4 ± 5.9 mL in group C. No statistically significant differences were found between the three groups in terms of age, testicular volume and tissue stiffness values. CONCLUSION: Tissue stiffness values were higher in our control group (healthy testicles) than in patients with varicocele.

CT-Based Radiomics to Predict KRAS Mutation in CRC Patients Using a Machine Learning Algorithm: A Retrospective Study.

Colorectal cancer (CRC) is one of the most common types of cancer worldwide. The KRAS mutation is present in 30-50% of CRC patients. This mutation confers resistance to treatment with anti-EGFR therapy. This article aims at proving that computer tomography (CT)-based radiomics can predict the KRAS mutation in CRC patients. The piece is a retrospective study with 56 CRC patients from the Hospital of Santiago de Compostela, Spain. All patients had a confirmatory pathological analysis of the KRAS status. Radiomics features were obtained using an abdominal contrast enhancement CT (CECT) before applying any treatments. We used several classifiers, including AdaBoost, neural network, decision tree, support vector machine, and random forest, to predict the presence or absence of KRAS mutation. The most reliable prediction was achieved using the AdaBoost ensemble on clinical patient data, with a kappa and accuracy of 53.7% and 76.8%, respectively. The sensitivity and specificity were 73.3% and 80.8%. Using texture descriptors, the best accuracy and kappa were 73.2% and 46%, respectively, with sensitivity and specificity of 76.7% and 69.2%, also showing a correlation between texture patterns on CT images and KRAS mutation. Radiomics could help manage CRC patients, and in the future, it could have a crucial role in diagnosing CRC patients ahead of invasive methods.

Usefulness of balanced SSFP sequence in robot-assisted MRI-guided prostate biopsy: Beyond scouting.

OBJECTIVES: To determine whether bSSFP images are useful for visualizing prostatic lesionsin MRI-guided in-bore transrectal biopsy. METHODS: This retrospective studyincluded 67 men witha single suspected cancer on MRI (PI-RADS 2.1 category ≥ 3) who underwent in-bore transrectal MRI-guided biopsy. Two uroradiologists independently rated lesion conspicuity on a 3-point scale (1:non-visible, 2:slightly visible, 3:clearly visible) on T2WI, DWI, and balanced SSFP.We used measures of frequency to compare lesion conspicuity in 3 sequences. We used Cohen's kappa to assess inter-rater reliability. RESULTS: Lesions were rated (1) non-visible in 18 % (12/67) of T2WI, 5 % (3/67) of DWI, and 10 % (7/67) of balanced SSFP images, (2) slightly visible in 56 % (37/67) on T2WI, 13 % (9/67) on DWI, and 48 % (32/67) on bSSFP, and (3) clearly visible in 27 %(18/67) on T2WI, 82 % (55/67) on DWI, and 42 % (28/67) on bSSFP. Lesions classified as prostate cancer at histology were slightly-clearly visible in 85 % (41/48) on T2WI, 100 % (48/48) on DWI, and 94 % (45/48) on bSSFP. Lesions classified as PI-RADS ≥ 4 were visible in 87 % (47/54) of T2WI, 100 % (54/54) of DWI, and 93 % (50/54) of bSSFP. Gleason ≥ 3 + 4 lesions were visible in 85 % (37/43) of T2WI, 100 % (43/43) of DWI, and 95 % (41/43) of bSSFP. Inter-rater agreement was excellent for T2WI (k = 0.97) and bSSFP (k = 0.94), and good for DWI (k = 0.75). CONCLUSION: Balanced SSFP is useful for visualizing prostatic lesions. Replacing T2WI with balanced SSFP can reduce the duration of in-bore transrectal MRI-guided biopsy.

Intussusception in adults: what radiologists should know.

Adult intussusception (AI) is a rare entity with an organic lesion within the intussusception in 70-90% of the cases. Intussusception is classified according to location, etiology, and to the presence or not of a lead point. We illustrate several causes of AI with a variety of radiological findings on plain film, ultrasonography, computed tomography, magnetic resonance, and endoscopy seen at our institution. Imaging plays a major role in their diagnosis and in determining the appropriate treatment.

"Rectal cancer survival: A retrospective analysis of MRI features and their association with prognosis".

PURPOSE: To assess rectal cancer aggressiveness using magnetic resonance (MR) imaging features and to investigate their relationship with patient prognosis. MATERIALS AND METHODS: Clinical information and Pelvic MR scans of 106 consecutive patients with primary rectal cancer (RC) were analyzed. Clinical symptoms, age, sex, tumor location, and patient´s survival were recorded. The variables investigated by MR were: depth or mural/extramural tumor involvement, distance to mesorectal margin, lymph node involvement, vascular, peritoneal or sphincter complex infiltration. The association between imaging features and disease-free survival (DFS) was also assessed using a Kaplan-Meier model. Differences between survival curves were tested for significance using the Mantel-Cox LogRank test. RESULTS: The final study population was 106 patients (65 males, 41 females). The median age was 69.5 years (range, 39-92 years). No significant differences were found between death risk and sex, age or tumor location (p>0,05). However, the relative risk (RR) of tumor mortality increased significantly with the presence of the variables: vascular infiltration (×5), T4 tumors (× 4.57), N2 lymph node involvement (more than 3 affected nodes × 4.11) and mesorectal fascia involvement (× 3,77). CONCLUSION: Tumor extension, number of pathological lymph nodes, mesorectal fascia involvement and vascular infiltration values obtained on initial MR imaging staging showed a significant difference for disease-free survival in RC at six years of control.

Extraocular muscle involvement in MALT lymphomas.

We report 3 cases of extraocular muscle involvement by MALT (mucosa-associated lymphoid tissue) lymphoma. The first case was a 68-year-old woman who presented with mild proptosis of the left eye and diplopia caused by a lymphoma in the medial rectus. The other two cases presented with ptosis caused by a lymphoma in the most anterior aspect of the levator muscle. MALT lymphoma may involve extraocular muscles, either as a primary or secondary presentation. Although localization of orbital lymphoma in extraocular muscles is rare, this possibility should be considered in the differential diagnosis with other conditions involving extraocular musculature.