Use of Spectral Detector Computed Tomography to Improve Liver Segmentation and Volumetry.

INTRODUCTION: Liver segmentation and volumetry have traditionally been performed using computed tomography (CT) attenuation to discriminate liver from other tissues. In this project, we evaluated if spectral detector CT (SDCT) can improve liver segmentation over conventional CT on 2 segmentation methods. MATERIALS AND METHODS: In this Health Insurance Portability and Accountability Act-compliant institutional review board-approved retrospective study, 30 contrast-enhanced SDCT scans with healthy livers were selected. The first segmentation method is based on Gaussian mixture models of the SDCT data. The second method is a convolutional neural network-based technique called U-Net. Both methods were compared against equivalent algorithms, which used conventional CT attenuation, with hand segmentation as the reference standard. Agreement to the reference standard was assessed using Dice similarity coefficient. RESULTS: Dice similarity coefficients to the reference standard are 0.93 ± 0.02 for the Gaussian mixture model method and 0.90 ± 0.04 for the CNN-based method (all 2 methods applied on SDCT). These were significantly higher compared with equivalent algorithms applied on conventional CT, with Dice coefficients of 0.90 ± 0.06 (P = 0.007) and 0.86 ± 0.06 (P < 0.001), respectively. CONCLUSION: On both liver segmentation methods tested, we demonstrated higher segmentation performance when the algorithms are applied on SDCT data compared with equivalent algorithms applied on conventional CT data.

A Technique to Identify Isoattenuating Gallstones with Dual-Layer Spectral CT: An ex Vivo Phantom Study.

Background Previously reported dual-energy CT methods for detecting noncalcified gallstones have reduced accuracy for gallstones smaller than 9 mm. Purpose To develop a dual-energy CT method for differentiating isoattenuating gallstones from bile and compare it with previously reported dual-energy CT methods by using a prospective ex vivo phantom reader study. Materials and Methods From May 2017 to May 2018, gallstones were collected from 105 patients (34 men; mean age, 51 years; age range, 18-84 years) undergoing cholecystectomy and placed inside 120-mL vials containing ox bile. The vials were placed inside a water-filled phantom and were scanned with dual-layer dual-energy CT. Thirty isoattenuating gallstones (4.3-24.7 mm in diameter) were evaluated. Conventional CT images, virtual noncontrast images, and monoenergetic images at 200 and 40 keV were created. Segmented images were created by using a two-dimensional histogram of Compton and photoelectric attenuation. Six readers evaluated the presence of isoattenuating gallstones in each image. Intra- and interreader agreement was measured by using percentage agreement, diagnostic performance was evaluated by using mean area under the receiver operating characteristic curve (AUC) estimates and pairwise comparisons, and the agreement of gallstone sizes measured at pathologic examination with those measured on segmented images was compared by using Bland-Altman analysis. Results For all gallstones, segmented images provided the highest mean intrareader (88.1%) and interreader (88.2% and 93.6%) agreements for all readers and reading sessions and the highest overall AUC (0.99; 95% confidence interval [CI]: 0.97, 1.00; adjusted P < .02 for all). For gallstones larger than 9 mm, no significant difference was found between the segmented and monoenergetic AUCs (all P > .94, adjusted P > .05 for all). For gallstones measuring 9 mm or smaller, the segmented images had the highest overall AUC (0.99; 95% CI: 0.97, 1.00; adjusted P < .01 for all). The mean difference in stone sizes was -0.6 mm, with limits of agreement from 2.6 to -3.8 mm. Conclusion Segmented images from Compton and photoelectric attenuation coefficients improve detection of isoattenuating gallstones compared with previously reported dual-energy CT methods. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Matos in this issue.

Phantom Validation of Spectral Detector Computed Tomography-Derived Virtual Monoenergetic, Virtual Noncontrast, and Iodine Quantification Images.

PURPOSE: Spectral detector computed tomography (SDCT) is a new CT technology that uses a dual-layer detector to perform energy separation. We aim to assess 3 clinical concepts using a phantom model: noise profile across the virtual monoenergetic (VME) spectrum, accuracy of iodine quantification, and virtual noncontrast (VNC) reconstructions' ability to remove iodine contribution to attenuation. METHODS: Six vials containing varying concentrations of iodinated contrast (0-6 mg/mL) diluted in water were placed in a water bath and scanned on an SDCT scanner. Virtual monoenergetic (40-200 keV at 10-keV increments), iodine-no-water, and VNC reconstructions were created. Attenuation (in Hounsfield units [HU]), VME noise at each energy level, CT-derived iodine concentration, and VNC attenuation were recorded. RESULTS: Virtual monoenergetic noise was improved at all energies compared with conventional images (conventional, 9.8-11.2; VME, 7.5-9.5). Noise profile showed a slightly higher image noise at 40 keV, but was otherwise relatively flat across the energy spectrum. On iodine-no-water reconstructions, measured varied from actual iodine concentration by ±0.1 mg/mL (SD, 0.16-0.36). Virtual noncontrast attenuation was within 5 HU of water attenuation at all iodine concentrations. CONCLUSION: Reconstructions of SDCT show lower VME image noise, accurate iodine quantification, and VNC attenuation values within 5 HU of expected in a phantom model.

Imaging across the life span: innovations in imaging and therapy for gynecologic cancer.

The focus of this article is radiation therapy for gynecologic cancers, with emphasis on imaging-based treatment planning and delivery. For the various gynecologic cancers, radiation oncologists rely on essential clinical information to triage treatment options, and various imaging studies are performed for treatment planning and radiation therapy delivery. A practical approach is provided to help radiologists tailor their reports for the needs of their radiation oncology and gynecologic oncology colleagues, to optimize multidisciplinary care for patients with gynecologic cancer. Template radiology reports are proposed to address the specific information needs of oncologists at each phase-before, during, and after treatment. Fueled by the rapid progress in engineering and computer sciences during the past 2 decades, remarkable advances have been made in anatomic, functional, and molecular imaging and in radiation treatment planning and delivery in patients with gynecologic cancer. Radiation therapy has evolved from a nontargeted approach to a precisely targeted, highly conformal treatment modality, to further improve treatment outcomes and reduce morbidity. High-quality imaging has become essential for staging of the disease, delineation of tumor extent for treatment planning and delivery, and monitoring therapy response. Anatomic and functional imaging has also been shown to provide prognostic information that allows clinicians to tailor therapy on the basis of personalized patient information. This field is an area of active research, and future clinical trials are warranted to validate preliminary results in the field.

Imaging the pregnant patient with abdominal pain.

Imaging of pregnant patients with non-obstetric abdominal pain is reviewed, with an accompanying pictorial essay of cases with concentration on magnetic resonance imaging. Non-obstetric causes of abdominal pain during pregnancy are similar to those of non-pregnant patients. The most common causes are appendicitis and cholecystitis. Other causes are myriad and include biliary, gastrointestinal, infectious, inflammatory, and malignant etiologies, among others. The approach to imaging in pregnant patient is unique, as it is imperative to minimize potentially harmful radiation exposures to the fetus. Ultrasound and MRI are the primary modalities for evaluation of the pregnant patient with abdominal pain. The use of intravenous contrast is discouraged, except in highly-selected patients where there is no other way to obtain vital diagnostic information. CT is still used as the mainstay of evaluation of blunt abdominal trauma and is commonly used for diagnosis of small bowel obstruction, stone disease, and work-up of malignancy during pregnancy. A discussion of test selection and underlying rationale is presented.

Performance of Multiple Pretrained BERT Models to Automate and Accelerate Data Annotation for Large Datasets.

Purpose: To develop and evaluate domain-specific and pretrained bidirectional encoder representations from transformers (BERT) models in a transfer learning task on varying training dataset sizes to annotate a larger overall dataset. Materials and Methods: The authors retrospectively reviewed 69 095 anonymized adult chest radiograph reports (reports dated April 2020-March 2021). From the overall cohort, 1004 reports were randomly selected and labeled for the presence or absence of each of the following devices: endotracheal tube (ETT), enterogastric tube (NGT, or Dobhoff tube), central venous catheter (CVC), and Swan-Ganz catheter (SGC). Pretrained transformer models (BERT, PubMedBERT, DistilBERT, RoBERTa, and DeBERTa) were trained, validated, and tested on 60%, 20%, and 20%, respectively, of these reports through fivefold cross-validation. Additional training involved varying dataset sizes with 5%, 10%, 15%, 20%, and 40% of the 1004 reports. The best-performing epochs were used to assess area under the receiver operating characteristic curve (AUC) and determine run time on the overall dataset. Results: The highest average AUCs from fivefold cross-validation were 0.996 for ETT (RoBERTa), 0.994 for NGT (RoBERTa), 0.991 for CVC (PubMedBERT), and 0.98 for SGC (PubMedBERT). DeBERTa demonstrated the highest AUC for each support device trained on 5% of the training set. PubMedBERT showed a higher AUC with a decreasing training set size compared with BERT. Training and validation time was shortest for DistilBERT at 3 minutes 39 seconds on the annotated cohort. Conclusion: Pretrained and domain-specific transformer models required small training datasets and short training times to create a highly accurate final model that expedites autonomous annotation of large datasets.Keywords: Informatics, Named Entity Recognition, Transfer Learning Supplemental material is available for this article. ©RSNA, 2022See also the commentary by Zech in this issue.

Segmentations of MRI images of the female pelvic floor: a study of inter- and intra-reader reliability.

PURPOSE: To describe the inter- and intra-operator reliability of segmentations of female pelvic floor structures. MATERIALS AND METHODS: Three segmentation specialists were asked to segment out the female pelvic structures in 20 MR datasets on three separate occasions. The STAPLE algorithm was used to compute inter- and intra-segmenter agreement of each organ in each dataset. STAPLE computed the sensitivity, specificity, and positive predictive values (PPV) for inter- and intra-segmenter repeatability. These parameters were analyzed using intra-class correlation analysis. Correlation of organ volume to PPV and sensitivity was also computed. RESULTS: Mean PPV of the segmented organs ranged from 0.82 to 0.99, and sensitivity ranged from 33 to 96%. Intra-class correlation ranged from 0.07 to 0.98 across segmenters. Pearson correlation of volume to sensitivity were significant across organs, ranging from 0.54 to 0.91. Organs with significant correlation of PPV to volume were bladder (-0.69), levator ani (-0.68), and coccyx (-0.63). CONCLUSION: Undirected manual segmentation of the pelvic floor organs are adequate for locating the organs, but poor at defining structural boundaries.

LI-RADS treatment response algorithm after first-line DEB-TACE: reproducibility and prognostic value at initial post-treatment CT/MRI.

PURPOSE: To evaluate the inter-reader reproducibility and prognostic accuracy of the Liver Imaging Reporting and Data System (LI-RADS) treatment response algorithm (LR-TR) at the time of initial post-treatment evaluation following drug-eluting beads transarterial chemoembolization (DEB-TACE) for hepatocellular carcinoma (HCC). METHODS: This retrospective study included patients with HCC who underwent first-line DEB-TACE between January 2011 and December 2015. Six readers (three fellowship-trained radiologists and three radiology trainees) independently assessed lesion-level response in up to two treated lesions per LR-TR and modified Response Evaluation Criteria in Solid Tumors (mRECIST)-target criteria, as well as patient-level response per mRECIST-overall criteria, on the initial post-treatment CT/MRI. Inter-reader agreement was calculated by Fleiss' multi-reader κ. We tested whether LR-TR, mRECIST-target, and mRECIST-overall response were associated with overall survival using Kaplan-Meier and Cox proportional hazard model analyses. RESULTS: A total of 82 patients with 113 treated target lesions were included. Inter-reader agreement was moderate for LR-TR and mRECIST-overall (κ range 0.42-0.57), and substantial for mRECIST-target (κ range 0.62-0.66), among all three reader-groups: all readers, experienced readers, and less-experienced readers. LR-TR and mRECIST-target response were not significantly associated with overall survival regardless of reader experience (P > 0.05). In contrast, mRECIST-overall response was significantly associated with overall survival when assessed by all readers (P = 0.02) and experienced readers (P = 0.03), but not by the less-experienced readers (P = 0.35). CONCLUSION: Although LR-TR algorithm has moderate inter-reader reproducibility, it alone may not predict overall survival on the initial post-treatment CT/MRI after first-line DEB-TACE for HCC.

MR defecography technique: recommendations of the society of abdominal radiology's disease-focused panel on pelvic floor imaging.

PURPOSE: To develop recommendations for magnetic resonance (MR) defecography technique based on consensus of expert radiologists on the disease-focused panel of the Society of Abdominal Radiology (SAR). METHODS: An extensive questionnaire was sent to a group of 20 experts from the disease-focused panel of the SAR. The questionnaire encompassed details of technique and MRI protocol used for evaluating pelvic floor disorders. 75% agreement on questionnaire responses was defined as consensus. RESULTS: The expert panel reached consensus for 70% of the items and provided the basis of these recommendations for MR defecography technique. There was unanimous agreement that patients should receive coaching and explanation of commands used during MR defecography, the rectum should be distended with contrast agent, and that sagittal T2-weighted images should include the entire pelvis within the field of view. The panel also agreed unanimously that IV contrast should not be used for MR defecography. Additional areas of consensus ranged in agreement from 75 to 92%. CONCLUSION: We provide a set of consensus recommendations for MR defecography technique based on a survey of expert radiologists in the SAR pelvic floor dysfunction disease-focused panel. These recommendations can be used to develop a standardized imaging protocol.

Variability in utilization and techniques of pelvic floor imaging: findings of the SAR pelvic floor dysfunction disease-focused panel.

Pelvic floor disorders are common and can negatively impact quality of life. Imaging of patients with pelvic floor disorders has been extremely heterogeneous between institutions due in part to variations in clinical expectations, technical considerations, and radiologist experience. In order to assess variations in utilization and technique of pelvic floor imaging across practices, the society of abdominal radiology (SAR) disease-focused panel on pelvic floor dysfunction developed and administered an online survey to radiologists including the SAR membership. Results of the survey were compared with published recommendations for pelvic floor imaging to identify areas in need of further standardization. MRI was the most commonly reported imaging technique for pelvic floor imaging followed by fluoroscopic defecography. Ultrasound was only used by a small minority of responding radiologists. The survey responses demonstrated variability in imaging utilization, patient referral patterns, imaging protocols, patient education, and interpretation and reporting of pelvic floor imaging examinations. This survey highlighted inconsistencies in technique between institutions as well as potential gaps in knowledge that should be addressed to standardize evaluation of patients with pelvic floor dysfunction.

Variations in use of "water soluble contrast challenge" for small bowel obstruction among academic radiologists: results of a national survey.

OBJECTIVE: To assess the frequency and indications for use of oral water-soluble contrast challenge as a diagnostic test for small bowel obstruction in four regions of the USA. MATERIALS AND METHODS: We distributed a 9-question web-based survey to the abdominal section heads of academic radiology departments throughout the USA (N = 97). The questions pertained to use of water-soluble contrast for management of small bowel obstruction. Descriptive statistics and Fisher's exact tests were used for data analysis. RESULTS: The overall response rate was 46%. Eighty percent of the responding hospitals had more than 500 beds in operation. Water-soluble contrast challenge was considered standard of care for management of non-operative small bowel obstruction in 60% of the responding radiology departments. The majority of the responding departments (41%) performed 2-8 contrast challenge studies per month on average. The most frequent indication for the study was distinguishing partial vs complete bowel obstruction. Eighty percent of the responding radiologists believed that the contrast challenge is useful for management of small bowel obstruction. Overall, there was no statistically significant difference in frequency and indication for use of water-soluble contrast challenge based on geographic location. CONCLUSION: The water-soluble contrast challenge was considered standard of care for non-operative management of small bowel obstruction in majority of the academic radiology departments represented in this survey. Surgeons were referring clinicians in every case. The most common clinical indication for the study was distinguishing partial versus complete small bowel obstruction.

Tumors of Renal Collecting Systems, Renal Pelvis, and Ureters: Role of MR Imaging and MR Urography Versus Computed Tomography Urography.

Hematuria evaluation remains a common problem, particularly in patients who smoke and are at risk for urothelial tumors. Lifetime surveillance of the urothelium is often required once urothelial cancer is diagnosed. Computed tomography urography (CTU) has exquisite sensitivity and specificity for identification of renal and urothelial lesions. The examination is well accepted by patients and physicians. Possible harms include radiation exposure and contrast-induced nephropathy. MR imaging is also an accurate test, but requires longer exam times, and may not demonstrate stones. We present the technical and interpretation skills required to use MR urography and CTU effectively.

Reproducibility of dynamic MR imaging pelvic measurements: a multi-institutional study.

PURPOSE: To assess the reproducibility of bone and soft-tissue pelvimetry measurements obtained from dynamic magnetic resonance (MR) imaging studies in primiparous women across multiple centers. MATERIALS AND METHODS: All subjects prospectively gave consent for participation in this institutional review board-approved, HIPAA-compliant study. At six clinical sites, standardized dynamic pelvic 1.5-T multiplanar T2-weighted MR imaging was performed in three groups of primiparous women at 6-12 months after birth: Group 1, vaginal delivery with anal sphincter tear (n = 93); group 2, vaginal delivery without anal sphincter tear (n = 79); and group 3, cesarean delivery without labor (n = 26). After standardized central training, blinded readers at separate clinical sites and a blinded expert central reader measured nine bone and 10 soft-tissue pelvimetry parameters. Subsequently, three readers underwent additional standardized training, and reread 20 MR imaging studies. Measurement variability was assessed by using intraclass correlation for agreement between the clinical site and central readers. Acceptable agreement was defined as an intraclass correlation coefficient (ICC) of at least 0.7. RESULTS: There was acceptable agreement (ICC range, 0.71-0.93) for eight of 19 MR imaging parameters at initial readings of 198 subjects. The remaining parameters had an ICC range of 0.13-0.66. Additional training reduced measurement variability: Twelve of 19 parameters had acceptable agreement (ICC range, 0.70-0.92). Correlations were greater for bone (ICC, >or=0.70 in five [initial readings] and eight of nine [rereadings] variables) than for soft-tissue measurements (ICC, >or=0.70 in three [initial readings] of 10 and four [rereadings] of 10 readings, respectively). CONCLUSION: Despite standardized central training, there is high variability of pelvic MR imaging measurements among readers, particularly for soft-tissue structures. Although slightly improved with additional training, measurement variability adversely affects the utility of many MR imaging measurements for multicenter pelvic floor disorder research.

Racial differences in pelvic anatomy by magnetic resonance imaging.

OBJECTIVES: To use static and dynamic magnetic resonance imaging (MRI) to compare dimensions of the bony pelvis and soft tissue structures in a sample of African-American and white women. METHODS: This study used data from 234 participants in the Childbirth and Pelvic Symptoms Imaging Study, a cohort study of 104 primiparous women with an obstetric anal sphincter tear, 94 who delivered vaginally without a recognized anal sphincter tear and 36 who underwent by cesarean delivery without labor. Race was self-reported. At 6-12 months postpartum, rapid acquisition T2-weighted pelvic MRIs were obtained. Bony and soft tissue dimensions were measured and compared between white and African-American participants using analysis of variance, while controlling for delivery type and age. RESULTS: The pelvic inlet was wider among 178 white women than 56 African-American women (10.7+/-0.7 cm compared with 10.0.+0.7 cm, P<.001). The outlet was also wider (mean intertuberous diameter 12.3+/-1.0 cm compared with 11.8+/-0.9 cm, P<.001). There were no significant differences between racial groups in interspinous diameter, angle of the subpubic arch, anteroposterior conjugate, levator thickness, or levator hiatus. In addition, among women who delivered vaginally without a sphincter tear, African-American women had more pelvic floor mobility than white women. This difference was not observed among women who had sustained an obstetric sphincter tear. CONCLUSION: White women have a wider pelvic inlet, wider outlet, and shallower anteroposterior outlet than African-American women. In addition, after vaginal delivery, white women demonstrate less pelvic floor mobility. These differences may contribute to observed racial differences in obstetric outcomes and to the development of pelvic floor disorders.

MRI of pelvic floor dysfunction: review.

OBJECTIVE: The purpose of this article is to review the anatomy and etiology of pelvic floor weakness in women and to discuss the role of MRI in the assessment of female pelvic floor dysfunction. CONCLUSION: In women with pelvic floor weakness, pelvic MRI, with its superior soft-tissue contrast resolution, allows direct visualization of the pelvic organs and their supportive structures in a single noninvasive examination. By providing useful and valuable information on the extent and severity of pelvic organ prolapse, MRI plays a valuable role in preoperative planning of complex cases.

MRI of pelvic floor dysfunction: self-assessment module.

OBJECTIVE: The educational objectives of this continuing medical education activity are for the reader to exercise, self-assess, and improve skills in diagnostic radiology with regard to the interpretation of MRI of the female pelvis in the evaluation of pelvic floor dysfunction, and to improve familiarity with the clinical features of female pelvic floor dysfunction. CONCLUSION: The articles in this activity review the anatomy and etiology of pelvic floor weakness in women and discuss the role of MRI in the assessment of female pelvic floor dysfunction.

Quantitative accuracy of positron emission tomography/magnetic resonance and positron emission tomography/computed tomography for cervical cancer.

With the spread of positron emission tomography/magnetic resonance (PET/MR), the question of comparability of studies becomes important. We aim to determine whether PET/MR and PET/computed tomography (PET/CT) are comparable for the case of cervical cancer. Fifteen cervical cancer patients identified by either a radiation oncologist or an oncologic surgeon had both PET/MR and PET/CT performed for initial staging within 3 weeks. We then compared the results both quantitatively (measuring standardized uptake values [SUVs] on visible lesions) as well as qualitatively (having radiologists and nuclear medicine physicians interprets the results). While interpretations between PET/MR and PET/CT varied in many cases, SUVs of primary lesions were similar to within 25% in all but one case, and correlation coefficient was 0.92. Maximum SUV ranged between 4.9 and 25.2 for PET-MR and between 5.8 and 30.4 for PET-CT for primary tumors and between 1.5 and 18.8 for PET-MR and between 1.8 and 20.8 for PET-CT for nodes. However, clinical reads often varied significantly between PET/MR and PET/CT. This suggests that SUV is similar on PET/MR and PET/CT although the differing anatomic modalities available for correlation may make the difference in terms of qualitative interpretation.