Wells, Michael L

AbstractPurposeConventional model observers (MO) in CT are often limited to a uniform background or varying background that is random and can be modeled in an analytical form. It is unclear if these conventional MOs can be readily generalized to predict human observer performance in clinical CT tasks that involve realistic anatomical background. Deep‐learning‐based model observers (DL‐MO) have recently been developed, but have not been validated for challenging low contrast diagnostic tasks in abdominal CT. We consequently sought to validate a DL‐MO for a low‐contrast hepatic metastases localization task.MethodsWe adapted our recently developed DL‐MO framework for the liver metastases localization task. Our previously‐validated projection‐domain lesion‐/noise‐insertion techniques were used to synthesize realistic positive and low‐dose abdominal CT exams, using the archived patient projection data. Ten experimental conditions were generated, which involved different lesion sizes/contrasts, radiation dose levels, and image reconstruction types. Each condition included 100 trials generated from a patient cohort of 7 cases. Each trial was presented as liver image patches (160×160×5 voxels). The DL‐MO performance was calculated for each condition and was compared with human observer performance, which was obtained by three sub‐specialized radiologists in an observer study. The performance of DL‐MO and radiologists was gauged by the area under localization receiver‐operating‐characteristic curves. The generalization performance of the DL‐MO was estimated with the repeated twofold cross‐validation method over the same set of trials used in the human observer study. A multi‐slice Channelized Hoteling Observers (CHO) was compared with the DL‐MO across the same experimental conditions.ResultsThe performance of DL‐MO was highly correlated to that of radiologists (Pearson's correlation coefficient: 0.987; 95% CI: [0.942, 0.997]). The performance level of DL‐MO was comparable to that of the grouped radiologists, that is, the mean performance difference was ‐3.3%. The CHO performance was poorer than the grouped radiologist performance, before internal noise could be added. The correlation between CHO and radiologists was weaker (Pearson's correlation coefficient: 0.812, and 95% CI: [0.378, 0.955]), and the corresponding performance bias (‐29.5%) was statistically significant.ConclusionThe presented study demonstrated the potential of using the DL‐MO for image quality assessment in patient abdominal CT tasks.

Background Dual-energy virtual monoenergetic images can increase iodine signal, potentially increasing the conspicuity of hepatic masses. Purpose To determine if dual-energy 50-keV virtual monoenergetic images improve visualization of key imaging findings or diagnostic confidence for small (≤2 cm) hepatocellular carcinomas (HCC) at multiphase, contrast-enhanced liver computed tomography (CT). Material and Methods Patients with chronic liver disease underwent multiphase dual-energy CT imaging for HCC, with late arterial and delayed phase dual-energy 50-keV images reconstructed. Two non-reader subspecialized gastrointestinal (GI) radiologists established the reference standard, determining the location and diagnosis of all hepatic lesions using predetermined criteria. Three GI radiologists interpreted mixed kV CT images without or with dual-energy 50-keV images. Radiologists identified potential HCCs and rated their confidence (0–100 scales) in imaging findings of arterial enhancement, enhancing capsule, tumor washout, and LI-RADS 5 (2018) category. Results In total, 45 patients (14 women; mean age = 59.5 ± 10.9 years) with chronic liver disease were included. Of them, 19 patients had 25 HCCs ≤2 cm (mean size = 1.5 ± 0.4 cm). There were 17 LI-RADS 3 and 4 lesions and 19 benign lesions. Reader confidence in imaging findings of arterial enhancement, enhancing capsule, and non-peripheral washout significantly increased with dual-energy images ( P ≤ 0.022). Overall confidence in HCC diagnosis increased significantly with dual-energy 50-keV images (52.4 vs. 68.8; P = 0.001). Dual-energy images demonstrated a slight but significant decrease in overall image quality. Conclusion Radiologist confidence in key imaging features of small HCCs and confidence in imaging diagnosis increases with use of dual-energy 50-keV images at multiphase, contrast-enhanced liver CT.

Background Due to their easy accessibility, CT scans have been increasingly used for investigation of gastrointestinal (GI) bleeding. Purpose To estimate the performance of a dual-phase, dual-energy (DE) GI bleed CT protocol in patients with overt GI bleeding in clinical practice and examine the added value of portal phase and DE images. Materials and Methods Consecutive patients with GI bleeding underwent a two-phase DE GI bleed CT protocol. Two gastroenterologists established the reference standard. Performance was estimated using clinical CT reports. Three GI radiologists rated confidence in GI bleeding in a subset of 62 examinations, evaluating first mixed kV arterial images, then after examining additional portal venous phase images, and finally after additional DE images (virtual non-contrast and virtual monoenergetic 50 keV images). Results 52 of 176 patients (29.5%) had GI bleeding by the reference standard. The overall sensitivity, specificity, and positive and negative predictive values of the CT GI bleed protocol for detecting GI bleeding were 65.4%, 89.5%, 72.3%, and 86.0%, respectively. In patients with GI bleeding, diagnostic confidence of readers increased after adding portal phase images to arterial phase images ( p = 0.002), without additional benefit from dual energy images. In patients without GI bleeding, confidence in luminal extravasation appropriately decreased after adding portal phase, and subsequently DE images ( p = 0.006, p = 0.018). Conclusion A two-phase DE GI bleed CT protocol had high specificity and negative predictive value in clinical practice. Portal venous phase images improved diagnostic confidence in comparison to arterial phase images alone. Dual-energy images further improved radiologist confidence in the absence of bleeding.

Objective: Transoral endoscopic laser-assisted diverticulotomy (TELD) with diverticulectomy and diverticuloplasty (TELD + DD) for the management of Zenker’s diverticulum (ZD) has been utilized by our institution since 2016 in attempts to reduce residual pouch size. This technique involves complete endoscopic pouch excision with partial advancement of mucosal flaps. Our study compares the subjective outcomes, objective outcomes, and complication rates between TELD and TELD + DD. Methods: A retrospective cohort study was performed on patients who underwent TELD or TELD + DD by a single surgeon at a tertiary academic center (2013-2019). Videofluoroscopic swallow studies (VFSS) with esophagram, Eating Assessment Tool (EAT-10), Reflux Symptom Index (RSI), and Functional Outcome Swallowing Scale (FOSS) were collected at preoperative and 3 month follow-up visits. A single blinded reviewer recorded height, width, and depth of pre and postoperative pouches with volumetric analysis performed assuming an ellipsoid shape. Comorbidities, complications, postoperative course, and recurrence were recorded. Results: Of the 75 patients that met criteria, 27 underwent TELD + DD and 48 underwent TELD. Eighteen TELD + DD and 37 TELD had both pre and post-operative VFSS. TELD + DD and TELD had a 96 ± 7% and 87 ± 16% reduction in pouch volume, respectively ( t-test; P = .01). Complications (TELD + DD 7%, TELD 17%, fisher’s exact; P = .31) and final subjective outcomes after adjusting for initial were not significantly different between methods (EAT-10 with TELD + DD ∆ + 1.3, P = .18; RSI ∆ + 1.4, P = .29; FOSS ∆-0.02, P = .91). One short-term recurrence was reported with TELD. Conclusion: Use of TELD + DD is associated with a statistically significantly decreased residual pouch size with no significant difference in short-term subjective outcomes. Complication rates and short-term recurrence rates are comparable. Long-term recurrence rates will require further studies to characterize. Level of Evidence: Level 3.

Background Low tube potential-high tube current computed tomography (CT) imaging allows reduction in iodine-based contrast dose and may extend the benefit of routine contrast-enhanced CT exams to patients at risk of nephrotoxicity. Purpose To determine the ability of an iodine contrast reduction algorithm to maintain diagnostic image quality for contrast-enhanced abdominal CT. Material and Methods CT exams with iodine contrast reduction were prescribed for patients at risk for renal dysfunction. The iodine contrast reduction algorithm combines weight-based contrast volume reduction with patient width-based low tube potential selection and bolus-tracking. Control exams with routine iodine dose were selected based on weight, width, and scan protocol. Three radiologists evaluated image quality and diagnostic confidence using a 4-point scale (<2 acceptable). Another radiologist assessed contrast reduction indications and measured portal vein and liver contrast-to-noise ratios. Results Forty-six contrast reduction algorithm and control exams were compared (mean creatinine 1.6 vs. 1.2 mg/dL, P ≤ 0.0001). Thirty-nine contrast reduction patients had an eGFR <60 mL/min/1.73m 2 and 15 had single or transplanted kidney. Mean iodine contrast dose was lower in the contrast reduction group (20.9 vs. 39.4 g/mL, P < 0.0001). Diagnostic confidence was rated as acceptable in 95% (131/138) of contrast reduction and 100% of control exams (1.18–1.28 vs. 1.02–1.13, respectively; P > 0.06). Liver attenuation and contrast-to-noise ratio (CNR) were similar ( P = 0.08), but portal vein attenuation and CNR were lower with contrast-reduction (mean 176 vs. 198 HU, P = 0.02; 13 vs. 16, P = 0.0002). Conclusion This size-based contrast reduction algorithm using low kV and bolus tracking reduced iodine contrast dose by 50%, while achieving acceptable image quality in 95% of exams.

Disease monitoring in nonalcoholic steatohepatitis (NASH) is limited by absence of noninvasive biomarkers of disease regression or progression. We aimed to examine the role of multiparametric three‐dimensional magnetic resonance elastography (3D‐MRE) and magnetic resonance imaging proton density fat fraction (MRI‐PDFF) in the detection of NASH regression after interventions. This is a single‐center prospective clinical trial of 40 patients who underwent bariatric surgery. Imaging and liver biopsies were obtained at baseline and 1 year after surgery. The imaging protocol consisted of multifrequency 3D‐MRE to determine the shear stiffness at 60 Hz and damping ratio at 40 Hz, and MRI‐PDFF to measure the fat fraction. A logistic regression model including these three parameters was previously found to correlate with NASH. We assessed the model performance in the detection of NASH resolution after surgery by comparing the image‐predicted change in NAFLD activity score (delta NAS) to the histologic changes. A total of 38 patients (median age 43, 87% female, 30 of 38 with NAS ≥ 1, and 13 of 38 with NASH) had complete data at 1 year. The NAS decreased in all subjects with NAS ≥ 1 at index biopsy, and NASH resolved in all 13. There was a strong correlation between the predicted delta NAS by imaging and the delta NAS by histology (r = 0.73, P < 0.001). The strength of correlation between histology and the predicted delta NAS using single conventional parameters, such as the fat fraction by MRI‐PDFF or shear stiffness at 60 Hz by MRE, was r = 0.69 (P < 0.001) and r = 0.43 (P = 0.009), respectively. Conclusion: Multiparametric 3D‐MRE and MRI‐PDFF can detect histologic changes of NASH resolution after bariatric surgery. Studies in a nonbariatric setting are needed to confirm the performance as a composite noninvasive biomarker for longitudinal NASH monitoring.

Abstract Background and Aims Our goal was to determine the importance of ileal inflammation at computed tomography or magnetic resonance enterography in Crohn’s disease patients with normal ileoscopy. Methods Patients with negative ileoscopy and biopsy within 30 days of CT or MR enterography showing ileal inflammation were included. The severity [0–3 scale] and length of inflammation within the distal 20 cm of the terminal ileum were assessed on enterography. Subsequent medical records were reviewed for ensuing surgery, ulceration at ileoscopy, histological inflammation, or new or worsening ileal inflammation or stricture on enterography. Imaging findings were classified as: Confirmed Progression [subsequent surgery or radiological worsening, new ulcers at ileoscopy or positive histology]; Radiologic Response [decreased inflammation with medical therapy]; or Unlikely/Unconfirmed Inflammation. Results Of 1471 patients undergoing enterography and ileoscopy, 112 [8%] had imaging findings of inflammation with negative ileoscopy, and 88 [6%] had negative ileoscopy and ileal biopsy. Half [50%; 44/88] with negative biopsy had moderate/severe inflammation at enterography, with 45%, 32% and 11% having proximal small bowel inflammation, stricture or fistulas, respectively. Two-thirds with negative biopsy [67%; 59/88] had Confirmed Progression, with 68%, 70% and 61% having subsequent surgical resection, radiological worsening or ulcers at subsequent ileoscopy, respectively. Mean length and severity of ileal inflammation in these patients was 10 cm and 1.6. Thirteen [15%] patients had Radiologic Response, and 16 [18%] had Unlikely/Unconfirmed Inflammation. Conclusion Crohn’s disease patients with unequivocal imaging findings of ileal inflammation at enterography despite negative ileoscopy and biopsy are likely to have active inflammatory Crohn’s disease. Disease detected by imaging may worsen over time or respond to medical therapy.

The lack of reliable, noninvasive methods to diagnose early nonalcoholic steatohepatitis (NASH) is a major unmet need. We aimed to determine the diagnostic accuracy of three‐dimensional magnetic resonance elastography (3D‐MRE), with shear stiffness measured at 60 Hz, damping ratio at 40 Hz, and magnetic resonance imaging proton density fat fraction (MRI‐PDFF) in the detection of NASH in individuals undergoing bariatric surgery. Obese adults at risk for NASH were enrolled between 2015 and 2017 (prospective cohort, n = 88) and 2010 and 2013 (retrospective cohort, n = 87). The imaging protocol consisted of multifrequency 3D‐MRE (mf3D‐MRE) with shear waves delivered at different frequencies to explore parameters that best correlated with histologic NASH, and MRI‐PDFF to estimate steatosis. The prospective cohort was used to establish the optimal mf3D‐MRE technical parameters for NASH detection. The two cohorts were then combined to derive predictive models of NASH and disease activity by nonalcoholic fatty liver disease activity score (NAS) using the three imaging parameters that correlated with NASH. A total of 175 patients (median age 45, 81% women, and 81 [46%] with histologic NASH) were used for model derivation. From the complex shear modulus output generated by mf3D‐MRE, the damping ratio at 40 Hz and shear stiffness at 60 Hz best correlated with NASH. The fat fraction obtained from MRI‐PDFF correlated with steatosis ( P < 0.05 for all). These three parameters were fit into a logistic regression model that predicted NASH with cross‐validated area under the receiver operating characteristic curve (AUROC) = 0.73, sensitivity = 0.67, specificity = 0.80, positive predictive value = 0.73 and negative predictive value = 0.74, and disease activity by NAS with cross‐validated AUROC = 0.82. Conclusion: The mf3D‐MRE allows identification of imaging parameters that predict early NASH and disease activity. This imaging biomarker represents a promising alternative to liver biopsy for NASH diagnosis and monitoring. The results provide motivation for further studies in nonbariatric cohorts.