Implementation of an Institution-Wide Rules-Based Automated CT Protocoling System

BACKGROUND. Examination protocoling is a noninterpretive task that increases radiologists' workload and can cause workflow inefficiencies. OBJECTIVE. The purpose of this study was to evaluate effects of an automated CT protocoling system on examination process times and protocol error rates. METHODS. This retrospective study included 317,597 CT examinations (mean age, 61.8 ± 18.1 [SD] years; male, 161,125; female, 156,447; unspecified sex, 25) from July 2020 to June 2022. A rules-based automated protocoling system was implemented institution-wide; the system evaluated all CT orders in the EHR and assigned a protocol or directed the order for manual radiologist protocoling. The study period comprised pilot (July 2020 to December 2020), implementation (January 2021 to December 2021), and postimplementation (January 2022 to June 2022) phases. Proportions of automatically protocoled examinations were summarized. Process times were recorded. Protocol error rates were assessed by counts of quality improvement (QI) reports and examination recalls and comparison with retrospectively assigned protocols in 450 randomly selected examinations. RESULTS. Frequency of automatic protocoling was 19,366/70,780 (27.4%), 68,875/163,068 (42.2%), and 54,045/83,749 (64.5%) in pilot, implementation, and postimplementation phases, respectively (p < .001). Mean [± SD] times from order entry to protocol assignment for automatically and manually protocoled examinations for emergency department examinations were 0.2 ± 18.2 and 2.1 ± 69.7 hours, respectively; mean inpatient examination times were 0.5 ± 50.0 and 3.5 ± 105.5 hours; and mean outpatient examination times were 361.7 ± 1165.5 and 1289.9 ± 2050.9 hours (all p < .001). Mean [± SD] times from order entry to examination completion for automatically and manually protocoled examinations for emergency department examinations were 2.6 ± 38.6 and 4.2 ± 73.0 hours, respectively (p < .001); for inpatient examinations were 6.3 ± 74.6 and 8.7 ± 109.3 hours (p = .001); and for outpatient examinations were 1367.2 ± 1795.8 and 1471.8 ± 2118.3 hours (p < .001). In the three phases, there were three, 19, and 25 QI reports and zero, one, and three recalls, respectively, for automatically protocoled examinations, versus nine, 19, and five QI reports and one, seven, and zero recalls for manually protocoled examinations. Retrospectively assigned protocols were concordant with 212/214 (99.1%) of automatically protocoled versus 233/236 (98.7%) of manually protocoled examinations. CONCLUSION. The automated protocoling system substantially reduced radiologists' protocoling workload and decreased times from order entry to protocol assignment and examination completion; protocol errors and recalls were infrequent. CLINICAL IMPACT. The system represents a solution for reducing radiologists' time spent performing noninterpretive tasks and improving care efficiency.

Cholangiocarcinoma imaging: from diagnosis to response assessment

Cholangiocarcinoma (CCA), a highly aggressive primary liver cancer arising from the bile duct epithelium, represents a substantial proportion of hepatobiliary malignancies, posing formidable challenges in diagnosis and treatment. Notably, the global incidence of intrahepatic CCA has seen a rise, necessitating a critical examination of diagnostic and management strategies, especially due to presence of close imaging mimics such as hepatocellular carcinoma (HCC) and combined hepatocellular carcinoma-cholangiocarcinoma (cHCC-CCA). Hence, it is imperative to understand the role of various imaging modalities such as ultrasound, computed tomography (CT), and magnetic resonance imaging (MRI), elucidating their strengths, and limitations in diagnostic precision and staging accuracy. Beyond conventional approaches, there is emerging significance of functional imaging tools including positron emission tomography (PET)-CT and diffusion-weighted (DW)-MRI, providing pivotal insights into diagnosis, therapeutic assessment, and prognostic evaluation. This comprehensive review explores the risk factors, classification, clinical features, and role of imaging in the holistic spectrum of diagnosis, staging, management, and restaging for CCA, hence serving as a valuable resource for radiologists evaluating CCA.

Society of Radiologists in Ultrasound Consensus Conference Recommendations for Incidental Gallbladder Polyp Management: Interreader Agreement Among Ten Radiologists

Background: The 2022 Society of Radiologists in Ultrasound (SRU) consensus conference recommendations support less-aggressive management of small gallbladder polyps on ultrasound versus earlier approaches and may help standardize polyp evaluation by radiologists. Objective: To assess radiologists' interreader agreement in applying the SRU recommendations for management of incidental gallbladder polyps on ultrasound. Methods: This retrospective study included 105 patients (median age, 52 years; 75 women, 27 men) with a gallbladder polyp on ultrasound (without features highly suspicious for invasive or malignant tumor) who underwent cholecystectomy between January 1, 2003 and January 1, 2021. Ten abdominal radiologists independently reviewed ultrasound examinations and, using SRU recommendations, assessed one polyp per patient for risk category (extremely low-risk, low-risk, or indeterminate risk) and possible recommendation for surgical consultation. Five radiologists were considered less-experienced (<5 years), and five more-experienced (≥5 years). Interreader agreement was evaluated. Polyps were classified pathologically as nonneoplastic or neoplastic. Results: For risk category assignments, interreader agreement was substantial among all readers (k=0.710), less-experienced readers (k=0.705), and more-experienced readers (k=0.692). For surgical consultation recommendations, interreader agreement was substantial among all readers (k=0.795) and more-experienced readers (kappa=0.740), and almost perfect among less-experienced readers (k=0.811). Of ten readers, a median of 5 (IQR, 2-8), 4 (IQR, 2-7), and 0 (IQR, 0-0) classified polyps as extremely low risk, low risk, and indeterminate risk, respectively. Across readers, the fraction of polyps classified as extremely low risk ranged from 32-72%, as low risk from 24-65%, and as indeterminate risk from 0-8%. Of ten readers, a median of 0 (IQR, 0-1) recommended surgical consultation; the fraction of polyps receiving a surgical consultation recommendation ranged from 4-22%. A total of 102/105 polyps were nonneoplastic; 3/105 were neoplastic (all benign). Based on readers' most-common assessments for the nonneoplastic polyps, the risk category was extremely low risk in 53, low risk in 48, and indeterminate risk in 1; surgical consultation was recommended in 16. Conclusion: Ten abdominal radiologists showed substantial agreement for polyp risk categorizations and surgical consultation recommendations, although areas of reader variability were identified. Clinical Impact: The findings support overall reproducibility of the SRU recommendations, while indicating opportunity for improvement.

Pancreatic Serous Cystadenoma: A Continuing Diagnostic Challenge

Objective:

Summary Background data:

Serous cystadenoma (SCA) is a benign cystic pancreatic neoplasm of the pancreas, accounting for approximately 15% of resected pancreatic cysts. Current recommendations are to proceed with surgical resection in symptomatic patients or when there is uncertainty regarding diagnosis. The latter continues to be a challenge since intentional resection of a serous cystadenoma account for only a minority of resected of cases.

Methods:

Retrospective single-institution review of patients who on final pathology had a diagnosis of pancreatic serous cystadenoma and of patients who had this diagnosis and were managed non-operatively. Demographic data, cyst characteristics, and growth rate were collected for analysis.

Results:

A total of 250 patients were analyzed. Median age was 62 (range 22 – 89), 65% were female, and 34% had symptoms. Tumor size ranged from 0.6 to 20, with a median of 3.4 cm. The morphological appearance was microcystic in 58%, macrocystic in 16%, mixed-type in 23%, and solid in 3%. Pancreatic duct dilation and pancreatic atrophy were found in 22% and 14%, respectively. The average growth rate was 1.8 mm/year regardless of tumor size. Of the 172 patients who underwent surgery, serous cystadenoma was the preoperative diagnosis in only 33%. A correct diagnosis was independently associated with large tumors and cyst fluid CEA analysis. Pancreatic duct dilation was independently associated with an in-growing cyst and presence of calcification.

Conclusion:

SCA is a slow-growing pancreatic cystic neoplasm that is mostly asymptomatic but can lead to pancreatic duct dilation and atrophy in some patients. A surprisingly small number of correct preoperative diagnoses confirms that this entity continues to be a diagnostic challenge. A more thorough preoperative workup that includes EUS should improve the rate of mis-diagnosis.

Intra-patient variability of iodine quantification across different dual-energy CT platforms: assessment of normalization techniques

OBJECTIVES

To investigate intra-patient variability of iodine concentration (IC) between three different dual-energy CT (DECT) platforms and to test different normalization approaches.

METHODS

Forty-four patients who underwent portal venous phase abdominal DECT on a dual-source (dsDECT), a rapid kVp switching (rsDECT), and a dual-layer detector platform (dlDECT) during cancer follow-up were retrospectively included. IC in the liver, pancreas, and kidneys and different normalized ICs (NICPV:portal vein; NICAA:abdominal aorta; NICALL:overall iodine load) were compared between the three DECT scanners for each patient. A longitudinal mixed effects analysis was conducted to elucidate the effect of the scanner type, scan order, inter-scan time, and contrast media amount on normalized iodine concentration.

RESULTS

Variability of IC was highest in the liver (dsDECT vs. dlDECT 28.96 (14.28-46.87) %, dsDECT vs. rsDECT 29.08 (16.59-62.55) %, rsDECT vs. dlDECT 22.85 (7.52-33.49) %), and lowest in the kidneys (dsDECT vs. dlDECT 15.76 (7.03-26.1) %, dsDECT vs. rsDECT 15.67 (8.86-25.56) %, rsDECT vs. dlDECT 10.92 (4.92-22.79) %). NICALL yielded the best reduction of IC variability throughout all tissues and inter-scanner comparisons, yet did not reduce the variability between dsDECT vs. dlDECT and rsDECT, respectively, in the liver. The scanner type remained a significant determinant for NICALL in the pancreas and the liver (F-values, 12.26 and 23.78; both, p < 0.0001).

CONCLUSIONS

We found tissue-specific intra-patient variability of IC across different DECT scanner types. Normalization mitigated variability by reducing physiological fluctuations in iodine distribution. After normalization, the scanner type still had a significant effect on iodine variability in the pancreas and liver.

CLINICAL RELEVANCE STATEMENT

Differences in iodine quantification between dual-energy CT scanners can partly be mitigated by normalization, yet remain relevant for specific tissues and inter-scanner comparisons, which should be taken into account at clinical routine imaging.

KEY POINTS

• Iodine concentration showed the least variability between scanner types in the kidneys (range 10.92-15.76%) and highest variability in the liver (range 22.85-29.08%). • Normalizing tissue-specific iodine concentrations against the overall iodine load yielded the greatest reduction of variability between scanner types for 2/3 inter-scanner comparisons in the liver and for all (3/3) inter-scanner comparisons in the kidneys and pancreas, respectively. • However, even after normalization, the dual-energy CT scanner type was found to be the factor significantly influencing variability of iodine concentration in the liver and pancreas.

Diagnostic performance and feasibility of dual-layer detector dual-energy CT for characterization of urinary stones in patients of different sizes

BACKGROUND

Urinary stones are frequently encountered in urology and are typically identified using non-contrast CT scans. Dual-energy CT (DECT) is a valuable imaging technique that produces material-specific images and allows for precise assessment of stone composition by estimating the effective atomic number (Zeff), a capability not achievable with the conventional single-energy CT's attenuation measurement method.

PURPOSE

To investigate the diagnostic performance and image quality of dual-layer detector DECT (dlDECT) in characterizing urinary stones in patients of different sizes.

METHODS

All consecutive dlDECT examinations with stone protocol and presence of urinary stones between July 2018 and November 2019 were retrospectively evaluated. Two radiologists independently reviewed 120 kVp and color-overlay Zeff images to determine stone composition (reference standard = crystallography) and image quality. The objective analysis included image noise and Zeff values measurement.

RESULTS

A total of 739 urinary stones (median size 3.7 mm, range 1-35 mm) were identified on 177 CT examinations from 155 adults (mean age, 57 ± 15 years, 80 men, median weight 82.6 kg, range 42.6-186.9 kg). Using color-overlay Zeff images, the radiologists could subjectively interpret the composition in all stones ≥ 3 mm (n = 491). For stones with available reference standards (n = 74), dlDECT yielded a sensitivity of 80% (95%CI 44-98%) and a specificity of 98% (95%CI 92-100%) in visually discriminating uric acid from non-uric acid stones. Patients weighing > 90 kg and ≤ 90 kg had similar stone characterizability (p = 0.20), with 86% of stones characterized in the > 90 kg group and 87% in the ≤ 90 kg group. All examinations throughout various patients' weights revealed acceptable image quality. A Zeff cutoff of 7.66 accurately distinguished uric acid from non-uric acid stones (AUC = 1.00). Zeff analysis revealed AUCs of 0.78 and 0.91 for differentiating calcium-based stones from other non-uric stones and all stone types, respectively.

CONCLUSION

dlDECT allowed accurate differentiation of uric acid and non-uric acid stones among patients with different body sizes with acceptable image quality.

CLINICAL IMPACT

The ability to accurately differentiate uric acid stones from non-uric acid stones using color-overlay Zeff images allows for better tailored treatment strategies, helping to choose appropriate interventions and prevent potential complications related to urinary stones in patient care.

Dual-Energy Computed Tomography to Photon Counting Computed Tomography: Emerging Technological Innovations

Computed tomography (CT) has seen remarkable developments in the past several decades, radically transforming the role of imaging in day-to-day clinical practice. Dual-energy CT (DECT), an exciting innovation introduced in the early part of this century, has widened the scope of CT, opening new opportunities due to its ability to provide superior tissue characterization. The introduction of photon-counting CT (PCCT) heralds a paradigm shift in CT scanner technology representing another significant milestone in CT innovation. PCCT offers several advantages over DECT, such as improved spectral resolution, enhanced tissue characterization, reduced image artifacts, and improved image quality.

Dual-Energy Computed Tomography: Technological Considerations

Compared to conventional single-energy CT (SECT), dual-energy CT (DECT) provides additional information to better characterize imaged tissues. Approaches to DECT acquisition vary by vendor and include source-based and detector-based systems, each with its own advantages and disadvantages. Despite the different approaches to DECT acquisition, the most utilized DECT images include routine SECT equivalent, virtual monoenergetic, material density (eg, iodine map), and virtual non-contrast images. These images are generated either through reconstructions in the projection or image domains. Designing and implementing an optimal DECT workflow into routine clinical practice depends on radiologist and technologist input with special considerations including appropriate patient and protocol selection and workflow automation. In addition to better tissue characterization, DECT provides numerous advantages over SECT such as the characterization of incidental findings and dose reduction in radiation and iodinated contrast.

Vascular Applications of Dual-Energy Computed Tomography

Dual- or multi-energy CT imaging provides several advantages over conventional CT in the context of vascular imaging. Specific advantages include the use of low-energy virtual monoenergetic images (VMIs) to boost iodine attenuation to salvage suboptimal enhanced studies, perform low-contrast material dose studies, and increase conspicuity of small vessels and lesions. Alternatively, high-energy VMIs reduce artifacts caused by some metals, endoprosthesis, calcium blooming, and beam hardening. Virtual non-contrast (VNC) images reduce radiation dose by eliminating the need for a true non-contrast acquisition in multiphasic CT studies. Iodine maps can be used to evaluate perfusion of tissues and lesions.

Optimal Abdominal CT Image Quality in Non-Lean Patients: Customization of CM Injection Protocols and Low-Energy Acquisitions

We compared the image quality of abdominopelvic single-energy CT with 100 kVp (SECT-100 kVp) and dual-energy CT with 65 keV (DECT-65 keV) obtained with customized injection protocols to standard abdominopelvic CT scans (SECT-120 kVp) with fixed volumes of contrast media (CM). We retrospectively included 91 patients (mean age, 60.7 ± 15.8 years) with SECT-100 kVp and 83 (mean age, 60.3 ± 11.7 years) patients with DECT-65 keV in portovenous phase. Total body weight-based customized injection protocols were generated by a software using the following formula: patient weight (kg) × 0.40/contrast concentration (mgI/mL) × 1000. Patients had a prior abdominopelvic SECT-120 kVp with fixed injection. Iopamidol-370 was administered for all examinations. Quantitative and qualitative image quality comparisons were made between customized and fixed injection protocols. Compared to SECT-120 kVp, customized injection yielded a significant reduction in CM volume (mean difference = 9-12 mL; p ≤ 0.001) and injection rate (mean differences = 0.2-0.4 mL/s; p ≤ 0.001) in all weight categories. Improvements in attenuation, noise, signal-to-noise and contrast-to-noise ratios were observed for both SECT-100 kVp and DECT-65 keV compared to SECT-120 kVp in all weight categories (e.g., pancreas DECT-65 keV, 1.2-attenuation-fold increase vs. SECT-120 kVp; p < 0.001). Qualitative scores were ≥4 in 172 cases (98.8.4%) with customized injections and in all cases with fixed injections (100%). These findings suggest that customized CM injection protocols may substantially reduce iodine dose while yielding higher image quality in SECT-100 kVp and DECT-65 keV abdominopelvic scans compared to SECT-120 kVp using fixed CM volumes.

A Multicenter Assessment of Interreader Reliability of LI-RADS Version 2018 for MRI and CT

Background Various limitations have impacted research evaluating reader agreement for Liver Imaging Reporting and Data System (LI-RADS). Purpose To assess reader agreement of LI-RADS in an international multicenter multireader setting using scrollable images. Materials and Methods This retrospective study used deidentified clinical multiphase CT and MRI and reports with at least one untreated observation from six institutions and three countries; only qualifying examinations were submitted. Examination dates were October 2017 to August 2018 at the coordinating center. One untreated observation per examination was randomly selected using observation identifiers, and its clinically assigned features were extracted from the report. The corresponding LI-RADS version 2018 category was computed as a rescored clinical read. Each examination was randomly assigned to two of 43 research readers who independently scored the observation. Agreement for an ordinal modified four-category LI-RADS scale (LR-1, definitely benign; LR-2, probably benign; LR-3, intermediate probability of malignancy; LR-4, probably hepatocellular carcinoma [HCC]; LR-5, definitely HCC; LR-M, probably malignant but not HCC specific; and LR-TIV, tumor in vein) was computed using intraclass correlation coefficients (ICCs). Agreement was also computed for dichotomized malignancy (LR-4, LR-5, LR-M, and LR-TIV), LR-5, and LR-M. Agreement was compared between research-versus-research reads and research-versus-clinical reads. Results The study population consisted of 484 patients (mean age, 62 years ± 10 [SD]; 156 women; 93 CT examinations, 391 MRI examinations). ICCs for ordinal LI-RADS, dichotomized malignancy, LR-5, and LR-M were 0.68 (95% CI: 0.61, 0.73), 0.63 (95% CI: 0.55, 0.70), 0.58 (95% CI: 0.50, 0.66), and 0.46 (95% CI: 0.31, 0.61) respectively. Research-versus-research reader agreement was higher than research-versus-clinical agreement for modified four-category LI-RADS (ICC, 0.68 vs 0.62, respectively; P = .03) and for dichotomized malignancy (ICC, 0.63 vs 0.53, respectively; P = .005), but not for LR-5 (P = .14) or LR-M (P = .94). Conclusion There was moderate agreement for LI-RADS version 2018 overall. For some comparisons, research-versus-research reader agreement was higher than research-versus-clinical reader agreement, indicating differences between the clinical and research environments that warrant further study. © RSNA, 2023 Supplemental material is available for this article. See also the editorials by Johnson and Galgano and Smith in this issue.

Uncinate Duct Dilatation Predicts Additional Risk for High-Grade Dysplasia or Invasive Carcinoma Among Fukuoka-Positive Intraductal Papillary Mucinous Neoplasms

OBJECTIVE

To determine whether uncinate duct dilatation (UDD) increases the risk of high-grade dysplasia or invasive carcinoma (HGD/IC) in Fukuoka-positive intraductal papillary mucinous neoplasms (IPMNs).

BACKGROUND

Though classified as a branch duct, the uncinate duct is the primary duct of the pancreatic ventral anlage. We hypothesized that UDD, like main duct dilatation, confers additional risk for HGD/IC.

METHODS

A total of 467 patients met inclusion criteria in a retrospective cohort study of surgically resected IPMNs at the Massachusetts General Hospital. We used multivariable logistic regression to analyze the association between UDD (defined as ≥4 mm) and HGD/IC, controlling for Fukuoka risk criteria. In a secondary analysis, the modeling was repeated in the 194 patients with dorsal branch duct IPMNs (BD-IPMNs) in the pancreatic neck, body, or tail.

RESULTS

Mean age at surgery was 70, and 229 (49%) patients were female. In total, 267 (57%) patients had only worrisome features and 200 (43%) had at least 1 high-risk feature. UDD was present in 164 (35%) patients, of whom 118 (73%) had HGD/IC. On multivariable analysis, UDD increased the odds of HGD/IC by 2.8-fold, even while controlling for Fukuoka risk factors (95% CI: 1.8-4.4, P <0.001). Prevalence of HGD/IC in all patients with UDD was 73%, compared with 74% in patients with high-risk stigmata and 73% in patients with main duct IPMNs. In the secondary analysis, UDD increased the odds of HGD/IC by 3.2-fold in patients with dorsal BD-IPMNs (95% CI: 1.3-7.7, P =0.010).

CONCLUSIONS

UDD confers additional risk for HGD/IC unaccounted for by current Fukuoka criteria. Further research can extend this study to Fukuoka-negative patients, including unresected patients.

A Gene Panel Associated With Abemaciclib Utility in ESR1-Mutated Breast Cancer After Prior Cyclin-Dependent Kinase 4/6-Inhibitor Progression

PURPOSE

For patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2-) metastatic breast cancer (MBC), first-line treatment is endocrine therapy (ET) plus cyclin-dependent kinase 4/6 inhibition (CDK4/6i). After disease progression, which often comes with ESR1 resistance mutations (ESR1-MUT), which therapies to use next and for which patients are open questions. An active area of exploration is treatment with further CDK4/6i, particularly abemaciclib, which has distinct pharmacokinetic and pharmacodynamic properties compared with the other approved CDK4/6 inhibitors, palbociclib and ribociclib. We investigated a gene panel to prognosticate abemaciclib susceptibility in patients with ESR1-MUT MBC after palbociclib progression.

METHODS

We examined a multicenter retrospective cohort of patients with ESR1-MUT MBC who received abemaciclib after disease progression on ET plus palbociclib. We generated a panel of CDK4/6i resistance genes and compared abemaciclib progression-free survival (PFS) in patients without versus with mutations in this panel (CDKi-R[-] v CDKi-R[+]). We studied how ESR1-MUT and CDKi-R mutations affect abemaciclib sensitivity of immortalized breast cancer cells and patient-derived circulating tumor cell lines in culture.

RESULTS

In ESR1-MUT MBC with disease progression on ET plus palbociclib, the median PFS was 7.0 months for CDKi-R(-) (n = 17) versus 3.5 months for CDKi-R(+) (n = 11), with a hazard ratio of 2.8 (P = .03). In vitro, CDKi-R alterations but not ESR1-MUT induced abemaciclib resistance in immortalized breast cancer cells and were associated with resistance in circulating tumor cells.

CONCLUSION

For ESR1-MUT MBC with resistance to ET and palbociclib, PFS on abemaciclib is longer for patients with CDKi-R(-) than CDKi-R(+). Although a small and retrospective data set, this is the first demonstration of a genomic panel associated with abemaciclib sensitivity in the postpalbociclib setting. Future directions include testing and improving this panel in additional data sets, to guide therapy selection for patients with HR+/HER2- MBC.

MRI-Based Tumor Necrosis Depiction in Pancreatic Ductal Adenocarcinoma: Can It Predict Tumor Aggressiveness?

The purpose of this study was to investigate whether tumor necrosis depicted on contrast-enhanced abdominal MRI can predict tumor aggressiveness in pancreatic ductal adenocarcinoma (PDAC). In this retrospective analysis, we included 71 patients with pathology-proven PDAC who underwent contrast-enhanced MRI from 2006 to 2020. Assessment for the presence/absence of imaging detected necrosis was performed on T2-weighted and contrast-enhanced T1-weighted images. Primary tumor characteristics, regional lymphadenopathy, metastases, stage, and overall survival were analyzed. Fisher's exact and Mann-Whitney U tests were used for statistical analysis. Of the 72 primary tumors, necrosis was identified on MRI in 58.3% (42/72). Necrotic PDACs were larger (44.6 vs. 34.5 mm, p = 0.0016), had higher rates of regional lymphadenopathy (69.0% vs. 26.7%, p = 0.0007), and more frequent metastases (78.6% vs. 40.0%, p = 0.0010) than those without MRI-evident necrosis. A non-statistically significant reduction in median overall survival was observed in patients with versus without MRI-evident necrosis (15.8 vs. 38.0 months, p = 0.23). PDAC tumor necrosis depicted on MRI was associated with larger tumors and higher frequency of regional lymphadenopathy and metastases.

CT image quality evaluation in the age of deep learning: trade-off between functionality and fidelity

OBJECTIVE

To quantitatively compare DLIR and ASiR-V with realistic anatomical images.

METHODS

CT scans of an anthropomorphic phantom were acquired using three routine protocols (brain, chest, and abdomen) at four dose levels, with images reconstructed at five levels of ASiR-V and three levels of DLIR. Noise power spectrum (NPS) was estimated using a difference image by subtracting two matching images from repeated scans. Using the max-dose FBP reconstruction as the ground truth, the structure similarity index (SSIM) and gradient magnitude (GM) of difference images were evaluated. Image noise magnitude (σ), frequency location of the NPS peak (f_peak), mean SSIM (MSSIM), and mean GM (MGM) were used as quantitative metrics to compare image quality, for each anatomical region, protocol, algorithm, dose level, and slice thickness.

RESULTS

Image noise had a strong (R² > 0.99) power law relationship with dose for all algorithms. For the abdomen and chest, f_peak shifted from 0.3 (FBP) down to 0.15 mm^-1 (ASiR-V 100%) with increasing ASiR-V strength but remained 0.3 mm^-1 for all DLIR levels. f_peak shifted down for the brain protocol with increasing DLIR levels. Three levels of DLIR produced similar image noise levels as ASiR-V 40%, 80%, and 100%, respectively. DLIR had lower MSSIM but higher MGM than ASiR-V while matching imaging noise.

CONCLUSION

Compared to ASiR-V, DLIR presents trade-offs between functionality and fidelity: it has a noise texture closer to FBP and more edge enhancement, but reduced structure similarity. These trade-offs and unique protocol-dependent behaviors of DLIR should be considered during clinical implementation and deployment.

KEY POINTS

• DLIR reconstructed images demonstrate closer noise texture and lower structure similarity to FBP while producing equivalent noise levels comparable to ASiR-V. • DLIR has additional edge enhancement as compared to ASiR-V. • DLIR has unique protocol-dependent behaviors that should be considered for clinical implementation.

Resection of NAFLD/NASH-related Hepatocellular Carcinoma (HCC): Clinical Features and Outcomes Compared with HCC Due to Other Etiologies

BACKGROUND

Non-alcoholic fatty liver disease (NAFLD) and non-alcoholic steatohepatitis (NASH) are the leading causes of hepatocellular carcinoma (HCC) worldwide. Limited data exist on surgical outcomes for NAFLD/NASH-related HCC compared with other HCC etiologies. We evaluated differences in clinicopathological characteristics and outcomes of patients undergoing surgical resection for NAFLD/NASH-associated HCC compared with other HCC etiologies.

METHODS

Demographic, clinicopathological features, and survival outcomes of patients with surgically resected HCC were collected. NAFLD activity score (NAS) and fibrosis score were assessed by focused pathologic review in a subset of patients.

RESULTS

Among 492 patients screened, 260 met eligibility (NAFLD/NASH [n = 110], and other etiologies [n = 150]). Median age at diagnosis was higher in the NAFLD/NASH HCC cohort compared with the other etiologies cohort (66.7 vs. 63.4 years, respectively, P = .005), with an increased percentage of female patients (36% vs. 18%, P = .001). NAFLD/NASH-related tumors were more commonly >5 cm (66.0% vs. 45%, P = .001). There were no significant differences in rates of lymphovascular or perineural invasion, histologic grade, or serum AFP levels. The NAFLD/NASH cohort had lower rates of background liver fibrosis, lower AST and ALT levels, and higher platelet counts (P < .01 for all). Median overall survival (OS) was numerically shorter in NAFLD/NASH vs other etiology groups, however, not statistically significant.

CONCLUSIONS

Patients with NAFLD/NASH-related HCC more commonly lacked liver fibrosis and presented with larger HCCs compared with patients with HCC from other etiologies. No differences were seen in rates of other high-risk features or survival. With the caveat of sample size and retrospective analysis, this supports a similar decision-making approach regarding surgical resection for NAFLD/NASH and other etiology-related HCCs.

Renal lesion characterization: clinical utility of single-phase dual-energy CT compared to MRI and dual-phase single-energy CT

OBJECTIVES

To assess the impact of dual-energy CT (DECT) utilization in practice by measuring the readers' confidence, the need for additional image requests, and diagnostic performance in renal lesion assessment, compared to single-energy CT (SECT) using contrast-enhanced MRI to establish the reference standard.

MATERIALS AND METHODS

Sixty-nine patients (M/F = 47/22) who underwent a dual-phase renal SECT (n = 34) or DECT (n = 35) and had a contrast-enhanced MRI within 180 days were retrospectively collected. Three radiologists assessed images on different sessions (SECT, DECT, and MRI) for (1) likely diagnosis (enhancing/non-enhancing); (2) diagnostic confidence (5-point Likert scale); (3) need for additional imaging test (yes/no); and (4) need for follow-up imaging (yes/no). Diagnostic accuracy was compared using AUC; p value < 0.05 was considered significant.

RESULTS

One hundred fifty-six lesions consisting of 18% enhancing (n = 28/156, mean size: 30.37 mm, range: 9.9-94 mm) and 82% non-enhancing (n = 128/156, mean size: 23.91 mm, range: 5.0-94.2 mm) were included. The confidence level was significantly lower for SECT than their MRI (4.50 vs. 4.80, p value < 0.05) but not significantly different for DECT and the corresponding MRI (4.78 vs. 4.78, p > 0.05). There were significantly more requests for additional imaging in the SECT session than the corresponding MRI (20% vs. 4%), which was not significantly different between DECT and their MRI counterpart session (5.7% vs. 4.9%). Inter-reader agreement was almost perfect for DECT and MRI (kappa: 0.8-1) and substantial in SECT sessions (kappa: 0.6-0.8) with comparable diagnostic accuracy between SECT, DECT, and MRI (p value > 0.05).

CONCLUSION

Single-phase DECT allows confident and reproducible characterization of renal masses with fewer recommendation for additional and follow-up imaging tests than dual-phase SECT and a performance similar to MRI.

KEY POINTS

• DECT utilization leads to similar additional image requests to MRI (5.7% vs. 4.9%, p value > 0.05), whereas single-energy CT utilization leads to significantly higher image requests (20% vs. 4%, p value < 0.05). • DECT and MRI utilization bring highly reproducible results with almost perfect inter-reader agreement (kappa: 0.8-1), better than the inter-reader agreement in SECT utilization (kappa: 0.6-0.8). • Readers' confidence was not significantly altered between DECT and their MRI readout session (p value > 0.05). In contrast, confidence in the diagnosis was significantly lower in the SECT session than their MRI readout (p value < 0.05).

Optional MRI sequences for LI-RADS: why, what, and how?

Hepatocellular carcinoma (HCC) is the most common primary malignant tumor of the liver worldwide. Noninvasive diagnosis of HCC is possible based on imaging features, without the need for tissue diagnosis. Liver Imaging Reporting and Data System (LI-RADS) CT/MRI diagnostic algorithm allows for standardized radiological interpretation and reporting of imaging studies for patients at high risk for HCC. Diagnostic categories of LR-1 to LR-5 designate each liver observation to reflect the probability of overall malignancy, HCC, or benignity based on imaging features, where LR-5 category has > 95% probability of HCC. Optimal imaging protocol and scanning technique as described by the technical recommendations for LI-RADS are essential for the depiction of features to accurately characterize liver observations. The LI-RADS MRI technical guidelines recommend the minimum required sequences of T1-weighted out-of-phase and in-phase Imaging, T2-weighted Imaging, and multiphase T1-weighted Imaging. Additional sequences, including diffusion-weighted imaging, subtraction imaging, and the hepatobiliary phase when using gadobenate dimeglumine as contrast, improve diagnostic confidence, but are not required by the guidelines. These optional sequences can help differentiate true lesions from pseudolesions, detect additional observations, identify parenchymal observations when other sequences are suboptimal, and improve observations conspicuity. This manuscript reviews the optional sequences, the advantages they offer, and discusses technical optimization of these sequences to obtain the highest image quality and to avoid common artifacts.

Postoperative surveillance of pancreatic ductal adenocarcinoma (PDAC) recurrence: practice pattern on standardized imaging and reporting from the society of abdominal radiology disease focus panel on PDAC

PURPOSE

Surgical resection is the only potential curative treatment for patients with pancreatic ductal adenocarcinoma (PDAC), but unfortunately most patients recur within 5 years of surgery. This article aims to assess the practice patterns across major academic institutions and develop consensus recommendations for postoperative imaging and interpretation in patients with PDAC.

METHODS

The consensus recommendations for postoperative imaging surveillance following PDAC resection were developed using the Delphi method. Members of the Society of Abdominal Radiology (SAR) PDAC Disease Focused Panel (DFP) underwent three rounds of surveys followed by live webinar group discussions to develop consensus recommendations.

RESULTS

Significant variations currently exist in the postoperative surveillance of PDAC, even among academic institutions. Differentiating common postoperative inflammatory and fibrotic changes from tumor recurrence remains a diagnostic challenge, and there is no reliable size threshold or growth rate of imaging findings that can provide differentiation. A new liver lesion or peritoneal nodule should be considered suspicious for tumor recurrence, and the imaging features should be interpreted in the appropriate clinical context (e.g., CA 19-9, clinical presentation, pathologic staging).

CONCLUSION

Postoperative imaging following PDAC resection is challenging to interpret due to the presence of confounding postoperative inflammatory changes. A standardized reporting template for locoregional findings and report impression may improve communication of relaying risk of recurrence with referring providers, which merits validation in future studies.

Abstract A028: The Early Detection Initiative trial version 2: A platform trial to test novel approaches to pancreatic cancer screening in patients with new onset hyperglycemia and diabetes

The Early Detection Initiative (EDI) is an innovative study designed to build a platform that will evaluate novel approaches to early detection of resectable pancreatic ductal adenocarcinoma (PDAC) in patients over age 50 with new onset hyperglycemia and diabetes (NOD). This randomized controlled trial (RCT) of algorithm-based screening for PDAC uses a modified Zelen’s design with post-randomization consent. Eligible subjects are identified through electronic medical record (EMR) surveillance and randomized 1:1 to the Observation or Intervention Arm. The Enriching New-onset Diabetes for Pancreatic Cancer (ENDPAC) score, an algorithm that further risk stratifies NOD based on age and changes in weight and glycemic parameters, is calculated in the Intervention Arm. Consenting subjects with ENDPAC &gt;0 have Computerized Tomography (CT) scan imaging for PDAC detection; potential harm, including over-diagnosis, is also estimated. At the time of abstract submission &gt;2000 individuals have been randomized and &gt;50 subjects consented for CT imaging. EDI version 2 adds several innovations in response to challenges encountered and experience gained so far. Most significantly, EDI v2 has a platform design with a common control arm and allows for multiple intervention arms. This opens the door for evaluating future new biomarkers for PDAC early detection in a high–risk NOD population, including new blood-based biomarkers for the early detection of cancer that are now commercially available. EDI v2 focuses primarily on co-efficacy endpoints (PDAC stage shift in ENDPAC &gt;0 group, and in all patients, excluding non-consented patients); effectiveness evaluation becomes a secondary objective. This addresses the challenges of low consent rate (~25%) due to lack of awareness of connection between NOD and PDAC and low acceptance for a novel research screening modality. The analyses of primary endpoints were adjusted to accommodate potential over-diagnosis due to screening and imbalance between ENDPAC &gt;0 and ENDPAC ≤0 groups due to low consent rate and likely imperfect enrichment by ENDPAC, when evaluating all patients. Electronic eligibility checks and consent shorten the recruitment time, a critical factor for stage shift due to rapid progression of PDAC. A pre-randomization screening pilot study is planned to enhance the post-randomization consent rate. Intervention to Control randomization ratio is changed to 2:1, allowing more rapid recruitment and, when factoring the consent rate, doubling the sample size of the observation arm. Through these innovations, EDI v2 maintains the full advantage of Zelen’s design that made the trial feasible in sample size and cost. Simulation studies demonstrate that our approach correctly controls the type-1 error and the trial has adequate statistical power. The EDI trial represents an innovative and contemporary approach to developing and refining an early detection strategy for pancreatic cancer.

Citation Format: Ying-Qi Zhao, Suresh T. Chari, Anirban Maitra, Lynn M. Matrisian, Eva E. Shrader, Bechien U. Wu, Avinash Kambadakone, Barbara Kenner, Jo Ann S. Rinaudo, Sudhir Srivastava, Ying Huang, Ziding Feng. The Early Detection Initiative trial version 2: A platform trial to test novel approaches to pancreatic cancer screening in patients with new onset hyperglycemia and diabetes [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer; 2022 Sep 13-16; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2022;82(22 Suppl):Abstract nr A028.

Concordance of EUS and MRI/MRCP findings among high-risk individuals undergoing pancreatic cancer screening

BACKGROUND/OBJECTIVES

Surveillance with endoscopic ultrasonography (EUS) and MRI/magnetic retrograde cholangiopancreatography (MRCP) is recommended for individuals at high risk for pancreatic cancer. We sought to characterize the findings of these surveillance exams and define the level of concordance between these two modalities.

METHODS

173 asymptomatic high-risk individuals (HRIs) meeting criteria for pancreatic cancer surveillance underwent EUS, MRI/MRCP, or both between 2008 and 2021. Clinical records were reviewed in all cases.

RESULTS

HRIs underwent an average of 3.6 ± 3.2 surveillance exams over a period of 3.3 ± 3.5 years. Abnormalities including intraductal papillary mucinous neoplasms (IPMNs), solid lesions, and parenchymal irregularities were identified in 50.9% (n = 88). Four of these abnormalities (2.3%) had worrisome features, defined by cyst size, thickened/enhancing cyst walls, rapid growth rate, or change in main pancreatic duct diameter. All four worrisome lesions were seen on both MRI/MRCP and EUS. No pancreatic cancers were detected. Baseline EUS and MRI/MRCP exams were compared in 106 patients for concordance, and most (n = 66, 62.3%) were concordant. High levels of concordance were specifically observed for a dilated main pancreatic duct (p < 0.01) and cystic lesions >5 mm (p = 0.01). Among discordant cases, most (30/40; 75%) involved abnormal tissue heterogeneity seen primarily on EUS. None of these discordant lesions ultimately developed worrisome features.

CONCLUSIONS

Worrisome pancreatic lesions were uncommon in our high-risk pancreatic cancer population and were detected by both EUS and MRI/MRCP. There was mild discordance with respect to less worrisome findings, but these discrepancies were not associated with any adverse clinical outcomes.

Attenuation values on virtual unenhanced images obtained with detector-based dual-energy computed tomography: observations on single- and split-bolus contrast protocols

PURPOSE

To compare virtual unenhanced (VUE) attenuation values and their agreement with true unenhanced (TUE) images in patients who underwent dual-layer detector-based dual-energy computed tomography (dlDECT) with single- vs. split-bolus contrast media protocol.

METHODS

In this HIPAA-compliant, IRB-approved retrospective analysis, a total of 105 patients who underwent nephrographic phase (NP) dlDECT between 07/2018 and 11/2019 were included: 55 patients received single bolus and 50 patients split-bolus examinations. Both scan protocols comprised a TUE and 120-kVp NP acquisition from which VUE images were reconstructed. A radiologist performed ROI-based attenuation measurements of liver parenchyma, main portal vein, aorta, spleen, renal parenchyma, and pelvis on TUE and VUE images. Agreement between TUE and VUE images was determined and compared for both protocols and each anatomic region.

RESULTS

VUE attenuation was significantly higher than TUE attenuation in both cohorts in the liver, portal vein, spleen, and renal parenchyma (p < 0.05), while it was similar in the abdominal aorta in both cohorts (p = 0.05, 0.7522, respectively). VUE attenuation was significantly higher than TUE attenuation in the renal pelvis of the split-bolus cohort (p < 0.05). When comparing VUE images between single- and split-bolus protocols, the renal parenchyma yielded a significantly higher VUE attenuation in the single-bolus cohort (single bolus: 38.8 ± 3.3 HU vs. split bolus: 36.8 ± 3.6 HU; p < 0.05), whereas the split-bolus cohort revealed markedly higher VUE attenuation in the renal pelvis (single bolus: 2.3 ± 10.8 HU vs. split bolus: 92.3 ± 76.8; p < 0.05). Mean intra-patient differences between TUE and VUE images were comparable between single- and split-bolus cohorts (p-range 0.09-0.35) except for the renal parenchyma and pelvis: in the first, the single-bolus cohort yielded a higher VUE attenuation, while in the second, attenuation was significantly higher in the split-bolus cohort (p < 0.05).

CONCLUSION

VUE attenuation overestimated TUE attenuation and differed between split- and single-bolus protocols for the renal parenchyma and pelvis, while all other tissues showed comparable VUE attenuation.

Role of Dual Energy Computed Tomography in Inflammatory Bowel Disease

Dual-energy computed tomography (DECT), which allows material-based differential X-ray absorption behavior from near simultaneously acquired low- and high-kilovolt datasets is finding increasing applications in the evaluation of bowel diseases. In patients with inflammatory bowel disease, DECT techniques permit both qualitative and quantitative assessment. Particularly in patients with Crohn's disease, monoenergetic and iodine specific images have been explored. This article focuses on the principles and applications of DECT in inflammatory bowel disease along with review of its limitations and challenges.

Dual-Energy CT of the Abdomen: Radiology In Training

A 61-year-old man with an esophageal cancer diagnosis underwent staging dual-energy CT of the chest and abdomen in the portal venous phase after contrast media administration. Aside from the primary tumor and suspicious local lymph nodes, CT revealed hypoattenuating ambiguous liver lesions, an incidental right adrenal nodule, and a right renal lesion with soft-tissue attenuation. In addition, advanced atherosclerosis of the abdominal aorta and its major branches was noted. This article provides a case-based review of dual-energy CT technologies and their applications in the abdomen. The clinical utility of virtual monoenergetic images, virtual unenhanced images, and iodine maps is discussed.

Number of Worrisome Features and Risk of Malignancy in Intraductal Papillary Mucinous Neoplasm

BACKGROUND

The 2017 revised International Association of Pancreatology guidelines for management of intraductal papillary mucinous neoplasm (IPMN) describe worrisome features (WF) and high-risk stigmata (HRS), recommending resection in the latter and further work-up and close surveillance for patients with WF. The effect of multiple WF on the likelihood of malignancy has not been evaluated.

STUDY DESIGN

Eight hundred ten patients who underwent pancreatic resection for IPMN in 2 tertiary referral centers were identified from prospective institutional databases. Patients were retrospectively categorized into subgroups according to the number of WF or HRS and presence of malignancy, defined as high-grade dysplasia (HGD) or invasive cancer on final pathology.

RESULTS

Three hundred seventy-nine (47%) patients had HRS, 370 (46%) had 1 or more WF, and 61 patients (7%) had neither. Malignancy was present in 70% (n = 267) of patients with HRS and in 30% (n = 127) of those with WF. Only 3 of 61 patients without WF/HRS had malignancy, and all only in the form of HGD. The risk of malignancy increased in a stepwise fashion with the number of WF, to 22%, 34%, and 59% with 1, 2, and 3 WF, respectively (p = 0.001), and reached 100% in patients with 4 or more WF. Although the relative risks differed for particular WF, the areas under the curve were not statistically different.

CONCLUSION

We confirm that presence of HRS in IPMN is associated with a very high likelihood of malignancy. The presence of a single WF has a malignancy risk of 22%, and additional WF increase this risk significantly. When 3 or more WF are present, the risk is similar to that of HRS.

Comparison of Four Dual-Energy CT Scanner Technologies for Determining Renal Stone Composition: A Phantom Approach

Background Studies have investigated the value of various dual-energy CT (DECT) technologies for determining renal stone composition. However, sparse multivendor comparison data exist. Purpose To compare the performance of four DECT technologies in determining renal stone composition at standard- and low-dose acquisitions. Materials and Methods This was an in vitro phantom study. Seventy-one urinary stones (size: 2.7-14.1 mm) of known chemical composition (51 calcium, four struvite, four cystine, and 12 urate) were placed in a custom-made cylindrical phantom. Consecutive scans with manufacturer-recommended protocols and dose-optimized institutional protocols (up to 80% reduction in volumetric CT dose index) were obtained with rapid kilovolt peak switching DECT (rsDECT) (n = 2), dual-source DECT (n = 2), twin-beam DECT (tbDECT) (n = 1), and dual-layer detector-based CT (dlDECT) (n = 1) scanners. The image data sets were analyzed using effective atomic number and dual-energy ratio indexes of maximally available and comparable spectra. The performance of each combination of scanner technology, method, and acquisition was assessed. Logistic regression models were used to calculate the area under the receiver operating characteristic curve (AUC). Results After image analysis, all scanners except tbDECT had an AUC greater than 0.95 in at least one acquisition in distinguishing urate from other stones. All DECT techniques were able to help differentiate calcium oxalate monohydrate stones with moderate accuracy (AUC: 0.70-0.83), and brushite was differentiated from urate with AUC greater than 0.99. There was no correlation between performance and acquisition with dose-optimized and/or vendor-recommended settings. Conclusion All four dual-energy CT (DECT) technologies enabled accurate determination of stone composition at standard- and low-dose acquisitions; however, performance varied based on the scanner parameters, DECT technique, and stone type. © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Ringl and Apfaltrer in this issue.

Dual-Energy CT in the Pancreas

Dual-energy computed tomography (DECT) is an evolving imaging technology that is gaining popularity, particularly in different abdominopelvic applications. Essentially, DECT uses two energy spectra simultaneously to acquire CT attenuation data which is used to distinguish among structures with different tissue composition. The wide variety of reconstructed image data sets makes DECT especially attractive in pancreatic imaging. This article reviews the current literature on DECT as it applies to imaging the pancreas, focusing on pancreatitis, trauma, pancreatic ductal adenocarcinoma, and other solid and cystic neoplasms. The advantages of DECT over conventional CT are highlighted, including improved lesion detection, radiation dose reduction, and enhanced image contrast. Additionally, data exploring the ideal protocol for pancreatic imaging using DECT is reviewed. Finally, limitations of DECT in pancreatic imaging as well as recommendations for future research are provided.

Gallbladder reporting and data system (GB-RADS) for risk stratification of gallbladder wall thickening on ultrasonography: an international expert consensus

The Gallbladder Reporting and Data System (GB-RADS) ultrasound (US) risk stratification is proposed to improve consistency in US interpretations, reporting, and assessment of risk of malignancy in gallbladder wall thickening in non-acute setting. It was developed based on a systematic review of the literature and the consensus of an international multidisciplinary committee comprising expert radiologists, gastroenterologists, gastrointestinal surgeons, surgical oncologists, medical oncologists, and pathologists using modified Delphi method. For risk stratification, the GB-RADS system recommends six categories (GB-RADS 0-5) of gallbladder wall thickening with gradually increasing risk of malignancy. GB-RADS is based on gallbladder wall features on US including symmetry and extent (focal vs. circumferential) of involvement, layered appearance, intramural features (including intramural cysts and echogenic foci), and interface with the liver. GB-RADS represents the first collaborative effort at risk stratifying the gallbladder wall thickening. This concept is in line with the other US-based risk stratification systems which have been shown to increase the accuracy of detection of malignant lesions and improve management.

Early Detection Initiative: A randomized controlled trial of algorithm-based screening in patients with new onset hyperglycemia and diabetes for early detection of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the only leading cause of cancer death without an early detection strategy. In retrospective studies, 0.5-1% of subjects >50 years of age who newly develop biochemically-defined diabetes have been diagnosed with PDAC within 3 years of meeting new onset hyperglycemia and diabetes (NOD) criteria. The Enriching New-onset Diabetes for Pancreatic Cancer (ENDPAC) algorithm further risk stratifies NOD subjects based on age and changes in weight and diabetes parameters. We present the methodology for the Early Detection Initiative (EDI), a randomized controlled trial of algorithm-based screening in patients with NOD for early detection of PDAC. We hypothesize that study interventions (risk stratification with ENDPAC and imaging with Computerized Tomography (CT) scan) in NOD will identify earlier stage PDAC. EDI uses a modified Zelen's design with post-randomization consent. Eligible subjects will be identified through passive surveillance of electronic medical records and eligible study participants randomized 1:1 to the Intervention or Observation arm. The sample size is 12,500 subjects. The ENDPAC score will be calculated only in those randomized to the Intervention arm, with 50% (n = 3125) expected to have a high ENDPAC score. Consenting subjects in the high ENDPAC group will undergo CT imaging for PDAC detection and an estimate of potential harm. The effectiveness and efficacy evaluation will compare proportions of late stage PDAC between Intervention and Observation arm per randomization assignment or per protocol, respectively, with a planned interim analysis. The study is designed to improve the detection of sporadic PDAC when surgical intervention is possible.

Virtual Unenhanced Images: Qualitative and Quantitative Comparison Between Different Dual-Energy CT Scanners in a Patient and Phantom Study

MATERIALS AND METHODS

Forty-four patients with clinical contrast-enhanced abdominal examinations on each of the 3 DECT scanner types and a phantom scanned with the same protocols were included in this retrospective study. Qualitative and quantitative assessment was performed on VUE images. Quantitative evaluation included measurement of attenuation and image noise for various tissues and the phantom. Virtual unenhanced image attenuation and noise were compared between scanner types, and intrapatient interscanner reproducibility of virtual unenhanced image attenuation was calculated as the percentage of measurement pairs with an interscanner difference ≤ 10 HU. Image quality, noise, sharpness, and iodine elimination were assessed qualitatively by 2 radiologists.

RESULTS

Significant interscanner differences in VUE attenuation and noise were found in all tissues. dlDECT and rsDECT showed significantly higher VUE attenuation than dsDECT in the aorta, portal vein, and kidneys (P < 0.05). Conversely, VUE attenuation in dsDECT was significantly higher than in dlDECT/rsDECT for subcutaneous and retroperitoneal fat (both P < 0.05). A total of 91.9% (385/419) of measurements were reproducible between rsDECT and dlDECT, 70.9% (297/419) between dsDECT and rsDECT, and 66.8% (280/419) between dsDECT and dlDECT. Virtual unenhanced image attenuation in the contrast media-filled phantom cavity was 12.7 ± 4.7 HU in dlDECT, -5.3 ± 4.2 HU in rsDECT, and -4.0 ± 10.7 HU in dsDECT with significant differences between dlDECT and rsDECT/dsDECT, respectively (P < 0.05), between which attenuation was comparable in the unenhanced extraluminal phantom component (P = 0.11-0.62). Qualitatively, dsDECT yielded best iodine elimination, whereas sharpness, image noise, and overall image quality were rated higher in dlDECT and rsDECT.

CONCLUSIONS

There are significant interscanner differences in the attenuation measurements and qualitative assessment of VUE images, which should be acknowledged when using these images in patients that are being scanned on different DECT scanner types during imaging follow-up.

Association of body composition parameters measured on CT with risk of hospitalization in patients with Covid-19

PURPOSE

To assess prognostic value of body composition parameters measured at CT to predict risk of hospitalization in patients with COVID-19 infection.

METHODS

177 patients with SARS-CoV-2 infection and with abdominopelvic CT were included in this retrospective IRB approved two-institution study. Patients were stratified based on disease severity as outpatients (no hospital admission) and patients who were hospitalized (inpatients). Two readers blinded to the clinical outcome segmented axial CT images at the L3 vertebral body level for visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), muscle adipose tissue (MAT), muscle mass (MM). VAT to total adipose tissue ratio (VAT/TAT), MAT/MM ratio, and muscle index (MI) at L3 were computed. These measures, along with detailed clinical risk factors, were compared in patients stratified by severity. Various logistic regression clinical and clinical + imaging models were compared to discriminate inpatients from outpatients.

RESULTS

There were 76 outpatients (43%) and 101 inpatients. Male gender (p = 0.013), age (p = 0.0003), hypertension (p = 0.0003), diabetes (p = 0.0001), history of cardiac disease (p = 0.007), VAT/TAT (p < 0.0001), and MAT/MM (p < 0.0001), but not BMI, were associated with hospitalization. A clinical model (age, gender, BMI) had AUC of 0.70. Addition of VAT/TAT to the clinical model improved the AUC to 0.73. Optimal model that included gender, BMI, race (Black), MI, VAT/TAT, as well as interaction between gender and VAT/TAT and gender and MAT/MM demonstrated the highest AUC of 0.83.

CONCLUSION

MAT/MM and VAT/TAT provides important prognostic information in predicting patients with COVID-19 who are likely to require hospitalization.

Imaging Evaluation of Living Liver Donor Candidates: Techniques, Protocols, and Anatomy

The need for liver transplants is increasing because the prevalence of liver diseases and the indications for transplants are growing. In response to the shortage of grafts from deceased donors, more transplants are being performed worldwide with grafts from living donors. Radiologic evaluation is an integral component in the assessment of donor candidates to ensure their eligibility and to choose the most appropriate surgical approach. MRI is the preferred modality for evaluation of the liver parenchyma and biliary tree. In most centers, a combination of MRI and CT is used to take advantage of the higher spatial resolution of CT for evaluation of arteries. However, MRI-only assessment is feasible. In addition to assessment of the liver parenchyma for abnormalities such as steatosis, a detailed evaluation of the hepatic vascular and biliary system for pertinent anatomic variants is crucial, because these variants can affect surgical techniques and outcomes in both recipients and donors. In this pictorial article, after a brief review of the most common surgical techniques and postsurgical liver anatomy, the biliary and vascular anatomy are discussed, with specific attention paid to the variants that are pertinent to this surgical procedure. The roles of liver segmentation and volumetric assessment and current imaging techniques and protocols are also discussed. Online supplemental material is available for this article. ©RSNA, 2021.

Dual-layer dual-energy CT for characterization of adrenal nodules: can virtual unenhanced images replace true unenhanced acquisitions?

PURPOSE

To investigate the diagnostic performance of dual-layer dual-energy CT (dlDECT) in the evaluation of adrenal nodules.

METHODS

In this retrospective study, 66 patients with triphasic dlDECT (unenhanced, venous phase (VP), delayed phase (DP)) for suspected adrenal lesions were included. Virtual unenhanced images (VUE) were derived from VP acquisitions. Reference diagnoses were established with true unenhanced (TUE) attenuation, absolute washout, follow-up imaging and pathological data. Attenuation for adrenal lesions and abdominal tissues was acquired on TUE, VUE, VP and DP images. VUE and TUE attenuation were compared in all included tissues. Characterization of adrenal nodules based on TUE and VUE attenuation was investigated. ROC analysis was used to determine an adjusted threshold for diagnosing lipid-rich adenomas.

RESULTS

Seventy-three adrenal nodules (mean size: 18.9 ± 8.9 mm) were identified in 66 patients (38 females, 28 males; age: 61 ± 13 years) including adenoma (n = 65), metastases (n = 2), pheochromocytoma (n = 3), adrenocortical carcinoma (n = 1) and myelolipoma (n = 2). Mean attenuation of all included tissues except for the abdominal aorta (p = 0.11) was significantly higher in VUE compared to TUE images, including the attenuation of adrenal nodules (20.0 ± 17.2 vs. 7.1 ± 19.8; p < 0.05). Classification of adrenal adenomas as lipid-rich based on VUE attenuation ≤ 10 HU yielded a sensitivity/specificity of 0.2/1.0, while an adjusted threshold of ≤ 22 HU yielded a sensitivity/specificity of 0.82/0.85.

CONCLUSION

dlDECT-derived VUE images overestimated attenuation in adrenal nodules, resulting in low sensitivity for diagnosis of lipid-rich adenomas using the established 10 HU threshold. Based on an adjusted threshold (≤ 22 HU) a higher sensitivity was attained, yet at the expense of a lower specificity, warranting further validation.

Parallel Genomic Alterations of Antigen and Payload Targets Mediate Polyclonal Acquired Clinical Resistance to Sacituzumab Govitecan in Triple-Negative Breast Cancer

Sacituzumab govitecan (SG), the first antibody-drug conjugate (ADC) approved for triple-negative breast cancer, incorporates the anti-TROP2 antibody hRS7 conjugated to a topoisomerase-1 (TOP1) inhibitor payload. We sought to identify mechanisms of SG resistance through RNA and whole-exome sequencing of pretreatment and postprogression specimens. One patient exhibiting de novo progression lacked TROP2 expression, in contrast to robust TROP2 expression and focal genomic amplification of TACSTD2/TROP2 observed in a patient with a deep, prolonged response to SG. Analysis of acquired genomic resistance in this case revealed one phylogenetic branch harboring a canonical TOP1 ^E418K resistance mutation and subsequent frameshift TOP1 mutation, whereas a distinct branch exhibited a novel TACSTD2/TROP2 ^T256R missense mutation. Reconstitution experiments demonstrated that TROP2^T256R confers SG resistance via defective plasma membrane localization and reduced cell-surface binding by hRS7. These findings highlight parallel genomic alterations in both antibody and payload targets associated with resistance to SG. SIGNIFICANCE: These findings underscore TROP2 as a response determinant and reveal acquired SG resistance mechanisms involving the direct antibody and drug payload targets in distinct metastatic subclones of an individual patient. This study highlights the specificity of SG and illustrates how such mechanisms will inform therapeutic strategies to overcome ADC resistance.This article is highlighted in the In This Issue feature, p. 2355.

Longitudinal reproducibility of attenuation measurements on virtual unenhanced images: multivendor dual-energy CT evaluation

OBJECTIVES

The accuracy of virtual unenhanced (VUE) images has been extensively investigated, yet data on their longitudinal reproducibility is limited. The study purpose was to evaluate the longitudinal reproducibility of VUE attenuation measurements on three different dual-energy CT (DECT) scanner types.

METHODS

A total of 137 patients with repeated abdominal DECT either on a rapid kV switching (rsDECT; n = 46), a dual-layer detector (dlDECT; n = 43), or a dual-source scanner (dsDECT; n = 48) were retrospectively included. Attenuation was measured on VUE and corresponding contrast-enhanced images in the liver, spleen, kidneys, aorta, portal vein, and fat. Longitudinal reproducibility was evaluated by calculating the absolute inter-scan differences (HU) and the inter-scan variation (%). Measurement pairs with differences ≤ 10 HU were considered reproducible. Influence of contrast-enhanced attenuation on VUE reproducibility was analyzed using linear regression.

RESULTS

The scanner-specific cohorts showed similar age (p-range: 0.35-0.99), sex (p-range: 0.68-1), body weight (p-range: 0.26-0.87), body diameter (p-range: 0.34-0.76), and inter-scan time (p-range: 0.52-0.83). In total, 94.9% of VUE measurements were reproducible for rsDECT, 93.8% for dlDECT, and 90.6% for dsDECT. Overall inter-scan variation was lowest in fat (4.0 (1.7-8.2)%) and highest in tissues with high contrast enhancement: the aorta (13.3 (4.6-21.3)%), portal vein (10.8 (5.7-19.8)%), and kidneys (10.7 (3.9-18.0)%). Significant differences in inter-scan variation were found between the scanner types for the aorta, portal vein, kidneys, and spleen. Inter-scan differences in contrast-enhanced attenuation significantly influenced inter-scan differences in VUE attenuation (p < 0.001; t-ratio: 4.34).

CONCLUSIONS

Longitudinal reproducibility of VUE attenuation was high for all scanners, yet inter-scan variation of VUE attenuation was influenced by contrast enhancement, showing greatest magnitude and discrepancy between scanner types in vessels and the kidneys.

KEY POINTS

• We found that 94.9% of attenuation measurements on virtual unenhanced images were reproducible for rapid kV switching DECT, 93.8% for dual-layer detector DECT, and 90.6% for dual-source DECT. • Inter-scan variation of attenuation in virtual unenhanced images was comparable between the three scanner types in the liver and fat, whereas inter-scan variation in the spleen, kidneys, portal vein, and aorta showed significant differences between scanner types (p < 0.05). • Inter-scan attenuation differences in contrast-enhanced images significantly influenced inter-scan differences in virtual unenhanced attenuation (p < 0.001, t-ratio: 4.34), suggesting a residual impact of contrast enhancement differences between examinations.

Multi-detector computed tomography (MDCT)-based severity score as a prognostic tool in patients with suspected immune checkpoint inhibitor therapy associated colitis

OBJECTIVE

This study aimed to assess MDCT as a diagnostic and prognostic tool in patients with suspected immune checkpoint inhibitor (ICI)-related colitis.

MATERIALS AND METHODS

This retrospective cohort study included patients receiving ICIs at three hospitals between 2015 and 2019 who underwent both abdominopelvic MDCT and endoscopic biopsy to workup suspected ICI-related colitis. Two radiologists independently reviewed MDCT images for signs of colitis based on pre-defined features. Diagnostic performance of MDCT was calculated and categorical variables between treatment subgroups were compared. Logistic regression was used to develop proposed MDCT criteria for diagnosis and MDCT severity score based on a combination of MDCT features of colitis to predict the patient outcomes in ICI-related colitis.

RESULTS

A total of 118 MDCT scans from 108 patients were evaluated for suspected colitis, with 72 confirmed ICI-related colitis cases. Sensitivity, specificity, PPV, and NPV of MDCT for diagnosis of ICI-related colitis was 81% (58/72), 52 % (24/46), 73% (58/80), and 63% (24/38), respectively. Small bowel involvement was visualized in 25% of cases with ICI-related colitis (18/72). In melanoma patients presenting with diarrhea grade ≥ 2 (n = 40), MDCT had the best diagnostic performance for ICI-related colitis (specificity = 80% [8/10], PPV = 92% [23/25]). MDCT severity scores predicted intravenous steroid use (OR 10.3, p = 0.004), length of stay > 7 days (OR 9.0, p < 0.001), and endoscopic mucosal ulceration (OR 4.7, p = 0.02).

CONCLUSION

MDCT is a useful diagnostic and prognostic tool for evaluating patients with immune checkpoint inhibitor-related colitis. An MDCT-based severity score enables assessment of disease severity and predicts outcome.

KEY POINTS

• MDCT is useful for the diagnosis of colitis in patients receiving immune checkpoint inhibitor (ICI) therapy, and an MDCT-based severity score allows for prognostication of patient outcomes. • MDCT yielded moderate sensitivity (81%) for diagnosis of ICI-related colitis but limited specificity (52%). However, in symptomatic melanoma patients (grade 2-4 diarrhea) with a high pretest probability, MDCT proved useful for diagnosis with a high PPV (92%). • For ICI-related colitis, our proposed MDCT severity score has prognostic value in predicting intravenous steroid use, prolonged length of stay during inpatient admission (> 7 days), and endoscopic mucosal ulceration.

Unilateral Lymphadenopathy After COVID-19 Vaccination: A Practical Management Plan for Radiologists Across Specialties

Reports are rising of patients with unilateral axillary lymphadenopathy, visible on diverse imaging examinations, after recent coronavirus disease 2019 vaccination. With less than 10% of the US population fully vaccinated, we can prepare now for informed care of patients imaged after recent vaccination. The authors recommend documenting vaccination information (date[s] of vaccination[s], injection site [left or right, arm or thigh], type of vaccine) on intake forms and having this information available to the radiologist at the time of examination interpretation. These recommendations are based on three key factors: the timing and location of the vaccine injection, clinical context, and imaging findings. The authors report isolated unilateral axillary lymphadenopathy (i.e., no imaging findings outside of visible lymphadenopathy), which is ipsilateral to recent (prior 6 weeks) vaccination, as benign with no further imaging indicated. Clinical management is recommended, with ultrasound if clinical concern persists 6 weeks after the final vaccination dose. In the clinical setting to stage a recent cancer diagnosis or assess response to therapy, the authors encourage prompt recommended imaging and vaccination (possibly in the thigh or contralateral arm according to the location of the known cancer). Management in this clinical context of a current cancer diagnosis is tailored to the specific case, ideally with consultation between the oncology treatment team and the radiologist. The aim of these recommendations is to (1) reduce patient anxiety, provider burden, and costs of unnecessary evaluation of enlarged nodes in the setting of recent vaccination and (2) avoid further delays in vaccinations and recommended imaging for best patient care during the pandemic.

Clinical Outcomes With Abemaciclib After Prior CDK4/6 Inhibitor Progression in Breast Cancer: A Multicenter Experience

BACKGROUND

Inhibitors of cyclin-dependent kinases 4 and 6 (CDK4/6i) are widely used as first-line therapy for hormone receptor-positive metastatic breast cancer (HR+ MBC). Although abemaciclib monotherapy is also FDA-approved for treatment of disease progression on endocrine therapy, there is limited insight into the clinical activity of abemaciclib after progression on prior CDK4/6i.

PATIENTS AND METHODS

We identified patients with HR+ MBC from 6 cancer centers in the United States who received abemaciclib after disease progression on prior CDK4/6i, and abstracted clinical features, outcomes, toxicity, and predictive biomarkers.

RESULTS

In the multicenter cohort, abemaciclib was well tolerated after a prior course of CDK4/6i (palbociclib)-based therapy; a minority of patients discontinued abemaciclib because of toxicity without progression (9.2%). After progression on palbociclib, most patients (71.3%) received nonsequential therapy with abemaciclib (with ≥1 intervening non-CDK4/6i regimens), with most receiving abemaciclib with an antiestrogen agent (fulvestrant, 47.1%; aromatase inhibitor, 27.6%), and the remainder receiving abemaciclib monotherapy (19.5%). Median progression-free survival for abemaciclib in this population was 5.3 months and median overall survival was 17.2 months, notably similar to results obtained in the MONARCH-1 study of abemaciclib monotherapy in heavily pretreated HR+/HER2-negative CDK4/6i-naïve patients. A total of 36.8% of patients received abemaciclib for ≥6 months. There was no relationship between the duration of clinical benefit while on palbociclib and the subsequent duration of treatment with abemaciclib. RB1, ERBB2, and CCNE1 alterations were noted among patients with rapid progression on abemaciclib.

CONCLUSIONS

A subset of patients with HR+ MBC continue to derive clinical benefit from abemaciclib after progression on prior palbociclib. These results highlight the need for future studies to confirm molecular predictors of cross-resistance to CDK4/6i therapy and to better characterize the utility of abemaciclib after disease progression on prior CDK4/6i.

Low keV portal venous phase as a surrogate for pancreatic phase in a pancreatic protocol dual-energy CT: feasibility, image quality, and lesion conspicuity

OBJECTIVE

To assess the feasibility of a proposed pancreatic protocol CT generated from portal-venous phase (PVP) dual-energy CT (DECT) acquisition and its impact on image quality, lesion conspicuity, and arterial visualization/involvement.

METHODS

We included 111 patients (mean age, 66.8 years) who underwent pancreatic protocol DECT (pancreatic phase, PP, and PVP). The original DECT acquisition was used to create two data sets-standard protocol (50 keV PP/65 keV PVP) and proposed protocol (40 keV/65 keV PVP). Three reviewers evaluated the two data sets for image quality, lesion conspicuity, and arterial visualization/involvement using a 5-point scale. The signal-to-noise ratio (SNR) of pancreas and lesion-to-pancreas contrast-to-noise ratio (CNR) was calculated. Qualitative scores, quantitative parameters, and dose-length product (DLP) were compared between standard and proposed protocols.

RESULTS

The image quality, SNR of pancreas, and lesion-to-pancreas CNR of the standard and proposed protocol were comparable (p = 0.11-1.00). Lesion conspicuity was comparable between the standard and proposed protocols for pancreatic ductal adenocarcinoma (p = 0.55) and pancreatic cysts (p = 0.28). The visualization of larger arteries and arterial involvement were comparable between the two protocols (p = 0.056-1.00) while the scores were higher for smaller vessels in the standard protocol (p < 0.0001-0.0015). DLP of the proposed protocol (670.4 mGy·cm) showed a projected 42% reduction than the standard protocol (1145.9 mGy·cm) (p < 0.0001).

CONCLUSION

Pancreatic protocol CT generated from a single PVP DECT acquisition is feasible and could potentially be an alternative to the standard pancreatic protocol with PP and PVP.

KEY POINTS

• The lesion conspicuity for focal pancreatic lesions was comparable between the proposed protocol and standard dual-phase pancreatic protocol CT. • Qualitative and quantitative image assessments were almost comparable between two protocols. • The radiation dose of a proposed protocol showed a projected 42% reduction from the conventional protocol.

Low-dose whole-body CT using deep learning image reconstruction: image quality and lesion detection

OBJECTIVES

To evaluate image quality and lesion detection capabilities of low-dose (LD) portal venous phase whole-body computed tomography (CT) using deep learning image reconstruction (DLIR).

METHODS

The study cohort of 59 consecutive patients (mean age, 67.2 years) who underwent whole-body LD CT and a prior standard-dose (SD) CT reconstructed with hybrid iterative reconstruction (SD-IR) within one year for surveillance of malignancy were assessed. The LD CT images were reconstructed with hybrid iterative reconstruction of 40% (LD-IR) and DLIR (LD-DLIR). The radiologists independently evaluated image quality (5-point scale) and lesion detection. Attenuation values in Hounsfield units (HU) of the liver, pancreas, spleen, abdominal aorta, and portal vein; the background noise and signal-to-noise ratio (SNR) of the liver, pancreas, and spleen were calculated. Qualitative and quantitative parameters were compared between the SD-IR, LD-IR, and LD-DLIR images. The CT dose-index volumes (CTDI_vol) and dose-length product (DLP) were compared between SD and LD scans.

RESULTS

The image quality and lesion detection rate of the LD-DLIR was comparable to the SD-IR. The image quality was significantly better in SD-IR than in LD-IR (p < 0.017). The attenuation values of all anatomical structures were comparable between the SD-IR and LD-DLIR (p = 0.28-0.96). However, background noise was significantly lower in the LD-DLIR (p < 0.001) and resulted in improved SNRs (p < 0.001) compared to the SD-IR and LD-IR images. The mean CTDI_vol and DLP were significantly lower in the LD (2.9 mGy and 216.2 mGy•cm) than in the SD (13.5 mGy and 1011.6 mGy•cm) (p < 0.0001).

CONCLUSION

LD CT images reconstructed with DLIR enable radiation dose reduction of >75% while maintaining image quality and lesion detection rate and superior SNR in comparison to SD-IR.

ADVANCES IN KNOWLEDGE

Deep learning image reconstruction algorithm enables around 80% reduction in radiation dose while maintaining the image quality and lesion detection compared to standard-dose whole-body CT.