Image quality of photon counting and energy integrating chest CT - Prospective head-to-head comparison on same patients.

PURPOSE: To prospectively compare the image quality of high-resolution, low-dose photon-counting detector CT (PCD-CT) with standard energy-integrating-detector CT (EID) on the same patients. METHOD: IRB-approved, prospective study; patients received same-day non-contrast CT on EID and PCD-CT (NAEOTOM Alpha, blinded) with clinical protocols. Four blinded radiologists evaluated subsegmental bronchial wall definition, noise, and overall image quality in randomized order (0 = worst; 100 = best). Cases were quantitatively compared using the average Global-Noise-Index (GNI), Noise-Power-Spectrum average frequency (fav), NPS frequency-peak (fpeak), Task-Transfer-Function-10%-frequency (f10) an adjusted detectability index (d'adj), and applied output radiation doses (CTDIvol). RESULTS: Sixty patients were prospectively imaged (27 men, mean age 67 ± 10 years, mean BMI 27.9 ± 6.5, 15.9-49.4 kg/m2). Subsegmental wall definition was rated significantly better for PCD-CT than EID (mean 71 [56-87] vs 60 [45-76]; P < 0.001), noise was rated higher for PCD-CT (48 [26-69] vs 34 [13-56]; P < 0.001). Overall image quality was rated significantly higher for PCD-CT than EID (66 [48-85] vs 61 [42-79], P = 0.008). Automated image quality measures showed similar differences for PCD-CT vs EID (mean GNI 70 ± 19 HU vs 26 ± 8 HU, fav 0.35 ± 0.02 vs 0.25 ± 0.02 mm-1, fpeak 0.07 ± 0.01 vs 0.09 ± 0.03 mm-1, f10 0.7 ± 0.08 vs 0.6 ± 0.1 mm-1, all p-values < 0.001). PCD-CT showed a 10% average d'adj increase (-49% min, 233% max). PCD-CT studies were acquired at significantly lower radiation doses than EID (mean CTDIvol 4.5 ± 2.1 vs 7.7 ± 3.2 mGy, P < 0.01). CONCLUSION: Though PCD-CT had higher measured and perceived noise, it offered equivalent or better diagnostic quality compared to EID at lower radiation doses, due to its improved resolution.

Optimization of non-endorectal prostate MR image quality using PI-QUAL: A multidisciplinary team approach.

PURPOSE: To evaluate the utility of the PI-QUAL score in assessing protocol changes aimed to improve image quality from a non-endorectal coil prostate MR imaging protocol during a 9-month quality improvement (QI) project and to quantify the inter-reader agreement of PI-QUAL scores between radiologists, technologists, and physicists. METHODS: This retrospective study audited 1,012 multiparametric prostate MRI examinations as part of a national QI project according to the PI-QUAL standard. PI-QUAL scores were used to inform MR protocol changes. Following the project, 4 radiologists, 2 technologists, and 1 medical physicist collectively audited an additional set of 150 examinations to identify statistical improvements in image quality using the two-tailed Wilcoxon rank sum test. The improvements due to individual protocol changes were assessed among subsets of the 1,012 examinations which compared examinations occurring before and after the isolated protocol change. Inter-reader variability was assessed using the percent majority agreement and the average standard deviation of PI-QUAL scores between evaluators. RESULTS: During this QI project, PI-QUAL scores improved from 3.67 ± 0.75 to 4.16 ± 0.59 (p < 0.01) after implementing a series of protocol changes. Among a subset of 451 cases, we found that adopting R/L rather than A/P phase encoding reduced distortion in diffusion-weighted imaging (DW) from 21.6% (41/190 A/P phase encoded cases) to 11.5% (30/261 R/L phase encoded cases) (p < 0.01). Similarly, in the same 451 cases, adopting R/L phase encoding in T2WI reduced breathing motion artifacts from 34.6% (94/272 A/P phase encoding cases) to 12.8% (23/179 R/L phase encoding cases) (p < 0.01). DWI wraparound artifact was mitigated by employing a full-pelvis shim and enabling the abdomen shim option. The occurrence of low signal-to-noise ratio was reduced from 19.4% (19/98 cases without a weight-based threshold) to 6.3% (10/160) by instituting a weight-based threshold for using an endorectal coil (p < 0.01). The percent majority agreement was similar between radiologists, technologists and physicists, and all evaluators combined (72%, 77%, and 67%, respectively). CONCLUSIONS: PI-QUAL can evaluate image quality changes resulting from protocol optimizations at both the exam- and series-levels. With training, radiologists, technologists, and physicists can perform PI-QUAL scoring with similar performance. Broadening the scope of the quality improvement team can result in meaningful and lasting change.

First experience of evaluation of the impact of high-matrix size reconstruction in image quality in arterial CT runoff studies of the lower extremities.

OBJECTIVES: To determine whether image reconstruction with a higher matrix size improves image quality for lower extremity CTA studies. METHODS: Raw data from 50 consecutive lower extremity CTA studies acquired on two MDCT scanners (SOMATOM Flash, Force) in patients evaluated for peripheral arterial disease (PAD) were retrospectively collected and reconstructed with standard (512 × 512) and higher resolution (768 × 768, 1024 × 1024) matrix sizes. Five blinded readers reviewed representative transverse images in randomized order (150 total). Readers graded image quality (0 (worst)-100 (best)) for vascular wall definition, image noise, and confidence in stenosis grading. Ten patients' stenosis scores on CTA images were compared to invasive angiography. Scores were compared using mixed effects linear regression. RESULTS: Reconstructions with 1024 × 1024 matrix were ranked significantly better for wall definition (mean score 72, 95% CI = 61-84), noise (74, CI = 59-88), and confidence (70, CI = 59-80) compared to 512 × 512 (wall = 65, CI = 53 × 77; noise = 67, CI = 52 × 81; confidence = 62, CI = 52 × 73; p = 0.003, p = 0.01, and p = 0.004, respectively). Compared to 512 × 512, the 768 × 768 and 1024 × 1024 matrix improved image quality in the tibial arteries (wall = 51 vs 57 and 59, p < 0.05; noise = 65 vs 69 and 68, p = 0.06; confidence = 48 vs 57 and 55, p < 0.05) to a greater degree than the femoral-popliteal arteries (wall = 78 vs 78 and 85; noise = 81 vs 81 and 84; confidence = 76 vs 77 and 81, all p > 0.05), though for the 10 patients with angiography accuracy of stenosis grading was not significantly different. Inter-reader agreement was moderate (rho = 0.5). CONCLUSION: Higher matrix reconstructions of 768 × 768 and 1024 × 1024 improved image quality and may enable more confident assessment of PAD. CLINICAL RELEVANCE STATEMENT: Higher matrix reconstructions of the vessels in the lower extremities can improve perceived image quality and reader confidence in making diagnostic decisions based on CTA imaging. KEY POINTS: • Higher than standard matrix sizes improve perceived image quality of the arteries in the lower extremities. • Image noise is not perceived as increased even at a matrix size of 1024 × 1024 pixels. • Gains from higher matrix reconstructions are higher in smaller, more distal tibial and peroneal vessels than in femoropopliteal vessels.

A Faster Prostate MRI: Comparing a Novel Denoised, Single-Average T2 Sequence to the Conventional Multiaverage T2 Sequence Regarding Lesion Detection and PI-RADS Score Assessment.

BACKGROUND: The T2 w sequence is a standard component of a prostate MRI examination; however, it is time-consuming, requiring multiple signal averages to achieve acceptable image quality. PURPOSE/HYPOTHESIS: To determine whether a denoised, single-average T2 sequence (T2 -R) is noninferior to the standard multiaverage T2 sequence (T2 -S) in terms of lesion detection and PI-RADS score assessment. STUDY TYPE: Retrospective. POPULATION: A total of 45 males (age range 60-75 years) who underwent clinically indicated prostate MRI examinations, 21 of whom had pathologically proven prostate cancer. FIELD STRENGTH/SEQUENCE: A 3 T; T2 w FSE, DWI with ADC maps, and dynamic contrast-enhanced images with color-coded perfusion maps. T2 -R images were created from the raw data utilizing a single "average" with iterative denoising. ASSESSMENT: Nine readers randomly assessed complete exams including T2 -R and T2 -S images in separate sessions. PI-RADS version 2.1 was used. All readers then compared the T2 -R and T2 -S images side by side to evaluate subjective preference. An additional detailed image quality assessment was performed by three senior level readers. STATISTICAL TESTS: Generalized linear mixed effects models for differences in lesion detection, image quality features, and overall preference between T2 -R and T2 -S sequences. Intraclass correlation coefficients (ICC) were used to assess reader agreement for all comparisons. A significance threshold of P = 0.05 was used for all statistical tests. RESULTS: There was no significant difference between sequences regarding identification of lesions with PI-RADS ≥3 (P = 0.10) or PI-RADS score (P = 0.77). Reader agreement was excellent for lesion identification (ICC = 0.84). There was no significant overall preference between the two sequences regarding image quality (P = 0.07, 95% CI: [-0.23, 0.01]). Reader agreement was good regarding sequence preference (ICC = 0.62). DATA CONCLUSION: Use of single-average, denoised T2 -weighted images was noninferior in prostate lesion detection or PI-RADS scoring when compared to standard multiaverage T2 -weighted images. EVIDENCE LEVEL: 3. TECHNICAL EFFICACY: Stage 3.

Comparing Survival Outcomes of Patients With LI-RADS-M Hepatocellular Carcinomas and Intrahepatic Cholangiocarcinomas.

BACKGROUND: There is a sparsity of data evaluating outcomes of patients with Liver Imaging Reporting and Data System (LI-RADS) (LR)-M lesions. PURPOSE: To compare overall survival (OS) and progression free survival (PFS) between hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (iCCA) meeting LR-M criteria and to evaluate factors associated with prognosis. STUDY TYPE: Retrospective. SUBJECTS: Patients at risk for HCC with at least one LR-M lesion with histologic diagnosis, from 8 academic centers, yielding 120 patients with 120 LR-M lesions (84 men [mean age 62 years] and 36 women [mean age 66 years]). FIELD STRENGTH/SEQUENCE: A 1.5 and 3.0 T/3D T1 -weighted gradient echo, T2 -weighted fast spin-echo. ASSESSMENT: The imaging categorization of each lesion as LR-M was made clinically by a single radiologist at each site and patient outcome measures were collected. STATISTICAL TESTS: OS, PFS, and potential independent predictors were evaluated by Kaplan-Meier method, log-rank test, and Cox proportional hazard model. A P value of <0.05 was considered significant. RESULTS: A total of 120 patients with 120 LR-M lesions were included; on histology 65 were HCC and 55 were iCCA. There was similar median OS for patients with LR-M HCC compared to patients with iCCA (738 days vs. 769 days, P = 0.576). There were no significant differences between patients with HCC and iCCA in terms of sex (47:18 vs. 37:18, P = 0.549), age (63.0 ± 8.4 vs. 63.4 ± 7.8, P = 0.847), etiology of liver disease (P = 0.202), presence of cirrhosis (100% vs. 100%, P = 1.000), tumor size (4.73 ± 3.28 vs. 4.75 ± 2.58, P = 0.980), method of lesion histologic diagnosis (P = 0.646), and proportion of patients who underwent locoregional therapy (60.0% vs. 38.2%, P = 0.100) or surgery (134.8 ± 165.5 vs. 142.5 ± 205.6, P = 0.913). Using multivariable analysis, nonsurgical compared to surgical management (HR, 4.58), larger tumor size (HR, 1.19), and higher MELD score (HR, 1.12) were independently associated with worse OS. DATA CONCLUSION: There was similar OS in patients with LR-M HCC and LR-M iCCA, suggesting that LR-M imaging features may more closely reflect patient outcomes than histology. EVIDENCE LEVEL: 3 TECHNICAL EFFICACY: Stage 5.

Immune Checkpoint Inhibitor Therapy-related Pneumonitis: Patterns and Management.

In recent years, the use of immune checkpoint inhibitor (ICI) therapy has rapidly grown, with increasing U.S. Food and Drug Administration approvals of a variety of agents used as first- and second-line treatments of various malignancies. ICIs act through a unique mechanism of action when compared with those of conventional chemotherapeutic agents. ICIs target the cell surface receptors cytotoxic T-lymphocyte antigen-4, programmed cell death protein 1, or programmed cell death ligand 1, which result in immune system-mediated destruction of tumor cells. Immune-related adverse events are an increasingly recognized set of complications of ICI therapy that may affect any organ system. ICI therapy-related pneumonitis is an uncommon but important complication of ICI therapy, with potential for significant morbidity and mortality. As the clinical manifestation is often nonspecific, CT plays an important role in diagnosis and triage. Several distinct radiographic patterns of pneumonitis have been observed: (a) organizing pneumonia, (b) nonspecific interstitial pneumonia, (c) hypersensitivity pneumonitis, (d) acute interstitial pneumonia-acute respiratory distress syndrome, (e) bronchiolitis, and (f) radiation recall pneumonitis. Published guidelines outline the treatment of ICI therapy-related pneumonitis based on the severity of symptoms. Treatment is often effective, although recurrence is possible. This article reviews the mechanism of ICIs and ICI therapy complications, with subsequent management techniques and illustrations of the various radiologic patterns of ICI-therapy related pneumonitis.©RSNA, 2019.

MRI Evaluation of the Response of Rectal Cancer to Neoadjuvant Chemoradiation Therapy.

MRI plays a critical role in the staging and restaging of rectal cancer. Although newly diagnosed early-stage rectal cancers may immediately be amenable to surgical resection, patients with advanced disease first undergo neoadjuvant therapy that consists of a combination of chemotherapy and radiation therapy. Evaluation of rectal cancer after neoadjuvant therapy is best performed with MRI, given its superior soft-tissue contrast and its ability to allow multiplanar imaging and functional evaluation. In this setting, MRI allows accurate evaluation of primary tumor staging, which is determined on the basis of the depth of invasion within and through the rectal wall and the involvement of adjacent organs. MRI can also be used to evaluate posttreatment morphologic components within the tumors, including fibrosis and mucinous changes that have been shown to correlate with the response to treatment. Additional features such as the circumferential resection margin and extramural vascular invasion-factors shown to affect prognosis and local recurrence-are also assessed before and after therapy. Functional assessment with diffusion-weighted MRI and perfusion MRI plays a role in predicting tumor aggressiveness and the likelihood of response to treatment, as well as the extent of residual tumor after therapy. Lymph node staging is also performed at MRI, with assessment of not only lymph node size but also the internal architecture and signal intensity characteristics. ©RSNA, 2019 See discussion on this article by Wasnik and Al-Hawary .

Detection of renal dysfunction by point-of-care creatinine testing in patients undergoing peripheral MR angiography.

OBJECTIVE: The objective of our study was to analyze the effectiveness of prestudy questionnaires in identifying at-risk patients and estimate the prevalence of chronic kidney disease (CKD), nephrogenic systemic fibrosis risk factors, and other comorbidities in patients scheduled to undergo lower extremity MR angiography (MRA) studies using gadolinium-based contrast agents. MATERIALS AND METHODS: Patent demographics, comorbidities, contrast type, and point-of-care (POC) serum creatinine values were recorded from the medical records of consecutive patients undergoing lower extremity MRA examinations in a single year. Patients were divided into groups by CKD stage (non-CKD, stage III, stage IV, or stage V) on the basis of estimated glomerular filtration rate values determined from POC creatinine results. Patient awareness of a history of CKD was noted if patients admitted to any form of CKD on prestudy questionnaires. RESULTS: Of 199 patients, 72 patients (36.2%) had stage III CKD, six patients (3.0%) had stage IV CKD, and seven patients (3.5%) had stage V CKD. Comorbidities-including smoking status, transplant status, and presence of diabetes, hypertension, and coronary artery disease-as well as administered contrast type and dosage showed significant differences among the CKD groups (p < 0.05). Only five stage III patients (7%) were aware of any history of renal dysfunction, whereas three stage IV patients (50%) and seven stage V patients (100%) admitted any history of renal dysfunction via questionnaires. CONCLUSION: Compared with POC creatinine testing, a prestudy questionnaire used alone is ineffective in identifying all patients with histories of CKD who are scheduled to undergo gadolinium-based peripheral MRA studies.