Iodine overlays to improve differentiation between peritoneal carcinomatosis and benign peritoneal lesions.

OBJECTIVES: Peritoneal carcinomatosis (PC) is a prognostically relevant metastatic disease which may be difficult to depict in postoperative patients, particularly in early stages. This study aimed to determine whether PC could be diagnosed more accurately when using a combination of spectral detector CT (SDCT)-derived conventional images (CI) and iodine overlay images (IO) compared with CI only. METHODS: Thirty patients with PC and 30 patients with benign peritoneal alterations (BPA) who underwent portal-venous abdominal SDCT were included. Four radiologists determined the presence/absence of PC for each patient and assessed lesion conspicuity, diagnostic certainty, and image quality using 5-point Likert scales. Subjective assessment was conducted in two sessions comprising solely CI and CI/IO between which a latency of 6 weeks was set. Iodine uptake and HU attenuation were determined ROI-based to analyze quantitative differentiation of PC/BPA. RESULTS: Specificity for PC was significantly higher when using CI/IO compared with using CI only (0.86 vs. 0.78, p ≤ 0.05), while sensitivity was comparable (0.79 vs. 0.81, p = 1). In postoperative patients, the increase in specificity was the highest (0.93 vs. 0.80, p ≤ 0.05). Lesion conspicuity was rated higher in CI/IO (4 (3-5)) compared with that in CI only (3 (3-4); p ≤ 0.05). Diagnostic certainty was comparable (both 4 (3-5); p = 0.5). CI/IO received the highest rating for overall image quality and assessability (CI/IO 5 (4-5) vs. CI 4 (4-4) vs. IO 4 (3-4); p ≤ 0.05). Area under the receiver operating characteristics curve (AUC) for quantitative differentiation between PC and BPA was higher for iodine (AUCIodine = 0.95, AUCHU = 0.90). CONCLUSIONS: Compared with CI, combination of CI/IO improves specificity in the assessment of peritoneal carcinomatosis at comparable sensitivity, particularly in postoperative patients. KEY POINTS: • Combination of iodine overlays and conventional images improves specificity when assessing patients with peritoneal carcinomatosis at comparable sensitivity. • Particularly in postsurgical patients, iodine overlays could help to avoid false-positive diagnosis of peritoneal disease. • Iodine overlays alone provided inferior image quality and assessability than conventional images, while the combination of both received the highest ratings. Iodine overlays should therefore be used in addition to and not as a substitute for conventional images.

Dual-Energy CT-derived Iodine Maps: Use in Assessing Pleural Carcinomatosis.

Purpose To evaluate the use of spectral CT for differentiation between noncalcified benign pleural lesions and pleural carcinomatosis. Materials and Methods In this retrospective study, patients who underwent contrast agent-enhanced late venous phase spectral CT of the chest between June 1, 2016, and July 1, 2018 with histopathologic and/or imaging confirmation of noncalcified pleural lesions were evaluated. Conventional images, iodine overlay (IO) images, and virtual monoenergetic images at 40 keV (hereafter, VMI40keV) were reconstructed from contrast-enhanced spectral chest CT. Four blinded radiologists determined lesion presence and indicated lesion conspicuity and diagnostic certainty. Hounsfield unit attenuation from conventional images and iodine concentration (IC) (in milligrams per milliliter) from IO images were determined. Area under the receiver operating characteristics curve determined thresholds for quantitative lesion differentiation and cutoff values were validated in an independent data set. Results Eighty-four patients were included (mean age, 66.2 years; 54 men and 30 women; 44 patients with cancer with confirmed pleural carcinomatosis and 40 patients with benign pleural lesions). The area under the receiver operating characteristics curve for IC was greater than that of conventional Hounsfield units (0.96 vs 0.91; P ≤ .05, respectively). The optimal IC threshold was 1.3 mg/mL, with comparable sensitivity and specificity when applied to the test data set. The sensitivities to depict pleural carcinomatosis with spectral reconstructions versus conventional CT were 96% (199 of 208) and 83% (172 of 208), respectively, with specificities of 84% (161 of 192) and 63% (120 of 192), respectively (P ≤ .001 each). Conclusion Compared with conventional images, spectral CT with iodine maps improved both quantitative and qualitative determination of pleural carcinomatosis versus noncalcified benign pleural lesions. © RSNA, 2019 See also the editorial by K. S. Lee and H. Y. Lee .

Correction to: CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar.

The original version of this article, published on 03 May 2018, unfortunately contained a mistake. The following correction has therefore been made in the original.

Accuracy of iodine density thresholds for the separation of vertebral bone metastases from healthy-appearing trabecular bone in spectral detector computed tomography.

PURPOSE: To evaluate quantitative iodine density mapping (IDM) with spectral detector computed tomography (SDCT) as a quantitative biomarker for separation of vertebral trabecular bone metastases (BM) from healthy-appearing trabecular bone (HTB). MATERIALS AND METHODS: IRB-approved retrospective single-center-study of portal venous SDCT datasets acquired between June 2016 and March 2017. Inclusion of 43 consecutive cancer patients with BM and 40 without. Target lesions and non-affected control vertebrae were defined using follow-up imaging, MRI, and/or bone scintigraphy. ID and standard deviation were determined with ROI measures by two readers in (a) bone metastases, (b) HTB of BM patients and controls, and (c) ID of various vessels. Volumetric bone mineral density (vBMD) of the lumbar spine and age were recorded. Multivariate ROC analyses und Wilcoxon test were used to determine thresholds for separation of BM and HTB. p < 0.05 was considered significant. RESULTS: ID measurements of 40 target lesions and 83 reference measurements of HTB were acquired. Age (p < 0.0001) and vBMD (p < 0.05) affected ID measurements independently in multivariate models. There were significant differences of ID between metastases (n = 43) and HTB ID (n = 124; mean 5.5 ± 0.9 vs. 3.5 ± 0.9; p < 0.0001), however, with considerable overlap. In univariate analysis, increased ID discriminated bone lesions (AUC 0.90) with a maximum combined specificity/sensitivity of 77.5%/90.7% when applying a threshold of 4.5 mg/ml. Multivariate regression models improved significantly when considering vBMD, the noise of ID, and vertebral venous ID (AUC 0.98). CONCLUSION: IDM of SDCT yielded a statistical separation of vertebral bone lesions and HTB. Adjustment for confounders such as age and lumbar vBMD as well as for vertebral venous ID and lesion heterogeneity improved discrimination of trabecular lesions. KEY POINTS: • SDCT iodine density mapping provides the possibility for quantitative analysis of iodine uptake in tissue, which allows to differentiate bone lesions from healthy bone marrow. • Age and vBMD have a significant impact on iodine density measurements. • Iodine density measured in SDCT yielded highest sensitivity and specificity for the statistical differentiation of vertebral trabecular metastases and healthy trabecular bone using an iodine density threshold of 4.5 mg/ml (most performant)-5.0 mg/ml (optimized for specificity).

CT metal artifacts in patients with total hip replacements: for artifact reduction monoenergetic reconstructions and post-processing algorithms are both efficient but not similar.

OBJECTIVES: This study compares metal artifact (MA) reduction in imaging of total hip replacements (THR) using virtual monoenergetic images (VMI), for MA-reduction-specialized reconstructions (MAR) and conventional CT images (CI) from detector-based dual-energy computed tomography (SDCT). METHODS: Twenty-seven SDCT-datasets of patients carrying THR were included. CI, MAR and VMI with different energy-levels (60-200 keV) were reconstructed from the same scans. MA width was measured. Attenuation (HU), noise (SD) and contrast-to-noise ratio (CNR) were determined in: extinction artifact, adjacent bone, muscle and bladder. Two radiologists assessed MA-reduction and image quality visually. RESULTS: In comparison to CI, VMI (200 keV) and MAR showed a strong artifact reduction (MA width: CI 29.9±6.8 mm, VMI 17.6±13.6 mm, p<0.001; MAR 16.5±14.9 mm, p<0.001; MA density: CI -412.1±204.5 HU, VMI -279.7±283.7 HU; p<0.01; MAR -116.74±105.6 HU, p<0.001). In strong artifacts reduction was superior by MAR. In moderate artifacts VMI was more effective. MAR showed best noise reduction and CNR in bladder and muscle (p<0.05), whereas VMI were superior for depiction of bone (p<0.05). Visual assessment confirmed that VMI and MAR improve artifact reduction and image quality (p<0.001). CONCLUSIONS: MAR and VMI (200 keV) yielded significant MA reduction. Each showed distinct advantages both regarding effectiveness of artifact reduction, MAR regarding assessment of soft tissue and VMI regarding assessment of bone. KEY POINTS: • Spectral-detector computed tomography improves assessment of total hip replacements and surrounding tissue. • Virtual monoenergetic images and MAR reduce metal artifacts and enhance image quality. • Evaluation of bone, muscle and pelvic organs can be improved by SDCT.

Effects of Intermediate Catheter Evolution on Technical Outcome of Mechanical Thrombectomy-A Comparison of the Performance of Two Distal Access Catheters in Mechanical Thrombectomy of Acute Ischemic Stroke.

OBJECTIVE: Fast and secure access to intracranial vessel occlusion is essential for mechanical thrombectomy (MT) in the treatment of acute ischemic stroke. We compared 2 intermediate distal access catheters (DAC: Distal Access Catheter [C1] and SOFIA: Soft torquable catheter Optimized For Intracranial Access [C2]) for procedural speed and safety of MT as well as clinical outcome at discharge and after 90 days. METHODS: This is a retrospective study of all 398 consecutive patients receiving MT with C1 or C2 for the treatment of acute ischemic stroke between September 2010 and June 2016, using a propensity score matched cohort. Baseline characteristics, clinical outcome, and procedural factors such as the number of retrieval attempts or duration of procedure were analyzed. RESULTS: A total of 282 patients (70.9%) underwent MT with C1 and 116 patients (29.1%) with C2. MT with C2 was faster with an average duration of 69.8 ± 51 minutes (mean ± standard deviation) compared with 80.6 ± 54 minutes with C1 (P < 0.05). The average number of necessary stent-retriever maneuvers was significantly lower with C2 (1.8 ± 1.7 vs. 3.2 ± 2.5, P < 0.0001). Successful MT with aspiration only yielded higher modified Thrombolysis in Cerebral Infarction rates (mTIC 2b/3 69.9% vs. 31.5%, P < 0.0001) with C2. Modified Rankin Scale at discharge was significantly lower with C2 (3.5 ± 1.9) versus C1 (3.9 ± 1.7, P < 0.05). No significant differences of modified Rankin Scale 90 were observed. CONCLUSIONS: The use of C2 resulted in reduced procedural times with less stent-retriever maneuvers. Clinical outcome at discharge was better for C2 catheters, whereas no significant difference of outcome was apparent after 90 days.

Diagnostic value of spectral reconstructions in detecting incidental skeletal muscle metastases in CT staging examinations.

BACKGROUND: To investigate if iodine density overlay maps (IDO) and virtual monoenergetic images at 40 keV (VMI40keV) acquired from spectral detector computed tomography (SDCT) can improve detection of incidental skeletal muscle metastases in whole-body CT staging examinations compared to conventional images. METHODS: In total, 40 consecutive cancer patients who underwent clinically-indicated, contrast-enhanced, oncologic staging SDCT were included at this retrospective study: 16 patients with n = 108 skeletal muscle metastases confirmed by prior or follow-up CT, 18F-FDG-PET, MRI or histopathology, and a control group of 24 patients without metastases. Four independent readers performed blinded, randomized visual detection of skeletal muscle metastases in conventional images, IDO and VMI40keV, indicating diagnostic certainty for each lesion on a 5-point Likert scale. Quantitatively, ROI-based measurements of attenuation (HU) in conventional images and VMI40keV and iodine concentration in IDO were conducted. CNR was calculated and receiver operating characteristics (ROC) analysis of quantitative parameters was performed. RESULTS: Regarding subjective assessment, IDO (63.2 (58.5-67.8) %) and VMI40keV (54.4 (49.6-59.2) %) showed an increased sensitivity for skeletal muscle metastases compared to conventional images (39.8 (35.2-44.6) %). Specificity was comparable in VMI40keV (69.8 (63.2-75.8) %) and conventional images (69.2 (60.6-76.9) %), while in IDO, it was moderately increased to 74.2 (65.3-78.4) %. Quantitative image analysis revealed that CNR of skeletal muscle metastases to circumjacent muscle was more than doubled in VMI40keV (25.8 ± 11.1) compared to conventional images (10.0 ± 5.3, p ≤ 0.001). Iodine concentration obtained from IDO and HU acquired from VMI40kev (AUC = 0.98 each) were superior to HU attenuation in conventional images (AUC = 0.94) regarding differentiation between healthy and metastatic muscular tissue (p ≤ 0.05). CONCLUSIONS: IDO and VMI40keV provided by SDCT improve diagnostic accuracy in the assessment of incidental skeletal muscle metastases compared to conventional CT.

Dual-layer detector CT of the head: Initial experience in visualization of intracranial hemorrhage and hypodense brain lesions using virtual monoenergetic images.

PURPOSE: Retrospective comparison of diagnostic quality of virtual monoenergetic images (VMI) and conventional images (CI) reconstructed from dual-layer detector CT (DLCT) regarding intraparenchymal hemorrhage (IPH) and hypodense parenchymal lesions (HPL) of the brain. METHODS: 58 patients underwent unenhanced DLCT of the head. CI and VMI ranging from 40 to 120 keV were reconstructed. Objective image quality was assessed using ROI-based measurements within IPH, HPL, grey matter, white matter and cerebrospinal fluid, from which contrast to noise ratio (CNR) was calculated. Two radiologists assessed IPH, HPL, artifacts and image noise on a 5-point Likert-scale. Statistical significance was determined using Wilcoxon rank sum test. RESULTS: In comparison to conventional images, CNR of HPL to white matter was significantly increased in VMI at 120 keV (p ≤ 0.01), whereas at 40 keV, CNR to grey matter was enhanced (p ≤ 0.0001). Contrary, CNR of IPH to white matter was increased at 40 keV (p ≤ 0.01), while CNR to grey matter was improved at 120 keV (p ≤ 0.01). Subjective readings confirmed best delineation of IPH within grey matter at 120 keV. Both readers detected four additional hyperdense lesions within white and one within grey matter at 40 keV. CONCLUSIONS: VMI obtained with DLCT can improve depiction of hypodense parenchymal lesions and intraparenchymal hemorrhage. The initial data show a great dependency on the type of pathology and on its location: hypodense lesions in white matter and hyperdense lesions in grey matter are better visualized in higher keV reconstructions, while hyperdense lesion in white matter and hypodense lesions in grey matter are better visualized at low keV values.