Pancreatic cancer detection with dual-energy CT: diagnostic performance of 40 keV and 70 keV virtual monoenergetic images.

PURPOSE: To compare the diagnostic performance of 40 keV and 70 keV virtual monoenergetic images (VMIs) generated from dual-energy CT in the detection of pancreatic cancer. METHODS: This retrospective study included patients who underwent pancreatic protocol dual-energy CT from January 2019 to August 2022. Four radiologists (1-11 years of experience), who were blinded to the final diagnosis, independently and randomly interpreted 40 keV and 70 keV VMIs and graded the presence or absence of pancreatic cancer. For each image set (40 keV and 70 keV VMIs), the sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy were calculated. The diagnostic performance of each image set was compared using generalized estimating equations. RESULTS: Overall, 137 patients (median age, 71 years; interquartile range, 63-78 years; 77 men) were included. Among them, 62 patients (45%) had pathologically proven pancreatic cancer. The 40 keV VMIs had higher specificity (75% vs. 67%; P < .001), PPV (76% vs. 71%; P < .001), and accuracy (85% vs. 81%; P = .001) than the 70 keV VMIs. On the contrary, 40 keV VMIs had lower sensitivity (96% vs. 98%; P = .02) and NPV (96% vs. 98%; P = .004) than 70 keV VMIs. However, the diagnostic confidence in patients with (P < .001) and without (P = .001) pancreatic cancer was improved in 40 keV VMIs than in 70 keV VMIs. CONCLUSIONS: The 40 keV VMIs showed better diagnostic performance in diagnosing pancreatic cancer than the 70 keV VMIs, along with higher reader confidence.

Deep learning image reconstruction algorithm for pancreatic protocol dual-energy computed tomography: image quality and quantification of iodine concentration.

OBJECTIVES: To evaluate the image quality and iodine concentration (IC) measurements in pancreatic protocol dual-energy computed tomography (DECT) reconstructed using deep learning image reconstruction (DLIR) and compare them with those of images reconstructed using hybrid iterative reconstruction (IR). METHODS: The local institutional review board approved this prospective study. Written informed consent was obtained from all participants. Thirty consecutive participants with pancreatic cancer (PC) underwent pancreatic protocol DECT for initial evaluation. DECT data were reconstructed at 70 keV using 40% adaptive statistical iterative reconstruction-Veo (hybrid-IR) and DLIR at medium and high levels (DLIR-M and DLIR-H, respectively). The diagnostic acceptability and conspicuity of PC were qualitatively assessed using a 5-point scale. IC values of the abdominal aorta, pancreas, PC, liver, and portal vein; standard deviation (SD); and coefficient of variation (CV) were calculated. Qualitative and quantitative parameters were compared between the hybrid-IR, DLIR-M, and DLIR-H groups. RESULTS: The diagnostic acceptability and conspicuity of PC were significantly better in the DLIR-M group compared with those in the other groups (p < .001-.001). The IC values of the anatomical structures were almost comparable between the three groups (p = .001-.9). The SD of IC values was significantly lower in the DLIR-H group (p < .001) and resulted in the lowest CV (p < .001-.002) compared with those in the hybrid-IR and DLIR-M groups. CONCLUSIONS: DLIR could significantly improve image quality and reduce the variability of IC values than could hybrid-IR. KEY POINTS: Image quality and conspicuity of pancreatic cancer were the best in DLIR-M. DLIR significantly reduced background noise and improved SNR and CNR. The variability of iodine concentration was reduced in DLIR.

Optimized Bolus Threshold for Dual-Energy CT Angiography with Monoenergetic Images: A Randomized Clinical Trial.

Background The bolus-tracking technique from single-energy CT has been applied to dual-energy CT (DECT) without optimization or validation. Further optimization is imperative because of a paucity of literature and differences in the attenuation profile of virtual monoenergetic images (VMIs). Purpose To determine the optimal trigger threshold with bolus-tracking technique for DECT angiography (DECTA) in a phantom study and assess the feasibility of an optimized threshold for bolus-tracking technique in DECTA at 40 keV with a 50% reduced iodine dose in human participants. Materials and Methods A phantom study with rapid kilovoltage-switching DECT was performed to determine the optimal threshold for each kiloelectron-volt VMI. In a prospective study, consecutive participants who underwent whole-body CT angiography (CTA) from August 2018 to July 2019 were randomized into three groups: single-energy CTA (SECTA) with standard iodine dose (600 mg of iodine per kilogram), DECTA with 50% reduced iodine dose (300 mg of iodine per kilogram) by using a conventional threshold, and DECTA with 300 mg of iodine per kilogram by using an optimized threshold. A trigger threshold of 100 HU at 120 kVp was used as a reference for comparison. Injected iodine doses and aortic CT numbers were compared among the three groups using Kruskal-Wallis test. Results Ninety-six participants (mean age ± standard deviation, 72 years ± 9; 80 men) were evaluated (32 participants in each group). The optimized threshold for VMIs at 40 keV was 30 HU. The median iodine dose was lower in the optimized DECTA group (13 g) compared with conventional DECTA (19 g) and SECTA (26 g) groups (P < .017 for each comparison). The median aortic CT numbers were higher in the order corresponding to conventional DECTA (655-769 HU), optimized DECTA (543-610 HU), and SECTA (343-359 HU) groups (P < .001). Conclusion The optimized trigger threshold of 30 HU for bolus-tracking technique during dual-energy CT angiography at 40 keV achieved lower iodine load while maintaining aortic enhancement. ©RSNA, 2021 Online supplemental material is available for this article. See also the editorial by Malayeri in this issue.

Assessing Chemotherapeutic Response in Pancreatic Ductal Adenocarcinoma: Histogram Analysis of Iodine Concentration and CT Number in Single-Source Dual-Energy CT.

OBJECTIVE: The objective of this study was to evaluate the feasibility of histographic analysis of iodine concentration (IC) and CT number on single-source dual-energy CT (DECT) to assess response to first-line chemotherapy in patients with pancreatic ductal adenocarcinoma (PDAC) who received first-line chemotherapy but not radiation therapy. SUBJECTS AND METHODS: This prospective study was approved by our institutional review board, and patients gave written informed consent. Sixty consecutive patients with PDAC undergoing first-line chemotherapy underwent DECT during the pancreatic parenchymatous phase (PPP) and the equilibrium phase (EP). The IC and CT number of PDAC were measured using PPP and EP iodine-based material decomposition and monochromatic images (65 keV), respectively. Histographic parameters for the IC and CT number of PDACs were obtained, and differences in mean IC (ΔIC) and CT number (ΔHU) between the PPP and the EP were calculated. These parameters were then compared between the response (partial response or stable disease) and nonresponse (progressive disease) groups. RESULTS: Among the histographic parameters, the kurtosis of IC during the PPP (p = 0.018) and ΔIC (p = 0.0004) were identified as significant for differentiating between the two groups. IC diagnostic factor was calculated using the following coefficients of logistic regression analysis: 0.52 - (1.45 × kurtosis of IC during PPP) + (0.69 × ΔIC). The sensitivity, specificity, and area under the ROC curve for differentiating between the two groups were 97.7%, 70.6%, and 0.889, respectively. CONCLUSION: The IC diagnostic factor is a potential biomarker for assessing chemotherapeutic response in patients with PDAC.

Modified National Comprehensive Cancer Network Criteria for Assessing Resectability of Pancreatic Ductal Adenocarcinoma.

OBJECTIVE: The objective of our study was to assess the preoperative resectability of pancreatic ductal adenocarcinoma (PDAC) using the National Comprehensive Cancer Network (NCCN) guideline, the general rules of the Japan Pancreas Society (JPS), and both of them combined. MATERIALS AND METHODS: Eighty-six consecutive patients with PDAC (50 men and 36 women; mean age ± SD, 70.8 ± 9.0 years; age range, 49-86 years) underwent dynamic contrast-enhanced CT. Following the NCCN guideline, the degree of vascular invasion was evaluated to determine the NCCN score: 0 points for absence of vascular invasion, 1 point for tumor contact ≤ 180°, and 2 points for tumor contact > 180°. Direct invasion to adjacent structures was rated according to the general rules of JPS to determine the JPS score: 0 points for absence and 1 point for presence. The NCCN score, JPS score, and sum of the two scores, which we refer to as the "combined score," were compared with histopathologic or intraoperative findings as well as for the differentiation of R0 resection (negative resection margins) from R1 (microscopic tumor infiltration) and R2 (macroscopic residual tumor) using ROC curve analysis. RESULTS: The sensitivities, specificities, and areas under the ROC curves (AUCs) for the differentiation of R0 from R1 and R2 were 100.0%, 40.0%, and 0.725, respectively, with the NCCN score; 63.9%, 84.0%, and 0.824 with the JPS score; and 86.9%, 68.0%, and 0.874 with the combined score. The AUC of the combined score was significantly greater than that of the NCCN score (p = 0.0059). CONCLUSION: The assessment of resectability of PDAC based on the combined criteria of the NCCN guideline and general rules of JPS was superior to that based on either criterion alone.

[Plain X-ray or Computed Tomography Image of Epidural Catheters with Various Materials].

BACKGROUND: Although breakage of the epidural catheter inside patients is a rare complication, plain X-ray or computed tomography (CT) image is useful for diagnosis of catheter remnant However, it is not well known whether the catheter materials are visible in these images. METHODS: We examined 3 types of X-ray permeabil- ity catheters and 6 types of X-ray impermeability cath- eters available in Japan. We obtained plain X-ray images of catheters alone, plain X-ray images of cathe- ters with bone dummy and CT images of catheters in the model of epidural space. RESULTS: On plain X-ray images of catheters alone, we could confirm all 6 types of X-ray impermeability catheters. However, on plain X-ray images of catheters with bone dummy, we could confirm only 3 types of catheters among 6 X-ray impermeability catheters. On CT images, we could confirm all 6 types of X-ray impermeability catheters, but not X-ray permeability catheters. CONCLUSIONS: Plain X-ray image can not provide the detection for some X-ray impermeability catheters. CT image is useful- for diagnosis of X-ray impermeability catheters.

Low-Iodine-Load and Low-Tube-Voltage CT Angiographic Imaging of the Kidney by Using Bolus Tracking with Saline Flushing.

PURPOSE: To prospectively determine the feasibility of low-iodine-load and low-tube-voltage computed tomographic (CT) angiographic imaging of the kidney and to evaluate the opacification and image quality compared with moderate-iodine-load and high-iodine-load techniques. MATERIALS AND METHODS: Institutional review board approval and written informed consent was obtained. One hundred thirteen consecutive patients randomly underwent three protocols for dual-phase renal CT angiographic imaging: high-iodine-load (600 mg iodine per kilogram of body weight at 120 kVp); moderate-iodine-load (400 mg iodine per kilogram of body weight at 80 kVp); and low-iodine-load (contrast agent injection initially prepared at 400 mg iodine per kilogram of body weight but stopped immediately after bolus-tracking trigger at 80 kVp) scanning. CT numbers of vessels and kidneys were measured. CT numbers and signal-to-noise ratio (SNR) were compared with one-way analysis of variance and posthoc Tukey-Kramer test and depiction of vessels and image noise, with Kruskal-Wallis test and pair-wise Mann-Whitney test with Bonferroni correction. RESULTS: Mean iodine weight administered was significantly reduced in order of low- (16.4 g), moderate- (23.5 g), and high-iodine-load (33.7 g) protocols (P < .001). Mean CT numbers of abdominal aorta, renal artery, and renal cortex in first phase were significantly lower with high-iodine-load protocol (308, 274, and 132 HU, respectively) than with moderate- (347, 334, and 156 HU, respectively; P = .001-.006) or low-iodine-load (362, 316, and 161 HU, respectively; P = .001-.003) protocol. Mean CT number of renal vein in second phase was significantly lower with low-iodine-load protocol (223 HU) than with moderate- (299 HU; P < .001) or high-iodine-load (258 HU; P = .020). Mean SNR of renal medulla in second phase was significantly lower (P = .019) with moderate-iodine-load protocol (mean SNR, 7.2) than with high-iodine-load protocol (mean SNR, 10.0). No significant difference in image quality grades was found between high-iodine-load (mean grade, 2.6-2.9), moderate-iodine-load (mean grade, 2.6-3.0), and low-iodine-load (mean grade, 2.6-2.9) protocols (P = .018-.31). CONCLUSION: Combined application of low-iodine-load, bolus tracking with saline flushing, and low-tube-voltage scanning is feasible and resulted in substantial reduction of iodine dose for renal CT angiographic imaging without compromising image quality.

Whole-body CT angiography with low tube voltage and low-concentration contrast material to reduce radiation dose and iodine load.

OBJECTIVE: The purpose of this study was to prospectively evaluate the contrast enhancement, vascular depiction, image quality, and radiation dose of low-tube-voltage whole-body CT angiography (CTA) performed with low-concentration iodinated contrast material. SUBJECTS AND METHODS: Whole-body CTA was performed on 109 patients with a 64-MDCT scanner. Patients were randomized into three groups: CTA with 240-mg/mL contrast material at 80 kVp (240-80 group), 300-mg/mL at 80 kVp (300-80 group), and 370-mg/mL at 120 kVp (370-120 group). Signal-to-noise ratio (SNR), arterial depiction, image quality, and radiation dose were assessed. Figure of merit was computed to normalize signal-to-noise ratio, estimated effective dose, and iodine weight. RESULTS: In the 240-80 group, the mean load of administered iodine was 21.6 g; for the 300-80 group, 26.8 g; and the 370-120 group, 34.0 g (p < 0.05). The ranges of mean vascular enhancement were 508-521 HU, 546-593 HU, and 435-442 HU (p < 0.05). Arterial depiction and image quality were comparable for the 240-80 and 370-120 groups and were greater for the 300-80 group than the other two groups in selected arteries (p < 0.05). Effective dose was higher (p < 0.05) in the 370-120 group (2.8-5.4 mSv) than in the others (2.3-4.3 mSv). The figure of merit in the 240-80 group was greater than (p < 0.05) or comparable to that in the 370-120 group. CONCLUSION: Use of 240-mg/mL contrast material at 80 kVp seems appropriate for routine whole-body CTA and beneficial for reduction of iodine load and radiation dose, whereas use of 300-mg/mL contrast material may marginally improve delineation of selected small arteries.

Reduction of iodine load in CT imaging of pancreas acquired with low tube voltage and an adaptive statistical iterative reconstruction technique.

PURPOSE: To prospectively assess the contrast enhancement, image quality, radiation dose, and detectability of malignant pancreatic tumors with pancreatic computed tomography (CT) obtained at an 80-kilovolt (peak) (kV[p]) tube voltage setting and reduced iodine dose. METHODS: Institutional review board approval and written informed consent were obtained. During a recent 10-month period, 136 patients (66 men and 70 women; age range, 21-86 years; mean ± SD age, 65.9 ± 11.0 years) with suspected pancreatic disease were randomized into 3 groups according to the following iodine-load and tube-voltage protocols: 600 mg of iodine per kilogram body weight (mg/kg) and 120 kV(p) (600-120 group), 500 mg/kg and 80 kV(p) (500-80 group), and 400 mg/kg and 80 kV(p) (400-80 group). Analysis of variance was conducted to evaluate differences in CT number, background noise, signal-to-noise ratio, effective dose, lesion-to-pancreas contrast-to-noise ratio, and figure of merit. Sensitivity, specificity, and area under the receiver-operating-characteristic curve were compared to assess the detectability of malignant pancreatic tumors. RESULTS: The signal-to-noise ratios in vessels were greater (P < 0.05) in the 400-80 and 500-80 groups than in the 600-120 group, and those in pancreas were comparable between the 400-80 and 600-120 groups. No significant difference was found in effective dose, image quality, lesion-to-pancreas contrast-to-noise ratio, or figure of merit between the groups. Sensitivity, specificity, and area under the receiver-operating-characteristic curve for detecting malignant pancreatic tumors were comparable between the groups. CONCLUSIONS: Pancreatic CT with an 80-kV(p) setting and 400-mg iodine per kilogram contrast material load facilitates the reduction of iodine dose while maintaining image quality and the detectability of malignant pancreatic tumors.

Radiomics Features Using Dual-energy CT for Lymph Nodes After Preoperative Chemotherapy for Esophageal Cancer.

BACKGROUND/AIM: Progress has been made in a triplet preoperative chemotherapy regimen for advanced esophageal cancer. We performed a preliminary investigation of the radiomics features of pathological lymph node metastasis after neoadjuvant chemotherapy using dual-energy computed tomography (DECT). PATIENTS AND METHODS: From January to December 2022, 36 lymph nodes from 10 patients with advanced esophageal cancer who underwent contrast-enhanced DECT after neoadjuvant chemotherapy and radical surgery in our department were studied. Radiomics features were extracted from iodine-based material decomposition images at the portal venous phase constructed by DECT using MATLAB analysis software. Receiver operating characteristic (ROC) analysis and cut-off values were determined for the presence or absence of pathological metastasis. RESULTS: ROC for the short axis of the pathologically positive lymph nodes showed an AUC of 0.713. Long run emphasis (LRE) within gray-level run-length matrix (GLRLM) was confirmed with a high AUC of 0.812. Sensitivity and specificity for lymph nodes with a short axis >10 mm were 0.222 and 1, respectively. Sensitivity and specificity for LRE within GLRLM were 0.722 and 0.833, respectively. Sensitivity and specificity for small zone emphasis (SZE) within gray-level size zone matrix (GLSZM) were 0.889 and 0.667, and zone percentage (ZP) values within GLSZM were 0.722 and 0.778, respectively. Discrimination of existing metastases using radiomics showed significantly higher sensitivity compared to lymph node short axis >10 mm (odds ratios of LRE, SZE, and ZP: 9.1, 28, and 9.1, respectively). CONCLUSION: Evaluation of radiomics analysis using DECT may enable a more detailed evaluation of lymph node metastasis after neoadjuvant chemotherapy.

Assessment of Arterial Involvement in Pancreatic Cancer: Utility of Reconstructed CT Images Perpendicular to Artery.

The purpose of this study was to investigate the utility of reconstructed CT images perpendicular to the artery for assessing arterial involvement from pancreatic cancer and compare the interobserver variability between it and the current diagnostic imaging method. This retrospective study included patients with pancreatic cancer in the pancreatic body or tail who underwent preoperative pancreatic protocol CT and distal pancreatectomy. Five radiologists used axial and coronal CT images (current method) and perpendicular reconstructed CT images (proposed method) to determine if the degree of solid soft-tissue contact with the splenic artery was ≤180° or >180°. The generalized estimating equations were used to compare the diagnostic performance of solid soft-tissue contact >180° between the current and proposed methods. Fleiss' ĸ statistics were used to assess interobserver variability. The sensitivity and negative predictive value for diagnosing solid soft-tissue contact >180° were higher (p < 0.001 for each) and the specificity (p = 0.003) and positive predictive value (p = 0.003) were lower in the proposed method than the current method. Interobserver variability was improved in the proposed method compared with the current method (ĸ = 0.87 vs. 0.67). Reconstructed CT images perpendicular to the artery showed higher sensitivity and negative predictive value for diagnosing solid soft-tissue contact >180° than the current method and demonstrated improved interobserver variability.

Comparison of image quality, arterial depiction, and radiation dose between two rapid kVp-switching dual-energy CT scanners in CT angiography at 40-keV.

PURPOSE: To compare the quantitative parameters and qualitative image quality of dual-energy CT angiography (CTA) between two rapid kVp-switching dual-energy CT scanners. MATERIALS AND METHODS: Between May 2021 and March 2022, 79 participants underwent whole-body CTA using either Discovery CT750 HD (Group A, n = 38) or Revolution CT Apex (Group B, n = 41). All data were reconstructed at 40-keV and with adaptive statistical iterative reconstruction-Veo of 40%. The two groups were compared in terms of CT numbers of the thoracic and abdominal aorta, and the iliac artery, background noise, signal-to-noise ratio (SNR) of the artery, CT dose-index volume (CTDIvol), and qualitative scores for image noise, sharpness, diagnostic acceptability, and arterial depictions. RESULTS: The median CT number of the abdominal aorta (p = 0.04) and SNR of the thoracic aorta (p = 0.02) were higher in Group B than in Group A, while no difference was observed in the other CT numbers and SNRs of the artery (p = 0.09-0.23). The background noises at the thoracic (p = 0.11), abdominal (p = 0.85), and pelvic (p = 0.85) regions were comparable between the two groups. CTDIvol was lower in Group B than in Group A (p = 0.006). All qualitative scores were higher in Group B than in Group A (p < 0.001-0.04). The arterial depictions were nearly identical in both two groups (p = 0.005-1.0). CONCLUSION: In dual-energy CTA at 40-keV, Revolution CT Apex improved qualitative image quality and reduced radiation dose.

Deep-learning image reconstruction for 80-kVp pancreatic CT protocol: Comparison of image quality and pancreatic ductal adenocarcinoma visibility with hybrid-iterative reconstruction.

PURPOSE: To evaluate the image quality and visibility of pancreatic ductal adenocarcinoma (PDAC) in 80-kVp pancreatic CT protocol and compare them between hybrid-iterative reconstruction (IR) and deep-learning image reconstruction (DLIR) algorithms. METHOD: A total of 56 patients who underwent 80-kVp pancreatic protocol CT for pancreatic disease evaluation from January 2022 to July 2022 were included in this retrospective study. Among them, 20 PDACs were observed. The CT raw data were reconstructed using 40% adaptive statistical IR-Veo (hybrid-IR group) and DLIR at medium- and high-strength levels (DLIR-M and DLIR-H groups, respectively). The CT attenuation of the abdominal aorta, pancreas, and PDAC (if present) at the pancreatic phase and those of the portal vein and liver at the portal venous phase; background noise; signal-to-noise ratio (SNR) of these anatomical structures; and tumor-to-pancreas contrast-to-noise ratio (CNR) were calculated. The confidence scores for the image noise, overall image quality, and visibility of PDAC were qualitatively assigned using a five-point scale. Quantitative and qualitative parameters were compared among the three groups using Friedman test. RESULTS: The CT attenuation of all anatomical structures were comparable among the three groups (P = .26-.86), except that of the pancreas (P = .001). Background noise was lower (P <.001) and SNRs (P <.001) and tumor-to-pancreas CNR (P <.001) were higher in the DLIR-H group than those in the other two groups. The image noise, overall image quality, and visibility of PDAC were better in the DLIR-H group than in the other two groups (P <.001-.003). CONCLUSION: In 80-kVp pancreatic CT protocol, DLIR at a high-strength level improved image quality and visibility of PDAC.

Comparison of image quality and pancreatic ductal adenocarcinoma conspicuity between the low-kVp and dual-energy CT reconstructed with deep-learning image reconstruction algorithm.

PURPOSE: To compare the image quality and conspicuity of pancreatic ductal adenocarcinoma (PDAC) between the low-kVp and dual-energy pancreatic protocol CT reconstructed with deep-learning image reconstruction (DLIR). METHOD: A cohort of 111 consecutive patients (median age, 72 years; 56 men) undergoing a pancreatic protocol CT were retrospectively analyzed. Among them, 58 patients underwent 80-kVp CT (80-kVp group), and 53 patients underwent dual-energy CT and reconstructed at 40-keV (40-keV group). The medium-strength level of DLIR were used in both groups. Quantitative measurements, qualitative image quality, PDAC conspicuity, and dose-length product (DLP) were compared between the two groups using Mann-Whitney U test. RESULTS: A total of 20 and 16 PDACs were found in the 80-kVp and 40-keV groups, respectively. CT numbers of the vasculatures and parenchymal organs (P <.001 for all) and the background noise at both pancreatic and portal venous phases (P <.001) were higher in the 40-keV group than in the 80-kVp group. The signal-to-noise ratio (SNR) of all anatomical structures (P <.001-0.005), except for the liver in reviewer 2 (P =.47), and the tumor-to-pancreas contrast-to-noise ratio (CNR; P <.001-0.01) were higher in the 40-keV group than in the 80-kVp group. No difference was found in the image quality at both phases (P =.30-0.90). PDAC conspicuity was better in the 40-keV group than in the 80-kVp group (P =.007-0.03). DLP at pancreatic (275 vs. 313 mGy*cm; P =.05) and portal venous phases (743 vs. 766 mGy*cm; P =.20) was comparable between the two groups. CONCLUSION: Under the same DLP, virtual monoenergetic images at 40-keV demonstrated higher SNR and tumor-to-pancreas CNR and better PDAC conspicuity compared to the 80-kVp setting.

Unenhanced abdominal low-dose CT reconstructed with deep learning-based image reconstruction: image quality and anatomical structure depiction.

PURPOSE: To evaluate the utility of deep learning-based image reconstruction (DLIR) algorithm in unenhanced abdominal low-dose CT (LDCT). MATERIALS AND METHODS: Two patient groups were included in this prospective study: 58 consecutive patients who underwent unenhanced abdominal standard-dose CT reconstructed with hybrid iterative reconstruction (SDCT group) and 48 consecutive patients who underwent unenhanced abdominal LDCT reconstructed with high strength level of DLIR (LDCT group). The background noise and signal-to-noise ratio (SNR) of the liver, pancreas, spleen, kidney, abdominal aorta, inferior vena cava, and portal vein were calculated. Two radiologists qualitatively assessed the overall image noise, overall image quality, and abdominal anatomical structures depiction. Quantitative and qualitative parameters and size-specific dose estimates (SSDE) were compared between SDCT and LDCT groups. RESULTS: The background noise was lower in LDCT group than in SDCT group (P = 0.02). SNRs were higher in LDCT group than in SDCT group (P < 0.001-0.004) except for the liver. Overall image noise was superior in LDCT group than in SDCT group (P < 0.001). Overall image quality was not different between SDCT and LDCT groups (P = 0.25-0.26). Depiction of almost all abdominal anatomical structures was equal to or better in LDCT group than in SDCT group (P < 0.001-0.88). The SSDE was lower in LDCT group (4.0 mGy) than in SDCT group (20.6 mGy) (P < 0.001). CONCLUSIONS: DLIR facilitates substantial radiation dose reduction of > 75% and significantly reduces background noise. DLIR can maintain image quality and anatomical structure depiction in unenhanced abdominal LDCT.

Radiation and iodine dose reduced thoraco-abdomino-pelvic dual-energy CT at 40 keV reconstructed with deep learning image reconstruction.

OBJECTIVE: To evaluate the feasibility of a simultaneous reduction of radiation and iodine doses in dual-energy thoraco-abdomino-pelvic CT reconstructed with deep learning image reconstruction (DLIR). METHODS: Thoraco-abdomino-pelvic CT was prospectively performed in 111 participants; 52 participants underwent a standard-dose single-energy CT with a standard iodine dose (600 mgI/kg; SD group), while 59 underwent a low-dose dual-energy CT with a reduced iodine dose [300 mgI/kg; double low-dose (DLD) group]. CT data were reconstructed with a hybrid iterative reconstruction in the SD group and a high-strength level of DLIR at 40 keV in the DLD group. Two radiologists measured the CT numbers of the descending and abdominal aorta, portal vein, hepatic vein, inferior vena cava, liver, pancreas, spleen, and kidney, and background noise. Two other radiologists assessed diagnostic acceptability using a 5-point scale. The CT dose-index volume (CTDIvol), iodine weight, CT numbers of anatomical structures, background noise, and diagnostic acceptability were compared between the two groups using Mann-Whitney U test. RESULTS: The median CTDIvol [10 mGy; interquartile range (IQR), 9-13 mGy vs 4 mGy; IQR, 4-5 mGy] and median iodine weight (35 g; IQR, 31-38 g vs 16 g; IQR, 14-18 g) were lower in the DLD group than in the SD group (p < 0.001 for each). The CT numbers of all anatomical structures and background noise were higher in the DLD group than in the SD group (p < 0.001 for all). The diagnostic image quality was obtained in 100% (52/52) of participants in the SD group and 95% (56/59) of participants in the DLD group. CONCLUSION: Virtual monochromatic images at 40 keV reconstructed with DLIR could achieve half doses of radiation and iodine while maintaining diagnostic image quality. ADVANCES IN KNOWLEDGE: Virtual monochromatic images at 40 keV reconstructed with DLIR algorithm allowed to reduce the doses of radiation and iodine while maintaining diagnostic image quality.

Radiological Arterial Anatomy in Mature Microminipigs as a Pre-clinical Research Model in Interventional Radiology.

PURPOSE: To define the radiological arterial anatomy in mature microminipigs as a pre-clinical research animal model in interventional radiology. MATERIALS AND METHODS: Five female microminipigs (weighing 20.9 ± 2.9 kg) were used in this study. Under general anesthesia, computed tomography (CT) angiography was performed using a 16-slice CT scanner. CT was performed 12 s after initiation of an intravenous injection of 40 ml of nonionic contrast media at 3.0 ml/second using a power injector. The transverse CT angiography images were evaluated using a digital imaging and communication in medicine viewer, and the diameters of the following 41 arteries were measured.: ascending aorta, descending aorta, thoracoabdominal aorta, abdominal aorta, pulmonary artery trunk, both pulmonary, brachiocephalic artery, short common bicarotid, both common carotid artery, subclavian, bronchial, internal mammary, celiac, common hepatic, left lateral hepatic, middle hepatic, left hepatic, gastroduodenal, cranial duodenopancreatic, splenic, left gastric, cranial mesenteric, ileocolic , bilateral colic artery, caudal mesenteric, cranial rectal, renal, both external iliac arteries, internal iliac common trunk, and both internal iliac and femoral arteries. RESULTS: The microminipigs' vascular anatomy was the same as domestic pig anatomy and similar to human anatomy. The diameter of the aorta (ascending to abdominal) was 17.1-7.0 mm, iliac and femoral arteries (internal iliac common trunk to femoral artery): 5.5-3.8 mm, pulmonary arteries: 9.3-14.7 mm, and major first aortic branches (e.g., celiac or brachiocephalic artery): 2.2-9.2 mm. CONCLUSION: This study defined the microminipig arterial anatomy in the trunk.

Deep learning image reconstruction for pancreatic low-dose computed tomography: comparison with hybrid iterative reconstruction.

PURPOSE: To evaluate image quality, image noise, and conspicuity of pancreatic ductal adenocarcinoma (PDAC) in pancreatic low-dose computed tomography (LDCT) reconstructed using deep learning image reconstruction (DLIR) and compare with those of images reconstructed using hybrid iterative reconstruction (IR). METHODS: Our institutional review board approved this prospective study. Written informed consent was obtained from all patients. Twenty-eight consecutive patients with PDAC undergoing chemotherapy (14 men and 14 women; mean age, 68.4 years) underwent pancreatic LDCT for therapy evaluation. The LDCT images were reconstructed using 40% adaptive statistical iterative reconstruction-Veo (hybrid-IR) and DLIR at medium and high levels (DLIR-M and DLIR-H). The image noise, diagnostic acceptability, and conspicuity of PDAC were qualitatively assessed using a 5-point scale. CT numbers of the abdominal aorta, portal vein, pancreas, PDAC, background noise, signal-to-noise ratio (SNR) of the anatomical structures, and tumor-to-pancreas contrast-to-noise ratio (CNR) were calculated. Qualitative and quantitative parameters were compared between the hybrid-IR, DLIR-M, and DLIR-H images. RESULTS: CT dose-index volumes and dose-length product in pancreatic LDCT were 2.3 ± 1.0 mGy and 74.9 ± 37.0 mGy•cm, respectively. The image noise, diagnostic acceptability, and conspicuity of PDAC were significantly better in DLIR-H than those in hybrid-IR and DLIR-M (all P < 0.001). The background noise was significantly lower in the DLIR-H images (P < 0.001) and resulted in improved SNRs (P < 0.001) and CNR (P < 0.001) compared with those in the hybrid-IR and DLIR-M images. CONCLUSION: DLIR significantly reduced image noise and improved image quality in pancreatic LDCT images compared with hybrid-IR.

Optimized scan delay for late hepatic arterial or pancreatic parenchymal phase in dynamic contrast-enhanced computed tomography with bolus-tracking method.

OBJECTIVES: To determine the optimal scan delay corresponding to individual hemodynamic status for pancreatic parenchymal phase in dynamic contrast-enhanced CT of the abdomen. METHODS: One hundred and fourteen patients were included in this retrospective study (69 males and 45 females; mean age, 67.9 ± 12.1 years; range, 39-87 years). These patients underwent abdominal dynamic contrast-enhanced CT between November 2019 and May 2020. We calculated and recorded the time from contrast material injection to the bolus-tracking trigger of 100 Hounsfield unit (HU) at the abdominal aorta (s) (TimeTRIG) and scan delay from the bolus-tracking trigger to the initiation of pancreatic parenchymal phase scanning (s) (TimeSD). The scan delay ratio (SDR) was defined by dividing the TimeSD by TimeTRIG. Non-linear regression analysis was conducted to assess the association between CT number of the pancreas and SDR and to reveal the optimal SDR, which was ≥120 HU in pancreatic parenchyma. RESULTS: The non-linear regression analysis showed a significant association between CT number of the pancreas and the SDR (p < 0.001). The mean TimeTRIG and TimeSD were 16.1 s and 16.8 s, respectively. The SDR to peak enhancement of the pancreas (123.5 HU) was 1.00. An SDR between 0.89 and 1.18 shows an appropriate enhancement of the pancreas (≥120 HU). CONCLUSION: The CT number of the pancreas peaked at an SDR of 1.00, which means TimeSD should be approximately the same as TimeTRIG to obtain appropriate pancreatic parenchymal phase images in dynamic contrast-enhanced CT with bolus-tracking method. ADVANCES IN KNOWLEDGE: The hemodynamic state is different in each patient; therefore, scan delay from the bolus-tracking trigger should also vary based on the time from contrast material injection to the bolus-tracking trigger. This is necessary to obtain appropriate late hepatic arterial or pancreatic parenchymal phase images in dynamic contrast-enhanced CT of the abdomen.

Advantages and disadvantages of single-source dual-energy whole-body CT angiography with 50% reduced iodine dose at 40 keV reconstruction.

OBJECTIVES: To assess the feasibility of whole-body dual-energy computed tomographic angiography (DECTA) at 40 keV with 50% reduced iodine dose protocol. METHODS: Whole-body CTA was performed in 65 patients; 31 of these patients underwent 120 kVp single-energy computed tomographic angiography (SECTA) with standard iodine dose (600 mgI/kg) and 34 with 40 keV DECTA with 50% reduced iodine dose (300 mgI/kg). SECTA data were reconstructed with adaptive statistical iterative reconstruction of 40% (SECTA group), and DECTA data were reconstructed with adaptive statistical iterative reconstruction of 40% (DECTA-40% group) and 80% (DECTA-80% group). CT numbers of the thoracic and abdominal aorta, iliac artery, background noise, signal-to-noise ratio (SNR), and arterial depiction were compared among the three groups. The CT dose index volumes (CTDIvol) for the thorax, abdomen, and pelvis were compared between SECTA and DECTA protocols. RESULTS: The vascular CT numbers and background noise were found to be significantly higher in DECTA groups than in the SECTA group (p < 0.001). SNR was significantly higher in the order corresponding to DECTA-80%, SECTA, and DECTA-40% (p < 0.001). The arterial depiction was comparable in almost all arteries; however, intrapelvic arterial depiction was significantly worse in DECTA groups than in the SECTA group (p < 0.0001-0.017). Unlike the pelvic region (p = 0.055), CTDIvol for the thorax (p < 0.0001) and abdomen (p = 0.0031) were significantly higher in the DECTA protocol than in the SECTA protocol. CONCLUSION: DECTA at 40 keV with 50% reduced iodine dose provided higher vascular CT numbers and SNR than SECTA, and almost comparable arterial depiction, but had a degraded intrapelvic arterial depiction and required a larger radiation dose. ADVANCES IN KNOWLEDGE: DECTA enables 50% reduction of iodine dose while maintaining image quality, arterial depiction in almost all arteries, vascular CT numbers, and SNR; however, it does not allow clear visualization of intrapelvic arteries, requiring a slightly larger radiation dose compared with SECTA with standard iodine dose.