Preclinical safety evaluation of Lipase OF from Candida cylindracea.

Triacylglycerol lipases are enzymes commonly used to process foods and beverages such as oils, wines, and cheeses through catalyzation of long-chain triglyceride hydrolysis. Lipase OF derived from Candida cylindracea (strain MS-5-OF) is only intended for use as a processing aid in food production applications; however, it may be present at trace levels in some products. As such, the safety of Lipase OF was evaluated in this study that included a bacterial reverse mutation assay, an in vitro chromosome aberration test, and a 90-day subchronic toxicity study in rats. In the in vitro bacterial reverse mutation and chromosome aberration assays, Lipase OF was not observed to be mutagenic at concentrations up to 5000 µg/plate and 50 µg/ml, respectively, in the presence or absence of metabolic activation. Results from the 90-day subchronic toxicity study indicated only minimal adverse effects (i.e., increased platelet count and prothrombin time) in male rats from the high-dose group following administration of Lipase OF via the diet at levels of 0, 1.0, 2.5, and 5.0 w/w%. The no-observed-adverse-effect level (NOAEL) for Lipase OF was therefore considered 2.5 w/w% (1597.6 mg/kg body weight/day [1027.3 mg TOS/kg body weight/day]) in males and 5.0 w/w% (3700.4 mg/kg body weight/day [2379.4 mg TOS/kg body weight/day]) in females under the test conditions. Thus, the evidence presented within this study supports the safe use of Lipase OF as a processing aid in various food production applications for human consumption.

Non-contrast mDixon MR angiography of the neck: Comparison with time-of-flight MR angiography in normal subjects.

ABSTRACT: We investigated the feasibility of non-contrast three-dimensional modified Dixon (mDixon) magnetic resonance angiography (MRA) to evaluate the carotid artery.We studied 30 normal patients who underwent non-contrast mDixon and conventional time-of-flight (TOF) MRA of the neck with a clinical 3T MR scanner. Carotid artery signal-to-noise ratio (SNR) and contrast-to-noise ratio were compared between mDixon-MRA and TOF-MRA. Two readers independently evaluated vessel sharpness, image contrast, and overall image quality using a 4-point scale.SNR was significantly higher on mDixon-MRA than TOF-MRA (P < .01). There was no significant difference in contrast-to-noise ratio. The visual score for vessel sharpness was significantly higher on mDixon-MRA than TOF-MRA (P < .01), whereas the score for contrast was significantly higher on TOF-MRA (P < .01).Although non-contrast three-dimensional mDixon-MRA showed lower visual contrast than conventional TOF-MRA, it provided images with significantly higher SNR and better vessel sharpness than TOF-MRA.

The imaging findings of Peliosis hepatis on gadoxetic acid enhanced MRI.

Peliosis hepatis involves multiple blood-filled cystic spaces in the hepatic parenchyma. Using conventional imaging, distinguishing PH from other malignancies can be difficult. The findings of Peliosis hepatis on gadoxetic acid (Gd-EOB) enhanced magnetic resonance imaging are not well reported. Therefore, we report the imaging features of pathologically proven PH. On the hepatobiliary phase of Gd-EOB magnetic resonance imaging, most lesions showed unenhanced areas, but some lesions showed central enhancement "halo sign."

Nivolumab exerts therapeutic effects against metastatic lesions from early gastric adenocarcinoma with a small proportion of neuroendocrine carcinoma after gastrectomy: a case report.

Gastric neuroendocrine carcinoma (NEC) is an aggressive disease with high metastatic ability. Gastric cancer has intra-tumoral and intra-patient heterogeneity and may contain NEC. We discuss the case of a 75-year-old man who underwent distal gastrectomy for early gastric cancer. Tumor pathology revealed that nearly all of the tumor (> 95%) was well-differentiated adenocarcinoma, with NEC detected in a small area (< 5%) at the invasion front. No metastasis was identified in the dissected lymph nodes (LN). Multiple liver metastases were detected 3 months after surgery. The metastatic lesion was resistant to both chemotherapy regimens; namely, SOX (S-1 combined with oxaliplatin) and ramucirumab combined with paclitaxel. However, tumor regression was detected after nivolumab treatment. The tumor regression continued for 26 cycles (13 months). Irinotecan treatment was then administered. After 18 irinotecan treatment cycles for 11 months, the para-aortic LN rapidly enlarged. Following biopsy, the swollen para-aortic LN was diagnosed as the recurrence of NEC components of the gastric cancer. Treatment with carboplatin combined with etoposide has been effective and continued. We report a case of NEC para-aorta LN metastases from early gastric cancer with a low proportion of NEC (< 5%). A partial response of the distant metastatic lesions was observed with nivolumab therapy.

Prospective Comparison of 70-kVp Single-Energy CT versus Dual-Energy CT: Which is More Suitable for CT Angiography with Low Contrast Media Dosage?

RATIONALE AND OBJECTIVES: To compare the objective and subjective image qualities between single-energy computed tomography (CT) at 70 kVp and virtual monoenergetic imaging (VMI) of dual-source dual-energy CT for CT angiography with 180 mgI/kg. MATERIALS AND METHODS: Total 63 patients scanned with 180 mgI/kg were randomly divided into two groups: Group A (32 patients) underwent CT angiography at 70-kVp, and Group B (31 patients) underwent dual-energy CT. VMI sets were generated at 10-keV increments between 40 and 100 keV. We calculated aortic attenuation, contrast-to-noise-ratio (CNR), signal-to-noise-ratio, figure of merit of CNR, and effective dose for each protocol. Three radiologists scored overall image quality and various arteries' visibility using a four-point scale. Quantitative and qualitative comparisons between 70 kVp and VMI with the highest CNR were performed with the two-tailed t test or Kruskal-Wallis test. RESULTS: The 40-keV images offered the highest CNR among VMIs. Aortic attenuation at 70 kVp was significantly lower than that at 40 keV (p < 0.001). However, the signal-to-noise-ratio, CNR, and figure of merit of CNR were significantly higher at 70 kVp than those at 40-keV (p < 0.001, p < 0.05, and p < 0.05, respectively). The effective dose of each group was almost equal. The qualitative visibility scores for various arteries, except the ascending and upper-abdominal aorta, were also better at 70 kVp than those at 40 keV. CONCLUSION: Aortic attenuation at 70 kVp with 180 mg I/kg was lower than that of VMI at 40 keV, and the objective and subjective image qualities were higher at 70 kVp than those at 40 keV.

Prevalence of extracardiac findings in patients undergoing coronary computed tomography and additional low-dose whole-body computed tomography.

PURPOSE: In patients with suspected coronary artery disease (CAD), coexisting extracardiac abnormalities have a major impact on the patient management. This study aimed to evaluate the image quality of whole-body computed tomography (CT) immediately after the coronary computed tomography angiography (CTA) and investigate the incidence of extracardiac findings in patients with suspected CAD. MATERIALS AND METHODS: We enrolled 450 patients undergoing whole-body CT at 100 kVp and model-based iterative reconstruction immediately after the coronary CTA (Group A) and retrospectively reviewed 144 control patients who underwent conventional contrast-enhanced CT (120 kVp) with filtered back projection (Group B). We compared the signal-to-noise ratio (SNR) of the aorta and liver and radiation dose between the two groups. Then, we evaluated the prevalence of extracardiac findings in Group A. RESULTS: Compared with Group B, Group A demonstrated significantly higher aorta and liver SNR and lower radiation dose. In Group A, whole-body CT revealed 229 coexisting lesions in 165 patients, including 32 and 106 cases of oncologic and vascular diseases, respectively. CONCLUSION: Additional whole-body CT after coronary CTA may provide adequate image quality. Using additional whole-body CT, 36% of patients with suspected CAD had clinically relevant coexisting findings, including malignancy.

Dual-Energy Computed Tomography for Evaluating Acute Brain Infarction of Middle Cerebral Artery Territories: Optimization of Voltage Settings in Virtual Monoenergetic Imaging.

OBJECTIVE: To evaluate the optimal virtual monochromatic energy in dual-energy computed tomography for differentiating between infarcted areas and normal brain parenchyma. METHODS: We enrolled 29 patients with middle cerebral artery acute brain infarction of who underwent examination by dual-energy computed tomography. We calculated the contrast-to-noise ratio (CNR) between white or gray matter and the infarcted area (CNR(W-I) and CNR(G-I), respectively) and normalized CNRs. From the normalized CNRs, we assessed which monochromatic energy gave the best balance between the infarcted area and normal brain parenchyma. The 70-keV images were used for comparison. RESULTS: The 99-keV images demonstrated the best balance between the infarction and normal brain parenchyma. In quantitative analysis, the 99-keV images were not inferior to the 70-keV images. (CNR(G-I), 1.92 ± 0.80 vs 2.00 ± 0.70, respectively [P = 0.16]; CNR(W-I), 0.52 ± 0.72 vs 0.40 ± 0.64, P < 0.01, respectively). CONCLUSIONS: Monochromatic 99-keV energy images may be optimal for evaluating middle cerebral artery acute brain infarction.

Laparoscopic omental filling with intraoperative endoscopy for a perforated duodenal ulcer.

As a surgical treatment for a perforated duodenal ulcer, duodenal omental filling is effective. However, filling the perforation site with a sufficient amount of omentum is difficult in some situations. We herein report that we successfully filled a perforated duodenal ulcer with a sufficient amount of omentum using intraoperative endoscopy. The operation was performed with three ports, the operation time was 110 min, and the estimated blood loss was small. The postoperative course was good. No stenosis of deformity of the duodenum was observed on follow-up endoscopy. Laparoscopic surgery has a shorter operation time, shorter postoperative hospital stay, and less postoperative pain than open surgery. The combined use of intraoperative endoscopy with laparoscopic surgery is effective for a large perforation, and it can be expected to reduce the rate of conversion to open surgery. This combined procedure is considered useful as a laparoscopic omental filling operation.

Brain computed tomography using iterative reconstruction to diagnose acute middle cerebral artery stroke: usefulness in combination of narrow window setting and thin slice reconstruction.

PURPOSE: The purpose of this study is to determine whether iterative model reconstruction (IMR) optimized for brain CT could improve the detection of acute stroke in the setting of thin image slices and narrow window settings. METHODS: We retrospectively reviewed 27 patients who presented acute middle cerebral artery (MCA) stroke. Images were reconstructed using filtered back projection (FBP; 1- and 5-mm slice thickness) and IMR (1 mm thickness), and contrast-to-noise ratios (CNRs) of infarcted and non-infarcted areas were compared. To analyze the performance of acute MCA stroke detection, we used receiver operating characteristic (ROC) curve techniques and compared 5-mm FBP with standard and narrow window settings, and 1-mm FBP and IMR with narrow window settings. RESULTS: The CNR in 1-mm IMR (1.1 ± 1.0) was significantly higher than in 5- (0.8 ± 0.7) and 1-mm FBP (0.4 ± 0.4) (p < 0.001). Furthermore, the average area under the ROC curve was significantly higher with 1-mm IMR with narrow window settings (0.90, 95% CI: 0.86, 0.94) than it was with 5-mm FBP (0.78, 95% CI: 0.72, 0.83). CONCLUSION: The combination of thin image slices and narrow window settings under IMR reconstruction provide better diagnostic performance for acute MCA stroke than conventional reconstruction methods.

Magnetic resonance cholangiopancreatography with GRASE sequence at 3.0T: does it improve image quality and acquisition time as compared with 3D TSE?

OBJECTIVES: The current study evaluated the clinical usefulness of the gradient and spin-echo (GRASE) sequence with single breath-hold in 3.0 T magnetic resonance cholangiopancreatography (MRCP). We compared the acquisition time and image quality between GRASE and breath navigator-triggered 3D turbo spin echo (3D TSE). METHODS: We examined 54 consecutive patients who underwent MRCP with GRASE and 3D TSE. We compared the image acquisition time and contrast-to-noise ratio (CNR) between the common bile duct (CBD) and liver. Overall image quality, blurring, motion artifacts and CBD visibility were scored on a 4-point scale by two radiologists. Paired t-tests were used to compare the variables. RESULTS: The mean image acquisition time was 95 % shorter with the GRASE than with 3D TSE (GRASE: 20 s; 3D TSE: 6 min 27 s). The CNR of GRASE was significantly higher than that of 3D TSE (GRASE: 25.4 ± 13.9 vs. 3D TSE: 18.2 ± 9.6, p < 0.01). All qualitative scores for GRASE were significantly better than those for 3D TSE. CONCLUSIONS: 3.0 T MRCP with GRASE sequence with single breath-hold significantly improved the CNR of CBD with a 95 % shorter acquisition time compared with conventional 3D MRCP with 3D TSE. KEY POINTS: • MRCP acquisition time was 95% shorter with GRASE than with 3D TSE. • Overall image quality of GRASE was significantly better than 3D TSE. • Pancreaticobiliary tree visibility with GRASE was better than that with 3D TSE.

Case of cecal volvulus successfully treated with endoscopic colopexy.

We herein report a case of cecal volvulus successfully treated with endoscopic colopexy. A 73-year-old man with a high fever and abdominal fullness was diagnosed with ileus caused by cecal volvulus. CT showed a dilated cecum and small intestine without bowel strangulation as well as acute pneumonia. Because the pneumonia increased the risk associated with general anesthesia, we attempted decompression of the bowel using endoscopy to avoid surgery. On day 1, a transanal ileus tube was inserted to the terminal ileum through the dilated cecum. On day 7, the bowel torsion spontaneously released. On day 8, we performed percutaneous endoscopic colopexy to fix the cecum on the abdominal wall and prevent re-twisting. The patient was discharged on day 15 without postoperative complications. Percutaneous endoscopic colopexy for cecal volvulus may be a treatment option when the risk associated with general anesthesia or surgery is high because of a comorbidity.

Iterative Reconstruction Designed for Brain CT: A Correlative Study With Filtered Back Projection for the Diagnosis of Acute Ischemic Stroke.

OBJECTIVES: The objective of this study is to evaluate the usefulness of iterative model reconstruction designed for brain computed tomography (CT) (IMR-Neuro) for the diagnosis of acute ischemic stroke. METHODS: This retrospective study included 20 patients with acute middle cerebral artery infarction who have undergone brain CT and 20 nonstroke patients (control). We reconstructed axial images with filtered back projection (FBP) and IMR-Neuro (slice thickness, 1 and 5 mm). We compared the CT number of the infarcted area, the image noise, contrast, and the contrast to noise ratio of the infarcted and the noninfarcted areas between the different reconstruction methods. We compared the performance of 10 radiologists in the detection of parenchymal hypoattenuation between 2 techniques using the receiver operating characteristic (ROC) techniques with the jackknife method. RESULTS: The image noise was significantly lower with IMR-Neuro [5 mm: 2.5 Hounsfield units (HU) ± 0.5, 1 mm: 3.9 HU ± 0.5] than with FBP (5 mm: 4.9 HU ± 0.5, 1 mm: 10.1 HU ± 1.4) (P < 0.01). The contrast to noise ratio was significantly greater with IMR-Neuro (5 mm: 2.6 ± 2.1, 1 mm: 1.6 ± 1.3) than with FBP (5 mm: 1.2 ± 1.0; 1 mm: 0.6 ± 0.5) (P < 0.01). The value of the average area under the receiver operating curve was significantly higher with IMR-Neuro than FBP (5 mm: 0.79 vs 0.74, P = 0.04; 1 mm: 0.76 vs 0.69, P = 0.04). CONCLUSIONS: Compared with FBP, IMR-Neuro improves the image quality and the performance for the detection of parenchymal hypoattenuation with acute ischemic stroke.

Diagnosis of small posterior fossa stroke on brain CT: effect of iterative reconstruction designed for brain CT on detection performance.

OBJECTIVES: In this study, we aimed to determine whether iterative model reconstruction designed for brain CT (IMR-neuro) would improve the accuracy of posterior fossa stroke diagnosis on brain CT. METHODS: We enrolled 37 patients with ischaemic stroke in the posterior fossa and 37 patients without stroke (controls). Using axial images reconstructed using filtered back-projection (FBP) and IMR-neuro, we compared the CT numbers in infarcted areas, image noise in the pons, and contrast-to-noise ratios (CNRs) of infarcted and non-infarcted areas on scans subjected to IMR-neuro and FBP. To analyse the performance of hypo-attenuation detection, we used receiver-operating characteristic (ROC) curve techniques. RESULTS: The image noise was significantly lower (2.2 ± 0.5 vs. 5.1 ± 0.9 Hounsfield units, p < 0.01) and the difference in CNR between the infarcted and non-infarcted areas was significantly higher with IMR-neuro than with FBP (2.2 ± 1.7 vs. 4.0 ± 3.6, p < 0.01). Furthermore, the average area under the ROC curve was significantly higher with IMR-neuro (0.90 vs. 0.86 for FBP, p = 0.04). CONCLUSION: IMR-neuro yielded better image quality and improved hypo-attenuation detection in patients with ischaemic stroke. KEY POINTS: • Iterative model reconstruction of brain CT data can facilitate the diagnosis of ischaemic stroke. • IMR improved the detectability of low-contrast lesions in the posterior fossa. • IMR-neuro yielded better image quality and improved observer performance.

Submillisievert Radiation Dose Coronary CT Angiography: Clinical Impact of the Knowledge-Based Iterative Model Reconstruction.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the noise and image quality of images reconstructed with a knowledge-based iterative model reconstruction (knowledge-based IMR) in ultra-low dose cardiac computed tomography (CT). MATERIALS AND METHODS: We performed submillisievert radiation dose coronary CT angiography on 43 patients. We also performed a phantom study to evaluate the influence of object size with the automatic exposure control phantom. We reconstructed clinical and phantom studies with filtered back projection (FBP), hybrid iterative reconstruction (hybrid IR), and knowledge-based IMR. We measured effective dose of patients and compared CT number, image noise, and contrast noise ratio in ascending aorta of each reconstruction technique. We compared the relationship between image noise and body mass index for the clinical study, and object size for phantom study. RESULTS: The mean effective dose was 0.98 ± 0.25 mSv. The image noise of knowledge-based IMR images was significantly lower than those of FBP and hybrid IR images (knowledge-based IMR: 19.4 ± 2.8; FBP: 126.7 ± 35.0; hybrid IR: 48.8 ± 12.8, respectively) (P < .01). The contrast noise ratio of knowledge-based IMR images was significantly higher than those of FBP and hybrid IR images (knowledge-based IMR: 29.1 ± 5.4; FBP: 4.6 ± 1.3; hybrid IR: 13.1 ± 3.5, respectively) (P < .01). There were moderate correlations between image noise and body mass index in FBP (r = 0.57, P < .01) and hybrid IR techniques (r = 0.42, P < .01); however, these correlations were weak in knowledge-based IMR (r = 0.27, P < .01). CONCLUSION: Compared to FBP and hybrid IR, the knowledge-based IMR offers significant noise reduction and improvement in image quality in submillisievert radiation dose cardiac CT.

Efficacy of the projection onto convex sets (POCS) algorithm at Gd-EOB-DTPA-enhanced hepatobiliary-phase hepatic MRI.

PURPOSE: To investigate the efficacy of the projection onto convex sets (POCS) algorithm at Gd-EOB-DTPA-enhanced hepatobiliary-phase MRI. METHODS: In phantom study, we scanned a phantom and obtained images by conventional means (P1 images), by partial-Fourier image reconstruction (PF, P2 images) and by PF with the POCS algorithm (P3 images). Then we acquired and compared subtraction images (P2-P1 images and P3-P1 images). In clinical study, 55 consecutive patients underwent Gd-EOB-DTPA (EOB)-enhanced 3D hepatobiliary-phase MRI on a 1.5T scanner. Images were obtained using conventional method (C1 images), PF (C2 images), and PF with POCS (C3 images). The acquisition time was 17-, 14-, and 14 s for protocols C1, C2 and C3, respectively. Two radiologists assigned grades for hepatic vessel sharpness and we compared the visual grading among the 3 protocols. And one radiologist compared signal-to-noise-ratio (SNR) of the hepatic parenchyma. RESULTS: In phantom study, there was no difference in signal intensity on a peripheral phantom column on P3-P1 images. In clinical study, there was no significant difference between C1 and C3 images (2.62 ± 0.49 vs. 2.58 ± 0.49, p = 0.70) in the score assigned for vessel sharpness nor in SNR (13.3 ± 2.67 vs. 13.1 ± 2.51, p = 0.18). CONCLUSION: The POCS algorithm makes it possible to reduce the scan time of hepatobiliary phase (from 17 to 14 s) without reducing SNR and without increasing artifacts.

Usefulness of 3D hybrid profile order technique with 3T magnetic resonance cholangiography: Comparison of image quality and acquisition time.

PURPOSE: To evaluate the image quality and acquisition time of magnetic resonance cholangiopancreatography (MRCP) with and without the 3D hybrid profile order technique. MATERIALS AND METHODS: We studied 32 consecutive patients at 3T. They underwent MRCP with and without the 3D hybrid profile order imaging technique during free breathing and MRCP with the 3D hybrid profile order technique during a single breath-hold. The image acquisition time was 82% shorter with the 3D hybrid profile order technique than without it. The contrast, signal-to-noise-ratio (SNR), and contrast-noise-ratio (CNR) between the common bile duct (CBD) and periductal tissues on 3D-MRCP were evaluated quantitatively. RESULTS: The contrast, SNR, and CNR of the CBD under free breathing was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). The contrast, SNR, and CNR of the CBD under a single breath-hold was significantly higher with the 3D hybrid profile order technique than without it (P < 0.01). There were no significant differences in the contrast, SNR, and CNR of the CBD between the 3D hybrid profile order with a single breath-hold and with free breathing (P = 0.12, 0.28, 0.28, respectively). CONCLUSION: Using 3T MRI for MRCP with the 3D hybrid profile order sequence yielded significantly improved contrast and CNR with a shorter image acquisition time without sacrificing image quality when compared to imaging without the 3D hybrid profile order sequence. J. Magn. Reson. Imaging 2016;44:1346-1353.

Low-Contrast and Low-Radiation Dose Protocol in Cardiac Computed Tomography: Usefulness of Low Tube Voltage and Knowledge-Based Iterative Model Reconstruction Algorithm.

OBJECTIVE: This study aimed to evaluate the feasibility of a low contrast, low-radiation dose protocol of 80-peak kilovoltage (kVp) with prospective electrocardiography-gated cardiac computed tomography (CT) using knowledge-based iterative model reconstruction (IMR). METHODS: Thirty patients underwent an 80-kVp prospective electrocardiography-gated cardiac CT with low-contrast agent (222-mg iodine per kilogram of body weight) dose. We also enrolled 30 consecutive patients who were scanned with a 120-kVp cardiac CT with filtered back projection using the standard contrast agent dose (370-mg iodine per kilogram of body weight) as a historical control group. We evaluated the radiation dose for the 2 groups. The 80-kVp images were reconstructed with filtered back projection (protocol A), hybrid iterative reconstruction (HIR, protocol B), and IMR (protocol C). We compared CT numbers, image noise, and contrast-to-noise ratio among 120-kVp protocol, protocol A, protocol B, and protocol C. In addition, we compared the noise reduction rate between HIR and IMR. Two independent readers compared image contrast, image noise, image sharpness, unfamiliar image texture, and overall image quality among the 4 protocols. RESULTS: The estimated effective dose (ED) of the 80-kVp protocol was 74% lower than that of the 120-kVp protocol (1.4 vs 5.4 mSv). The contrast-to-noise ratio of protocol C was significantly higher than that of protocol A. The noise reduction rate of IMR was significantly higher than that of HIR (P < 0.01). There was no significant difference in almost all qualitative image quality between 120-kVp protocol and protocol C except for image contrast. CONCLUSIONS: A 80-kVp protocol with IMR yields higher image quality with 74% decreased radiation dose and 40% decreased contrast agent dose as compared with a 120-kVp protocol, while decreasing more image noise compared with the 80-kVp protocol with HIR.

Impact of Knowledge-Based Iterative Model Reconstruction in Abdominal Dynamic CT With Low Tube Voltage and Low Contrast Dose.

OBJECTIVE: The purpose of this study was to compare iterative model reconstruction (IMR) and hybrid iterative reconstruction (HIR) of 80-kVp abdominal dynamic CT scans obtained with a low-dose contrast agent. SUBJECTS AND METHODS: A group of 27 consecutively registered patients underwent abdominal dynamic CT with an 80-kVp protocol and a low dose of contrast agent (300 mg I/kg). Another 27 patients who had previously undergone a 120-kVp protocol with filtered back projection (FBP) and a standard contrast dose (600 mg I/kg) acted as control subjects. Effective dose, image noise, CT number, and contrast-to-noise ratio were compared between the 120-kVp and 80-kVp images with FBP, HIR, and IMR. Image contrast, image noise, image sharpness, noise texture, and overall image quality were evaluated for the four protocols. RESULTS: The effective dose of the 80-kVp protocol was lower than that with the 120-kVp protocol. The 80-kVp protocol with HIR and IMR decreased image noise by 45% and 70% compared with the 80-kVp protocol with FBP. The contrast-to-noise ratio of the 80-kVp protocol with IMR was higher than that of the 120-kVp protocol. Qualitatively, the 80-kVp protocol with IMR improved image noise more than the 120-kVp protocol did, but noise texture was worse. HIR and the 120-kVp protocol yielded similar subjective image quality. CONCLUSION: Use of the 80-kVp protocol with HIR allowed an approximately 50% reduction in contrast dose and an approximately 40% reduction in radiation dose compared with use of the 120-kVp protocol while preserving image quality. IMR reduced image noise more than HIR with this protocol but worsened noise texture.

Comparison of iterative model, hybrid iterative, and filtered back projection reconstruction techniques in low-dose brain CT: impact of thin-slice imaging.

INTRODUCTION: The purpose of this study was to evaluate the utility of iterative model reconstruction (IMR) in brain CT especially with thin-slice images. METHODS: This prospective study received institutional review board approval, and prior informed consent to participate was obtained from all patients. We enrolled 34 patients who underwent brain CT and reconstructed axial images with filtered back projection (FBP), hybrid iterative reconstruction (HIR) and IMR with 1 and 5 mm slice thicknesses. The CT number, image noise, contrast, and contrast noise ratio (CNR) between the thalamus and internal capsule, and the rate of increase of image noise in 1 and 5 mm thickness images between the reconstruction methods, were assessed. Two independent radiologists assessed image contrast, image noise, image sharpness, and overall image quality on a 4-point scale. RESULTS: The CNRs in 1 and 5 mm slice thickness were significantly higher with IMR (1.2 ± 0.6 and 2.2 ± 0.8, respectively) than with FBP (0.4 ± 0.3 and 1.0 ± 0.4, respectively) and HIR (0.5 ± 0.3 and 1.2 ± 0.4, respectively) (p < 0.01). The mean rate of increasing noise from 5 to 1 mm thickness images was significantly lower with IMR (1.7 ± 0.3) than with FBP (2.3 ± 0.3) and HIR (2.3 ± 0.4) (p < 0.01). There were no significant differences in qualitative analysis of unfamiliar image texture between the reconstruction techniques. CONCLUSION: IMR offers significant noise reduction and higher contrast and CNR in brain CT, especially for thin-slice images, when compared to FBP and HIR.

Effects of a high-pitch protocol and a hybrid iterative reconstruction algorithm on image quality of cerebral subtracted 3D CT angiography.

PURPOSE: To evaluate the image quality and the radiation dose of 3D-computed tomography angiography (3D-CTA) with a high-pitch protocol and a hybrid iterative reconstruction (HIR). MATERIALS AND METHODS: This was a prospective study and thirty patients were scanned at a 0.51-helical pitch with filtered back-projection (FBP, protocol-A), and 30 patients were scanned at a 0.91-helical pitch with FBP and HIR (protocol-B and C). The mean volume CT dose index (CTDI(vol)), image noise, and mean cerebral arterial and venous attenuation were compared between the three protocols. Two readers assessed image noise, arterial contrast and venous overlap. RESULTS: The mean CTDI(vol) of protocol-B/C (38.9 mGy) was lower than that of protocol-A (49.7 mGy). Mean image noise of protocol-B [12.6 ± 1.3 Hounsfield units (HU)] was higher than that of protocol-A (10.3 ± 1.2 HU). There was no significant difference in arterial attenuation between protocol-A (327.5 ± 57.5 HU) and C (327.7 ± 59.4 HU). Venous attenuation of protocol-C (148.5 ± 50.4 HU) was lower than that of protocol-A (185.9 ± 50.6 HU). In qualitative analysis, the image noise of protocol-B was higher than that of protocol-A/C. Venous enhancement of protocol-B/C was more inconspicuous than that of protocol-A. CONCLUSIONS: 3D-CTA with a high-pitch protocol and HIR can reduce radiation dose while decreasing venous enhancement and image noise to an adequate level for diagnosis.