Shushi Yoshikawa

Feasibility of low-volume injections of contrast material with a body weight-adapted iodine-dose protocol in 320-detector row coronary CT angiography.

RATIONALE AND OBJECTIVES To investigate the feasibility of low-volume injections of contrast material with a body weight-adapted iodine-dose protocol in computed tomography coronary angiography (CTCA) using a 320-detector row scanner. MATERIALS AND METHODS Ninety-eight patients who underwent CTCA in a single heartbeat with electrocardiogram-gating were divided into two groups, receiving 0.8 mL/kg of contrast material injected at a fixed duration of 12 seconds (A; n = 48) or 0.7 mL/kg of contrast material injected at a fixed duration of 10 seconds (B; n = 50); all patients then received 20 mL of saline. Contrast densities were assessed for the ascending aorta, left ventricle, right coronary artery (RCA), and left main coronary artery (LMA). RESULTS The mean flow rate was 4.00 + or - 0.56 mL/second in group A and 4.06 + or - 0.57 mL/second in group B (P = .51). There were no significant differences in the mean enhancement values of the ascending aorta, LMA and proximal RCA between the two groups. Also, there was no significant difference between the mean enhancement values at the three different levels of the RCA (proximal, middle, and distal segments) (group A; P = .27, group B; P = .07). CONCLUSION The use of 0.7 mL/kg of contrast material injected at a fixed duration of 10 seconds was feasible for CTCA using 320-detector row CT, with a sufficient and reliable contrast enhancement in the ascending aorta and coronary artery.

Preoperative Evaluation of Local Invasion and Metastatic Lymph Nodes of Colorectal Cancer and Mesenteric Vascular Variations Using Multidetector-Row Computed Tomography Before Laparoscopic Surgery

Objective: To evaluate local invasion and lymph nodes metastasis of colorectal cancer and mesenteric vascular variations using multidetector-row computed tomography (MDCT) before laparoscopic colorectal surgery. Methods: Fifty-one patients with colorectal cancer underwent MDCT. The evaluation items were as follows: (1) local invasion; (2) detected lymph nodes evaluated by short-axis diameter, long-axis diameter, short/long axis diameter ratio, and computed tomography (CT) attenuation; and (3) visualization of mesenteric artery and vein by 3-dimensional-CT angiography. Results: First, in the evaluation of local invasion, overall accuracy was 94.1%. Second, the point of 0.8 or greater in short/long-axis diameter ratio was best index for the diagnosis of metastatic lymph nodes. Using this index, the accuracy of the diagnosis per node was 80.5%. Third, 3-dimensional-CT angiography correctly demonstrated variations of the mesenteric artery and vein. Conclusions: The MDCT was effective for evaluation of local invasion and lymph nodes metastasis of colorectal cancer and mesenteric vascular variations before laparoscopic surgery.

Impact of adaptive iterative dose reduction (AIDR) 3D on low-dose abdominal CT: comparison with routine-dose CT using filtered back projection

Background While CT is widely used in medical practice, a substantial source of radiation exposure is associated with an increased lifetime risk of cancer. Therefore, concerns to dose reduction in CT examinations are increasing and an iterative reconstruction algorithm, which allow for dose reduction by compensating image noise in the image reconstruction, has been developed. Purpose To investigate the performance of low-dose abdominal CT using adaptive iterative dose reduction 3D (AIDR 3D) compared to routine-dose CT using filtered back projection (FBP). Material and Methods Fifty-eight patients underwent both routine-dose CT scans using FBP and low-dose CT scans using AIDR 3D in the abdomen. The image noise levels, signal-to-noise ratios (SNRs), and contrast-to-noise ratios (CNRs) of the aorta, portal vein, liver, and pancreas were measured and compared in both scans. Visual evaluations were performed. The volume CT dose index (CTDIvol) was measured. Results Image noise levels on low-dose CT images using AIDR 3D were significantly lower than, or not significantly different from, routine-dose CT images using FBP in reviewing the data on the basis of all patients and the three BMI groups. SNRs and CNRs on low-dose CT images using AIDR 3D were significantly higher than, or not significantly different from, routine-dose CT images using FBP in reviewing the data on the basis of all patients and the three BMI groups. In visual evaluation of the images, there were no statistically significant differences between the scans in all organs independently of BMI. The average CTDIvol at routine-dose and low dose CT was 21.4 and 10.8 mGy, respectively. Conclusion Low-dose abdominal CT using AIDR 3D allows for approximately 50% reduction in radiation dose without a degradation of image quality compared to routine-dose CT using FBP independently of BMI.

Virtual CT colectomy by three-dimensional imaging using multidetector-row CT for laparoscopic colorectal surgery

Laparoscopic colorectal surgery has been attracting attention for its capacity to improve the quality of life (QOL) of patients. However, there are disadvantages to this approach, namely, it is difficult to obtain an image of the entire view of the operative field, and organs and lesions cannot be manipulated directly by the surgeon during surgery. For this reason, it takes a relatively large amount of time to ligate vessel, which can vary between patients. Furthermore, vessels and organs can be damaged during lymph nodes dissection under laparoscopic guidance, leading to heavy bleeding that prevents the surgeon from having access to a good view of the operative field. Then, to assess preoperatively the vascular anatomy, we carried out multiphase, contrast-enhanced examinations using multidetector-row CT (MDCT) on patients with colorectal cancer, and prepared the fused image of 3D images of arteries, veins, the colorectum, organs, and tumor. We called the utilization of 3D imaging virtual CT colectomy, which contributed to rapid and safe manipulation of the origins of the arteries and the veins, as well as lymph nodes dissection, without incurring injury to the involved arteries and veins.

Hepatic Computed Tomography for Simultaneous Depiction of Hepatocellular Carcinoma, Intrahepatic Portal Veins, and Hepatic Veins in Real-time Virtual Sonography Initial Experience

The aim of this study was to examine a double‐step injection of contrast material in hepatic computed tomography (CT) for the simultaneous depiction of hepatocellular carcinoma (HCC), intrahepatic portal veins, and hepatic veins in real‐time virtual sonography.

Effect of Saline Pushing after Contrast Material Injection in Abdominal Multidetector Computed Tomography with the Use of Different Iodine Concentrations

Purpose: To investigate whether saline pushing after contrast material improves hepatic vascular and parenchymal enhancement, and to determine whether this technique permits decreased contrast material concentration. Material and Methods: 120 patients who underwent hepatic multidetector computed tomography were divided randomly into four groups (Groups A–D): receiving 100 ml of contrast material (300 mgI/ml) only (A) or with 50 ml of saline solution (B); or 100 ml of contrast material (350 mgI/ml) only (C) or with 50 ml of saline solution (D). Computed tomography (CT) values of the aorta in the arterial phase, the portal vein in the portal venous inflow phase, and the liver in the hepatic phase were measured. Visualization of the hepatic artery and the portal vein by 3D CT angiography was evaluated as well. Results: Although the enhancement values of the aorta were not improved significantly with saline pushing, they continued at a high level to the latter slices with saline pushing. The enhancement value of the portal vein increased significantly and CT portography was improved with saline pushing. The enhancement value of the liver was not improved significantly using saline pushing. In a comparison between groups B and C, the enhancement values of the aorta and portal vein and the visualization of CT arteriography and portography were not statistically different. Conclusion: The saline pushing technique can contribute to a decrease in contrast material concentration for 3D CT arteriography and portography.

Virtual CT gastrectomy by three-dimensional imaging using multidetector-row CT for laparoscopic gastrectomy

Key words: Virtual computed tomographic gastrec-tomy—Multidetector row computed tomogra-phy—Three-dimensional imaging—Multiphase fusionimaging—LaparoscopicgastrectomyLaparoscopicsurgeryhasgainedwideclinicalacceptancein various surgical practices and has become the goldstandard for cholecystectomy, Nissen fundoplication,and adrenal surgery. In 1994, the first laparoscopicallyassisted Billroth I gastrectomy was reported, and cur-rently a laparoscopic distal gastrectomy is commonlyperformedforearlystagegastriccancer[1].Thebenefitsof the laparoscopic approach include smaller surgicalincisions, less intraoperative blood loss, faster recoveryfor normal bowel function, and shorter hospital staysthaninthecaseofconventionalopensurgery[1–4].However, despite the advantages of this procedure,thereremainseveraldisadvantages:limitedimagesoftheentire operative field under laparoscopy and a lack oftactilesensationinterferewithdirectmanipulationbythesurgeonduringtheprocedure.Forthisreason,ittakesalongtimetoidentifythepropervesselswheretheremaybe major variations in each patient [2]. Moreover,arteriesrunalongoracrossveinsaroundthestomachina complicated fashion; therefore, veins can be injuredduring the dissection of lymph nodes along the arteriesandtheligationofarteriesunderlaparoscopicguidance,whichleadstoheavybleedingthatpreventsthesurgeonfromhavingaccesstoagoodviewoftheoperativefield[3].Therefore,itisquiteimportanttoperformapreop-erative assessment of vascular anatomy around thestomach using three-dimensional (3D) computed tomo-graphic(CT)angiography,whichcanbeveryhelpfultoachieve the safe and rapid ligation of vessels and dis-sectionoflymphnodes[5–9].We performed contrast-enhanced examinations atarterial and venous phase using 4 or 16 multidetector-rowCT(MDCT)beforealaparoscopicgastrectomyandslicedatafromtheindividualphaseswereconvertedintoa 3D imaging format using a volume-rendering tech-nique.Weusedthefusedimageof3Dimagesofarteriesand veins around the stomach for preoperative assess-ment and called the use of 3D imaging virtual CT gas-trectomy[5–9].In this study, we examined the usefulness of virtualCT gastrectomy for laparoscopic gastrectomy and,moreover, introduced our preliminary study of the vir-tualCTnavigationofsentinellymphnodes.

Reduction of interpatient variability of arterial enhancement using a new bolus tracking system in 320-detector computed tomographic coronary angiography.

Objective To investigate the effect of a new bolus tracking system on interpatient variability of aortic and coronary enhancement compared with the conventional system in 320-detector computed tomographic (CT) coronary angiography (CTCA). Methods Sixty-four patients who underwent CTCA were assigned to 1 of 2 protocols. In group A (n = 32), 7 seconds after triggering (150-Hounsfield unit [HU] threshold) in the ascending aorta, a CT scan was performed. In group B (n = 32), 2 thresholds were set in the ascending aorta. After the first triggering (100 HU threshold), the patient was instructed to take a breath and hold it. Approximately 3 seconds after the second triggering (300 HU threshold), a CT scan was started automatically. Results There were no significant differences in the mean CT attenuation for the ascending aorta between the 2 groups (P = 0.61), whereas the standard deviation of the CT attenuation in group B was significantly smaller than that in group A (P = 0.02). Conclusions The use of a 2-threshold setting in the new bolus tracking technique could reduce interpatient variability more than a protocol using a single threshold in CTCA.

Body size-adapted dose of contrast material and scanning protocol in 320-detector row CT coronary angiography.

Objective: Because an increase in patient body size produces lower vessel attenuation and higher image noise in computed tomography coronary angiography (CTCA), a protocol in which the dose of contrast material was adapted to the body weight, and tube voltage and current were adapted to the body mass index (BMI) was evaluated. Methods: A total of 136 patients who underwent CTCA were assigned to 1 of 2 protocols; the patients received 40 mL of contrast material (A; n = 52), or 0.7 mL/kg of contrast material (B; n = 84). Tube voltage and current were adapted to the BMI. Results: In group A, there was no significant correlation between BMI and image noise (r = −0.21, P = 0.15). However, BMI correlated inversely with contrast-to-noise ratio (CNR; right coronary artery, r = −0.29, P < 0.05; left main coronary artery, r = −0.33, P < 0.05) and image quality score (r = −0.55, P < 0.001). In group B, there was no significant correlation between BMI and image noise (r = −0.14, P = 0.21), CNR (right coronary artery: r = −0.09, P = 0.45; left main coronary artery: r = −0.07, P = 0.55), and image quality score (r = 0.03, P = 0.79). Conclusions: Use of a body size-adapted dose of contrast material and scanning protocol results in similar CNR and image quality independent of individual BMI.

Diagnostic performance of reduced-dose CT with a hybrid iterative reconstruction algorithm for the detection of hypervascular liver lesions: a phantom study

AbstractObjectivesTo investigate the diagnostic performance of reduced-dose CT with a hybrid iterative reconstruction (IR) algorithm for the detection of hypervascular liver lesions.MethodsThirty liver phantoms with or without simulated hypervascular lesions were scanned with a 320-slice CT scanner with control-dose (40 mAs) and reduced-dose (30 and 20 mAs) settings. Control-dose images were reconstructed with filtered back projection (FBP), and reduced-dose images were reconstructed with FBP and a hybrid IR algorithm. Objective image noise and the lesion to liver contrast-to-noise ratio (CNR) were evaluated quantitatively. Images were interpreted independently by 2 blinded radiologists, and jackknife alternative free-response receiver-operating characteristic (JAFROC) analysis was performed.ResultsHybrid IR images with reduced-dose settings (both 30 and 20 mAs) yielded significantly lower objective image noise and higher CNR than control-dose FBP images (P < .05). However, hybrid IR images with reduced-dose settings had lower JAFROC1 figure of merit than control-dose FBP images, although only the difference between 20 mAs images and control-dose FBP images was significant for both readers (P < .01).ConclusionsAn aggressive reduction of the radiation dose would impair the detectability of hypervascular liver lesions, although objective image noise and CNR would be preserved by a hybrid IR algorithm.Key points• A half-dose scan with a hybrid iterative reconstruction preserves objective image quality. • A hybrid iterative reconstruction algorithm does not improve diagnostic performance. • An aggressive dose reduction would impair the detectability of low-contrast lesions.