Hepatocellular carcinoma in patients weighing 70 kg or less: initial trial of compact-bolus dynamic CT with low-dose contrast material at 80 kVp.

OBJECTIVE: The purpose of this study was to compare the diagnostic capability of hepatic dynamic CT with low-dose contrast material (420 mg I/kg body weight) at 80 kVp with that of the same modality performed with standard-dose contrast material at 120 kVp. SUBJECTS AND METHODS: We randomly assigned 111 patients (50 women, 61 men; mean age, 69.1 years) with known or suspected hepatocellular carcinoma and a body weight of 70 kg or less to one of two protocols. In the 80-kVp protocol, the contrast material (444 mg I/kg body weight) was delivered over 15 seconds at a tube voltage of 80 kVp. In the 120-kVp protocol, a contrast dose of 600 mg I/kg was delivered over 30 seconds at 120 kVp. Of the 111 patients, 38 had hypervascular hepatocellular carcinoma. Using the Mann-Whitney U test, we compared the two protocols for the contrast-to-noise ratio of the tumors (difference between tumor attenuation and liver attenuation divided by noise in the liver) and the figure of merit (square of contrast-to-noise ratio divided by effective dose) of the tumors during the arterial phase of imaging. Effective doses also were compared. RESULTS: The contrast-to-noise ratio of the tumors was significantly higher with the 80-kVp than with the 120-kVp protocol (median, 5.3 vs 4.2; p = 0.04). The figure of merit also was significantly higher with the 80-kVp than with the 120-kVp protocol (10.2 vs 5.3, p = 0.02). The effective dose was significantly lower with the 80-kVp than with the 120-kVp protocol (2.97 vs 3.41 mSv, p < 0.01). CONCLUSION: With 80-kVp acquisition, the contrast-to-noise ratio and figure of merit of tumors during the arterial phase improved despite the lower contrast dose and radiation exposure.

Combination of a low-tube-voltage technique with hybrid iterative reconstruction (iDose) algorithm at coronary computed tomographic angiography.

We compare the performance of low tube voltage with the hybrid iterative reconstruction (iDose) with standard and low tube voltage with the filtered backprojection (FBP) using phantoms at computed tomographic coronary angiography. In computed tomographic coronary angiography, application of the combined low tube voltage with iDose resulted in significant image quality improvements compared to the low tube voltage with FBP. Image quality was the same or better despite a reduction in the radiation dose by 76% compared with standard tube voltage with FBP.

A low-kilovolt (peak) high-tube current technique improves venous enhancement and reduces the radiation dose at indirect multidetector-row CT venography: initial experience.

OBJECTIVE: The purpose was to evaluate the image noise, contrast-to-noise ratio, and radiation dose at indirect multidetector-row computed tomographic venography (CTV) using a low-kilovolt (peak) (kV[p]) high-tube current technique. MATERIALS AND METHODS: Thirty patients underwent indirect CTV of the lower extremity at 120 kV(p) with 170 mA and at 80 kV(p) with 426 mA (CT dose index volumes 11.8 and 9.0 mGy, respectively) on a 64-detector CT scanner. We assessed CT numbers, image noise, and contrast-to-noise ratio of deep (femoral and popliteal) veins. RESULTS: The mean (SD) CT numbers of the femoral and popliteal veins were significantly greater at 80 kV(p) than at 120 kV(p) (142.8 [24.5] and 147.0 [19.4] Hounsfield units [HU], respectively, vs 93.1 [15.5] and 105.0 [14.9] HU, respectively; P < 0.01). The mean (SD) image noise was significantly higher at 80 kV(p) than at 120 kV(p) (11.6 [2.6] and 7.4 [1.4] HU, respectively, vs 8.9 [1.6] and 6.2 [1.5] HU, respectively; P < 0.01). Contrast-to-noise ratios at the femoral and popliteal veins were significantly higher at 80 kV(p) than at 120 kV(p) (6.0 [2.2] and 9.7 [2.4], respectively vs 3.3 [1.8] and 6.9 [2.5], respectively; P < 0.01). CONCLUSION: At indirect CTV, 80 kV(p) and a high tube current setting yielded significantly improved image quality at a reduced radiation dose compared with 120 kV(p).

Baseline incidence and severity of renal insufficiency evaluated by estimated glomerular filtration rates in patients scheduled for contrast-enhanced CT.

BACKGROUND: Although pre-existing renal insufficiency (RI) is the most important risk factor for contrast-induced nephropathy (CIN), the background distribution of baseline renal function has not been investigated thoroughly in patients scheduled for contrast-enhanced CT. PURPOSE: To investigate the incidence and severity of baseline RI evaluated by estimated glomerular filtration rates (eGFR) in patients who underwent contrast-enhanced CT at an academic center. MATERIAL AND METHODS: A total of 6586 patients (3630 men and 2956 women; mean age 57.0 ± 11.9 years) who underwent contrast-enhanced CT between January and December 2008 were retrospectively studied. Of these, 829 had cardiovascular diseases (CVD), 5116 had oncologic diseases, 178 had diabetes mellitus (DM), and 1572 had chronic liver disease (CLD). The eGFR (mL/min/1.73 m(2)) was calculated from their serum creatinine level. Mild, moderate-a, moderate-b, and severe RI were recorded at 60 < =eGFR < 90, 45 < =eGFR < 60, 30 < =eGFR < 45 and eGFR < 30, respectively. RESULTS: Of the 6586 patients, 1.6%, 3.7%, 13.7%, and 54.2% were judged to present with severe, moderate-b, moderate-a, and mild RI, respectively. While moderate-b-to-severe RI was recorded in 133 (3.2%) of 4161 patients aged 70 years or less, it was observed in 218 (9.0%) of the 2425 patients who were 71 years or older. Among the 829 CVD patients, 9.9% manifested moderate-b-to-severe- and 73.0% mild-to-moderate-a RI. The corresponding rates were 4.4% and 68.9% for oncologic disease, 16.9% and 61.2% for DM, and 4.8% and 71.5% for CLD patients. By univariate analysis, there was a significant association between moderate-b-to-severe RI and the advanced age, CVD, DM, and non-oncologic disease. Multivariate analysis showed that the advanced age, DM, and non-oncologic disease were statistically associated with moderate-b-to-severe RI. CONCLUSION: The incidence of RI of eGFR < 45mL/min/1.73 m(2) at baseline was high in patients with advanced age, CVD and DM and in patients without oncologic disease.

Comparison of standard- and low-tube voltage MDCT angiography in patients with peripheral arterial disease.

OBJECTIVE: We investigated the effect of low-tube-voltage CT angiography with a reduced volume of contrast agent on qualitative and quantitative parameters and the radiation dose in patients with peripheral arterial disease. METHODS: Eighty consecutive patients were divided into two groups; the protocol was 120 kVp and 1.8 ml/kg contrast agent (300 mgI/ml) in one group and 80 kVp and 1.2 ml/kg in the other. For quantitative analysis we calculated the mean arterial attenuation, the mean difference between maximum and minimum attenuation values, contrast-to-noise ratio (CNR), and figure of merit (FOM). For qualitative evaluation, we used visual scores. RESULTS: There were no significant intergroup differences in mean arterial attenuation (120 vs. 80 kVp: 331.6 ± 61.6 vs. 354.9 ± 61.9 HU) and in the mean difference between maximum and minimum attenuation (120 vs. 80 kVp: 52.2 ± 25.5 vs. 61.5 ± 27.5 HU). While the mean CNR was significantly higher at 120 than 80 kVp (38.4 ± 18.8 vs. 31.1 ± 15.3), the mean FOM was not significantly different (120 vs. 80 kVp: 1.3 ± 1.5 vs. 1.2 ± 1.2), and there was no significant intergroup difference in visual scores. The mean dose-length product was significantly lower at 80 than 120 kVp (1,024.3 ± 151.3 vs. 1,464.7 ± 208.7 mGy·cm). CONCLUSION: The 80-kVp protocol allows for reduction of the radiation dose by approximately 30% and the volume of contrast agent by more than 30% without deterioration of vascular enhancement and image quality.

Computer-aided volumetry of pulmonary nodules exhibiting ground-glass opacity at MDCT.

OBJECTIVE: The purpose of this study was to investigate the accuracy and reproducibility of results acquired with computer-aided volumetry software during MDCT of pulmonary nodules exhibiting ground-glass opacity. MATERIALS AND METHODS: To evaluate the accuracy of computer-aided volumetry software, we performed thin-section helical CT of a chest phantom that included simulated 3-, 5-, 8-, 10-, and 12-mm-diameter ground-glass opacity nodules with attenuation of -800, -630, and -450 HU. Three radiologists measured the volume of the nodules and calculated the relative volume measurement error, which was defined as follows: (measured nodule volume minus assumed nodule volume / assumed nodule volume) x 100. Two radiologists performed two independent measurements of 59 nodules in humans. Intraobserver and interobserver agreement was evaluated with Bland-Altman methods. RESULTS: The relative volume measurement error for simulated ground-glass opacity nodules measuring 3 mm ranged from 51.1% to 85.2% and for nodules measuring 5 mm or more in diameter ranged from -4.1% to 7.1%. In the clinical study, for intraobserver agreement, the 95% limits of agreement were -14.9% and -13.7% and -16.6% to 15.7% for observers A and B. For interobserver agreement, these values were -16.3% to 23.7% for nodules 8 mm in diameter or larger. CONCLUSION: With computer-aided volumetry of ground-glass opacity nodules, the relative volume measurement error was small for nodules 5 mm in diameter or larger. Intraobserver and interobserver agreement was relatively high for nodules 8 mm in diameter or larger.

Contrast material injection protocol with the dose adjusted to the body surface area for MDCT aortography.

OBJECTIVE: The objective of our study was to investigate the effect on aortic enhancement of contrast material volumes adjusted for a patient's body surface area (BSA) at CT angiography (CTA). SUBJECTS AND METHODS: A 64-MDCT scanner was used to perform CTA of the whole aorta in 89 patients (mean age, 68.7 years) with confirmed or suspected aortoiliac disease. The patients were divided into groups: a body weight (BW) group (n = 45) and a BSA (n = 44) group. The contrast dose was 360 mg I/kg BW in the BW group and 12,753 mg I/m(2) BSA in the BSA group. Because the average BW of Japanese adults is approximately 60 kg, the contrast dose in the two protocols was identical in patients weighing 60 kg. We compared aortic enhancement achieved with the two protocols using the two-tailed Student's t test, and we used the generalized linear model to analyze the effect of patient age, sex, and BW on aortic enhancement in each protocol group. RESULTS: The mean aortic enhancement in the BW and BSA groups was 324.2 and 311.7 HU, respectively; the difference was not significant (p = 0.26). In the BW group, BW had a statistically significant effect on aortic enhancement (p < 0.01), whereas neither patient age nor sex did (p = 0.08 and 0.07, respectively). In the BSA group, the age, sex, BW, and BW by sex had no statistically significant effect on aortic enhancement (p = 0.33, 023, 0.10, and 0.16, respectively). CONCLUSION: Under the BSA protocol, aortic enhancement tended to be consistent and adequate regardless of patient BW.

Role of diffusion-weighted imaging in the diagnosis of gynecological diseases.

Recent technical advances in diffusion-weighted imaging (DWI) greatly enhanced the clinical value of magnetic resonance imaging (MRI) of the body. DWI can provide excellent tissue contrast based on molecular diffusion and may be able to demonstrate malignant tumors. Quantitative measurement of the apparent diffusion coefficient (ADC) may be valuable in distinguishing between malignant and benign lesions. We reviewed DWI and conventional MRI of the female pelvis to study the utility of DWI in patients with gynecological diseases. Although the ADC can help to differentiate between normal and cancerous tissue in the uterine cervix and endometrium, its utility may be limited by the large overlap of the uterine myometrium and ovaries. On the other hand, the ADC may be useful for monitoring the therapeutic outcome after uterine arterial embolizati (UAE), chemotherapy and/or radiation therapy. In patients with ovarian cancer, DWI demonstrates high intensity not only at the primary cancer site but also in disseminated peritoneal implants. When added to conventional MRI findings, DWI and ADC values provide additional information and DWI may play an important role in the diagnosis of patients with gynecological diseases.

Combined use of T2-weighted and diffusion-weighted 3-T MR imaging for differentiating uterine sarcomas from benign leiomyomas.

The objective of our study was to compare diffusion-weighted imaging (DWI) alone and DWI combined with T2-weighted MRI for the differentiation of uterine sarcomas from benign leiomyomas. T2-weighted imaging and DWI were performed in 103 patients with 103 myometrial tumours, including 8 uterine sarcomas and 95 benign leiomyomas on 3-T MR imaging. The signal intensity (SI) of the tumour on T2-weighted images was quantified as the tumour-myometrium contrast ratio (TCR) by using the following formula: (SI(tumour)-SI(myometrium))/SI(myometrium). The TCR or apparent diffusion coefficient (ADC) value alone and then the ADC value combined with T2-weighted imaging were evaluated for differentiation between sarcomas and leiomyomas. The mean ADC value of sarcomas was 0.86 +/- 0.11 x 10(-3) m(2)/s, which was significantly lower than that of leiomyomas 1.18 +/- 0.24 x 10(-3) m(2)/s; however, there was a substantial overlap. The mean TCR of sarcomas was 0.66 +/- 0.71, which was significantly higher than that of the leiomyomas, -0.37 +/- 0.34; however, again, there was a considerable overlap. When ADC was less than 1.05 x 10(-3) mm(2)/s and TCR was greater than 0 this condition was considered to confirm a sarcoma; a combination of ADC and TCR achieved a significant improvement without any overlap between sarcomas and leiomyomas (sensitivity 100%, specificity 100%). Our preliminary results indicate that combined DWI and T2-weighted MR imaging is better than DWI alone in the differentiation of uterine sarcomas from benign leiomyomas.

Cone-beam technique for 64-MDCT of lung: image quality comparison with stepwise (step-and-shoot) technique.

OBJECTIVE: The purpose of this study was to use phantom and patient data acquired with 64-MDCT to compare the image quality and characteristics of helical high-resolution CT images obtained with cone-beam reconstruction with those of stepwise high-resolution CT images obtained with fan-beam reconstruction. SUBJECTS AND METHODS: We reconstructed helical high-resolution CT images with cone-beam technique and stepwise high-resolution CT images with fan-beam technique. In the phantom study, we measured high-contrast spatial resolution and image noise using a phantom. Streak artifact was evaluated by five radiologists using the phantom. In the clinical phase of the study, two radiologists independently evaluated high-resolution helical and stepwise CT images of the lung fields of 30 patients with diffuse lung disease. Using a 3-point ordinal scale, the radiologists assessed the sharpness of peripheral vessels and interlobular fissures, artifacts, and graininess in the lung fields; overall image quality; and the sharpness of the contour of the left ventricle. RESULTS: In high-contrast spatial resolution, the contrast curves in each spatial frequency were similar on the helical and stepwise images. In the clinical study, there was no statistically significant difference between helical and stepwise images with respect to sharpness of the contour of the left ventricle, peripheral vessels, or interlobular fissures (p>0.05). With respect to streak artifacts and graininess in the lung fields, helical images received a significantly higher quality grade than did stepwise images (p<0.05). CONCLUSION: Our phantom and clinical evaluation showed that the quality of high-resolution CT images of the lung obtained with helical scanning was comparable with the quality of stepwise scans.

Low-dose MDCT urography: feasibility study of low-tube-voltage technique and adaptive noise reduction filter.

OBJECTIVE: The purpose of this study was to investigate the feasibility of performance of MDCT urography with low tube voltage and an adaptive noise reduction filter. SUBJECTS AND METHODS: Thirty-one patients underwent excretory phase (300 seconds after administration of 100 mL of iopamidol) 40-MDCT of the urinary tract at 120 and 80 kVp. The 80-kVp images were postprocessed with an adaptive noise reduction filter. Using a 3-point scale for homogeneity of the urinary tract and sharpness of contour, streak artifacts, and overall image quality, two radiologists evaluated coronal multiplanar reconstruction images generated from 120-kVp, unfiltered 80-kVp, and filtered 80-kVp images. Attenuation values of the abdominal aorta, renal pelvis, renal cortex, psoas muscle, vertebral body, and retroperitoneal fat and image noise of the psoas muscle were measured. The effective radiation dose was estimated for each patient. RESULTS: At visual evaluation of images of the upper urinary tract, the quality of filtered 80-kVp images was comparable with that of 120-kVp images. At evaluation of images of the lower urinary tract, however, filtered 80-kVp images were of inferior quality. Except for those of fat tissue, attenuation values were significantly higher on 80-kVp than on 120-kVp images (paired Student's t test, p < 0.01). Noise values did not differ significantly between 120- and filtered 80-kVp images (Dunnett test, p = 0.37). The mean effective doses for 120- and 80-kVp scans were 7.0 and 2.9 mSv. CONCLUSION: MDCT urography is feasible with a low-tube-voltage technique and an adaptive noise reduction filter. The technique allows reduction in radiation dose without marked degradation of image quality and can be used in clinical assessment of the renal collecting system and upper ureter. For evaluation of the pelvic ureter and urinary bladder, however, image quality is not sufficient, and a compensatory increase in tube current may be necessary.

Performance of radiologists in detection of small pulmonary nodules on chest radiographs: effect of rib suppression with a massive-training artificial neural network.

OBJECTIVE: A massive-training artificial neural network is a nonlinear pattern recognition tool used to suppress rib opacity on chest radiographs while soft-tissue contrast is maintained. We investigated the effect of rib suppression with a massive-training artificial neural network on the performance of radiologists in the detection of pulmonary nodules on chest radiographs. MATERIALS AND METHODS: We used 60 chest radiographs; 30 depicted solitary pulmonary nodules, and 30 showed no nodules. A stratified random-sampling scheme was used to select the images from the standard digital image database developed by the Japanese Society of Radiologic Technology. The mean diameter of the 30 pulmonary nodules was 14.7 +/- 4.1 (SD) mm. Receiver operating characteristic analysis was used to evaluate observer performance in the detection of pulmonary nodules first on the chest radiographs without and then on the radiographs with rib suppression. Seven board-certified radiologists and five radiology residents participated in this observer study. RESULTS: For all 12 observers, the mean values of the area under the best-fit receiver operating characteristic curve for images without and with rib suppression were 0.816 +/- 0.077 and 0.843 +/- 0.074; the difference was statistically significant (p = 0.019). The mean areas under the curve for images without and with rib suppression were 0.848 +/- 0.059 and 0.883 +/- 0.050 for the seven board-certified radiologists (p = 0.011) and 0.770 +/- 0.081 and 0.788 +/- 0.074 for the five radiology residents (p = 0.310). CONCLUSION: In the detection of pulmonary nodules, evaluation of a combination of rib-suppressed and original chest radiographs significantly improved the diagnostic performance of radiologists over the use of chest radiographs alone.

Effect of contrast injection protocols with dose adjusted to the estimated lean patient body weight on aortic enhancement at CT angiography.

OBJECTIVE: The objective of our study was to investigate the effect on aortic enhancement of iodine doses adjusted for the patient estimated lean body weight (LBW) at CT angiography (CTA). SUBJECTS AND METHODS: CTA for the whole aorta using a 64-MDCT scanner was performed in 97 patients (mean age, 67.4 years) with confirmed or suspected aortoiliac disease. The patients were divided into two groups: a total body weight (TBW) group (n = 49) and an estimated LBW group (n = 48). LBW was estimated from the patient weight (TBW) and height. The TBW and estimated LBW groups received 360 mg I/kg of TBW and 450 mg I/kg of estimated LBW of contrast medium, respectively. The relative dose ratio for the estimated LBW group versus the TBW group was based on the fact that the standard percentage of body fat in Japanese adults with an average TBW of 60 kg is 20% (360 = 0.8 x 450). Differences in the degree of aortic enhancement and interpatient variability in aortic enhancement between the estimated LBW and TBW group were evaluated. RESULTS: Mean aortic enhancement was 308.9 HU for the estimated LBW group and 314.1 HU for the TBW group, indicating no significant difference in the degree of enhancement (Welch's t test, p = 0.61). The interquartile range was smaller for the LBW group than the TBW group (52.8 vs 79.1 HU, respectively); interpatient variability was lower in the estimated LBW group. The aortic attenuation gradient in the TBW group and estimated LBW group was 20.7 and 25.8 HU, respectively; the difference was not statistically significant. CONCLUSION: The CTA protocol using an estimated LBW-tailored dose yielded more consistent aortic enhancement with reduced interpatient variability than the CTA protocol using a TBW-based dose.

Detection of nodules showing ground-glass opacity in the lungs at low-dose multidetector computed tomography: phantom and clinical study.

OBJECTIVE: To investigate the effect of the radiation dose (tube current second product) and the attenuation value of nodules with ground-glass opacity (GGO) on their detectability at multidetector computed tomography (MDCT). METHODS: We scanned a chest CT phantom that included simulated GGO nodules with an MDCT scanner. The attenuation value of the simulated lung parenchyma was -900 Hounsfield units (HU); it was -800 and -650 HU for the simulated GGO nodules. We used a tube current second product of 180 mA as the standard and 21, 45, 60, and 90 mAs as the low-dose and performed receiver operating characteristic analysis to compare the performance of 5 radiologists in detecting GGO nodules at each milliampere. To assess the detectability of GGO nodules on human lung images, the observers were presented with 38 GGO nodules from 15 patients. The 5 radiologists independently reviewed chest CT images at 21 and 45 mAs. RESULTS: In the phantom study, the Az value for GGO nodules with a CT number of -800 HU was significantly lower at 21 than 180 effective mA (0.86 vs. 0.96; P < 0.01). There was no statistically significant difference in the Az value of GGO nodules with a CT number of -650 HU, irrespective of milliamperes used (P = 0.165). In the clinical study, 39.5% and 25.8% of GGO were missed at 21 and 45 mAs, respectively. CONCLUSIONS: At MDCT, GGO nodules with a CT number of -650 HU or less were difficult to detect at the lower milliampere settings (21 and 45 mAs).

Optimal contrast dose for depiction of hypervascular hepatocellular carcinoma at dynamic CT using 64-MDCT.

OBJECTIVE: The objective of our study was to investigate prospectively the optimal contrast dose for the depiction of hypervascular hepatocellular carcinoma (HCC) during the hepatic arterial phase (HAP) at dynamic CT using a 64-MDCT scanner. SUBJECTS AND METHODS: The study included 135 patients with known or suspected HCC who underwent dynamic CT on a 64-detector scanner and 47 were found to have 71 hypervascular HCCs. The patients were randomly assigned to one of three protocols: A contrast dose of 450, 525, or 600 mg I/kg of body weight was delivered over 30 seconds in protocols A, B, and C, respectively. We measured the tumor-liver contrast (TLC) during HAP in the three groups and compared the results. Two radiologists qualitatively evaluated tumor conspicuity during HAP using a 3-point scale; their results were compared. RESULTS: The TLC in protocols A, B, and C was 26.5, 38.4, and 52.3 H, respectively; the difference was significant between protocols A and B (p = 0.05), A and C (p < 0.01), and B and C (p = 0.02). In our qualitative analysis of tumor conspicuity, the mean score for protocols A, B, and C was 1.6, 2.3, and 2.7, respectively; there was a significant difference between protocols A and B and A and C, but not between protocols B and C. CONCLUSION: The administration of a total iodine dose of 525 mg or more per kilogram of body weight is desirable for the good or excellent depiction of hypervascular HCC, although the administration of 450 mg I/kg of body weight can depict hypervascular HCC.

Ground-glass opacities on thin-section helical CT: differentiation between bronchioloalveolar carcinoma and atypical adenomatous hyperplasia.

OBJECTIVE: The purpose of our study was to investigate the differentiation between bronchioloalveolar carcinoma and atypical adenomatous hyperplasia manifesting pure ground-glass opacity (GGO) based on selected features on thin-section helical CT scans. MATERIALS AND METHODS: We evaluated 35 bronchioloalveolar carcinomas and 17 atypical adenomatous hyperplasias that were histologically confirmed and that manifested pure GGO on thin-section helical CT scans. We recorded the age, sex, and smoking history (Brinkman index) of the patients. Two board-certified radiologists measured the maximum diameter and mean attenuation value of the nodules; the measured values were averaged for each nodule. Using a 3-point scale, they visually assessed the images for consensus with respect to nodular sphericity, marginal irregularity, vascular convergence, pleural retraction, and findings of an internal air bronchogram. CT findings of atypical adenomatous hyperplasia and bronchioloalveolar carcinoma were compared using univariate and multivariate logistic regression analysis; the odds ratio was computed using the atypical adenomatous hyperplasia group as the reference group. RESULTS: By univariate analysis, the patient age, nodular maximum diameter, mean attenuation value, and findings of an internal air bronchogram were statistically significantly associated with bronchioloalveolar carcinoma (odds ratio [OR] = 1.10 [p = 0.012], OR = 1.27 [p < 0.01], OR = 1.01 [p = 0.023], and OR = 25.30 [p < 0.001], respectively), and sphericity was significantly associated with atypical adenomatous hyperplasia (OR = 0.059, p < 0.001). By multivariate analysis, sphericity was significantly associated with atypical adenomatous hyperplasia (OR = 0.125, p = 0.042) and findings of an internal air bronchogram were associated with bronchioloalveolar carcinoma (OR = 16.10, p = 0.007). CONCLUSION: Nodular sphericity and an internal air bronchogram were useful at thin-section helical CT performed to differentiate between bronchioloalveolar carcinoma and atypical adenomatous hyperplasia. Interobserver agreement was high for each finding.

Detection of early enhancement of hypervascular hepatocellular carcinoma using single breath-hold 3D pixel shift dynamic subtraction MDCT.

OBJECTIVE: The objective of our study was to evaluate the effect of single breath-hold dynamic subtraction MDCT of the liver on the performance of radiologists in detecting focal enhancement during the hepatic arterial phase. SUBJECTS AND METHODS: This prospective study included 40 patients: 22 had hypervascular hepatocellular carcinoma (HCC), and 18 were without liver tumors. We obtained four-phase contrast-enhanced scans using a 16-MDCT unit. The section thickness and interval were 2 and 0.5 mm, respectively. Scanning for the first through fourth scans was started 10, 35, 70, and 180 seconds after the inception of contrast injection, respectively. Scanning for the first and second phase was within a single breath-hold. We subtracted the first-phase images from the second-phase images using software developed in-house. We used receiver operating characteristic (ROC) analysis with a continuous rating scale from 1 to 100 to compare observer performance in the detection of focal enhancement on second-phase images. Eight radiologists participated in the observer performance test, and their performances with unenhanced and contrast-enhanced original images were compared with their performances using contrast-enhanced subtracted images. RESULTS: For the eight observers, the mean area under the best-fit ROC curve (A(z)) values without and with the subtracted images were 0.86 +/- 0.05 (SD) and 0.91 +/- 0.03, respectively. The difference was significant (p < 0.01, two-tailed paired Student's t test). CONCLUSION: The display of subtracted images significantly improved the diagnostic performance of radiologists in the detection of focal enhancement during the hepatic arterial phase (p < 0.01).

Identification and characterization of focal ground-glass opacity in the lungs by high-resolution CT using thin-section multidetector helical CT: experimental study using a chest CT phantom.

PURPOSE: The aim of this study was to investigate how much the radiation dose can be reduced for the identification and characterization of focal ground-glass opacities (GGOs) by high resolution computed tomography (HRCT). MATERIALS AND METHODS: A chest CT phantom including GGO nodules was scanned with a 40-detector CT scanner. The scanning parameters were as follows: tube voltage 120 kVp; beam collimation 32 x 1.25 mm; thickness and intervals 1.25 mm; tube current and rotation time 180, 150, 120, 90, 60, and 30 mA. 180 mA was the standard. Using a three-point scale at different currents, we visually evaluated image quality. Furthermore, we carried out observer performance tests using receiver operating characteristic (ROC) analysis to evaluate the ability to identify GGO nodules at each current. RESULTS: By visual analysis, the scores for all particulars were significantly lower on images obtained at less than 120 mA than at 180 mA (Steel's test, P < 0.05). There was no statistically significant difference in any particulars other than artifact on images obtained at 180, 150, and 120 mA. By ROC analysis there was no statistical difference in the Az value to identify GGO nodules on images obtained at 180, 150, 120, 90, or 60 mA. However, the Az value at 30 mA was significantly lower than at 180 mA (Dunnett's test, P < 0.01). CONCLUSION: The minimum current necessary for the characterization of GGO nodules on HRCT was 120 mA, although their identification was possible at currents of >30 mA.

Optimal dose and injection duration (injection rate) of contrast material for depiction of hypervascular hepatocellular carcinomas by multidetector CT.

PURPOSE: The aim of this study was to investigate the optimal dose and injection duration of contrast material (CM) for depicting hypervascular hepatocellular carcinomas (HCCs) during the hepatic arterial phase with multidetector row computed tomography (CT). MATERIALS AND METHODS: The study population consisted of 71 patients with hypervascular HCCs. After unenhanced scans, the first (early arterial phase, or EAP), second (late arterial phase, or LAP), and third (equilibrium phase) scanning was started at 30, 43, and 180 s after injection of contrast material (CM). During a 33-s period, patients with a body weight < or =50 kg received 100 ml of non-ionic CM with an iodine concentration of 300 mg I/ml; patients whose body weight was >50 kg received 100 ml of CM with an iodine concentration of 370 mg I/ml. First, we measured enhancement in the abdominal aorta and tumor-to-liver contrast (TLC) during the EAP and LAP. Next, to investigate the relation between aortic enhancement and TLC during the LAP, two radiologists visually assessed the conspicuity of hypervascular HCCs during the LAP using a 3-point scale: grade 1, poor; grade 2, fair; grade 3, excellent. Finally, to examine the effect of the CM dose and injection duration on aortic enhancement during the EAP, we simulated aortic enhancement curves using test bolus data obtained for 10 HCC patients and the method of Fleischmann and Hittmair. RESULTS: A relatively strong correlation was observed between aortic enhancement during the EAP and TLC during the LAP (correlation coefficient r = 0.75, P < 0.001). The 95% confidence intervals for the population mean for aortic enhancement during EAP in patients with tumor conspicuity grades of 1, 2, and 3 were 188.5, 222.4; 228.8, 259.3; and 280.2, 322.5 HU (Hounsfield Unit), respectively. Thus, we considered the lower limit of the aortic enhancement value for excellent depiction of HCCs during EAP to be 280 HU. To achieve an aortic enhancement value of >280 HU for aortic enhancement simulations during EAP, the injection duration should be <25 s for patients receiving a CM dose of 1.7 ml/kg with 300 mg I/ml iodine and <30 s for those receiving 2.0 ml/kg. CONCLUSIONS: For excellent depiction of hypervascular HCCs during the hepatic arterial phase, the injection duration should be <25 s in patients receiving a CM dose of 1.7 ml/kg with 300 mg I/ml iodine and <30 s for patients receiving 2.0 ml/kg.

Prediction of aortic peak enhancement in monophasic contrast injection protocols at multidetector CT: phantom and patient studies.

PURPOSE: The aim of this study was to investigate whether it is possible to predict aortic peak enhancement (APE) from the contrast dose and injection rate. MATERIALS AND METHODS: We first undertook an experimental study using a flow phantom that simulates the human circulation. We delivered 90-150 ml of iomeprol-350 at various injection rates and measured the APE values of the simulated aorta. In our clinical study we randomized 20 patients into four groups. In groups A, B, and C the iodine dose per kilogram of body weight (BW) ranged from 450 to 600 mg, and the injection duration was fixed at 30 s; group D received 450 mg/kg over 25 s. We then measured APE in all patients at the whole aorta, averaged the three highest values, and took the result as APE. RESULTS: In the phantom study, the decision coefficient for the best-fit equation obtained by multiple regression analysis of the relation between the iodine dose and injection rate and the simulated APE was high (0.93). In the patient study, the predicted APE values almost corresponded with the averaged APE values when we applied the fitness equation. CONCLUSION: Using our fitness equation, APE on contrast-enhanced computed tomography can be predicted from the iodine dose and the contrast injection rate per patient weight.