Occupational radiation exposure among medical personnel in university and general hospitals in Japan.

OBJECTIVE: This study aimed to compare the occupational radiation exposure of medical workers between general hospitals and university hospitals. METHODS: Radiation exposure data from three hospitals in Hiroshima city, including one university hospital and two general hospitals, were collected using personal dosimeters. Monthly radiation doses were analyzed, and the annual sum of radiation exposure dose was calculated for 538 subjects in general hospitals and 1224 subjects in the university hospital. To assess the impact of locality, additional data from Nagasaki University Hospital and Fukushima Medical University Hospital were included for comparative analysis. Professional affiliations, such as doctors, nurses, and radiological technologists, were considered in the evaluation. RESULTS: The study revealed slight but significant differences in radiation doses between general and university hospitals. In general hospitals, except for radiological technologists, a slightly higher radiation dose was observed compared to university hospitals. Despite the annual increase in the use of medical radiation, the majority of hospital workers in both settings adhered to safety guidelines, with occupational radiation exposure remaining below the limit of detection (LOD). Workers who involved in fluoroscopic procedure, whether at university or general hospitals, had higher radiation doses than those who did not. CONCLUSION: The study's primary conclusion is that workers in general hospitals experience a slight but significantly higher radiation dose and a lower percentage below the LOD compared to university hospitals. The observed difference is attributed to the greater workload at general hospitals than at university hospitals, and also may be due to the different nature of university hospital and general hospital. University hospitals, characterized by greater academic orientation, tend to benefit from comprehensive support systems, specialized expertise, and advanced technology, leading to more structured and regulated radiation control. These findings provide a basis for targeted interventions, improved safety protocols.

Comparison of pediatric lens scattered dose measurements between axial 40-mm and helical 160-mm detector width computed tomography scan modes.

BACKGROUND: Reports comparing field lens doses between helical scans with a 40-mm detector width and axial scans with a 160-mm detector width using different computed tomography (CT) scanners are currently scarce. OBJECTIVE: To compare scatter doses for lenses between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width when using different CT scanners in the context of pediatric chest examinations. MATERIALS AND METHODS: Two different CT machines were used: Revolution CT (GE Healthcare, Waukesha, WI) with a 256-row, 0.625-mm multidetector; and Aquilion ONE GENESIS Edition (Canon Medical Systems, Otawara, Japan) with a 320-row, 0.5-mm multidetector. Three pediatric anthropomorphic phantoms were used, with optically stimulated luminescence dosimeters (OSLDs) placed on the left and right lenses. The scatter dose values measured by the OSLDs were compared between a helical scan with a 40-mm detector width and an axial scan with a 160-mm detector width during pediatric chest CT examinations. RESULTS: Median equivalent doses for the helical and axial scans were 0.12 and 0.12 mSv/mGy for the newborn, 0.17 and 0.16 mSv/mGy for the 1-year-old, and 0.18 and 0.15 mSv/mGy for the 5-year-old, respectively, when using the Revolution CT. With the Revolution CT, no significant differences were observed in the scatter doses between helical and axial scans in the newborn and 1-year-old phantoms. However, the lens scatter dose for the helical scan was approximately 20-35% higher than that for the axial scan in the 5-year-old phantom (P<0.01). The median equivalent doses of eye lenses for the helical and axial scans were 0.12 and 0.07 mSv/mGy for the newborn, 0.07 and 0.05 mSv/mGy for the 1-year-old, and 0.14 and 0.12 mSv/mGy for the 5-year-old, respectively, when using the Aquilion ONE. With the Aquilion ONE, lens scatter doses for the helical scan were approximately 70%, 40%, and 30% higher in the newborn, 1-year-old, and 5-year-old phantoms, respectively, than those for the axial scan (P<0.01). CONCLUSIONS: When using the Aquilion ONE, lens scatter doses for the helical scan were significantly higher in all three phantoms than those for the axial scan. In contrast, when using the Revolution CT, the lens scatter dose for the helical scan was significantly higher in the 5-year-old phantom than that for the axial scan. These results suggest that although scattered doses may vary with respect to the CT scanner and body size, they are generally lower in the case of axial scans.

[Validation of Optimal Imaging Conditions for Coronary Computed Tomography Angiography Using High-definition Mode and Deep Learning Image Reconstruction Algorithm].

PURPOSE: To verify the optimal imaging conditions for coronary computed tomography angiography (CCTA) examinations when using high-definition (HD) mode and deep learning image reconstruction (DLIR) in combination. METHOD: A chest phantom and an in-house phantom using 3D printer were scanned with a 256-row detector CT scanner. The scan parameters were as follows - acquisition mode: ON (HD mode) and OFF (normal resolution [NR] mode), rotation time: 0.28 s/rotation, beam coverage width: 160 mm, and the radiation dose was adjusted based on CT-AEC. Image reconstruction was performed using ASiR-V (Hybrid-IR), TrueFidelity Image (DLIR), and HD-Standard (HD mode) and Standard (NR mode) reconstruction kernels. The task-based transfer function (TTF) and noise power spectrum (NPS) were measured for image evaluation, and the detectability index (d') was calculated. Visual evaluation was also performed on an in-house coronary phantom. RESULT: The in-plane TTF was better for the HD mode than for the NR mode, while the z-axis TTF was lower for DLIR than for Hybrid-IR. The NPS values in the high-frequency region were higher for the HD mode compared to those for the NR mode, and the NPS was lower for DLIR than for Hybrid-IR. The combination of HD mode and DLIR showed the best value for in-plane d', whereas the combination of NR mode and DLIR showed the best value for z-axis d'. In the visual evaluation, the combination of NR mode and DLIR showed the best values from a noise index of 45 HU. CONCLUSION: The optimal combination of HD mode and DLIR depends on the image noise level, and the combination of NR mode and DLIR was the best imaging condition under noisy conditions.

Impact of beam collimation of z-overscanning on dose to the lens and thyroid gland in paediatric thoracic computed tomography imaging.

BACKGROUND: Adaptive collimation reduces the dose deposited outside the imaged volume along the z-axis. An increase in the dose deposited outside the imaged volume (to the lens and thyroid) in the z-axis direction is a concern in paediatric computed tomography (CT). OBJECTIVE: To compare the dose deposited outside the imaged volume (to the lens and thyroid) between 40-mm and 80-mm collimation during thoracic paediatric helical CT. MATERIALS AND METHODS: We used anthropomorphic phantoms of newborns and 5-year-olds with 40-mm and 80-mm collimation during helical CT. We compared the measured dose deposited outside the imaged volume using optically stimulated luminescence dosimeters (OSLD) at the surfaces of the lens and thyroid and the image noise between the 40-mm and 80-mm collimations. RESULTS: There were significant differences in the dose deposited outside the imaged volume (to the lens and thyroid) between the 40-mm and 80-mm collimations for both phantoms (P < 0.01). CONCLUSION: Compared with that observed for 80-mm collimation in helical CT scans of the paediatric thorax, the dose deposited outside the imaged volume (to the lens and thyroid) was significantly lower in newborns and 5-year-olds with 40-mm collimation.

Effectiveness of low tube voltage scan in the exposure dose for lenses during paediatric thoracic CT examination: anthropomorphic phantoms study.

To determine whether using lower-tube voltage reduces the scattered dose for the lens during paediatric thoracic computed tomography (CT). Two paediatric anthropomorphic phantoms (ATOM Phantom, CIRS, Norfolk, Virginia, USA) representing a newborn and 5-year-old were placed on the gantry of CT scanner, and optically stimulated luminescence dosemeters were placed on the left and right lenses, in front of the left and right thyroid glands, in front of the left and right mammary glands, and in front of and behind the mammary gland level and we measured scattered dose of the optically stimulated luminescence dosemeter was compared for each phantom between 80 and 120 kVp. Significant differences were observed in the scatter doses for the lens between 80 and 120 kVp (p < 0.01). Compared with the 120 kVp scan, the scatter doses for the lens were ~15-40% lower in newborn and 5-year-olds using the 80 kVp scan during paediatric CT.

Task-based assessment of resolution properties of CT images with a new index using deep convolutional neural network.

In this study, we propose a method for obtaining a new index to evaluate the resolution properties of computed tomography (CT) images in a task-based manner. This method applies a deep convolutional neural network (DCNN) machine learning system trained on CT images with known modulation transfer function (MTF) values to output an index representing the resolution properties of the input CT image [i.e., the resolution property index (RPI)]. Sample CT images were obtained for training and testing of the DCNN by scanning the American Radiological Society phantom. Subsequently, the images were reconstructed using a filtered back projection algorithm with different reconstruction kernels. The circular edge method was used to measure the MTF values, which were used as teacher information for the DCNN. The resolution properties of the sample CT images used to train the DCNN were created by intentionally varying the field of view (FOV). Four FOV settings were considered. The results of adapting this method to the filtered back projection (FBP) and hybrid iterative reconstruction (h-IR) images indicated highly correlated values with the MTF10% in both cases. Furthermore, we demonstrated that the RPIs could be estimated in the same manner under the same imaging conditions and reconstruction kernels, even for other CT systems, where the DCNN was trained on CT systems produced by the same manufacturer. In conclusion, the RPI, which is a new index that represents the resolution property using the proposed method, can be used to evaluate the resolution of a CT system in a task-based manner.

Radio Frequency Identification Gate System to Identify Misused Personal Dosimeters.

The use of two personal dosimeters, one worn over and one worn under a protective apron, provides the best estimate of effective dose. However, inappropriate positioning of dosimeters is a common occurrence, resulting in abnormally high or low radiation exposure records. Although such incorrect positioning can be identified by radiation exposure records, doing so is time-consuming and labor-intensive for administrators. Therefore, a system that can identify incorrect locations of dosimeters without burdening administrators must be developed. In this study, we developed a radio frequency identification (RFID) gate system that can differentiate between two RFID-tagged dosimeters placed over and under a metal apron and identify misused dosimeters. To simulate the position of the RFID-tagged dosimeters, we designed four dosimeter-wearing classes, including "proper use" and three types of "misuse" (i.e., "reversed," "both under," and "both over"). When the system predicts "misuse" based on the tag reading, the worker is alerted with lights and alarms. The system performance was evaluated using a confusion matrix, with an overall accuracy of 97.75%, demonstrating high classification performance. The safety of the system against life support devices was also investigated, demonstrating that they were not affected by the electric field at 0.3 m or more from the antenna of the system under any transmit powers tested. This RFID gate system is highly capable of identifying incorrectly positioned dosimeters, enabling real-time monitoring of dosimeters to manage their positioning.

Evaluation of the second-generation whole-heart motion correction algorithm (SSF2) used to demonstrate the aortic annulus on cardiac CT.

The main purpose of pre-transcatheter aortic valve implantation (TAVI) cardiac computed tomography (CT) for patients with severe aortic stenosis is aortic annulus measurements. However, motion artifacts present a technical challenge because they can reduce the measurement accuracy of the aortic annulus. Therefore, we applied the recently developed second-generation whole-heart motion correction algorithm (SnapShot Freeze 2.0, SSF2) to pre-TAVI cardiac CT and investigated its clinical utility by stratified analysis of the patient's heart rate during scanning. We found that SSF2 reconstruction significantly reduced aortic annulus motion artifacts and improved the image quality and measurement accuracy compared to standard reconstruction, especially in patients with high heart rate or a 40% R-R interval (systolic phase). SSF2 may contribute to improving the measurement accuracy of the aortic annulus.

Usefulness of large beam-shaping filters at different tube voltages of newborn chest CT.

BACKGROUND: To investigate optimizing the use of different beam shaping filters (viz. small, medium and large) when using different tube voltages during the newborn chest computed tomography (CT) on a GE Lightspeed VCT scanner. METHODS: We used pediatric anthropomorphic phantoms with a 64 detector-row CT scanner while scanning the chest. A real-time skin dosimeter (RD - 1000; Trek Corporation, Kanagawa, Japan) was positioned into the phantom center of the body, the surface of the body back, and the right and left mammary glands. We performed and compared six scan protocols using small, medium, and large beam shaping filters at 80 and 120 kVp protocols. RESULT: There were no significant differences in the image noise for the chest scan among the different beam shaping filters. By using the large beam shaping filter at 80 kVp, it was possible to reduce the exposure dose by 5% in comparison with the small beam shaping filter, and by 10% in comparison with the medium beam shaping filter. By using the large beam shaping filter at 120 kVp, it was possible to reduce the exposure dose by 15% in comparison with the small beam shaping filter and by 20% in comparison with the medium beam shaping filter (p < 0.01). CONCLUSION: The large beam shaping filter had the most dose reduction effect during newborn chest CT on a GE Lightspeed VCT scanner. The additional copper filtration being present in the large bowtie filter of the GE Lightspeed CT scanner when using different tube voltages is more effective in reducing radiation exposure in children.

Evaluation of Inappropriate Positioning of Dosimeters in Medical Workers Based on Dose Equivalent Hp(10).

ABSTRACT: This report presents a new method to characterize the inappropriate positioning of dosimeters based on the dose equivalent Hp(10). The Hp(10) values of medical workers were measured monthly for 12 mo using two personal dosimeters. Using the ratio between the values of Hp(10) recorded from dosimeters worn over and under protective aprons [Hp(10) over and Hp(10) under , respectively], 670 pairs of dosimeter readings were categorized into a proper use group [Hp(10) over /Hp(10) under ≥ 5] and a misuse group [Hp(10) over /Hp(10) under < 5]. Following personal interviews, the readings in the misuse group were classified into the following six subgroups: "reversed," "sometimes reversed," "both under," "both over," "without apron," and "not specified." Ultimately, the scatter plot of "Hp(10) over - Hp(10) under " vs. Hp(10) over was identified as the most promising tool for clarifying the misuse patterns of dosimeters, as individual readings were mapped to the locations of the corresponding subgroups in the obtained graphs. Our results are expected to facilitate efficient and accurate usage of dosimeters by medical workers.

COMPARISON OF PEDIATRIC LENS DOSE MEASUREMENTS BETWEEN AXIAL SCAN MODE WITHOUT ACTIVE COLLIMATOR AND HELICAL SCAN MODE WITH ACTIVE COLLIMATOR BY USING A 64 DETECTOR-ROW COMPUTED TOMOGRAPHY SCANNER.

To investigate the pediatric eye lens entrance surface dose for both axial scan modes without an active collimator and helical scan modes with an active collimator on 64 detector-row computed tomography (CT) scanner. We used three pediatric anthropomorphic phantoms with axial and helical scan modes from the superior orbitomeatal line to the crown of the head. We compared the measured dose values of the real-time skin dosemeter at the surfaces of the lens and the image noise at different scan modes. The median measured dose values for the lens of newborn, 1-year-old and the 5-year-old phantom were 31.3, 0.97 and 0.65 mGy, respectively, in the axial scan mode and 0.89, 1.21 and 0.71 mGy, respectively, in the helical scan mode. Compared with helical scans with an active collimators, axial scans can reduce the lens dose by ∼10% during head CT on 64 detector-row CT scanner without deterioration of image noise.

Performance of Ultra-High-Resolution Computed Tomography in Super High-Resolution Mode at the Routine Radiation Dose: Phantom Study.

OBJECTIVE: Using a chest phantom, we compared the image quality of ultra-high-resolution computed tomography (U-HRCT) images acquired in super high-resolution (SHR) and normal resolution (NR) mode and at the routine radiation dose. The detector size was 0.25 and 0.5 mm, respectively. METHODS: A chest phantom was scanned on a U-HRCT scanner. The scan parameters were tube voltage 120 kV and volume CT dose index 13.0 mGy, the routine radiation dose for conventional scans. The rotation time was 0.5 s/rot, the number of matrices was 512 in NR and 1024 in SHR mode. For physical evaluation, the modulation transfer function was measured on the spherical simulated nodule, and the noise power spectrum on the cylindrical water phantom. A CT value profile curve was created using an in-house simulated bronchial phantom. For visual evaluation, 3 radiologists and 3 radiology technologists evaluated overall image quality using a 4-grade scale (grade 1, poor; and grade 4, excellent). RESULTS: The 10% of modulation transfer function was 13.5 lp/cm in NR and 14.9 lp/cm in SHR mode ( P <0.01). ƒ peak was 5.6 lp/cm in NR and 8.8 lp/cm in SHR mode ( P <0.01), and the peak of noise power spectrum shifted. On the profile curves, the CT value at the edge changed in NR but not in SHR mode. The overall image quality was grade 3.0 ± 0.7 in SHR and grade 2.0 ± 0.7 in NR mode ( P <0.01). CONCLUSIONS: The image quality of SHR mode with U-HRCT was superior to that of NR mode at the routine radiation dose.

USE OF VACUUM MATTRESSES CAN REDUCE THE ABSORBED DOSE DURING PEDIATRIC CT.

To evaluate and compare the absorbed dose and image quality when applying a commercially produced fixation device (group A) and a vaccum mattress fixation device to pediatric patients (group B). We compared the absorbed dose and image noise between the groups at the phantom and clinical study. For phantom study, the measurement absorbed dose for a real time skin dosimeter was 3.0 mGy at the group A and 1.9 mGy at the group B (p < 0.05). For clinical study, computed tomography dose index product, dose-length and effective radiation dose were significantly lower with the group B compared to the group A, (3.4 mGy, 27.0 mGy-cm, and 2.2 mSv vs 4.4 mGy, and 36.7 mGy-cm, and 3.0 mSv), p < 0.05 for all comparisons. Compared to the commercially produced fixation device, the vaccum mattress fixation device composed of a less absorptive material enabled a reduction in the absorbed dose while maintaining the image quality during pediatric CT examinations.

[Organ-based Tube-current Modulation Applied on Different MDCT Scanners: Reduction in the Radiation Dose to the Eye Lens at Head CT].

PURPOSE: Organ-based tube current modulation (OB-TCM) techniques, which are provided by three vendors, reduces the radiation dose to the lens of the eyes by decreasing the tube current, when the X-ray tube passes over the anterior surface of critical organs. However, the characteristics of dose modulation of these techniques are different. The purpose of this study was to understand the performance characteristics of OB-TCM technique of each computed tomography (CT) vendor at head CT. METHODS: We used three CT scanners (SOMATOM Definition Flash; Siemens Healthcare, Revolution CT; GE Healthcare, and Aquilion ONE Genesis Edition; Canon Medical Systems). We measured the radiation dose to the lens surface as evaluation of radiation dose reduction and measured the image noise as index of image quality. We measured the radiation dose rate in the air for analysis of the characteristics of dose modulation in each OB-TCM. RESULTS: When applying OB-TCM, the radiation doses for the lens surface were decreased by 28%, 22%, and 25% for Siemens, GE, and Canon CT scanners, respectively, and the image noise level was increased by 5.6%, 8.5%, and 15.1% for Siemens, GE, and Canon CT scanners, respectively. The characteristics of dose modulation in each OB-TCM were also confirmed by measured the radiation dose rate. CONCLUSION: We confirmed that each OB-TCM has different influence on image quality and radiation doses for lens surface, due to the different characteristics of dose modulation for each CT vendor.

Contrast enhancement on 100- and 120 kVp hepatic CT scans at thin adults in a retrospective cohort study: Bayesian inference of the optimal enhancement probability.

PURPOSE: To assess the probability of achieving optimal contrast enhancement in 100 kVp and 120 kVp-protocol on hepatic computed tomography (CT) scans. MATERIALS AND METHODS: We enrolled 200 patients in a retrospective cohort study. Hundred patients were scanned with 120 kVp setting, and other 100 patients were scanned with 100 kVp setting. We measured the CT number in the abdominal aorta and hepatic parenchyma on unenhanced scans and hepatic arterial phase (HAP)-, and portal venous phase (PVP). The aortic enhancement at HAP and the hepatic parenchymal enhancement at PVP were compared between the two scanning protocols. Bayesian inference was used to assess the probability of achieving optimal contrast enhancement in each protocol. RESULTS: The Bayesian analysis indicated that when 100 kVp-rotocol was used, the probability of achieving optimal aortic enhancement (>280 HU) was 98.8% ±â€Š0.6%, whereas it was 88.7% ±â€Š2.5% when 120 kVp-protocol was used. Also, the probability of achieving optimal hepatic parenchymal enhancement (>50 HU) was 95.3% ±â€Š1.5%, whereas it was 64.7% ±â€Š3.8% when 120 kVp-protocol was used. CONCLUSION: Bayesian inference suggested that the post-test probability of optimal contrast enhancement at hepatic dynamic CT was lower under the 120 kVp than the 100 kVp-protocol.

Development and Validation of Generalized Linear Regression Models to Predict Vessel Enhancement on Coronary CT Angiography.

Objective: We evaluated the effect of various patient characteristics and time-density curve (TDC)-factors on the test bolus-affected vessel enhancement on coronary computed tomography angiography (CCTA). We also assessed the value of generalized linear regression models (GLMs) for predicting enhancement on CCTA. Materials and Methods: We performed univariate and multivariate regression analysis to evaluate the effect of patient characteristics and to compare contrast enhancement per gram of iodine on test bolus (ΔHUTEST) and CCTA (ΔHUCCTA). We developed GLMs to predict ΔHUCCTA. GLMs including independent variables were validated with 6-fold cross-validation using the correlation coefficient and Bland-Altman analysis. Results: In multivariate analysis, only total body weight (TBW) and ΔHUTEST maintained their independent predictive value (p < 0.001). In validation analysis, the highest correlation coefficient between ΔHUCCTA and the prediction values was seen in the GLM (r = 0.75), followed by TDC (r = 0.69) and TBW (r = 0.62). The lowest Bland-Altman limit of agreement was observed with GLM-3 (mean difference, -0.0 ± 5.1 Hounsfield units/grams of iodine [HU/gI]; 95% confidence interval [CI], -10.1, 10.1), followed by ΔHUCCTA (-0.0 ± 5.9 HU/gI; 95% CI, -11.9, 11.9) and TBW (1.1 ± 6.2 HU/gI; 95% CI, -11.2, 13.4). Conclusion: We demonstrated that the patient's TBW and ΔHUTEST significantly affected contrast enhancement on CCTA images and that the combined use of clinical information and test bolus results is useful for predicting aortic enhancement.

Radiation Dose Reduction With a Low-Tube Voltage Technique for Pediatric Chest Computed Tomographic Angiography Based on the Contrast-to-Noise Ratio Index.

INTRODUCTION: The aim of this study was to evaluate the radiation dose and image quality at low tube-voltage pediatric chest computed tomographic angiography (CTA) that applies the same contrast-to-noise ratio (CNR) index as the standard tube voltage technique. MATERIALS AND METHODS: Contrast-enhanced chest CTA scans of 100 infants were acquired on a 64-row multidetector computed tomography (MDCT) scanner. In the retrospective study, we evaluated 50 images acquired at 120 kVp; the image noise level was set at 25 Hounsfield units. In the prospective study, we used an 80-kVp protocol; the image noise level was 40 Hounsfield units because the iodine contrast was 1.6 times higher than on 120-kVp scans; the CNR was as in the 120-kVp protocol. We compared the CT number, image noise, CT dose index volume (CTDIvol), and the dose-length product on scans acquired with the 2 protocols. A diagnostic radiologist and a pediatric cardiologist visually evaluated all CTA images. RESULTS: The mean CTDIvol and the mean dose-length product were 0.5 mGy and 7.8 mGy-cm for 80- and 1.2 mGy and 20.8 mGy-cm for 120-kVp scans, respectively (P < .001). The mean CTDIvol was 42% lower at 80 kVp than at 120 kVp, and there was no significant difference in the visual scores assigned to the CTA images (P = .28). CONCLUSIONS: With the CNR index being the same at 80-kVp and 120-kVp imaging, the radiation dose delivered to infants subjected to chest CTA can be reduced without degradation of the image quality.

Improved differentiation between high- and low-grade gliomas by combining dual-energy CT analysis and perfusion CT.

The purpose of this study was to investigate the value of the cerebral blood volume (CBV) obtained with perfusion computed tomography (CT) and the electron density (ED) measured by dual-energy CT for differentiating high- from low-grade glioma (HGG, LGG).The CBV and ED were obtained in 9 LGG and 7 HGG patients. The CBV and ED of LGGs and HGGs were compared. Receiver operating characteristic (ROC) curves were generated for CBV, ED, and CBV plus ED. The correlation between CBV, ED, and the MIB-1 labeling index of the tumors was examined. All of these analyses were also performed using relative CBV (rCBV) and ED (rED) (the value of tumors/the value of contralateral white matter).The mean CBV, ED, rCBV, and rED values were significantly higher in HGG than LGG (P < .05). By ROC analysis, the combination of rCBV plus rED as well as CBV plus ED were more accurate than CBV, ED, rCBV, rED alone. There was a significant correlation between ED and MIB-1 (P = .04).ED improved diagnostic accuracy of perfusion CT for differentiating HGG from LGG.

Effect of Patient Characteristics on Vessel Enhancement at Lower Extremity CT Angiography.

Objective: To evaluate the effect of patient characteristics on popliteal aortic contrast enhancement at lower extremity CT angiography (LE-CTA) scanning. Materials and Methods: Prior informed consent to participate was obtained from all 158 patients. All were examined using a routine protocol; the scanning parameters were tube voltage 100 kVp, tube current 100 mA to 770 mA (noise index 12), 0.5-second rotation, 1.25-mm detector row width, 0.516 beam pitch, and 41.2-mm table movement, and the contrast material was 85.0 mL. Cardiac output (CO) was measured with a portable electrical velocimeter within 5 minutes of starting the CT scan. To evaluate the effects of age, sex, body size, CO, and scan delay on the CT number of popliteal artery, the researchers used multivariate regression analysis. Results: A significant positive correlation was seen between the CT number of the popliteal artery and the patient age (r = 0.39, p < 0.01). A significant inverse correlation was observed between the CT number of the popliteal artery and the height (r = -0.48), total body weight (r = -0.52), body mass index (r = -0.33), body surface area (BSA) (r = -0.56), lean body weight (r = -0.56), and CO (r = -0.35) (p < 0.001 for all). There was no significant correlation between the enhancement and the scan delay (r = 0.06, p = 0.47). The BSA, CO, and age had significant effects on the CT number (standardized regression: BSA -0.42, CO -0.22, age 0.15; p < 0.05, respectively). Conclusion: The BSA, CO, and age are significantly correlated with the CT number of the popliteal artery on LE-CTA.

Hepatocellular carcinoma treated with sorafenib: Arterial tumor perfusion in dynamic contrast-enhanced CT as early imaging biomarkers for survival.

OBJECTIVES: To investigate whether hepatic perfusion CT yields early imaging biomarkers predictive of the prognosis of hepatocellular carcinoma (HCC) patients treated with sorafenib. METHODS: We evaluated 36 HCC patients who underwent hepatic perfusion CT before- and one week after sorafenib therapy. We measured arterial and portal perfusion in the hepatic tumor and liver parenchyma [(AP)(PP)tumor], [(AP)(PP)liver]. The perfusion ratio was calculated by dividing the post- by the pre-sorafenib value. The effect of each value on the overall survival rate was analyzed with the Cox proportional hazards model; statistically significant parameters were subjected to receiver operating characteristic analysis based on median survival after sorafenib administration to determine the overall survival rate with the Kaplan-Meier method. RESULTS: Pre-APtumor was significantly associated with the overall survival rate (hazard ratio (HR) and 95% confidence interval (CI), 0.16 and 0.02-0.84, p=0.03). The APtumor ratio tended to be associated with the overall survival rate (HR and 95% CI, 2.94 and 0.94-7.88, p=0.06). The overall survival rate was higher in patients with pre-APtumor>71.7mL/min/100mL, and with APtumor ratio≦1.1 (p<0.01 and 0.03, respectively, in Kaplan-Meier method with log-rank). CONCLUSION: Hepatic perfusion CT yields early imaging biomarkers for predicting overall survival in HCC patients treated with sorafenib.