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Background: Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs., Purpose: The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρ e )., Methods: A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρ e over the multiple points on the curve (Δρ m and Δρ e,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρ e for the specific TEMs (Δρ TEM and Δρ e,TEM , respectively) were calculated by subtracting the ρ or ρ e of the TEMs from the theoretical CT-ρ or CT-ρ e calibration curve., Results: The mean ± standard deviation (SD) of Δρ m and Δρ e,m for the Gammex phantom were -1.1 ± 1.2 g/cm 3 and -0.2 ± 1.1, -0.3 ± 0.9 g/cm 3 and 0.8 ± 1.3, and -0.9 ± 1.3 g/cm 3 and 1.0 ± 1.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρ m and Δρ e,m for the CIRS phantom were 0.3 ± 0.8 g/cm 3 and 0.9 ± 0.9, 0.6 ± 0.6 g/cm 3 and 1.4 ± 0.8, and 0.2 ± 0.5 g/cm 3 and 1.6 ± 0.5 for lung, soft tissues, and bones, respectively. The mean ± SD of Δρ m for Tomotherapy TPSs was 2.1 ± 1.4 g/cm 3 for soft tissues, which is larger than those for other TPSs. The mean ± SD of Δρ e,TEM for the Gammex brain phantom (BRN-SR2) was -1.8 ± 0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs., Conclusions: Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes., (© 2023 The Authors. Medical Physics published by Wiley Periodicals LLC on behalf of American Association of Physicists in Medicine.)

Purpose: The present study introduced the half-dose method (HDM), which halves the radiation dose for conventional head computed tomography (CT), for postoperative hydrocephalus and follow-up for craniosynostosis at a children's hospital. This study aimed to evaluate the contribution of selective head CT scanning optimization towards the overall reduction of radiation exposure., Materials and Methods: We retrospectively assessed 1227 and 1352 head CT examinations acquired before and after the introduction of the HDM, respectively, in children aged 0-15 years. The radiation exposure was evaluated using the CT dose index volume (CTDI-vol), dose-length product (DLP), rate of HDM introduction, and effect of reducing in-hospital radiation dose before and after the introduction of the HDM. For an objective evaluation of the image quality, head CT scans acquired with HDM and full-dose method (FDM) were randomly selected, and the image noise standard deviation (SD) was measured for each scan. In addition, some HDM images were randomly selected and independently reviewed by two radiologists., Results: The HDM was introduced in 27.9% of all head CTs. The mean CTDI-vol of all head CTs was 21.5 ± 6.9 mGy after the introduction, a 14.9% reduction. The mean DLP was 418.4 ± 152.9 mGy.cm after the introduction, a 17.2% reduction. Compared to the FDM images, the noise SD of the HDM ones worsened by almost 0.9; however, none of the images were difficult or impossible to evaluate., Conclusion: The HDM yielded diagnostically acceptable images. In addition, a change in protocol for only two diseases successfully reduced the patients' overall radiation exposure by approximately 15%. Introducing and optimizing the HDM for frequently performed target diseases will be useful in reducing the exposure dose for the hospital's patient population., (© 2023. The Author(s).)

Purpose: Treatment planning for ion therapy involves the conversion of computed tomography number (CTN) into a stopping-power ratio (SPR) relative to water. The purpose of this study was to create a CTN-to-SPR calibration table using a stoichiometric CTN calibration model with a three-parameter fit model for ion therapy, and to demonstrate its effectiveness by comparing it with a conventional stoichiometric CTN calibration model., Methods: We inserted eight tissue-equivalent materials into a CTN calibration phantom and used six CT scanners at five radiotherapy institutes to scan the phantom. We compared the theoretical CTN-to-SPR calibration tables created using the three-parameter fit and conventional models to the measured CTN-to-SPR calibration table in three tissue types: lung, adipose/muscle, and cartilage/spongy bone. We validated the estimated SPR differences in all cases and in a worst-case scenario, which revealed the largest estimated SPR difference in lung tissue., Results: For all cases, the means ± standard deviations of the estimated SPR difference for the three-parameter fit method model were -0.1 ± 1.0%, 0.3 ± 0.7%, and 2.4 ± 0.6% for the lung, adipose/muscle, and cartilage/spongy bone, respectively. For the worst-case scenario, the estimated SPR differences of the conventional and the three-parameter fit models were 2.9% and -1.4% for the lung tissue, respectively., Conclusions: The CTN-to-SPR calibration table of the three-parameter fit model was consistent with that of the measurement and decreased the calibration error for low-density tissues, even for the worst-case scenario., (Copyright © 2022 Associazione Italiana di Fisica Medica e Sanitaria. Published by Elsevier Ltd. All rights reserved.)

Purpose: To evaluate the frequency of ice ball cracks on CT during cryoablation of renal tumors and assess the severity of hemorrhagic complications associated with this finding., Materials and Methods: Between March 2014 and March 2019, 130 patients underwent CT-guided cryoablation using cryoprobes with a diameter of 1.5 mm for 138 renal tumors (mean diameter, 23.6 mm; standard deviation [SD], 7.5; range, 8.3-43). Two blinded board-certified radiologists retrospectively reviewed the presence of cracks on CT obtained during the procedure. The incidence of major hemorrhage and changes in hemoglobin levels after cryoablation were examined. Factors influencing the appearance of ice ball cracks were assessed with multivariate analyses., Results: Cracks were observed in 25 of the138 procedures (18%). Inter-reader reliabilities with kappa statistics were 0.90 and 0.84 for first and second freeze sessions, respectively. There were no major hemorrhagic events requiring blood transfusion or arterial embolization. Mean (± SD) decreases in hemoglobin levels between pre- and postoperative day 1 were 1.15 ± 0.86 g/dl in the cracks group and 1.01 ± 0.80 g/dl in the no cracks group with no significant difference (p = 0.14). Multivariate analyses identified a higher number of cryoprobes (odds ratio, 4.1; 95% confidence interval [CI] 1.7-11; p = 0.001) and no hydrodissection (odds ratio 6.7; 95% CI 2.1-28; p < 0.001) as factors associated with ice ball cracks., Conclusion: Ice ball cracks were frequently observed on CT during cryoablation for renal tumors and were seemingly self-limiting events requiring no intervention.

Purpose: In photon radiation therapy, computed tomography (CT) numbers are converted into values for mass density (MD) or relative electron density to water (RED). CT-MD or CT-RED calibration tables are relevant for human body dose calculation in an inhomogeneous medium. CT-MD or CT-RED calibration tables are influenced by patient imaging (CT scanner manufacturer, scanning parameters, and patient size), the calibration process (tissue-equivalent phantom manufacturer, and selection of tissue-equivalent material), differences between tissue-equivalent materials and standard tissues, and the dose calculation algorithm applied; however, a CT number calibration audit has not been established. The purposes of this study were to develop a postal audit phantom, and to establish a CT number calibration audit process., Methods: A conventional stoichiometric calibration conducts a least square fit of the relationships between the MD, material weight, and measured CT number, using two parameters. In this study, a new stoichiometric CT number calibration scheme has been empirically established, using three parameters to harmonize the calculated CT number with the measured CT number for air and lung tissue. In addition, the suitable material set and the minimal number of materials required for stoichiometric CT number calibration were determined. The MDs and elemental weights from the International Commission on Radiological Protection Publication 110 were used as standard tissue data, to generate the CT-MD and CT-RED calibration tables. A small-sized, CT number calibration phantom was developed for a postal audit, and stoichiometric CT number calibration with the phantom was compared to the CT number calibration tables registered in the radiotherapy treatment planning systems (RTPSs) associated with five radiotherapy institutions., Results: When a least square fit was performed for the stoichiometric CT number calibration with the three parameters, the calculated CT number showed better agreement with the measured CT number. We established stoichiometric CT number calibration using only two materials because the accuracy of the process was determined not by the number of used materials but by the number of elements contained. The stoichiometric CT number calibration was comparable to the tissue-substitute calibration, with a dose difference less than 1%. An outline of the CT number calibration audit was demonstrated through a multi-institutional study., Conclusions: We established a new stoichiometric CT number calibration method for validating the CT number calibration tables registered in RTPSs. We also developed a CT number calibration phantom for a postal audit, which was verified by the performances of multiple CT scanners located at several institutions. The new stoichiometric CT number calibration has the advantages of being performed using only two materials, and decreasing the difference between the calculated and measured CT numbers for air and lung tissue. In the future, a postal CT number calibration audit might be achievable using a smaller phantom., (© 2020 The Authors. Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

Computed tomography (CT) data are required to calculate the dose distribution in a patient's body. Generally, there are two CT number calibration methods for commercial radiotherapy treatment planning system (RTPS), namely CT number-relative electron density calibration (CT-RED calibration) and CT number-mass density calibration (CT-MD calibration). In a previous study, the tolerance levels of CT-RED calibration were established for each tissue type. The tolerance levels were established when the relative dose error to local dose reached 2%. However, the tolerance levels of CT-MD calibration are not established yet. We established the tolerance levels of CT-MD calibration based on the tolerance levels of CT-RED calibration. In order to convert mass density (MD) to relative electron density (RED), the conversion factors were determined with adult reference computational phantom data available in the International Commission on Radiological Protection publication 110 (ICRP-110). In order to validate the practicability of the conversion factor, the relative dose error and the dose linearity were validated with multiple RTPSes and dose calculation algorithms for two groups, namely, CT-RED calibration and CT-MD calibration. The tolerance levels of CT-MD calibration were determined from the tolerance levels of CT-RED calibration with conversion factors. The converted RED from MD was compared with actual RED calculated from ICRP-110. The conversion error was within ±0.01 for most standard organs. It was assumed that the conversion error was sufficiently small. The relative dose error difference for two groups was less than 0.3% for each tissue type. Therefore, the tolerance levels for CT-MD calibration were determined from the tolerance levels of CT-RED calibration with the conversion factors. The MD tolerance levels for lung, adipose/muscle, and cartilage/spongy-bone corresponded to ±0.044, ±0.022, and ±0.045 g/cm 3 , respectively. The tolerance levels were useful in terms of approving the CT-MD calibration table for clinical use., (© 2019 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

Ice ball fracture and massive hemorrhage are serious complications associated with renal cryoablation. When cracks occur in an ice ball, it is usually associated with adjacent renal parenchymal fracture, leading to massive hemorrhage. However, few studies have examined ice ball fracture under image-guided percutaneous renal cryoablation. We herein describe an 80-year-old male patient who had undergone CT-guided cryoablation for a left renal tumor using four cryoprobes (1.5 mm diameter each). Ice ball cracks were observed on CT images during cryoablation. However, there was no massive hemorrhage and further treatments were not necessary. This is the first report of ice ball cracks with a smaller diameter cryoprobe, which has not been considered to be associated with ice ball fracture.

Early identification of high-risk or vulnerable atherosclerotic plaques prone to rupture and performing preemptive therapy prior to catastrophic cardiovascular events are optimal goals of plaque imaging. Despite the advances in imaging modalities to identify vulnerable characteristics, the predictive value of the imaging techniques in the clinical setting is still developing. In this regard, reliable and high-sensitive imaging modalities identifying vulnerable plaque characters that may lead to future cardiovascular events will be useful. In this review article, we describe a current non-invasive plaque imaging technique to identify high-risk coronary plaque features.

To perform dynamic tumor tracking (DTT) for clinical applications safely and accurately, gimbaled head swing verification is important. We propose a quantitative gimbaled head swing verification method for daily quality assurance (QA), which uses feature point tracking and a web camera. The web camera was placed on a couch at the same position for every gimbaled head swing verification, and could move based on a determined input function (sinusoidal patterns; amplitude: ± 20 mm; cycle: 3 s) in the pan and tilt directions at isocenter plane. Two continuous images were then analyzed for each feature point using the pyramidal Lucas-Kanade (LK) method, which is an optical flow estimation algorithm. We used a tapped hole as a feature point of the gimbaled head. The period and amplitude were analyzed to acquire a quantitative gimbaled head swing value for daily QA. The mean ± SD of the period were 3.00 ± 0.03 (range: 3.00-3.07) s and 3.00 ± 0.02 (range: 3.00-3.07) s in the pan and tilt directions, respectively. The mean ± SD of the relative displacement were 19.7 ± 0.08 (range: 19.6-19.8) mm and 18.9 ± 0.2 (range: 18.4-19.5) mm in the pan and tilt directions, respectively. The gimbaled head swing was reliable for DTT. We propose a quantitative gimbaled head swing verification method for daily QA using the feature point tracking method and a web camera. Our method can quantitatively assess the gimbaled head swing for daily QA from baseline values, measured at the time of acceptance and commissioning., (© 2016 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.)

Several studies have noted benign thecoma‑fibroma tumors with positive F‑18 fluorodeoxyglucose (FDG) accumulation mimicking malignant ovarian tumors following F‑18 FDG positron emission tomography (PET). The present study analyzed four cases with false‑positive F‑18 FDG PET/computed tomography (CT) diagnoses of thecoma‑fibroma tumors as malignant tumors due to F‑18 FDG accumulation, compared with eight cases of FDG‑positive ovarian cancers and two cases of FDG‑negative fibromas. Hypoxia inducible factor (HIF)‑1α expression was examined in the six thecoma‑fibroma tumors using reverse transcription‑polymerase chain reaction (RT‑PCR). The four F‑18 FDG‑positive cases exhibited higher cellularity, maximum standard uptake and signal intensity on T2‑weighted imaging, and gadolinium (Gd) enhancement using magnetic resonance imaging than the two FDG-negative fibroma cases. In the F‑18 FDG‑positive thecoma‑fibroma group, Ki‑67 expression was low and LAT1 expression was not identified, ruling out the diagnosis and potential for malignancy. However, considerable glucose transporter 1, HIF‑1α, and vascular endothelial growth factor expression was observed. HIF‑1α expression was elevated in all four false‑positive cases by RT‑PCR. From these results, it was hypothesized that hypoxia due to elevated cellularity may stimulate HIF‑1α expression and be associated with F‑18 FDG accumulation in F‑18‑positive thecoma‑fibroma tumors.

Background: In preoperative lipiodol marking for small pulmonary nodules, lipiodol has a potential risk of distribution in the surrounding lung structure. There are no reports about the detailed accumulation and distribution of lipiodol., Purpose: To evaluate computed tomography (CT) findings after lipiodol marking before thoracoscopic surgery for pulmonary nodules., Material and Methods: Sixty-four consecutive CT-guided lipiodol markings for 103 nodules were performed in 55 patients. Lipiodol (0.2-0.4 mL) was injected using a 21-gauge needle near the nodule. The appearance of lipiodol spots was classified into the following three types on CT: type 1, dense; type 2, punctate; and type 3, unclear. The distribution of lipiodol was also investigated. Statistical analyses were performed on the accumulation and distribution related to nodule factors. Incidences of complications were also investigated., Results: A total of 110 markings were performed because of seven additional procedures due to insufficient marking. All nodules were successfully resected on the same day. The appearances of the lipiodol spots were type 1 (82%), type 2 (11%), and type 3 (7.3%). The areas of distribution were lung parenchyma (54%), central bronchus (39%), peripheral bronchovascular bundle (24%), needle tract (20%), pleural space (19%), another segment of ipsilateral lung (5.5%), and contralateral lung (0.9%). Distribution into pleural space and central bronchus was frequently seen in the shallow nodules (P < 0.05). Complications were pneumothorax (61%) and pulmonary hemorrhage (35%). There were no serious symptoms., Conclusion: The appearance of the lipiodol spot was dense in most cases, despite frequent distribution in the surrounding lung structures without serious complications., (© The Foundation Acta Radiologica 2015.)

Background: Previous anthropometric studies have reported gender differences in distal femoral morphology. However, to date, very few studies have investigated the knee morphology of Japanese adults and possible gender differences. The purpose of this study was to examine the distal femoral morphology of Japanese patients, to characterize anatomical differences between male and female, and to evaluate the need to create gender-specific knee prostheses., Material and Methods: We evaluated 80 knees in 40 male and 40 female Japanese patients scheduled for total knee arthroplasty (TKA). The mediolateral (ML) and anteroposterior (AP) dimensions of the knees at different levels were measured preoperatively using three-dimensional computed tomography, and ML/AP aspect ratios were calculated., Results: On the distal femoral cut surface, the mean ML widths were 74.9 mm for male and 65.1mm for female, and the mean AP lengths were 63.4mm for male and 58.9 mm for female. Such values were generally smaller compared to data from European and North American studies. In this study, the mean ML/AP aspect ratios were 1.31 for male and 1.25 for female, higher than those from non-Asian regions. The ML/AP ratios of Japanese patients were negatively correlated with distal femoral AP length., Conclusions: Japanese female had a relatively narrower femoral width for a given AP length than male. Our study suggests the utility of Japanese-specific implants and provides useful insights for manufacturers to design components of appropriate sizes and aspect ratios for Japanese TKA patients., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The purpose of this study was to investigate the relationship between tumor size and blood volume for patients with lung tumors, using dual-energy computed tomography (DECT) and a gemstone spectral imaging (GSI) viewer. During the period from March 2011 to March 2013, 50 patients with 57 medically inoperable lung tumors underwent DECT before stereotactic body radiotherapy (SBRT) of 50-60 Gy in 5-6 fractions. DECT was taken for pretreatment evaluation. The region-of-interest for a given spatial placement of the tumors was set, and averages for CT value, water density and iodine density were compared with tumor size. The average values for iodine density in tumors of ≤ 2 cm, 2-3 cm, and >3 cm maximum diameter were 24.7, 19.6 and 16.0 (100 µg/cm(3)), respectively. The average value of the iodine density was significantly lower in larger tumors. No significant correlation was detected between tumor size and average CT value or between tumor size and average water density. Both the average water density and the average CT value were affected by the amount of air in the tumor, but the average iodine density was not affected by air in the tumor. The average water density and the average CT value were significantly correlated, but the average iodine density and the average CT value showed no significant correlation. The blood volume of tumors can be indicated by the average iodine density more accurately than it can by the average CT value. The average iodine density as assessed by DECT might be a non-invasive and quantitative assessment of the radio-resistance ascribable to the hypoxic cell population in a tumor., (© The Author 2014. Published by Oxford University Press on behalf of The Japan Radiation Research Society and Japanese Society for Radiation Oncology.)

Purpose: To evaluate the correlation between computed tomography (CT) findings after therapeutic lymphangiography for lymphatic leakage and the clinical course of lymphatic leakage., Materials and Methods: Therapeutic lymphangiography for lymphatic leakage was performed in 14 patients. In all patients, CT was performed 0.5-26 h (mean 6.9 h) after lymphangiography and results were retrospectively evaluated., Results: In 8 of the 14 patients (57 %), lymphatic leakage stopped after lymphangiography. Lymphatic leakage was detected on CT in 9 of the 14 patients (64 %) and had either a nodular (n = 4) or beaded appearance (n = 5). The amount of drainage had decreased the day after lymphangiography, and leakage finally stopped in all 4 patients in whom the leakage had a nodular appearance. However, leakage did not stop in 3 of the 5 patients having leakage with a beaded appearance., Conclusion: A nodular appearance of leakage might predict success of therapeutic lymphangiography.

We report the case of a 12-year-old boy with a huge liver tumour 20 cm in diameter with multiple lung metastases. Six months after systemic chemotherapy was initiated, all tumours had disappeared with the exception of the liver tumour and a tiny lung tumour 2.5 mm in diameter. Fluoroscopy-assisted thoracoscopic resection of the pulmonary nodule was performed to evaluate whether viable tumour tissue remained in the lung lesion. Before moving the patient to the operating room, the nodule was marked by Lipiodol under CT fluoroscopic guidance with the patient under local anaesthesia. This procedure allowed correct visualisation of the area that should be resected., (© 2011 The Authors. Journal of Medical Imaging and Radiation Oncology © 2011 The Royal Australian and New Zealand College of Radiologists.)

We describe a 71-year-old woman with a hepatocellular carcinoma who underwent percutaneous radiofrequency ablation (RF) with a single internally cooled electrode under computed tomography (CT) fluoroscopic guidance. Nine months after the procedure, CT images showed herniation of the large intestine into the right pleural cavity. To our knowledge this complication of RF performed with a single internally cooled electrode under CT guidance has not been previously reported.

We have evaluated relationship between planning CT slice thickness and the accuracy of automatic target registration using cone-beam CT (CBCT). Planning CT images were acquired with reconstructed slice thickness of 1, 2, 3, 5, and 10mm for three different phantoms: Penta-Guide phantom, acrylic ball phantom, and pelvic phantom. After correctly placing the phantom at the isocenter using an in-room laser, we purposely displaced it by moving the treatment couch and then obtained CBCT images. Registration between the planning CT and the CBCT was performed using automatic target registration software, and the registration errors were recorded for each planning CT data set with different slice thickness. The respective average and standard deviation of errors for 10 mm slice thickness CT in the lateral, longitudinal, and vertical directions (n=15 data sets) were: 0.7 +/- 0.2mm, 0.8 +/- 0.2mm, and 0.2 +/- 0.2mm for the Penta-Guide phantom; 0.5 +/- 0.4 mm, 0.6 +/- 0.3 mm, and 0.4 +/- 0.3 mm for the acrylic ball phantom; and 0.6 +/- 0.2 mm, 0.9 +/- 0.2 mm, and 0.2 +/- 0.2 mm for the pelvic phantom. We found that the mean registration errors were always less than 1 mm regardless of the slice thickness tested. The results suggest that there is no obvious correlation between the planning CT slice thickness and the registration errors.

Background: Various treatments for hepatocellular carcinoma (HCC) beneath the diaphragm have been reported. Transpulmonary radiofrequency (TPRF) ablation for HCC beneath the diaphragm has been developed as a safe treatment, but pneumothorax has been reported as the most common complication of TPRF ablation., Purpose: To evaluate the relationship between the incidence of pneumothorax and various variables after TPRF ablation., Material and Methods: Seventy-six TPRF ablation sessions for unresectable HCC were performed in 66 patients (19 women, 47 men; mean age 69.6 years) under computed tomography (CT)-fluoroscopic guidance between November 2005 and April 2009. All patients had HCC beneath the diaphragm, not visible by ultrasonography. In 62 of the 76 sessions, the number of transpulmonary approaches was one as adequate, while multiple transpulmonary approaches were performed in 14 of the 76 sessions. The rate of pneumothorax and risk factors for pneumothorax were investigated., Results: Among the 76 sessions, pneumothorax was detected in 51 sessions (67.1%). Among the 14 sessions with multiple transpulmonary passages, pneumothorax was detected in 13 (92.9%), while in the 62 sessions with a single transpulmonary passage, pneumothorax occurred in 38 sessions (61.3%). Hence, the number of transpulmonary approaches was a significant factor (P=0.0232). Among 13 variables investigated for the 62 sessions with a single transpulmonary approach, the only significant factor correlated with the occurrence of pneumothorax was the length of the needle trajectory through the aerated lung (P=0.0014). The incidence of chest tube placement was 7.9%., Conclusion: Pneumothorax occurred frequently after TPRF ablation for HCC. The main risk factors for pneumothorax after TPRF ablation for HCC were increased length of needle trajectory through the aerated lung and multiple transpulmonary approaches in one session. Even if pneumothorax occurred, pneumothorax disappeared spontaneously or with simple treatment such as manual aspiration in most cases.

Background: Pneumothorax is the most common complication after computed tomography (CT)-guided lung biopsy. The presence of a pneumothorax per se does not complicate patient management, but an increasing pneumothorax, making chest tube placement necessary, is highly problematic., Purpose: To evaluate the efficacy and limitations of simple aspiration of air from the pleural space to prevent increased pneumothorax and avoid chest tube placement in cases of pneumothorax following CT-guided lung biopsy., Material and Methods: The subjects of our study were 642 consecutive lung lesions in 594 patients for which percutaneous needle lung biopsies were performed using CT guidance. While patients were on the CT scanner table, percutaneous manual aspiration was performed in all patients with a non-small pneumothorax demonstrated on post-biopsy chest CT images. The frequency of pneumothorax, management of each such case, and factors influencing the incidence of worsening pneumothorax that finally required chest tube placement were evaluated., Results: Post-biopsy pneumothorax occurred in 243 of 642 (38%) procedures. Of the 243 cases, 112 were treated with manual aspiration immediately after biopsy. In 210 (86.4%), the pneumothorax had resolved completely on follow-up chest radiographs without chest tube placement. Only 33 patients required chest tube placement. Requirement of chest tube insertion significantly increased in parallel with the degree of pneumothorax as shown on post-biopsy CT images. The rate of chest tube insertion was statistically higher in subjects with values for aspirated air above 543 ml., Conclusion: Percutaneous manual aspiration of biopsy-induced pneumothorax performed immediately after biopsy may prevent worsening of pneumothorax and avoid chest tube placement. The amount of aspirated air can be predictive of the requirement for chest tube placement.

We evaluated the postoperative alignment of 37 primary total knee arthroplasties performed using a computed tomography-based navigation system (Vector Vision Knee 1.5; Brain Lab, Germany) with a new 3-dimensional analysis. The mean coronal femoral angle was 89.0 degrees +/- 1.4 degrees (85.5 degrees -92.8 degrees ), and the coronal tibial component was 89.2 degrees +/- 1.0 degrees (87.4 degrees -91.6 degrees ). The hip-knee-ankle angle was observed to be 178.2 degrees +/- 1.5 degrees (173.9 degrees -181.8 degrees ). The external rotational alignment of the femoral component relative to the surgical epicondylar axis was -0.5 degrees +/- 1.7 degrees (-3.2 degrees to 3.4 degrees ). The results demonstrated that a computed tomography-based navigation system provided a reasonably satisfactory component alignment. The discrepancy between the 2-dimensional and 3-dimensional evaluations was 1.0 degrees +/- 0.9 degrees (0.1 degrees -3.4 degrees ). Three-dimensional analysis is necessary to evaluate the accuracy of the navigation system.

Objectives: The goal of our study was to determine the usefulness of percutaneous abscess drainage under guidance of computed tomography (CT) fluoroscopy., Materials and Methods: Our subjects were 21 patients (seven women, 14 men; mean age 64 years; age range 30-87 years) who had undergone percutaneous drainage of 26 psoas abscess lesions under CT fluoroscopic guidance between May 2001 and January 2008. Drainage methods involved a needle puncture, insertion of a guidewire, serial dilations, and the exchange of the needle with a drainage tube. The procedures were guided by use of a helical CT scanner that provided real-time fluoroscopic reconstruction., Results: Percutaneous drainage under real-time CT fluoroscopic guidance was successfully performed in every procedure. Use of real-time CT fluoroscopy allowed rapid assessment of needle, guidewire, and catheter placement. No patient had serious complications related to the drainage procedure. The mean procedure time required to drain one lesion was 35.6 +/- 13.6 min. Mean period after the drainage procedure until complete disappearance of the abscess as confirmed by CT was 12.4 +/- 10.0 days (range 3-46 days)., Conclusion: CT fluoroscopy is useful in achieving accurate and safe drainage of abnormal psoas fluid collections.

Objective: Finite element analysis of clinical computed tomography (CT) scans provides a noninvasive means of assessing vertebral strength that is superior to dual x-ray absorptiometry (DXA)-measured areal bone mineral density. The present study was undertaken to compare strength changes, measured using this newer method, in rheumatoid arthritis (RA) patients who were treated with alendronate (ALN) versus those who were not., Methods: Thirty female RA patients without radiologic signs of L3 compression fractures or a history of osteoporosis medication were enrolled in a prospective randomized clinical trial. Patients were randomly assigned to the ALN group (5 mg orally, once daily) or the control group not receiving antiresorptive treatment. All patients were evaluated by DXA and quantitative CT at baseline and reevaluated after a mean of 12.2 months. Nonlinear finite element analysis was performed on the CT scans (n = 29 available for analysis) to compute an estimate of vertebral compressive strength and to assess strength changes associated with changes in the trabecular compartment and the outer 2 mm of bone (peripheral compartment)., Results: On average, vertebral strength was significantly decreased from baseline in the control group (n = 15) (median change -10.6%; P = 0.008) but was maintained in the ALN group (n = 14) (median change +0.4%; P = 0.55), with a significant difference between the 2 groups (P < 0.01). Strength decreased more rapidly within the trabecular bone, and ALN treatment was much more effective in the peripheral than the trabecular compartment., Conclusion: Our results indicate that patients with RA can lose a substantial amount of vertebral strength over a relatively short period of time, and this loss can be prevented by ALN, primarily via its positive effect on the outer 2 mm of vertebral bone.

Purpose: We evaluated the difference in computed tomography (CT) attenuation values of the intracranial arterial and venous systems among the various contrast injection protocols (higher iodine delivery rate or higher concentration of the agent) on the source images of intracranial three-dimensional CT angiography (3D-CTA) using a multidetector-row CT (MDCT) scanner., Materials and Methods: We used 100 ml of iopamidol 300 at an injection rate of 3.0 ml/s, 100 ml of iopamidol 300 at an injection rate of 3.7 ml/s, and 80 ml of iopamidol 370 at an injection rate of 3.0 ml/s. There were 10 patients in each group. Attenuation values of the bilateral internal carotid arteries (ICAs), basilar artery trunk, bilateral cavernous sinuses (CSs), and Galenic vein were measured quantitatively on the axial CT angiographic source images obtained by four-channel MDCT., Results: Injection of the high-concentration contrast with a higher iodine-delivery rate achieved good arteriovenous contrast at the cavernous portion. With the same rate of iodine delivery, injection of the intermediate concentrate agent increased the CT value of not only the ICAs but also the CSs., Conclusion: High-concentration contrast could increase ICA attenuation without intracavernous attenuation gain during the "first-pass" phase.

We compared the alignment of 39 total knee replacements implanted using the conventional alignment guide system with 37 implanted using a CT-based navigation system, performed by a single surgeon. The knees were evaluated using full-length weight-bearing anteroposterior radiographs, lateral radiographs and CT scans. The mean hip-knee-ankle angle, coronal femoral component angle and coronal tibial component angle were 181.8 degrees (174.2 degrees to 188.3 degrees), 88.5 degrees (84.0 degrees to 91.8 degrees) and 89.7 degrees (86.3 degrees to 95.1 degrees), respectively for the conventional group and 180.8 degrees (178.2 degrees to 185.1 degrees), 89.3 degrees (85.8 degrees to 92.0 degrees) and 89.9 degrees (88.0 degrees to 93.0 degrees), respectively for the navigated group. The mean sagittal femoral component angle was 85.5 degrees (80.6 degrees to 92.8 degrees) for the conventional group and 89.6 degrees (85.5 degrees to 94.0 degrees) for the navigated group. The mean rotational femoral and tibial component angles were -0.7 degrees (-8.8 degrees to 9.8 degrees) and -3.3 degrees (-16.8 degrees to 5.8 degrees) for the conventional group and -0.6 degrees (-3.5 degrees to 3.0 degrees) and 0.3 degrees (-5.3 degrees to 7.7 degrees) for the navigated group. The ideal angles of all alignments in the navigated group were obtained at significantly higher rates than in the conventional group. Our results demonstrated significant improvements in component positioning with a CT-based navigation system, especially with respect to rotational alignment.

While mechanical strength of bone can be explained by measures of quantity up to 60 - 80%, several additional factors called 'quality' including microarchitecture have been proposed for better prediction of fracture risks. Osteoporosis medication can exert favorable effects on bone microarchitecture and strength, and has been evaluated by micro-CT using animal models. Studies are now moving toward the in vivo study using clinical imaging. Finite element analysis has been introduced for biomechanical evaluation of the bone, and this can be also applied to in vivo data. Several aspects of these basic and clinical researches will be discussed in this review.

Determination of the region of interest (ROI) for dynamic renal function has been highly discordant among operators because of the dependence on factors such as the rate of injection of radioactive medicines, constitution, and renal function. To simplify this problem, we developed a computer algorithm that provides automatic analysis for both localization of the kidney and automatic determination of ROIs using computed tomographic (CT) images. The bilateral kidneys were extracted from enhanced CT images, and the CT pixel size was adjusted to dynamic renal function images. The template-matching technique was used for these images, and the kidney renal location was analyzed on additional functional images constructed by dynamic renal function images. As a result, we were able to obtain time-activity curves of both renal function and quantified glomerular filtration rate (GFR). In conclusion, the computer algorithm we developed was considered to provide reliable results, apart from the variability among operators, because of its good reproducibility.

We reported the case of an 84-year-old female suffering from chemosis and exophthalmos. Carotid arteriograms revealed a direct carotid-cavernous fistula (CCF) but could not clearly show the fistula point because of its high-flow nature. We then performed three-dimensional computed tomographic angiography (3D-CTA) using a multi detector-row CT (MDCT) scanner. Multi-planar reformatted CT images distinctly revealed a right carotid aneurysm at the cavernous portion and a shunting point between the aneurysm and the cavernous sinus. Based on this information, we opted to performa transvenous coil embolization to treat this patient. Successful selective coil embolization was performed at the fistulous point was done with a smaller number of coils than ordinarily required in sinus packing. Performing 3D-CTA by using a MDCT was helpful in decision making for the selective coil embolization to treat direct CCF.

Computed tomography (CT)-guided thoracic sympathetic blockade with ethanol was performed while monitoring sympathetic nerve activity, with an alternating current (AC) galvanic skin reflex (GSR) monitor, in a patient with palmar hyperhidrosis in whom endoscopic thoracic sympathectomy was impossible because of pleural adhesion. Sweating was suppressed after the thoracic sympathetic blockade, and the monitor showed a significant increase in skin resistance. The effect of sympathetic blockade could be evaluated directly and in real time using a GSR monitor.

Our study evaluated the accuracy of an image-guided total knee replacement system based on CT with regard to preparation of the femoral and tibial bone using nine limbs from five cadavers. The accuracy was assessed by direct measurement using an extramedullary alignment rod without radiographs. The mean angular errors of the femur and tibia, which represent angular gaps from the real mechanical axis in the coronal plane, were 0.3 degrees and 1.1 degrees, respectively. The CT-based system, provided almost perfect alignment of the femoral component with less than 1 degrees of error and excellent alignment with less than 3 degrees of error for the tibial component. Our results suggest that standardisation of knee replacement by the use of this system will lead to improved long-term survival of total knee arthroplasty.

Although duodenal diverticulum is not uncommon, precise preoperative diagnosis is occasionally difficult. We report a patient with perforated duodenal diverticulum successfully diagnosed preoperatively by an upper gastrointestinal series followed by abdominal computed tomography (CT) scanning. An 81-year-old Japanese woman visited a local hospital because of right-sided abdominal pain. Physical examination revealed diffuse muscle guarding localized in the entire right-side of the abdomen indicative of peritonitis. While plain abdominal X-ray film revealed no free air, abdominal ultrasound and abdominal CT scanning revealed fluid collection and gas in the anterior perirenal space. An emergency upper gastrointestinal series, using water-soluble contrast media, demonstrated multiple diverticula in the descending portion and the horizontal portion of the duodenum. Leakage of the contrast material was found by the upper gastrointestinal series followed by the abdominal CT scanning, suggesting that the peritonitis was caused by the perforated duodenal diverticulum, and an emergency laparotomy was performed. The diverticulum in the descending portion of the duodenum was mobilized from the retroperitoneum and complete resection and peritoneal drainage were performed. The resected specimen showed that the diverticulum was 42 x 23 mm in size, and two separate sites of perforation were identified. The present case suggests that upper gastrointestinal series followed by CT scan is useful for the preoperative diagnosis of perforated duodenal diverticulum.

We evaluated the tibial tubercle position in knees with patellar instability. CT in full extension and at 30 degree flexion was used in 18 knees with instability and 18 control knees. Scans were taken at the level of the femoral epicondyles, tibial tubercle and distal tibia. We found that in full extension, the tibial tubercle was in a more lateral position in the unstable than in the control knees. At 30 degree flexion, the tibial tubercle in the unstable knees rotated internally, but it was never within the normal range. CT scans taken in full extension and at 30 degree flexion seem to be of value for ascertaining the degree of tibial tubercle malposition during knee flexion in patellar instability.

The anatomy of the portal vein branches in the caudate lobe of the liver was studied in 20 patients by double-phase CT arterial portography (DP-CTAP). DP-CTAP provided excellent images of the portal venous system in the first phase and the perfusion defects of intrahepatic tumors in the second phase. From DP-CTAP images of the first phase, a sufficient number of interpolated images were created for a smooth paging display. The ramifying structures of the portal system were traced on the monitor using the tracking ball. This method was found to be very effective and reliable for the anatomical assessment of the caudate lobe. The number and origins of the caudal portal branches were investigated in each case, and the caudate lobe of the liver could be divided into right and left segments.

The purpose of this study was to define the role of three-dimensional (3D) computed tomography (CT) in the head and neck diseases with bony abnormalities. Thirty-two patients were examined with a low dose radiation technique. Three-dimensional CT clearly delineated bony lesions in 27 of 32 patients. Three-dimensional CT could not demonstrate subtle bony erosions infiltrated by tumor, a temporal bone fracture, and a blow-out fracture, although two-dimensional (2D) images obtained before the 3D reconstructions clearly depicted those lesions. These two kinds of CT technique were thought to be complimentary.