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.

Application of a true lateral virtual radiograph from 3D-CT to identify the femoral reference point of the medial patellofemoral ligament.

PURPOSE: The purpose of this study is two-fold: (1) to describe the femoral reference point of the medial patellofemoral ligament (MPFL) on a virtual true lateral radiograph reconstructed from a three-dimensional computed tomography (3D-CT) image and (2) to compare this point with that of patients without patellofemoral instability and with Schöttle's point. METHODS: A total of 26 consecutive patients (29 affected knees) with recurrent patellar dislocation (RPD), who underwent MPFL reconstruction were included in this study (4 males; 22 females; mean age, 24.0 years old). Using a true lateral 3DCT image, the MPFL femoral insertion was identified and marked with a 2-mm circle, and this image was reconstructed as a virtual true lateral radiograph. Following Schöttle's method, the point of intersection was described by their anterior-posterior and proximal-distal positions. As a control population, 29 age- and gender-matched patients with anterior cruciate ligament (ACL) injuries were also analysed. RESULTS: The points in RPD patients were located significantly posterior (-2.5 ± 2.3 mm, p < 0.01) to the line representing an extension of the posterior cortex of the femur and distal (- 6.9 ± 2.4 mm, p < 0.01) to the posterior origin of the medial femoral condyle compared with those in the control population. The mean reference point of RPD patients was located in a 3.8-mm posterior and 4.4-mm distal position compared with Schöttle's point. CONCLUSIONS: An anatomical and radiographic femoral reference point of the MPFL on a true lateral virtual radiograph was described with our method. In patients with RPD, this reference point was identified to be more posterior and distal to Schöttle's point. More anatomical and individualized MPFL reconstruction will be secured using our method. LEVEL OF EVIDENCE: Level IV.

[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.

Preoperative simulation of the running course of the abducens nerve in a large petroclival meningioma: a case report and literature review.

One of the most important and useful pieces of information in the preoperative evaluation of a large petroclival meningioma is the running course of the abducens nerve. The abducens nerve is small and has a long intracranial course, making it prone to compression by the tumor at various anatomical points. In relatively large tumors, it is difficult to confirm the entire course of the abducens nerve, even by heavy T2-thin slice imaging. We report a case of successful preoperative estimation of the course of the abducens nerve that aided in its complete preservation during the resection of a large petroclival tumor.

Morphologic evaluation of remnant anterior cruciate ligament bundles after injury with three-dimensional computed tomography.

PURPOSE: This study aimed to investigate the morphological patterns of remnant anterior cruciate ligament bundles after injury (ACL remnant) on three-dimensional computed tomography (3DCT) and compare them with those on arthroscopy. METHODS: Sixty-three patients (33 males and 30 females; mean age 25.2 ± 10.1 years) who had undergone primary ACL reconstruction between March 2011 and December 2012 were included in this study. The average durations between traumas and 3DCT and between 3DCT and surgery were 101.7 ± 87.2 and 38.2 ± 38.7 days, respectively. ACL remnants were classified into four morphological patterns on 3DCT. 3DCT findings were compared with arthroscopic findings with and without probing. RESULTS: The morphological patterns of the ACL remnants on 3DCT were well matched with those on arthroscopy without probing (the concordance rate was 77.8%). However, the concordance rate was reduced to 49.2% when arthroscopic probing was used to confirm the femoral attachment of ACL remnants (p ≤ 0.05). CONCLUSIONS: This study demonstrates that the morphological patterns of ACL remnants on 3DCT were well matched with those on arthroscopy without probing. Therefore, the technique can be useful for preoperative planning of the ACL reconstruction or informed consent to the patients. However, for definitive diagnosis, arthroscopic probing is required. LEVEL OF EVIDENCE: IV.

Simulated anterior cruciate ligament reconstruction using preoperative three-dimensional computed tomography.

PURPOSE: The aim of this study was to ascertain the ideal far anteromedial portal location to avoid damaging the medial femoral condyle in anterior cruciate ligament (ACL) reconstruction. METHODS: Forty patients received preoperative computed tomography (CT) scans at 120° of knee flexion. Three-dimensional CT (3D CT) reconstruction of the knee was performed using volume rendering. The insertion of anteromedial (AM) and posterolateral bundle of ACL of the femur was marked on the 3D CT. A line (Line A) was drawn 8-mm proximal and parallel to the anterior ridge of the medial tibial plateau. A tangential line to the medial femoral condyle was drawn from the AM position that was already marked to Line A. The length from the intersection of the lines to the medial edge of the patellar tendon was measured. RESULTS: In all 40 patients, the mean length between the medial edge of the patellar tendon and the far anteromedial portal was 27.5 ± 0.7 mm (range 19.8-34.5). In men 29.5 ± 0.7 mm (range 25-34.5); 28.7 ± 0.8 mm in the shorter group (height ≤ 170 cm) and 30.1 ± 1.2 mm in the taller group (height ≥ 170 cm). In women 25.5 ± 1.0 mm (range 19.8-30.5); 22.9 ± 1.0 mm in the shorter group (height ≤ 158 cm) and 29.6 ± 0.5 mm in the taller group (height ≥ 158 cm). CONCLUSIONS: An optimum far anteromedial portal position was proposed. Knowing the optimum location of the far anteromedial portal position before surgery allows the surgeons to perform more safety ACL reconstruction. LEVEL OF EVIDENCE: IV.

[Effects of differences in head holder on image quality and radiation dose in head CT].

PURPOSE: For emergency or pediatric head CT scans, a simplified pillow made of hard sponge instead of a dedicated head holder may be used if it is difficult to immobilize the head. However, the radiation dose when using a simplified head holder may be increased due to radiation absorption by the patient couch if the automatic exposure control (AEC) system is used. In this phantom study, we compared the radiation dose delivered when using a dedicated and a simplified head holder. MATERIALS AND METHODS: We used a dedicated-type and a pillow-type head holder made of hard sponge (simplified head holder). We placed a 20 cm-diameter cylindrical phantom made of water-equivalent material and an anthropomorphic head phantom in the head holders and then scanned them five times with a 64-detector CT scanner (VCT, GE Healthcare). We performed step-and-shoot and helical scanning with AEC; the noise index was set to 2.8. We measured the radiation dose using fluorescent glass dosimeters in the head phantom and the image noise at five sites in the cylindrical phantom. All values were averaged. RESULTS: With step-and-shoot scans, the mean image noise with the dedicated and the simplified head holder was 3.30 ± 0.05 [SD] and 3.20 ± 0.05, respectively. With helical scans they were 3.00 ± 0.09 and 2.88 ± 0.03, respectively. There was no statistically significant difference (p = 0.02 and 0.04, Student's t-test). The radiation doses with the dedicated and the simplified head holder were 58.6 and 70.4 mGy, respectively, for step-and-shoot scanning and 41.8 and 49.0 mGy, respectively, for helical scanning. The doses were thus significantly higher with the simplified head holder for both step-and-shoot and helical scanning (p < 0.01 and < 0.01). CONCLUSION: We recommend the use of a dedicated head holder for head scanning with AEC since the radiation dose was lower than with the simplified head holder.

Development of an Original Three-Dimensional Computed Tomography Scan Method and Imaging Process for Surgical Support of the Anterior Cruciate Ligament.

Three-dimensional computed tomography (3D CT) scan images are useful as they can provide information essential for surgical support, particularly in orthopedic surgery. In the case of anterior cruciate ligament (ACL) reconstruction, a 3D CT scan is important in preoperative simulation. Furthermore, it is associated with a reduced risk of revision surgery because the angle of the foramen magnum changes with the femoral muscle mass. However, the CT scan system geometry has several limitations. For example, the patient's posture is limited during the procedure. Herein, we report an original CT scan method and 3D imaging process for surgical support of the ACL.

[Transorbital penetrating intracranial injury by a chopstick: a case report and review of the literature].

This 4-year-old girl fell while holding plastic chopsticks and a chopstick penetrated her left eye. The chopstick was removed immediately by herself. Conventional CT and MR images showed a penetration track from the orbital roof to the basal ganglia. On susceptibility-and diffusion-weighted images the track and surrounding cytotoxic edema were visualized more clearly. Although antibiotics were started at the time of admission to prevent intracranial infection, she developed meningitis. Subsequent treatment with carbapenem antibiotic-and vancomycin therapy was curative and she was discharged home 4 weeks after the injury. In our review of the literature on intracranial penetrating injuries via the orbita we compared the injury patterns inflicted by and the clinical observations reported on damage induced by wooden-, plastic-, and metal chopsticks. We also evaluated diagnostic CT and MR images in patients with intracranial penetrating injuries caused by chopsticks and documented the advantage of susceptibility-and diffusion-weighted imaging over conventional CT-and MR imaging.

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.

Utility of dual-energy CT for predicting the vascularity of meningiomas.

PURPOSE: Dual-energy computed tomography (DECT) can provide iodine, electron density (ED), and effective atomic number Z (Zeff) maps, facilitating the identification of tissue types. We investigated whether DECT parameters can predict the vascularity of meningiomas. METHOD: We acquired DECT and perfusion CT (PCT) images in 24 patients with histologically diagnosed meningioma. Regions of interest (ROIs) were placed at the tumor in iodine, ED, and Zeff maps derived from DECT and in a blood volume (BV) map derived from PCT. To normalize these parameters' values, we divided them by the values of contralateral normal-appearing white matter, i.e., the relative (r)ED, rZeff, and rBV. The vascular density of the tumor specimens was immunohistochemically analyzed by calculating the von Willebrand factor-positive vessel wall. We calculated Pearson's correlation coefficients to determine the correlation with PCT/DECT parameters and an immunohistopathological index. RESULTS: Contrast rZeff (r = 0.7020, p = 0.0001) and iodine (r = 0.5814, p = 0.0029) both had positive correlations with rBV derived from PCT. The rED values were negatively correlated with the rBV values (r = -0.4735, p = 0.0194), and the vascular density results confirmed positive correlations with rBV (r = 0.6909, p = 0.0002) and contrast rZeff (r = 0.4982, p = 0.0132) and a negative correlation with rED (r = -0.4265, p = 0.0377). Regarding the radiation exposure, the mean estimated volume CT dose index (CTDIvol) of DECT was 33.1 ± 1.72 mGy, much lower than that of PCT (103.3 ± 4.65 mGy). CONCLUSIONS: DECT predicted vascular density with lower radiation exposure compared to PCT. DECT could potentially replace PCT for evaluating the vascularity of meningiomas.

Significant correlation between spleen volume and thrombocytopenia in liver transplant patients: a concept for predicting persistent thrombocytopenia.

Interferon (IFN) therapy with or without ribavirin treatment is well established as a standard antiviral treatment for hepatitis C virus (HCV)-infected patients. However, susceptibility to thrombocytopenia is a major obstacle for initiating or continuing this therapy, particularly in liver transplant (LTx) recipients with HCV. Studies have reported that splenectomy performed concurrently with LTx is a feasible strategy for conditioning patients for anti-HCV IFN therapy. However, the relationship between the severity of splenomegaly and alterations in the blood cytopenia in LTx recipients remains to be clarified. Here, we analyzed the relationship between spleen volume (SV) and thrombocytopenia in 45 patients who underwent LTx at Hiroshima University Hospital. The extent of pre-LTx splenomegaly [the SV to body surface area (BSA) ratio in an individual] was inversely correlated with both the post-LTx white blood cell count and platelet (PLT) count (P < 0.001). Furthermore, the PLT count of patients with thrombocytopenia (PLT count or= 400), persistent thrombocytopenia is predictable after LTx.

Perfusion Computed Tomography Parameters Are Useful for Differentiating Glioblastoma, Lymphoma, and Metastasis.

BACKGROUND: Perfusion computed tomography (PCT) reflects blood flow and capillary condition, which is valuable in assessing brain tumors. We evaluated PCT parameters at the tumor (t) and peritumoral (p) region to differentiate malignant brain tumors. METHODS: We performed PCT in 39 patients with supratentorial malignant brain tumors (22 glioblastomas, 6 lymphomas, 11 metastases). Regions of interests were placed manually at tumor, peritumoral region, and contralateral normal-appearing white matter. Cerebral blood volume (CBV), cerebral blood flow (CBF), mean transit time (MTT), and permeability surface (PS) were measured. These parameters were divided by those of contralateral normal-appearing white matter to normalize at tumor (relative [r]CBVt, rCBFt, rMTTt, rPSt) and peritumoral regions (rCBVp, rCBFp, rMTTp, rPSp). The parameters were evaluated with Mann-Whitney U test and receiver operating characteristics analyses. Stepwise analyses also were performed to select useful PCT parameters for differentiating these tumors. RESULTS: The rCBFt and rCBVt of glioblastoma (GBM) were greater than those of primary central nervous system lymphoma (PCNSL) (P = 0.0005, 0.0002) and brain metastasis (METS) (P = 0.0044, 0.0028). The rMTTp of METS was greater than that of GBM and PCNSL (P = 0.0001, 0.0007). The combination of rCBVt and rPSt could differentiate GBM from other tumors with sensitivity and specificity of 81.8% and 94.1%. The combination of rCBFp and rMTTp could differentiate METS from other tumors with sensitivity and specificity of 90.9% and 82.1%. CONCLUSIONS: Our study introduces and supports the usefulness of PCT parameters for differentiation among GBM, PCNSL, and METS. rCBVt and rPSt may be the best predictors of GBM. rCBFp and rMTTp may be the best predictors of METS.

[Evaluation of improvement of the detection of interstitial lung diseases by using the dual-energy subtraction radiography method of a flat-panel detector system].

We investigated and evaluated the detection of simulated lesions in various interstitial lung diseases using the dual-energy subtraction radiography method and flat-panel detector (FPD) images. We obtained a FPD system (GE Revolution XR/d), and employed dual-energy 60 kV and 130 kV exposure techniques. Three types of lung lesions, namely, micro-nodule, ground-glass, and honeycomb patterns were simulated with interstitial lung disease on a chest phantom. Chest images with and without simulated lesions were exposed and compared with standard images and subtraction images. We carried out evaluations with and without subtraction images and performed the analysis by using receiver operating characteristic (ROC) analysis of detection. Results showed that the detection of interstitial lung diseases was significantly improved by the use of subtraction images. The area under the ROC curve (AUC) values of micro-nodule images obtained with and without subtraction images were 0.768 and 0.963, ground-glass images 0.670 and 0.917, and honeycomb images 0.768 and 0.996, respectively. A significant difference of p<0.05 was accepted. The use of dual-energy subtraction radiography with a FPD improved diagnostic accuracy in detecting cases of multiple interstitial lung diseases and was considered useful.

Bone tunnel change develops within two weeks of double-bundle anterior cruciate ligament reconstruction using hamstring autograft: A comparison of different postoperative immobilization periods using computed tomography.

BACKGROUND: The purpose of this study was to evaluate bone tunnel changes following anterior cruciate ligament (ACL) reconstruction during the early postoperative period using computed tomography (CT), and to understand the impact of postoperative immobilization on these changes. METHODS: Twenty patients who underwent double-bundle ACL reconstruction using hamstring tendon autografts were included. We subcategorized patients into two groups: patients who underwent isolated ACL reconstruction and had three days of knee immobilization (Group A, n=10); and patients with concomitant meniscus injuries who underwent ACL reconstruction and meniscus repair simultaneously (Group B, n=10) had their knees immobilized for two weeks after surgery. Bone tunnel enlargement was evaluated using CT imaging at one to three days, two weeks, one month, three months and six months after surgery. The cross-sectional area of the femoral and tibial tunnels was measured, and enlargement rate was calculated. The tunnel center location at two weeks after surgery was also evaluated. RESULTS: The mean cross-sectional area adjacent to the joint space of the femoral and tibial tunnels significantly increased immediately after surgery, especially in the first month (P<0.01). However, after one to six months they were not increased (P>0.01). There was no significant difference in tunnel enlargement rate between group A and B. Tunnel center location changed even in the first two weeks. CONCLUSIONS: Bone tunnel enlargement following double-bundle ACL reconstruction occurred at an earlier time point after surgery than anticipated. Postoperative immobilization could not prevent bone tunnel enlargement, but might prevent tunnel migration.

Permeability Surface Area Product Using Perfusion Computed Tomography Is a Valuable Prognostic Factor in Glioblastomas Treated with Radiotherapy Plus Concomitant and Adjuvant Temozolomide.

OBJECTIVE: The current standard treatment protocol for patients with newly diagnosed glioblastoma (GBM) includes surgery, radiotherapy, and concomitant and adjuvant temozolomide (TMZ). We hypothesized that the permeability surface area product (PS) from a perfusion computed tomography (PCT) study is associated with sensitivity to TMZ. The aim of this study was to determine whether PS values were correlated with prognosis of GBM patients who received the standard treatment protocol. METHODS: This study included 36 patients with GBM that were newly diagnosed between October 2005 and September 2014 and who underwent preoperative PCT study and the standard treatment protocol. We measured the maximum value of relative cerebral blood volume (rCBVmax) and the maximum PS value (PSmax). We statistically examined the relationship between PSmax and prognosis using survival analysis, including other clinicopathologic factors (age, Karnofsky performance status [KPS], extent of resection, O6-methylguanine-DNA methyltransferase [MGMT] status, second-line use of bevacizumab, and rCBVmax). RESULTS: Log-rank tests revealed that age, KPS, MGMT status, and PSmax were significantly correlated with overall survival. Multivariate analysis using the Cox regression model showed that PSmax was the most significant prognostic factor. Receiver operating characteristic curve analysis showed that PSmax had the highest accuracy in differentiating longtime survivors (LTSs) (surviving more than 2 years) from non-LTSs. At a cutoff point of 8.26 mL/100 g/min, sensitivity and specificity were 90% and 70%, respectively. CONCLUSIONS: PSmax from PCT study can help predict survival time in patients with GBM receiving the standard treatment protocol. Survival may be related to sensitivity to TMZ.

A feasibility study: evaluation of radiofrequency ablation therapy to hepatocellular carcinoma using image registration of preoperative and postoperative CT.

RATIONALE AND OBJECTIVES: The therapeutic response to radiofrequency ablation (RFA) of hepatocellular carcinoma (HCC) often is evaluated by comparing pre- and post-RFA computed tomography (CT). However, judgment about whether an ablative margin, ie, 5-10 mm of normal hepatic tissue, is ensured sometimes is difficult. The aim of this study is to assess the feasibility of fusion images of pre- and post-RFA CT. MATERIALS AND METHODS: HCCs (n = 20) sized 13 +/- 5 mm (range, 4-23 mm) were included. For pre-RFA CT, the arterial phase of intravenous dynamic CT (n = 17), CT arterioportography (n = 2), and CT hepatic arteriography (n = 1) was used. Using automatic image registration software (n = 20) and a manual segmentation technique (n = 4), fusion images were created in combination with post-RFA CT (equilibrium phase of intravenous CT). RESULTS: Automatic image registration and manual segmentation technique took approximately 2-3 and 5 minutes, respectively. Total time required for the creation of fusion images was less than 10 minutes in all cases. Fusion images enabled easier understanding of the relationship between the tumor and ablation zone, helping judge whether an ablative margin was ensured. CONCLUSION: Fusion of pre- and post-RFA CT images is considered a feasible tool in the evaluation of RFA therapy for HCC.

Timing on 16-slice scanner and implications for 64-slice cardiac CT: do you start scanning immediately after breath hold?

RATIONALE AND OBJECTIVES: Slow heart rate and small changes in heart rate are factors for improving image quality on spiral cardiac computed tomography (CT). The purpose of this study is to investigate whether it is possible to improve non-enhanced cardiac CT quality by delaying the data-acquisition window after breath hold. MATERIALS AND METHODS: Electrocardiograph files (n = 240) for 16-slice non-enhanced cardiac CT scans were analyzed. Mean heart rates and maximal changes in heart rates between adjacent cardiac cycles were compared between phase 1 (defined as cardiac cycles 1-5), phase 2 (cardiac cycles 2-6), ... , and phase 6 (cardiac cycles 6-10). RESULTS: Heart rates gradually increased by phases, but were limited to a range of 66.8-68.0 beats/min. Maximal changes in heart rates were 2.5 beats/min (phase 1) at the highest and 1.3 beats/min (phases 5 and 6) at the lowest (t-test; P < .01). Maximal changes in heart rates for more than five beats/min occurred in 24, eight, and eight patients on phases 1, 5, and 6, respectively (chi-square test; P < .01). CONCLUSION: The delayed scan (four or five cardiac cycles after breath hold) has the potential to improve the quality of non-enhanced cardiac CT.