Occupational radiation exposure of orthopedists at different locations during pedicle screw insertion: An anthropomorphic phantom study.

BACKGROUND: The purpose of this work was to evaluate orthopedic surgeons' exposure to occupational radiation doses from scattering using a mobile flat panel C-arm X-ray machine at different standing positions during an intraoperative pedicle screw implantation. OBJECTIVE: Evaluate the radiation dose received by medical staff, by applying flat X-ray machine in surgical room during an intraoperative pedicle screw implantation. METHODS: A mobile flat-panel C-arm X-ray machine at a dedicated orthopedic operating room was used to image an anthropomorphic female phantom which was set in a prone position on the operating table. The X-ray was projected horizontally, and 1 minute continuous fluoroscopy was used for lumbar spine and thoracolumbar spine during pedicle screw implantation. Scattering radiation doses to orthopedic surgeons were measured at different standing positions and body heights (50, 100, 150 cm above the ground) with and without limited collimations. RESULTS: The dose area product (DAP) in this experiment is normalized as 343 µGy⋅m2. In the four areas, the lowest scattered radiation measured by DF is 11.2 vs. 0.7 µSv, outside and inside the lead suit, respectively, with or without restricted field, 150 cm above the ground, and the lowest scattered radiation dose inside the lead suit. It is 1.3 vs. 0.5 µSv. Comparing the highest dose of the TF at with the lowest dose of the DF, the average result is 73.7 vs. 11.1 µSv, P< 0.05. CONCLUSIONS: Using a mobile flat-panel C-arm X-ray machine during a pedicle screw implantation, the minimum scattering radiation to surgeons was found to be at the terminal DF area based on the analysis of the scattering doses orthopedic surgeons were exposed to.

Evaluation of scattered radiation dose received by medical staff during uterine artery embolization in the operating room.

BACKGROUND: The air kerma radiation doses have gained much attention since the operating room interventional radiology is a place where medical staff are exposed to a fluoroscopy environment and gain a cumulative dose during the uterine artery embolization procedure. OBJECTIVE: We aimed to evaluate the radiation dose received by medical staff by applying a flat X-ray machine in the surgical room during uterine artery embolization. METHODS: An ATOM humanoid model was laid on the operating table and simulated a patient. The scattered radiation dose received by the radiologist, anesthetist and radiologic technologist was evaluated. The scintillation detector was adopted. The measurement points were 50 cm, 100 cm and 150 cm above the floor, representing the limbs, abdomen and thyroid level, respectively. We compared the X-rays under different tube voltages of 70, 80, and 90, respectively and frames per second (FPS) of 30, 15, and 7.5, respectively. We configured the dose level per pulse of 40 nGy with a fixed detector. RESULTS: In Section 1, when the tube voltage was 70 kVp and 7.5 FPS, the average radiation doses of limbs, abdomen and thyroid level was 0.48, 1.3 and 1.9 µSv/min respectively. When the tube voltage was 80 kVp and the fluoroscopy decreases from 30 FPS to 7.5 FPS, 58% of the radiation dose was reduced. When the tube voltage was 90 kVp, the radiation dose in the lead garment increased 31-177% in comparison to when the tube voltage was 80 kVp. Sections 2 and 3 were far away from the central ray, so the highest radiation dose 100 cm above the floor were 0.05 and 0.02 µSv/min. CONCLUSIONS: Lead garment can effectively reduce medical staff from occupational doses with an average attenuation rate of 90%. 80 kVp was most commonly used. Fluoroscopy 7.5 FPS was used 100 cm above the floor in A section and the lowest radiation dose was 1.33 µSv/min. The operator should decrease the duration of X-rays or adopt suspended lead shielding to decrease the radiation dose received by the operator. When kVp increases, the penetration increases. Decreasing FPS cannot decrease occupational doses of medical staff.

Quantitative assessment of three vendor's metal artifact reduction techniques for CT imaging using a customized phantom.

A metal implant was placed in an acrylic phantom to enable quantitative analysis of the metal artifact reduction techniques used in computed tomography (CT) scanners from three manufacturers. Two titanium rods were placed in a groove in a cylindrical phantom made by acrylic, after which the groove was filled with water. The phantom was scanned using three CT scanners (Toshiba, GE, Siemens) under the abdomen CT setting. CT number accuracy, contrast-to-noise ratio, area of the metal rods in the images, and fraction of affected pixel area of water were measured using ImageJ. Different iterative reconstruction, dual energy, and metal artifact reduction techniques were compared within three vendors. The highest contrast-to-noise ratio of three scanners were 85.7 ± 8.4 (Toshiba), 85.9 ± 11.7 (GE), and 55.0 ± 14.8 (Siemens); and the most correct results of metal area were 157.1 ± 1.4 mm2 (Toshiba), 155.0 ± 1.0 (GE), and 170.6 ± 5.3 (Siemens). The fraction of affected pixel area obtained using single-energy metal artifact reduction of Toshiba scanner was 2.2% ± 0.7%, which is more favorable than 4.1% ± 0.7% obtained using metal artifact reduction software of GE scanner (p = 0.002). Among all quantitative results, the estimations with fraction of affected pixel areas matched the effect of metal artifact reduction in the actual images. Therefore, the single-energy metal artifact reduction technique of Toshiba scanner had a desirable effect. The metal artifact reduction software of GE scanner effectively reduced the effect of metal artifacts; however, it underestimated the size of the metal rods. The monoenergetic and dual energy composition techniques of Siemens scanner could not effectively reduce metal artifacts.

Personal Exposure Prescription Method Reduces Dose in Radiography.

PURPOSE: To evaluate the effectiveness of an automatic, personalized exposure prescription method designed to reduce radiation dose during radiography examinations. METHODS: Using standard imaging parameters of average-sized patients, the authors measured individual body-part thicknesses or imaging regions of 116 patients (69 men, 47 women) and calculated each patient's exposure amount according to the thickness of the part or region. The data were used to develop each patient's personalized exposure prescription. Using the personalized exposure prescriptions, authors acquired chest images of the patients on a Carestream DRX-Revolution mobile digital radiography system. RESULTS: All images acquired using the personalized exposure prescription method were satisfactory for diagnosis; exposure indexes were above 1300, a figure deemed acceptable for diagnosis by the manufacturer. The personalized exposure method reduced the amount of radiation each patient received. DISCUSSION: Variation of tube voltage alone can control patients' exposure levels; however, using the personalized exposure prescription method eliminates the need to use automatic exposure controls. CONCLUSION: The personalized exposure prescription method is an effective tool for reducing radiation to patients during radiography as well as for eliminating dose creep.

Cancer Patient-Derived Circulating Microparticles Enhance Lung Metastasis in a Rat Model: Dual-Source CT, Cellular, and Molecular Studies.

PURPOSE: This study aimed to test the hypothesis that lung cancer patient-derived circulating microparticles (LCC-MPs) enhance metastatic lung tumors in a rat model. PROCEDURES: The controls (n = 6) and LCC-MP-treated rats (n = 6) with N1S1-induced pulmonary metastatic hepatocellular carcinoma (HCC) underwent dual-source CT (DSCT) on days 10, 15, and 20. Cellular and molecular studies were performed subsequently. RESULTS: DSCT revealed slow progression of metastatic lung tumors in the controls. Compared with the controls, the LCC-MP-treated rats exhibited significantly more and larger metastatic tumors on days 15 and 20 on DSCT, enhanced angiogenesis with higher microvessel count (CD34+), more CXCR4+ and VEGF+ cells in immunohistofluorescence studies, and higher protein expression levels of eNOS, angiopoietin, vascular endothelial growth factor, and CD31 on western blotting (Mann-Whitney test, all P < 0.05). CONCLUSIONS: LCC-MPs can elicit oncogenic stimulation and accelerate metastatic HCC growth in rat lung as demonstrated on DSCT and enhanced tumoral angiogenesis as confirmed in cellular and molecular studies.

Accuracy of dual-energy computed tomography for the quantification of iodine in a soft tissue-mimicking phantom.

The objective of this study was to evaluate the accuracy of dual-energy CT (DECT) for quantifying iodine using a soft tissue-mimicking phantom across various DECT acquisition parameters and dual-source CT (DSCT) scanners. A phantom was constructed with plastic tubes containing soft tissue-mimicking materials with known iodine concentrations (0-20 mg/mL). Experiments were performed on two DSCT scanners, one equipped with an integrated detector and the other with a conventional detector. DECT data were acquired using two DE modes (80 kV/Sn140 kV and 100 kV/Sn140 kV) with four pitch values (0.6, 0.8, 1.0, and 1.2). Images were reconstructed using a soft tissue kernel with and without beam hardening correction (BHC) for iodine. Using the dedicated DE software, iodine concentrations were measured and compared to true concentrations. We also investigated the effect of reducing gantry rotation time on the DECT-based iodine measurement. At iodine concentrations higher than 10 mg/mL, the relative error in measured iodine concentration increased slightly. This error can be decreased by using the kernel with BHC, compared with the kernel without BHC. Both 80 kV/Sn140 kV and 100 kV/Sn140 kV modes could provide accurate quantification of iodine content. Increasing pitch value or reducing gantry rotation time had only a minor impact on the DECT-based iodine measurement. The DSCT scanner, equipped with the new integrated detector, showed more accurate iodine quantification for all iodine concentrations higher than 10 mg/mL. An accurate quantification of iodine can be obtained using the second-generation DSCT scanner in various DE modes with pitch values up to 1.2 and gantry rotation time down to 0.28 s. For iodine concentrations ≥ 10 mg/mL, using the new integrated detector and the kernel with BHC can improve the accuracy of DECT-based iodine measurements.

Assessment of hepatic fatty infiltration using dual-energy computed tomography: a phantom study.

The purpose of this study was to examine the performance of dual-energy computed tomography (DECT) for the quantification of liver fat content (LFC). We prepared two phantoms: homogenized mixtures of porcine liver and fat and homogeneous mixtures of liver- and fat-equivalent solutions. Tubes containing mixtures with known fat concentrations were scanned on a dual-source CT scanner using two DE scanning protocols (80 kV/Sn140 kV and 100 kV/Sn140 kV). Attenuation curves obtained from DECT were used to describe attenuations of various degrees of LFC at different energies. LFC was calculated from DECT data and compared with the known LFC. The phantom made of liver/fat mixtures was not used for liver fat quantification because the increase of fat content did not show a decline of CT numbers. This may be due to inhomogeneity as observed in CT images. Attenuation curves obtained from two DE scanning protocols had the ability to discriminate small differences in fat concentrations. Our results also showed a strong correlation between DECT measurements and known LFC (R(2) > 0.99, P < 0.005). DECT will be a reliable tool for liver fat quantification. Furthermore, attenuation curves obtained from DECT data can be used for discriminating various degrees of LFC.

Detection of receiver location and migration after cochlear implantation using 3D rendering of computed tomography.

OBJECTIVES: The purpose of this study was to objectively evaluate the position and migration of the cochlear implant receiver and ball electrode using 3-dimensional (3D) rendering of computed tomography. STUDY DESIGN: Retrospective case review. SETTING: Tertiary referral center. PATIENTS: Thirty-one patients were treated for profound sensorineural hearing loss with cochlear implant. The operative methods were divided into 2 groups: an inverted J-shaped incision with bony tie-down suture, and a minimally invasive incision without tie-down suture. INTERVENTION(S): When the receiver and ball electrode were detected in 3D imaging, the zygomatic process-receiver angle (ZRA), ear canal to receiver distance (ERD), and ear canal to ball electrode distance (EBD) were measured. MAIN OUTCOME MEASURE(S): Comparison and statistical analysis of postoperative angle and distances. RESULTS: The mean ZRA, EBD, and ERD values were 139.1 degrees, 20.7 mm, and 36.0 mm, respectively. The mean ZRA in patients with an inverted J-shaped incision was significantly wider than for those with a minimally invasive incision (151.2 versus 136.9, p = 0.002). In 10 patients who received postoperative computed tomography 2 times, ZRA increased from 138.6 to 144.4 degrees (p < 0.001) and ERD decreased from 37.0 to 34.9 mm (p = 0.001). CONCLUSION: 3D computed tomography is a useful tool for localization and migration of the receiver and ball electrode. Micro downward movements of the receiver were found in both bony tie-down and non-tie-down suture groups.

Nasal leech infestation: report of seven leeches and literature review.

Nasal leech infestation rarely occurs in society today and it is usually reported as an anecdote. In this study, we present seven nasal leeches in six patients from 1984 to 2008. All patients initially presented with epistaxis. Four patients were less than 8 years old and two patients were older than 60 years old. All patients had spent time in rural streams 2 weeks to 2 months before the symptoms occurred. All of the seven leeches were removed smoothly and one leech migrated to the oropharynx during the operation. The length of the leeches ranged from 2 to 12 cm with an average length of 4.6 cm. Attention should be given to nasal leech infestation, especially in children and senior citizens who have visited rural streams and have been exposed to freshwater. One of our patients had two leeches lodged in his nasal cavities. Therefore, it is also important to re-examine both nasal cavities after the removal of one leech.