C-arm Machine Research Articles

Application of a self-designed handy body position scaffold in fluoroscopy for lower limb surgery

Objective To evaluate the application of a self-designed handy body position scaffold in the fluoroscopy for lower limb surgery. Methods We reviewed the intraoperative X-ray films of 161 patients with lower limb fracture who had undergone intraoperative fluoroscopy using our self-made handy body position scaffold during surgery from October 2013 to May 2017. They were 105 males and 56 females, aged from 10 to 91 years (mean, 39.7 years). There were 42 femoral fractures of middle or lower shaft, 12 fractures of medial or lateral condyle or tibial plateau, 96 tibiofibular fractures, 7 ankle fractures and 4 foot fractures. The operation time, intraoperative fluoroscopy time, intraoperative bleeding, rate and time of fracture union, and complications were recorded. Results All the 161 patients completed intraoperative fluoroscopy and radiography uneventfully, indicating that the handy body position scaffold effectively maintained the body position of the affected ipsilateral lower limb. The body position scaffold was slightly deviated due to one overweight (121 kg) patient when the knee joint was flexed 90°, but the fluoroscopy and radiography was completed after adjustment of the C-arm roentgenographic machine. The operation time averaged 71.5 minutes (from 28 to 119 minutes), the X-ray exposure time 9.8 seconds (from 6 to 31 seconds), and the intraoperative bleeding 157.2 mL (from 80 to 500 mL). The 161 patients obtained follow-up for 5 to 22 months (average, 14.1 months). The rate of primary union was 97.5% (157/161). The time for fracture union averaged 8.8 weeks (from 4 to 17 weeks). Fracture nonunion occurred in one case, and delayed union in 3 cases. The final follow-ups revealed normal functional recovery of the affected knees and ankles, but no limb shortening, or no rotational, lateral or anteroposterior angulation deformity. Conclusion In the lower limb surgery, the intraoperative fluoroscopy can be completed better with the aid of our self-designed handy body position scaffold that prevents movement of the affected lower limb and lowers the risk of radiation exposure. Key words: Lower limbs; Fractures, bone; Fracture fixation, internal; External fixator

Monte Carlo Study of 3D Stray Radiation during Interventional Procedures

In interventional medical procedures, other than the highly important issue of optimizing image quality and patient exposure using the primary beam, there remains a continuing need for the study of staff exposure from the scattered radiation. Herein, investigation is made of the 3D stray-radiation distribution, the simulation being made of a realistic interventional scenario through use of the Monte Carlo code Geant4 (version 10.3). The simulation is conducted based on the high definition reference Korean-man (HDRK-man) computational phantom and a GE Infinia 3/8” C-arm machine, focusing on the effect of variation of kVp and field of view (FoV) on the scattered particles’ spatial distribution. With direct measurement of the absorbed dose remaining challenging, not least in respect of the organs at risk, we computed the scatter fractions, defined as the ratio of the air kerma free-in-air to the entrance surface air kerma (ESAK), which are both easily quantifiable. Scatter fraction distributions were simulated for X-ray tube outputs (and half-value layers, HVL) of 60 kVp (2.3 mm Al), 80 kVp (3.2 mm Al) and 120 kVp (4.3 mm Al) and FoV of 15, 20, 25 and 30 cm. The distributions are obtained for different height levels, corresponding to the lens of the eye, and the lung and prostate, all radiosensitive organs. Investigations are made for eight likely locations around the patient. At fixed FoV results reveal an inverse relationship between ESAK and kVp, also that change in kVp from 60 to 80 has a greater effect than from 80 to 120. For change in FoV at fixed kVp, the scatter fraction remains constant. The particular staff locations are found to be optimal in seeking mitigation of dose. Moreover, the combined usage of numerical human model and Monte Carlo simulation can be considered as an added value to the radiation safety research field, especially to the interventional radiology staff and to the patient.

Accuracy of C-arm measurements in assessment of paediatric femoral fracture shortening.

PurposeSpica casting of femoral shaft fractures is standard practice for young children. In 1983, Dr. Rang published an illustration demonstrating that radiographs can be misleading when measuring femoral fracture shortening. Today, fluoroscopy is used to determine shortening after closed reduction and spica casting. This paper aims to determine the accuracy of fluoroscopy when measuring 25 mm of shortening in a femur fracture sawbone model.MethodsMagnification, elevation and angulation were evaluated using a femur fracture sawbone model with a fixed overlap of 25 mm. Two C-arm machines used in clinical practice were studied: the OEC 9900 Elite GE C-arm and the Fluoroscan InSight mini C-arm.ResultsThe OEC 9900 Elite GE C-arm demonstrated a 1.75 × magnification. The Fluoroscan InSight mini C-arm demonstrated a 2.5 × magnification. An 11% and a 17% magnification with elevation of the femur to 8 cm occurred using the OEC 9900 Elite GE and the Fluoroscan InSight mini C-arm respectively. Changing the tube angulation from 0° to 60° resulted in a 36% and 16% change in measured femur fracture shortening on the OEC C-arm and Fluoroscan mini C-arm respectively.ConclusionC-arm images are inaccurate. When measuring 25 mm of shortening of a paediatric femur fracture, each machine has a unique amount of magnification that should be determined and accounted for in clinical practice. Elevation of the femur above the C-arm receiver and angulation of the femur further increase the inaccuracies when measuring 25 mm of fracture shortening. Images perpendicular to the fracture are most accurate.

Trajectory Optimization for VMAT Treatment Aided by Artificial Intelligence

Artificial Intelligence (AI) recently beat the top GO players. With the help of AI, here we tried to tackle one of the most difficult optimization problems in radiation oncology: designing an efficient trajectory to deliver an isocentric VMAT treatment with an optimum dose distribution on a C-arm machine, where the gantry and couch move in coordination. The state of art trajectory optimization still requires human expert to design heuristic algorithms such as those based on BEV or BEVD. We discretize the 4pi space into 2701 nodes, where the gantry and couch rotations are separated by 5 degrees. To search through the vast number of possible trajectories, we implemented Monte Carlo Tree Search (MCTS), the same method used by the AI which mastered the game of GO. Each simulated trajectory picks the nodes one by one. The next selected node would firstly need to be physically reachable, constrained by the rotation speed of the gantry and couch, as well as collision. Secondly it would have the maximum Upper Confidence Bounds for Trees (UCT), which is a function of average objective function value, the number of time this node has been selected and the total number of simulations. After forming a full trajectory, we run an inverse fluence map optimization with an infinity norm regularization term and the alternating direction method of multipliers (ADMM), using all the nodes on the trajectory. The obtained objective function value is then fed back to update the statistic of the nodes on the trajectory. The infinity norm regularization forces a solution with uniform fluence maps, close to that of VMAT treatment. The MCTS continues until the solution does not improve anymore or a predetermined time is reached. We tested the MCTS method with two challenging patient cases, one chest wall, and one skull and compared the dosimetry with coplanar plans. Without loss of generality, we confine the couch rotate uniformly from -90° to 90° with a speed of 0.5 degree/second and put no constraint on the gantry movement. The dose calculations are performed on the fly with the aid of GPU. For both patient cases, the AI with MCTS found optimum trajectories within an hour after ∼360 simulations with superior dosimetric qualities for OARs and same PTV coverages compared with coplanar plans. For the skull case, the brain V30, V20, and V10 are reduced by 21%, 38%, and 27%, respectively. The mean dose of the temporal lobe is decreased by 10%. For the chest wall case, the heart mean dose is reduced from 15 Gy to 7 Gy and V30 from 7.5% to 1.7%. The left and right lung mean dose decreased from 16 Gy and 8 Gy to 11 Gy and 3 Gy. The left and right lungs V20 are reduced from 27% and 4.4% to 15% and 0.9%. The estimated delivery time is ∼ 6 min. AI with MCTS successfully designed trajectories that are efficient to deliver and dosimetric superior compared with coplanar VMAT. The method can also be easily generalized to include non-isocentric treatments.

Minimizing Ionizing Radiation Exposure in Invasive Cardiology Safety Training for Medical Doctors

Advanced imaging systems, such as C-Arm machines, greatly improve physicians' diagnostic abilities and provide greater precision. Yet, these benefits come with a price of ionizing radiation exposure to medical teams and patients. Supplying proper training and skill improvement to operators on how to use this technology safely can help minimize risk of exposure. Previous studies on radiation knowledge among physicians and radiologists presented disturbing results of underestimated risk of exposure. The following research is based on an innovation in simulation-based training (SBT), a simulator using the Wizard of Oz (WOZ) concept that incorporates an online human trainer and was used for training emergency room (ER) physicians and ultrasound medical personnel. This research integrated WOZ technology with a radiation exposure formula for training to minimize unnecessary radiation exposure. The exposure formula presents real-time and overall exposure levels to operators based on their technique. The simulator also incorporates 3D animation graphics, enabling trainees to simulate the control of various factors. Image quality and the operator's radiation exposure levels are also animated, assisting trainees to focus on their exposure based on their device settings. Contrary to most previous studies, we measured radiation dose to the operator and quantified image quality accordingly. Validation was done on different C-Arm machines. Validation of learning outcomes was done using knowledge exams. Results from our knowledge exams presented significant improvement. The average result of knowledge exams given prior to training was 54%, whereas the average result after training was 94% (p < 0.001). Additionally, after a gap of 2–3 months, high retention was also found.

How to obtain and identify the acetabular anterior column axial view projection in patients?

This study aims at sharing our experience as how to obtain and identify axial view image of the acetabular anterior column in patients. Pelvic computed tomography data of six normal adults were used to reconstruct three-dimensional (3D) models. The transparency of each 3D model was downgraded at the view perpendicular to the cross section of the anterior column axis to simulate the anterior column axial view image. Fluoroscopy was performed in all patients to obtain the anterior column axial view image in the operating room. Each fluoroscopic image was compared with the corresponding simulation image to analyze potential anatomic landmarks that were helpful to identify the translucent area (projection of the screw path) in the patients. To obtain ideal anterior column axial fluoroscopic image, the patient should be positioned supine with the leg of "abnormal side" straight and contralateral side flexion, abduction, and external rotation; the C-arm machine should be placed at the caudal end of the operation table with the C-arm fluoroscopic intensifier first positioned at the pelvic lateral view and then tilted approximately 30° toward the "abnormal side" and rotated approximately 45° toward the caudal end of the operation table. To identify the translucent area on the anterior column axial view fluoroscopic image obtained from the patient, the greater sciatic notch, the true pelvis edge, and the acetabulum should be identified first and the translucent area is located in the area surrounded by these three anatomic landmarks.

Quality control in Computed Tomography

Computed Tomography (CT) is considered as one of the most important imaging techniques of modern times. The introduction of multi-detector CT (MDCT) with sub second acquisition and CT fluoroscopy have further advanced CT applications by enabling interventional radiological (IR) procedures which were traditionally performed using C-arm machines. CT use is extended to CT fluoroscopy, angiography, cardiac CT, screening, multi-phase dynamic CT, urography and other applications. Due to the shorter MDCT scanning times, increasing number of patients receive repeat CT examinations especially in the oncology and emergency departments of hospitals. The development of hybrid systems such as PET/CT, SPECT/CT, CT simulators in radiotherapy and its incorporation in CT planning and dose delivery systems, progressed CT from the domain of diagnostic radiology to other specialities. Although vendors have invested time and exhausting efforts in development of radiation dose optimization techniques, contribution of CT to patient radiation dose continues to increase. Furthermore, growing number of adverse events related to excessive CT radiation exposure, as well as its relation to elevated risk of radiation induced cancer are reported in the media. All these clearly point to the critical need for ongoing quality control (QC) and cautious relation of radiation dose and image quality. An extensive review of the latest routine QC tests will be presented, based on the most recent publications, starting from more simple tests that can be easily performed by a radiation technologist to the more complex ones that must be executed and analysed by a medical physicist.

Scattered radiation doses absorbed by technicians at different distances from X-ray exposure: Experiments on prosthesis.

This work aimed to investigate the spatial distribution of scattered radiation doses induced by exposure to the portable X-ray, the C-arm machine, and to simulate the radiologist without a shield of lead clothing, radiation doses absorbed by medical staff at 2 m from the central exposure point. With the adoption of the Rando Phantom, several frequently X-rayed body parts were exposed to X-ray radiation, and the scattered radiation doses were measured by ionization chamber dosimeters at various angles from the patient. Assuming that the central point of the X-ray was located at the belly button, five detection points were distributed in the operation room at 1 m above the ground and 1-2 m from the central point horizontally. The radiation dose measured at point B was the lowest, and the scattered radiation dose absorbed by the prosthesis from the X-ray's vertical projection was 0.07 ±0.03 μGy, which was less than the background radiation levels. The Fluke biomedical model 660-5DE (400 cc) and 660-3DE (4 cc) ion chambers were used to detect air dose at a distance of approximately two meters from the central point. The AP projection radiation doses at point B was the lowest (0.07±0.03 μGy) and the radiation doses at point D was the highest (0.26±0.08 μGy) .Only taking the vertical projection into account, the radiation doses at point B was the lowest (0.52 μGy), and the radiation doses at point E was the highest (4 μGy).The PA projection radiation at point B was the lowest (0.36 μGy) and the radiation doses at point E was the highest(2.77 μGy), occupying 10-32% of the maximum doses. The maximum dose in five directions was nine times to the minimum dose. When the PX and the C-arm machine were used, the radiation doses at a distance of 2 m were attenuated to the background radiation level. The radiologist without a lead shield should stand at point B of patient's feet. Accordingly, teaching materials on radiation safety for radiological interns and clinical technicians were formulated.

Precise locating fluoroscopy reduces radiation exposure during the surgical procdure for thoracolumbar fracture

Objective To study the effect of precise locating technique of C-arm fluoroscopy in order to reduce the radiation exposure during the surgical procdure for thoracolumbar fracture. Methods From March 2010 to Octorber 2012, a total of 92 cases with thoracolumbar fracture underwent postierior internal fixation procdures with pedicle instrumentation. C-arm fluoroscopy was used in 44 cases with precise locating technique, while in 48 cases with traditional methods. In precise locating group, C-arm fluoroscopy was used after anesthesia. Once an ideal view was got, the position parameters of C-arm fluoroscopy machine were recorded. The machine was positioned according to the recording for the secondary fluoroscopy. Pre-operative and intra-operative number of times of exposure, length of exposure time, time for fluoroscopy and total operating time were recorded and compared between two groups. Results Pre-operative number of times of exposure, exposure time, and time for fluoroscopy in precise locating group were (5.51±2.47), (2.26±1.05) s and (9.83±3.67) min, which were higher than those of (4.02±2.42), (1.78±0.98) s and (8.29±3.52) min in traditional group. However, intra-operative number of times of exposure, exposure time, and time for fluoroscopy in precise locating group were (5.26±3.64), (2.24±1.24) s and (10.39±4.82) min, which were lower than those of (9.74±4.38), (4.21±2.38) s and (24.69±6.35) min in traditional group, and total number of times of exposure, exposure time, time for fluoroscopy and total operating time in precise locating group were (10.77±4.16) , (4.50±1.83) s, (20.22±5.03) min and (70.52±18.33) min, which were also lower than those of (13.76±5.31), (5.99±3.27) s, (32.98±7.83) min and (81.86±21.57) min in traditional group. Conclusion Precise locating technique of C-arm fluoroscopy reduces the radiation exposure during the surgical procdure for thoracolumbar fracture. Key words: Thoracic vertebrae; Lumbar vertebrae; Spinal fractures; Spinal fusion; Fluoroscopy

New method for geometric calibration and distortion correction of conventional C-arm

Image distortion correction and geometric calibration are critical operations for using C-arm DSA (Digital Subtraction Angiography) images to digitally navigate vascular interventional surgery. In traditional ways, C-arm images are corrected with global or local correction methods where a supposed virtual ideal image is needed, and then the corrected images are utilized to calibrate the C-arm with a pin-hole model. In this paper, we propose a new method to calibrate the C-arm with a nonlinear model and to improve navigation performance. We first calibrate the C-arm with a nonlinear model and then the distortion correction is accomplished without virtual ideal image. In this paper, the nonlinear model of C-arm imaging system is addressed at first, and then the C-arm is calibrated with a two-stage method. In the first stage, the C-arm is calibrated with the markers in image center by RAC (radial alignment constraint) method, and in the second stage the calibration parameters are optimized with Levenberg-Marquadt algorithm by minimizing the sum of the square of difference between all markers׳ real distorted positions and their theoretical distorted positions in the phantom image. Based on the calibration result, the image distortion can be corrected. To verify our method, experiments were conducted with a conventional DSA C-arm machine in hospital. The errors in distortion correction and 3D (three-dimensional) reconstruction were quantitatively compared with the global polynomial correction method and visual model method, and the results showed that the proposed method had better performance in distortion correction and 3D reconstruction.

Application of laparoscopy combined with C-arm machine in the diagnosis and treatment of abdominal ectopic intrauterine device

Objective To investigate the application of laparoscopy combined with C-arm machine in the diagnosis and treatment of abdominal ectopic intrauterine device (IUD).Method From December 2005 to December 2013 in our hospital 10 cases of ectopic IUD in abdominal cavity with the diagnosis and treatment were analyzed retrospectively.Result The surgery for 10 patients to remove ectopic IUD under the laparoscopy were successful by the C-arm to help locate.Conclusions For the complex situation diagnosed with abdominal ectopic IUD but not clear ectopic sites,accurate positioning is a guarantee of successful operation.Laparoscopy combined with C-arm machine surgery to remove the abdominal ectopic IUD is minimally invasive,intuitive,accurate,safe,effective,etc.Good clinical results obtained. Key words: Laparoscopy; C-arm machine; Intrauterine device; Ectopia

Management of severe pelvic injury following road traffic accident in a resource-limited setting

A 34 year old woman involved in road traffic accident with severe anterior and posterior pelvic fractures with associated soft tissue injury was referred from Wa Regional Hospital 18 hours after the accident to Tania Specialist Hospital in Tamale. Emergency resuscitative measures such as catheterization and management of pain with analgesics were initiated. Computed topography (CT scan) or Magnetic resonance imaging has been recommended as the appropriate tools for risk assessment in such cases however none of this was available at the time of the accident. The only assessment tool available was the C-arm machine which was used to X-ray the pelvis in the follow-ing plane; anterio – posterior pelvic - inlet and pelvic – outlet. Early internal reduction and stabili-zation of pelvis was immediately carried out using the procedure of open reduction and internal fixation (ORIF). Approximately 2 weeks after the operation, radiographs showed signs of healing and the patient was discharged on partial body weight bearing. Upon second review 12 weeks post operatively, complete recovery was accomplished.Keywords: Anatomy, pelvic injury, motor accident, resource-limited setting, Ghana

Contrast-Enhanced Intraoperative Ultrasonic Cholangiography for Real-Time Biliary Navigation in Hepatobiliary Surgery

Recent progress in medical technology, perioperative management, and surgical technique has contributed greatly to the safety of hepatobiliary surgery. In particular, imaging techniques, including intraoperative imaging, have played a major role in advancing the success of these operations. Precise assessment of biliary anatomy before and during surgery reduces biliary complications. More than 42% of the population is reported to have anatomical variations of the biliary tree. If a biliary anatomical variation is suspected before surgery, confirmatory intraoperative cholangiography (IOC) is recommended. Using radiography and iodinated contrast medium, IOC was first reported by Mirizzi in 1937 and has been widely used to define the biliary tree in surgery for benign and malignant diseases. However, radiographic IOC has several drawbacks; it exposes patients and medical staff to radiation, it requires a large C-arm machine for fluoroscopy and an attendant to operate it, and it requires special techniques to generate 3-dimensional (3D) images. Intraoperative ultrasonography, specifically, contrast-enhanced intraoperative ultrasonic cholangiography (CE-IOUSC), can address these issues. Intraoperative ultrasonography has become an essential tool for the identification of intrahepatic vessels, tumor location, and definition of surgical margins for safe and effective hepatic surgery. Its diagnostic accuracy has been enhanced by the introduction of intravascular ultrasound contrast agents. However, it is still limited in visualization of nondilated bile ducts.

Comparison of Image Quality and Radiation Exposure From C-Arm Fluoroscopes When Used for Imaging the Spine

Cadaveric imaging study. We sought to compare the fluoroscopic images produced by 4 different fluoroscopes for image quality and radiation exposure when used for imaging the spine. There are no previous published studies comparing mobile C-arm machines commonly used in clinical practice for imaging the spine. Anterior-posterior and lateral images of the cervical, thoracic, and lumbar spine were obtained from a cadaver placed supine on a radiolucent table. The fluoroscopy units used for the study included (1) GE OEC 9900 Elite (2010 model; General Electric Healthcare, Waukesha, WI), (2) Philips BV Pulsera (2009 model; Philips Healthcare, Andover, MA), (3) Philips BV Pulsera (2010 model; Philips Healthcare, Andover, MA), and (4) Siemens Arcadis Avantic (2010 model; Siemens Medical Solutions, Malvern, PA). The images were then downloaded, placed into a randomizer program, and evaluated by a group of spine surgeons and neuroradiologists independently. The reviewers, who were blinded to the fluoroscope the images were from, ranked them from best to worst using a numeric system. In addition, the images were rated according to a quality scale from 1 to 5, with 1 representing the best image quality. The radiation exposure level for the fluoroscopy units was also compared and was based on energy emission. According to the mean values for rank, the following order of best to worst was observed: (1) GE OEC > (2) Philips 2010 > (3) Philips 2009 > (4) Siemans. The exact same order was found when examining the image quality ratings. When comparing the radiation exposure level difference, it was observed that the OEC was the lowest, and there was a minimum 30% decrease in energy emission from the OEC versus the other C-arms studied. This is the first time that the spine image quality and radiation exposure of commonly used C-arm machines have been compared. The OEC was ranked the best, produced the best quality images, and had the least amount of radiation.

Evaluation the treatment outcomes of intracapsular femoral neck fractures with closed or open reduction and internal fixation by screw in 18-50-year-old patients in Isfahan from Nov 2010 to Nov 2011.

Background:There is conflict of interest in the treatment of intracapsular femoral neck fractures and the outcomes. The aim of this study was evaluation the treatment outcomes of closed and open reduction and internal fixation with screw in 18–50-year-old patients.Materials and Methods:This clinical randomized study was conducted in Ayatollah Kashani Center in Isfahan from Nov 2010 to Nov 2011. In 42 patients selected in a randomized manner, fractures were reduced by closed reduction or open if necessary and C-ARM was controlled in AP and lateral plans. Movement range and femur pain severity were evaluated according to Visual analogue Scale (VAS) score at 3 and 6 months after surgery. Data were analyzed by SPSS 18. Chi-square, t-test, one-way analysis of variance (ANOVA), and descriptive statistics such as frequency distribution, mean, and mean deviation were used.Results:Forty-two patients with femoral neck fracture were treated by open [31 patients (73.8%)] or closed reduction [11 patients (26.2%)] and also osteosynthesis. Their mean age was 47.3 ± 9.8 years; 29 of them were males and 13 were females. Twelve patients had bad range of motion (ROM) (28.6%), 16 had intermediate ROM (38%), and 14 had good ROM (33.4%). After 6 months, 12 patients (28.6%) had bad ROM, 10 (23.8%) had intermediate ROM, and 20 (47.6%) had good ROM. There were 11 cases of non-union (35.5%) in the open reduction group and 4 in the closed group.Conclusion:This study showed that femoral neck fracture is associated with several complications, especially if open reduction was necessary. So, the surgical method and necessary equipments such as radiolucent bed, C-ARM machine, and implant cannulated screw set should be considered.

TU-G-BRB-01: Continuous Path Optimization for Non-Coplanar Variant SAD IMRT Delivery Using C-Arm Machines.

To develop and investigate a continuous path optimization methodology to traverse prescribed non-coplanar IMRT beams with variant SADs, by orchestrating the couch and gantry movement with zero-collision, minimal patient motion consequence and machine travel time. We convert the given collision zone definition and the prescribed beam location/angles to a tumor-centric coordinate, and represent the traversing path as a continuous open curve. We proceed to optimize a composite objective function consisting of (1) a strong attraction energy to ensure all prescribed beams are en-route, (2) a penalty for patient-motion inducing couch motion, and (3) a penalty for travel-time inducing overall path-length. Feasibility manifold is defined as complement to collision zone and the optimization is performed with a level set representation evolved with variational flows. The proposed method has been implemented and tested on clinically derived data. In the absence of any existing solutions for the same problem, we validate by: (1) visual inspecting the generated path rendered in the 3D tumor-centric coordinates, and (2) comparing with a traveling-salesman (TSP) solution obtained from relaxing the variant SADs and continuous collision-avoidance requirement. The proposed method has generated delivery paths that are smooth and intuitively appealing. Under relaxed settings, our results outperform the generic TSP solutions and agree with specially tuned versions. We have proposed a novel systematic approach that automatically determines the continuous path to cover non-coplanar, varying SAD IMRT beams. The proposed approach accommodates patient-specific collision zone definition and ensures its avoidance continuously. The differential penalty to couch and gantry motions allows customizable tradeoff between patient geometry stability and delivery efficiency. This development paves the path to achieve safe, accurate and efficient non-coplanar IMRT delivery with the advanced robotic controls in new-generation C-arm systems, enabling practical harvesting of the dose benefit offered by non-coplanar, variant SAD IMRT treatment.

Modified Map-Seeking Circuit: Use of Computer-Aided Detection in Locating Postoperative Retained Foreign Bodies

More than 98% of intra-operative X-rays taken to search for postoperative retained foreign bodies (RFBs) have negative findings; in over 30% of cases of such X-rays, the finding is a false negative. Newer technologies created to find RFBs must not only reduce the false-negative rate, but also must not increase the burden of detecting RFBs. We have introduced the use of computer-aided detection (CAD) to facilitate the detection of RFBs on X-rays utilizing a modified version of map-seeking circuit (MSC) algorithm the referenced map-seeking circuit (RMSC), for our proof-of-concept study for detection of needles in plain abdominal X-rays. Images were obtained by using a portable cassette-based X-ray machine and a C-arm (digital) machine, both of which are commonly used in the operating room. The images obtained using these machines were divided into subimages of approximately 250 × 250 pixels each, for a total of 455 subimages from the cassette-based machine (A) and 365 from the digital machine (B) for use as test samples. Images obtained from A and B were analyzed separately using our modified MSC algorithm with a minimum (τ = 0) and a maximum threshold (τ = 0.5). The automated detection rate (positive predictive value) was 86%, with a false positive/negative rate of 10% to 15% when τ was zero. The CAD-based RMSC algorithm has the potential to improve the accuracy with which RFBs can be found in X-rays. Further research is needed to optimize the detection rate and to identify a wider range of RFBs.

Radiation exposure during 3D fluoroscopy of the knee: an experimental study.

To measure the radiation exposure at the knee and surrounding area during the use of 3D fluoroscopy. An experimental study was conducted by using a human cadaveric knee as a focus point for the 3D fluoroscope. An isocentric C-arm fluoroscope machine was applied on the lateral side of the knee. The radiation dosage at the focus point and surrounding area was measured. The mean radiation exposure in each location was compared between low- and high-resolution scanning. The mean radiation sustained at the focus point was 44.0±5.6μSv and 20.0±1.0μSv in high- and low-resolution scanning, respectively. Radiation exposure on the opposite side of the C-arm machine was found to be higher than that on the other locations with the same distance from the focus point. In low-resolution scanning, radiation could not be detected beyond 75cm from the focus point at the proximal, distal and same side of the machine. Radiation could be measured at a distance of up to 1.25m on the opposite side of the machine. In high-resolution scanning, radiation could be measured at a distance of up to 1m at the proximal, distal and same side of the C-arm, but up to 1.5m on the opposite side. Radiation exposure during 3D fluoroscopy of the knee decreases with increasing distance from the focus point. A higher number of scans in the high-resolution mode causes greater radiation exposure. In isocentric 3D fluoroscopy of the knee, a safe zone is located at least 1.5m away from the focus point.

Evaluation of radiation dose during pacemaker implantations

The purpose was to evaluate patient radiation doses and compare with other interventional procedures. One hundred and twenty-eight procedures were carried out with a recently installed mobile undercouch C-arm machine with a 23-cm diameter image intensifier. The radiation dose is provided by the X-ray machine, in terms of cumulative dose (CD). Kerma-Area product (KAP) was then estimated from CD and the X-ray field size. Other patient parameters recorded were patient weight, age, kilovolt, milliampere and fluoroscopy time (T). Median (range) CD, KAP and T were 15.2 mGy (3.2-110 mGy), 6.3 Gy cm(2) (1.3-45.7 Gy cm(2)) and 5.2 (1.5-27.4 min) min, respectively. Median E was 1.1 mSv (conversion factor: 0.18 mSv per Gy cm(2)), which corresponds to approximately one lumbar spine X-ray radiography. The effective dose is much lower than a coronary angiography (8 mSv) or an electrophysiology study (6 mSv). Radiation dose is low compared with other interventional cardiology procedures.

Key points of intramedullary nailing for subtrochanteric femoral fractures

Objective To summarize the key points of intramedullary nailing in the treatment of subtrochanteric femoral fractures. Methods From December 2004 to July 2008, 69 cases of subtrochanteric femoral fractures were treated with intramedullary nailing. There were 42 males and 27 females.Their ages ranged from 28 to 68 years, averaging 48.6 years. According to Russell-Taylor classification, there were 17 cases of ⅠA type, 11 cases of ⅠB type, 28 cases of ⅡA type, and 13 cases of ⅡB type. After reduction and an opening at the top of the greater trochanter, the entry point was located to insert the intramedullary nail under the surveillance of the C-arm machine and maintenance of an accurate nail channel.Results Eight cases were lost to the follow-up and 2 cases died during the follow-up. The remaining 59 cases were followed up for 8 to 20 months, with an average of 13 months. The time for clinical bone union ranged from 2.5 to 8.0 months, with a mean period of 3.9 months. According to the scoring system recommended by Sandes et al. for the traumatic hip recovery, 18 cases were excellent, 32 good, 6 fair, and 3 poor.The excellent to good rate was 84.7%. Conclusions A suitable internal fixation, good reduction and exact entrance point are very important. If surgeons follow the key operation points, intramedullary nailing can lead to fine outcomes in treatment of subtrochanteric femoral fractures. Key words: Hip fractures; Fracture fixation, intramedullary; Bone nails