AP Position Research Articles

Comparison of the Surface Dose of the Thyroid according to AP versus PA Positioning in Cervical Spine Oblique View

Comparison of the Surface Dose of the Thyroid according to AP versus PA Positioning in Cervical Spine Oblique View

Comparison of volar and dorsal percutaneous screw fixation in acute scaphoid waist fracture

Objective To compare volar and dorsal percutaneous screw fixation in acute scaphoid waist fracture. Methods Retrospectively collected patients received percutaneous screw fixation after acute scaphoid fracture between January 2009 and December 2014 with non-displacement/minimal displacement waist fracture, patients with open fracture or combined with perilunate dislocation or fracture which need reduce were excluded, 28 patients with intact follow-up were enrolled, 26 men and 2 women, with an average age of 31 years old. Based on Herbert classification, there were 15 A2 type, 5 B1 type, 8 B2 type. 7 cases were high energy trauma and 21 were low energy. The patients were divided into 2 groups by volar and dorsal approach. The general condition, surgery notes, radiological evidence and follow-up were collected and analyzed. Results 28 cases with full follow-up were enrolled, 18 cases received surgery via volar approach, and 10 cases via dorsal approach, the mean follow-up period is 33 months. Peri-operative data showed that operation time in dorsal approach group was longer (75 min vs. 54 min). We evaluated screw position by measuring the angulation between screw and fracture line as well as screw and long axis of scaphoid based on AP view and lateral view of wrist X-rays. There was no significant difference in length of screws (21.4 mm vs. 21.8 mm). Patients gradually went back to work after 2 weeks and got fracture healing within 12 weeks after operation. Radiological evidence showed that angulation between screw and long axis of scaphoid was 6.11°±4.82° in AP position and 8.48°±5.77° in lateral position, angulation between screw and fracture line was 73.58°±20.75° in AP position and 70.72°±21.19° in lateral position. There were no significant differences between screw insertion positions between 2 groups. Visual analogue scale (VAS) was used to evaluate wrist pain in the follow-up, Mayo wrist score and Patient-Rated Wrist Evaluation (PRWE) were also used to assess wrist function in the follow-up. The clinical results were promising, the excellent or good rate of Mayo wrist score was 100%, there were no significant difference in VAS, Mayo wrist score and PRWE between volar and dorsal approach. No complications such as failure of screws, orthopaedic arthritis or scaphoid necrosis were observed. Conclusion Percutaneous screw fixation have a satisfied effect in the treatment of acute scaphoid waist fracture, and there are no differences in clinical efficacy between volar and dorsal approach. Key words: Scaphoid bone; Fractures, bone; Carpal joints; Fracture fixation, internal

Effect of C-Arm Year Model on Radiation Scatter

Since the 1980’s C-arm fluoroscopy has been an integral part of orthopaedic trauma surgery. The advancement in C-arm technology has resulted in different generations of C-arms co-existing in the operating rooms. The purpose of this study was to compare the radiation scatter patterns of different generation C-arms. Three generation of C-arms were tested: GE OEC 9800 Plus (1999/2000), Siemens Arcadis Orbic 3D (2004), Philips BV Pulsera 2.3 (2008). Radiation scatter was measured using six real-time dosimetry badges set up on either side of the surgical table (Mizuho OSI, flat-top). Distance of C-arm was normalized at 20 in. and 10 in. from Image Intensifier. Each device was set to the automatic brightness control (ABC) setting. A phantom limb was irradiated for 120 s and radiation scatter was summed for both AP and lateral positions. At their typical operating room settings there was a reduction in radiation scatter using the newer generation C-arms. Results for total radiation, normalized to Philips, are as follows: Philips 1 (100%), GE 2.4 (240%), and Siemens 1.4 (140%). Newer generation C-arms can be expected to generate lower radiation scatter. Special care should be taken to attempt a lower dose setting, especially when utilizing older generation C-arms to minimize radiation scatter to practitioner.

Optimal position and posture of operating surgeon to reduce radiation during intra-operative use of image intensifier in extremity surgeries

Background: Popularity of closed techniques in fracture fixation has led to the operating surgeon getting exposed to increasing amount of radiation. Though extensive work has been undertaken to decrease risk of radiation to the operating personnel, the variation in the amount of radiation in relation to the differing axis of the image intensifier and optimal surgeon’s posture has not been documented. The purpose of this study was to find out the optimal position and posture of the operating surgeon relative to the differing axis and viewing angles of the image intensifier in order to minimize intra operative radiation. Materials and methods: A simulated observational study was made using an image intensifier, operating table, a water phantom in lieu of the patient and a dosimeter used to record the amount of radiation at various positions. Results: Standard AP view- along the axis of the image intensifier, 58% reduction in radiation was observed when surgeon was standing as compared to sitting. Correspondingly perpendicular to the axis of the image intensifier 46% reduction in radiation was noted. Inverted position-along the axis of the image intensifier, 29% reduction in radiation was observed when surgeon was standing as compared to sitting. Correspondingly perpendicular to the axis of the image intensifier 20.5% reduction in radiation was noted. Lateral view- when surgeon was closer to the intensifier, 28% reduction in radiation was observed in sitting compared to standing. Correspondingly closer to the x ray source 58% reduction in radiation was noted. Conclusions: Radiation exposure to the surgeon was less in standard AP position of imaging compared to lateral and inverted views. In standard AP position, standing along the axis of the C arm caused less radiation to the surgeon. In inverted position surgeon sitting along the axis of the image intensifier was optimal. The surgeon received less radiation when positioned closer to the intensifier and sitting during the lateral view.

Response to Letter to the Editor regarding 'establishing advanced practice for medical imaging in New Zealand'

Re: Yielder J, Young A, Park S, Coleman K. Establishing advanced practice for medical imaging in New Zealand. J Med Radiat Sci 2014;61(1):14–21 Thank you for providing the opportunity to reply to Mr Hayes’ Letter to the Editor, written with respect to our article ‘Establishing advanced practice for medical imaging in New Zealand’. We would like to raise a number of points in response: The two first authors for the parallel medical imaging and radiation therapy articles have been appointed to the NZIMRT advanced practice working parties since 2005. The current research has built on this work. The original research (2005–2008) included surveys of all stakeholders. The second stage was a qualitative study that did not seek to be representative of the medical imaging profession. Its purpose was to qualitatively explore and ‘flesh out’ potential profiles, from experienced MRTs working in specialty areas. The profiles used generic criteria established in the first stage of the research that were formally accepted by the NZIMRT in 2009, in addition to asking respondents to comment on further specialist‐focused skills. The study was not seeking support for advanced practice per se, but to establish what an advanced practice profile may potentially ‘look like’. The recommendation is that one advanced scope of practice is established, consisting of the generic criteria plus specialist skills that would be department‐dependent and negotiated for an individual AP position. This recommendation was based on the small numbers of MRTs likely to seek advanced practitioner status. No profiles have been recommended from this exploratory research, so although the findings about profiles were interesting, Mr Hayes’ concerns regarding over‐claiming results are redundant. It was not the intention of the article to advocate that the University of Auckland is the only provider capable of establishing postgraduate courses for advanced practice in medical imaging. Any institution that has the ability to offer master's programmes to support MRT advanced practice would be an option, noting that any provider will need to consider student numbers for viability. The point was being made that the University of Auckland and University of Otago are currently able to offer education to support advanced practice, contextualised specifically to the profession. We were drawing the readers’ attention to the understanding that advanced practice is more than a collection of specialist skills – these are important, as are the generic criteria. A master's qualification to support advanced practice needs to include both. It is hoped that now that the AIR has called for nominations for an advanced practice pathway, that New Zealand MRTs will support initiatives to move advanced practice ahead in a similar, and timely, fashion. Interested MRTs, including Mr Hayes, need to register their willingness to be actively involved. It would be most detrimental to the profession in New Zealand to be left behind in this initiative.

No radiographic difference between patient-specific guiding and conventional Oxford UKA surgery.

Implant position is an important factor in unicompartmental knee arthroplasty (UKA) surgery. Results on conventional UKA alignment are commonly described in literature. Patient-specific guiding (PSG) is a new technique for positioning the Oxford UKA. Our hypothesis is that PSG improves component position without affecting the HKA angle. This prospective study compares the results of our first thirty cases of cementless Oxford UKA using PSG with thirty cases using conventional outlining. Baseline characteristics for both groups were identical. Details on handling of the guide, estimated blood loss and operation time were recorded. Postoperative screened radiographs and standing long-leg radiographs of both groups were compared. Median AP position of the femoral component was 3 degrees varus (-5 to 9) using PSG versus 2 degrees varus (-10 to 8) for the conventional group. For the femoral flexion, this was 9 degrees flexion (0-16) using PSG versus 12 degrees flexion (0-20). The tibial median AP position was 1 degree varus (-3 to 7) using PSG versus 2 degrees varus (-5 to 10). The median tibial posterior slope was 5 degrees (1-10) using PSG versus 5 degrees (0-12). All guides aligned well. No conversion to conventional outlining was performed, and no significant changes had to be made to the original approved plan. Operation time, estimated blood loss and postoperative haemoglobin drop were not significantly different between both groups. Implant position was not different between both groups, even in the early phase of the learning curve. Perioperative results were not different between both groups. III.

흉부 측와위 촬영 시 전후방향과 후전방향 검사의 유용성 비교

Chest lateral decubitus 촬영은 일반적으로 PA 검사를 시행하여 왔으나, 응급환자나 몸이 불편한 환자의 검사에 있어 많은 불편이 있었다. 이에 본 연구에서는 AP 검사와 PA 검사를 비교하여 영상의 질, 환자의 안전성, 검사 효율성을 분석하고 두 검사간의 유용성을 알아보고자 하였다. 본원에서 2011.10.1 ~ 2012.7.30까지 늑막염 또는 기흉으로 의심되거나 진단된 환자들 중 chest lateral decubitus 촬영을 시행한 30명(남자 20명, 여자 10명)을 대상으로 하였다. 영상 화질 평가방법은 폐야의 미세구조, 진단영역의 넓음, air-fluid 경계면의 명확 유무, 환자 회전유무, 심장음영과 횡격막의 선명유무를 기준으로 하였으며, 영상의학과 전문의 2명, 호흡기내과 전공의 2명이 blind test로 평가하였다. 환자 안정성 및 방사선 검사의 효율성 평가는 환자 position의 안정성, 환자 상태 확인 등의 기준으로 일반촬영 5년 이상 경력의 방사선사 15명이 5점 척도로 평가를 하였고, 통계 분석은 Paired T-test로 분석하였다. Chest decubitus 촬영 시 AP와 PA자세에 따른 검사의 유용성을 비교 분석한 결과 영상의 화질에서 AP와 PA자세는 큰 차이가 없었던 반면, 환자의 안정성 및 방사선사의 검사 효율성에 있어 PA자세에 비해 AP자세의 평가 점수가 높게 나타났다. 이에 특별히 PA자세가 요구되지 않는다면 AP자세로 검사하여도 무방할 것으로 사료된다. Chest lateral decubitus radiation exposure PA be carried out in general, but emergency patient or the patient's discomfort in the body examination had a lot of inconvenience. In this study, we compared AP and PA image quality, patient safety, and analysis of the examination effectiveness between the two tests was to evaluate the usefulness. Pleurisy or pneumothorax in patients with suspected or diagnosed chest lateral decubitus radiation exposure 30 consecutive patients (male 20 patients, 10 females) were included in the study. Image quality evaluation method microstructure of lung, wide areas of diagnosis, a clear air-fluid interface, the patient rotate, cardiac shadow and sharp diaphragmatic was based on Department of Radiology specialist, division of pulmonology resident blind test was evaluated by four people. Chest decubitus by radiation exposure the AP and PA position examination the usefulness of comparative analysis Image quality in the AP and PA, whereas there was no significant difference in attitude, Stability of the patient and Radiation's examination efficiency AP position compared to the position of PA scores were higher. PA position does not require a examination may be of AP position in a position to suggest that.

Factors in High-Flex Posterior Stabilized Fixed-Bearing Total Knee Arthroplasty Affecting In Vivo Kinematics and Anterior Tibial Post Impingement During Gait

One of the most important issues in high-flex posterior stabilized total knee arthroplasty (TKA) is anterior tibial post impingement. We examined 20 knees and 2 TKA designs to evaluate the in vivo kinematics during gait using fluoroscopic image analysis. The AP positions in both stance and swing phases were significantly larger and more anterior in J-curved design TKA compared with Single radius design TKA. Anterior tibial post impingement was observed in five knees implanted with Legacy-flex, and in four of the five knees they were not hyperextended. No impingement was observed with NRG. Less constraint and tibial posterior slope might lead to large AP translations and anterior tibial post impingement. Implant design and operative procedures for high-flexion TKAs affect the in vivo kinematics and the occurrence of anterior tibial post impingement.

Preferences of AP position of the straight Caucasian facial profile

IntroductionSeveral investigators have compared the perception of profile attractiveness between professional and non-professional people, different groups of clinicians, and different ethnic groups. Our aim was to study preferences for facial protrusion in the lateral view for a straight Class I profile and to study the influence of gender, age, sex preference, and profession. Material and methodsPortrait images of one male and one female model with a Class I occlusal relationship were warped into nine different antero-posterior positions. An internet site was established to reach as many people as possible, and a request was sent by email to participate in a scientific experiment. Finally, 1707 Caucasion assessors could be grouped. ResultsThe preferred male profile is the straight full ante profile. For a feminine facial profile, the straight average and the straight 2/3 ante profiles were perceived as the most attractive. Surgeons tended to give significantly higher scores to attractive (ante) profiles, which correlated strongly with scores of the orthodontists. ConclusionWhenever possible with combined orthodontic/surgery treatment, straight ante profiles should be aimed for.

SU-E-J-25: Dosimetric Characterization of an OBI System Using Gafchromic XRQA2 Film.

Accurate knowledge about the radiation dose due to the imaging component of an OBI supported linear accelerator is very important. Though films provide excellent spatial resolution, there are problems regarding sensitivity and energy dependence at kV energies. XRQA2 film (0.1-20 cGy) is primarily for measurements in kV range. We demonstrate their use for absolute dosimetry for an OBI system. H&D curves were generated using a kV therapy x-ray unit in the range of 0-15 cGy. A 25-cm diameter water-equivalent cylindrical phantom with 2.5-cm thick slabs was used on Varian Trilogy linac. XRQA2 films were cut into circular diameter and sandwiched between 2 slabs of the cylindrical phantom to measure the percentage depth dose of the CBCT scans. Additional film pieces were wrapped around the cylinder for surface dose. To get sufficient signal, 5 CBCT scans were taken per imaging acquisition template e.g. head standard dose. After 24 hours post-irradiation, films were scanned using Epson V700 scanner in reflection mode. Only red channel was used for dosimetric analysis using RIT software. High-Quality head acquisition template resulted in a dose at 0.2, 1.3, 2.7, and 2.7 cGy on AP, left-lateral, posterior and right-lateral positions of the phantom, respectively. Low-quality thorax acquisition resulted in 1.4, 1.6, 1.5, and 1.4 cGy. The PDD at 12.5-cm (isocenter) was of the order of 40%. While the PDD was fairly uniform from left to right, the PDD along the AP/PA direction were showing almost continuous fall off with PDD at isocenter of ∼40%. Analysis of low-quality head PDDs show little fall off dose with depth though the overall magnitude was less with PDD at the isocenter only marginally lower than the maximum along the medial and anterior posterior axis. Gafchromic XRQA2 film provides a useful tool to evaluate and characterize an OBI system.

SU-E-J-03: The Modeling of Cone Beam Computed Tomography in a Treatment Planning System

Purpose: The purpose of this study is to demonstrate how to model a cone beam computed tomography(CBCT) beam into a treatment planning system (TPS).Methods: An Elekta Synergy LINAC equipped with CBCT was used in this study. Profiles and depth dose curves were measured in a water tank with the kV source in the AP position. Monoenergetic energy deposition kernels from 20 to 110 keV were added to Philips Pinnacle Beta. An energy spectrum was imported to create a model for the scanned profiles for a CBCT beam with 120 kVp, 40 mA, and 10 ms/frame. Film,TLD, and ion chamber measurements were used to verify the model in a stack of water equivalent material at 100 SSD. TLDs were used to measure the dose within the complex geometry of an anthropomorphic phantom. Additionally, this research is being carried out on an Oncentra treatment planning system from Nucletron Corporation.Results: The TPS model accurately represents the depth dose and profiles of the scanned CBCT beam. The dose that was predicted by the TPS versus absolute measurement with TLD and ion chamber were within 3% in tissue and tissue equivalent materials. However, it was not as accurate for heterogeneities such as bone anatomy Conclusions: The results show that a diagnostic beam modeled in the TPS can calculate the dose to a homogenous volume within 3%. However, further work is needed to accurately predict dose in a heterogeneous media and ultimately onto a patient.

Assistant principals in high-stakes accountability environments: The effects of job attributes and school characteristics

This study addressed the topic of job specifications and school characteristics since there is a shortage of quality AP applicants in high-stakes accountability environments. It is important to learn about allocation of duties from educational administrators with on-the-job experience as well as to learn why current APs would consider applying for other AP positions. The purpose of this study was to investigate the impact of job attributes (instruction, discipline), school level (elementary, middle, high), and school achievement (in-need-of-assistance, progressing, meets goal) on applicant’s rating of an AP position. This research study used an experimental design. A main effect for job attributes indicated that instruction was significantly higher than discipline when attracting assistant principals. Implications for practice and research are discussed.

Imaging Innovations Lead to Advances in Radiation Therapy

Imaging Innovations Lead to Advances in Radiation Therapy

An examination of practice during radiography of the clavicle

Background Variation in techniques is a well reported phenomenon in Radiography that can lead to dose discrepancies. Radiography of the clavicle is an examination which can result in a scattered extra-focal radiation dose to the radiosensitive organs of the thyroid, breast and eyes. Techniques for imaging the clavicle are examined and causal factors of repeats examined. Given the recent increase of the tissue weighting factor of breast tissue, an increased importance is placed upon dose reduction techniques to this area. Aims This study aims to investigate the variation in techniques used in imaging of the clavicle and to investigate whether AP or PA position resulted in a higher level of repeat imaging. Method To investigate current practice amongst hospitals a sample of large teaching hospitals was chosen ( n = 5). An interview with radiographers was carried out along with an examination of the stated protocols in each of these hospital plus retrospective analysis of the images produced in each of these hospitals. Results Variations in practice were established, significant differences in collimation and vertical centring were found. AP coned view of the clavicle was performed by 80% of radiographers interviewed with 20% of radiographers performing an AP shoulder. This variation being 100% correlated with country of training. 60% of radiographers were found to perform AP15° cranial angulation clavicle as a second projection with 28%, 8% and 4% of those interview performing AP25°, AP20°, and AP30° cranial angulation, respectively. The comparison of error and repeat rates study demonstrated a lack of confidence, reduced employment of collimation and reduced accuracy while centring in the PA position and it was deemed necessary to repeat in 30% of cases compared to 40% repeats were necessary. Conclusion Wide variation exists in technique and PA imaging is not being implemented. The author recommends training and information on PA technique be disseminated and the local protocols address variations in practice.

Tibiofemoral kinematic analysis of knee flexion for a medial pivot knee

The performance of total knee arthroplasty in deeply flexed postures is of increasing concern as the procedure is performed on younger, more physically active and more culturally diverse populations. Several implant design factors, including tibiofemoral conformity, tibial slope and posterior condylar geometry have been shown directly to affect deep flexion performance. The goal of this study was to evaluate the kinematics of a fixed-bearing, asymmetric, medial rotation arthroplasty design in moderate and deep flexion. Thirteen study participants (15 knees) with a medial rotation knee arthroplasty were observed performing a weight-bearing lunge activity to maximum comfortable flexion and kneeling on a padded bench from 90 degrees to maximum comfortable flexion using lateral fluoroscopy. Subjects averaged 74 years of age and nine were female. At maximum weight-bearing flexion, the knees exhibited 115 degrees of implant flexion (102 degrees-125 degrees) and 7 degrees (-3 degrees to 12 degrees) of tibial internal rotation. The medial and lateral condylar translated posteriorly by 2 and 5 mm, respectively. At maximum kneeling flexion, the knees exhibited 119 degrees of implant flexion (101 degrees-139 degrees ) and 5 degrees (-2 degrees to 14 degrees) of tibial internal rotation. The lateral condyle translated posteriorly by 11 mm. The medial rotation knee exhibited motion patterns similar to those observed in the normal knee, but less tibial rotation. The medially conforming articulation beneficially controls femoral AP position in deep flexion, in patients who require such motion as part of their lifestyle.

Navigated femoral anteversion measurements: general precision and registration options

Intraoperative reduction of femoral fractures can result in rotational malalignment. Navigation modules allow fluoroscopy-based femoral anteversion (AV) measurements; however, their clinical feasibility has not been fully evaluated. An important technical consideration when obtaining navigated femoral rotational alignment is the necessity for orthogonal navigated fluoroscopic images. The current investigators hypothesized that there would be a critical imaging angle between the fluoroscopic images which optimized the acquisition of accurate rotational measurements. Following initial testing in plastic femora, 14 intact human cadaveric femora were subjected to CT and navigated fluoroscopic assessment of AV. The navigated registration process included the following test series: Standard perpendicular AP and lateral imaging at a 90 degrees angle; planar rotation of the lateral fluoroscopy position perpendicular to the axis of femoral neck and angled to the AP position at 75 degrees, 60 degrees, and 50 degrees; inlet and outlet imaging of the axis of the femoral neck at angles of 10 degrees, 20 degrees, and 30 degrees. For all setups, the difference between the AV angle of the navigation system and the CT-measured angle was calculated. Results revealed no relevant differences between CT and navigated determination of plastic femora (1.5 degrees). No significant deviations of cadaver femora with 90 degrees angle imaging (mean 2.00 degrees, range 0.00 degrees-4.33 degrees), 75 degrees angle imaging (mean 1.95 degrees, range 0.00 degrees-3.33 degrees) and 60 degrees imaging (mean 2.00 degrees, range 0.00 degrees-3.33 degrees) were found. However, significant deviations were found for the navigated 50 degrees angled imaging technique (mean 5.02 degrees, range 2.33 degrees-7.67 degrees). These data demonstrated that the femoral AV angle can be calculated accurately by using two navigated fluoroscopic images when a minimum angle of 60 degrees is utilized between the angled fluoroscopic images for the registration process. A difference of <60 degrees does not allow for accurate navigated measurements.

SU-GG-J-20: A Trajectory Estimation Method of Moving Target From Cone Beam CT Projection Images

Purpose: The aim of this work was to develop and investigate a method for trajectory estimation of a moving target from cone beam CT projection images. It can be useful for assessment of respiratory tumor motion just before or during treatment, and for developing further respiratory compensation strategies. Method and Materials: Six lungtumor trajectories with range of motion larger than 10 mm, acquired using a CyberKnife system, were used to simulate CBCT acquisition. To reconstruct 3D positions from projected positions, the two nearest angular projection images with the same SI‐projection positions were used for triangulation. With the triangulated positions, a linear correlation was assumed for tumor motion. LR and AP positions were then derived from SI positions using the linear model. The estimated 3D tumor positions were compared with the known positions. To demonstrate the real simulation, CBCT projection images for a seed‐embedded moving phantom were acquired using a Varian OBI system. A 3D motion platform was used to drive the phantom with one of six trajectories. The marker position from each projection image was extracted using Varian RPM‐Fluoro application. Results: The mean estimation errors were within 0.3±1.8 mm while errors of up to 4 mm were observed. In general, higher correlation coefficients with SI‐motion provide better estimation of AP and LR positions. Applying the center offset of OBI imager (xOffset=−2 pixel, yOffset=0 pixel), the remaining uncertainty associated with gantry sag and marker extraction (∼1 pixel) was within ∼0.5 mm. Conclusion: The proposed method provides useful information for tumor motion characteristics such as the mean position, range, and principal direction of motion which can be useful for respiratory compensation treatments. Conflict of Interest: Research supported by Varian Medical Systems.

SU-GG-T-214: On Technical Aspects of the Implementation of a New Respiratory Gating System with the Option of Three-Dimensional Tracking of a Surrogate's Motion Via a Wall-Mounted Camera

Purpose: To optimize performance of a new respiratory gating system with 3D tracking of a surrogate and to evaluate the performance of the system in clinical conditions. Method and Materials: An accuracy of the system was checked by calibrating the system using water parallel surface and then locating a surrogate at different positions on the surface and detecting its position. A clinically representative bending profile of a couch was found. While respecting restrictions resulting from the calibration procedure, three points on the profile that ensure the profile's optimal linear fit were selected. The system was recalibrated by positioning a surrogate into the found positions and the system's performance was checked. The longitudinal speed and the AP position of a surrogate were recorded simultaneously to quantify observed artifacts when the surrogate was moving in the longitudinal direction. Results: The values of the AP position of a surrogate on the leveled plane change less than ±1 mm (SD of a readout is 0.18 mm). The measured bending profiles exhibit non‐linearity and changes in the AP position are up to 8 mm (weight of 60 kg). After the proposed calibration, couch induced changes in the AP position during a CT acquisition are less than ±1 mm. The AP position readout varies linearly with the longitudinal speed of a surrogate (approx. 0.6 mm change at the speed of 10 mm/s). Conclusion: The new system enables an accurate readout of a surrogate's position. However, its accuracy is limited by the presumption that the surrogate's motion induced by a couch happens within a plane. A mean how to bring the model closest to the clinical conditions was proposed. Dependence of the AP position readout on the surrogate's longitudinal speed is an inconvenient property of the system, which has a little impact in clinical conditions though.

SU‐GG‐J‐132: Motion Characterization for Early Stage Non‐Small Cell Lung Cancer

Purpose: With the increasing use of conformal radiation therapy methods for lung cancer, it is a necessity to accurately determine respiratory induced tumor motion. The purpose of this study is to analyze the motion characteristics of early stage lung tumors in a large population, and correlate tumor motion with position and other clinical factors. Method and Materials: 113 patients with 119 early stage non‐small cell lung tumors were analyzed. Each patient received a 4DCT scan. To determine tumor motion, a soft‐tissue based rigid registration algorithm was used to track the tumor position in ten respiratory phases. Tumor positions were standardized to correlate with their motion characteristics and other clinical factors, which included the lobe location, TMN staging information and etc. Diaphragm motion was calculated by subtracting the diaphragm position between the expiration and the inspiration phase. Tumor volumes were determined based on the GTV drawn by physicians on the expiration phase. Results: Average tumor motion in the AP, SI, and RL directions were 3.1±2.2mm, 6.3±6mm, and 1.5±1.4mm respectively. Lower lobe tumors showed an average vector motion (±1SD) of 11.6±7mm while upper/mid lobe tumors only averaged 5.3±4mm. To fully cover 95% of the tumors, a margin of 6.8mm, 18.3mm, and 3.9mm was needed in the AP, SI, and RL directions. From two‐tailed Spearman's rho correlations, tumor SI motion was strongly correlated with AP and SI positions of the tumor in the thorax, with correlation coefficients of −0.418 and 0.584 respectively. Diaphragm motion and tumor volume were not correlated with tumor motion. Conclusion: Respiratory induced lung tumor motion is primarily in the SI direction. Tumors in the lower lobe on average double the motion range of upper/mid tumors. Because the magnitude of tumor motion is different in each direction, it is beneficial to use an asymmetrical CTV margin for radiotherapy planning.

Synthesis, Structure and Conformational Properties of Fluoroformylchlorodifluoroacetyl Disulfide, FC(O)SSC(O)CF2Cl: Conformational Transferability in –C(O)SSC(O)– Compounds

AbstractPure fluoroformylchlorodifluoroacetyl disulfide, FC(O)SSC(O)CF2Cl, has been prepared by the reaction of FC(O)SCl and CF2ClC(O)SH in quantitative yield. The conformational properties of the novel molecule have been studied by vibrational spectroscopy (IR – gas phase, Raman – liquid phase) and quantum chemical calculations (B3LYP and MP2 methods). The gaseous compound exhibits a conformational equilibrium at room temperature where the most stable form adopts a C1 symmetry and a syn‐periplanar (sp) orientation of both carbonyl groups with respect to the disulfide bond. A second form, observed in the IR spectrum of the vapor, corresponds to a conformer in which the carbonyl bond of the FC(O) moiety adopts an anti‐periplanar (ap) position with respect to the S–S single bond, and gauche with respect to the ClC–C=O moiety in the chlorodifluoroacetyl group. The experimental free energy difference value ΔG0 = G0(ap–sp) – G0(sp–sp) = 1.4(3) kcal/mol (IR) is reproduced well by the B3YLP/6‐311+G(3df) (1.1 kcal/mol) and the MP2/6‐31G* (1.8 kcal/mol) methods. In addition, the structure of a single‐crystal, grown in situ, was determined by X‐ray diffraction analysis at low temperature. The crystalline solid [monoclinic, P21/n, a = 5.579(3) Å, b = 16.615(7), c = 8.455(4) Å, β = 106.876(8)°] consists exclusively of molecules with the (sp–sp) conformation and the usual gauche orientation around the disulfide bond [φ(CS–SC) = 84.2°]. Conformational transferability is thus demonstrated once again for species that contain the –C(O)SSC(O)– group as part of a systematic program designed to analyze the behavior of this class of molecules. (© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2006)