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Utilizing intraoral bite blocks can aid in stabilizing the mandible during radiation treatment (RT) and minimizing side effects to healthy tissues. This report describes a technique to fabricate a customized acrylic repositioning immobilization bite block that was integrated into the clinical workflow of radiation appointments with no delay in starting RT and with increased patient comfort. [ABSTRACT FROM AUTHOR]

The positions of EMG electrodes over the knee extensor muscles were examined in 19 healthy men using MR images; electrodes were placed according to the SENIAM (surface electromyography for non-invasive assessment of muscles) guidelines. From axial images, the medial and lateral borders of the muscles were identified, and the arc length of the muscle surface was measured. The electrode location was expressed as a percentage value from the muscle's medial border. EMGs were recorded during isometric maximal contraction, squat jumps, and countermovement jumps and analyzed for cross-correlation. The results showed that variations in lateral positioning were greatest in vastus medialis (47% SD 11) and rectus femoris (68% SD 15). In vastus lateralis, the electrode was usually placed close to the rectus femoris (19% SD 6). The peak cross-correlation coefficient varied between 0.15 and 0.68, but was not associated with electrode location. It is recommended that careful consideration is given to the medial-lateral positioning of the vastus lateralis electrodes especially, so that the electrodes are positioned over the mid-muscle rather than in close proximity to rectus femoris. [ABSTRACT FROM AUTHOR]

Purpose: To propose a framework for optimal pairing of radiologists when reading mammograms based on their search patterns. Materials and Methods: Four experienced and four less‐experienced radiologists were asked to assess 120 cases (59 with cancers) while their eye positions were tracked. Fourteen eye‐tracking metrics were extracted to quantify the differences among radiologists' visual search pattern. For each radiologist and metric, less‐experienced radiologists and expert readers were ranked based on the level of similarities in gaze patterns (from the most different to the most similar). Less‐experienced readers and experts were also ranked based on the values of area under the receiver operating characteristic curve (AUC) after pairing (the best possible way of ranking). Using the Kendall's tau distance, rankings based on different metrics were compared with the best possible ranking. Using paired Wilcoxon signed‐rank test, the AUC values when pairing in the best way were compared with pairing based on different metrics. Finally, we investigated the robustness of pairing strategies against the small sample size. Results: For ranking the experienced radiologists, results from eight metrics were as good as the best possible ranking. For the less‐experienced ones, only one metric resulted in a ranking comparable to the best possible way of ranking. The AUC values of pairings based on these metrics did not differ significantly from the best pairing scenario. Compared to the pairings based on the cognitive metrics, the ranking based on AUC values varied more greatly with the sample size, suggesting that it is less robust against the small sample size compared to the cognitive metrics. Conclusion: Different pairings may have different effects on performance; some are detrimental while some improve the performance of the pair. Using the suggested cognitive metrics, we can optimize the pairings even with a small dataset. [ABSTRACT FROM AUTHOR]

Objective: The objective of the study was to perform the control study between the electrocardiogram (ECG)-guided tip positioning and traditional radiological confirmation method in peripherally inserted central catheters (PICC) placement; the accuracy and applicability of ECG-guided tip positioning were investigated. It aimed to expand the scope of PICC applications.Methods: From March 2016 to August 2017, 101 cases of patient with tumor admitted to the hospital were included in this study. The control study was performed before and after PICC placement. The tip positioning of PICC placement was performed under the guidance of bedside ECG system. The X-ray confirmation was applied for confirmation. Several parameters were observed, including positioning accuracy, success rate of primary catheterization, incidence of ectopic catheter, average catheterization time, and incidence of complications.Results: Position accuracy was 100%. The success rate of primary catheterization was 99%. The incidence of ectopic catheter was 1%. Average catheterization time was (49.59 ± 21.45) min. Incidence of postoperative complications within 1 week was 4%.Conclusion: ECG-guided PICC tip positioning was safe and accurate. Success rate of catheterization could be improved. ECG-guided PICC tip positioning can be applied as an alternative approach for patients with P-wave fluctuations. [ABSTRACT FROM AUTHOR]

We propose a method for the automatic positioning of pre-defined landmarks on 3-D models of anatomical structures. We exploit a group of atlases consisting of multiple triangular meshes for which the defined landmarks have been placed by experts. We compute an initial coarse global registration of the patient mesh with an expert mesh by using a curvature-enhanced Iterative Closest Point (ICP) algorithm. Adaptive local rigid registrations refine the fit for the projection of reference landmarks onto the surface of the patient structure. An automatic selection based on a fit criterion computes a final position for each landmark. Our positioning method improves the efficiency of the positioning task, being completely unsupervised and yielding results competitive with those of the manual positioning. We provide comparisons with previous works of the literature. The automatic positioning for each target structure is completely reproducible as opposed to manual positioning, affected by intra-operator variability. [ABSTRACT FROM AUTHOR]

Objectives: To estimate the radiation dose reduction to the thyroid for an anterior oblique occlusal view from the use of a thyroid shield, compare this with the variation in thyroid dose resulting from differences in examination positioning and discuss the additional considerations associated with the use of a thyroid shield before making a recommendation on their routine use for this examination. Methods: Doses to the oral mucosa, the salivary glands, the thyroid, the extrathoracic airways, the oesophagus and the lungs were directly measured for anterior oblique occlusal X-rays of a Rando phantom with and without a thyroid shield using strips of calibrated XRQA Gafchromic film. The examination was also simulated using Monte Carlo software for the without thyroid shield case for a comparison of the dose and to evaluate the dosimetric effect of suboptimal examination positioning. Results: A 36% reduction in thyroid dose was measured as a result of thyroid shield use; the effective dose reduction is of the order of 22%. Suboptimal positioning was found to increase thyroid dose by a far more significant amount. Conclusions: Despite the reduction in thyroid dose, cost-benefit considerations mean that the purchase of a thyroid shield is only recommended where a very high number of anterior oblique occlusal views are undertaken. Optimization efforts for this examination are better focussed on training in examination positioning. [ABSTRACT FROM AUTHOR]

Purpose: To assess current practices in digital mammography (DM) in Portuguese healthcare providers using digital systems. To investigate compliance with European standards regarding mean glandular dose and quality control practice and to identify optimisation needs. Methods: Two questionnaires, targeted at breast radiographers and chief radiographers, were designed and applied in 65 imaging departments offering DM. Questions fielded were focused on the staff profile and technical/clinical practice. Results: Prior to starting their activity in DM, 70% (82 out of 118) of the respondents received training in DM. The practice in 29 out of 59 providers was established by the manufacturers' recommendations for image acquisition. Variations were observed between radiographers who belong to the same provider namely the selection of exposure parameters such as the target-filter combination and automatic mode. The use of the manual exposure mode was reported for imaging breast implants (44%) and surgical specimens (22%). The main causes of repeat examinations were skin folding (21%) and absence of pectoral muscle (PM) (20%). Conclusions: The study revealed opportunities to optimise radiographers' practice in DM regarding the selection of exposure parameters. A robust and consistent training programme in DM and established local protocols can help to reduce the variations observed and improve clinical practice. Main Messages: • Radiographers adopted different practices selecting AEC modes and T/F combinations. • Radiographer practice is more consistent using DR than using CR systems. • The main causes for rejecting images were the visibility of skin folding and PM absence. • Radiographers were partly unaware of the dose indicator. • Radiographers' training needs: QC, interventional procedures and breast dose optimisation. [ABSTRACT FROM AUTHOR]

Background: Upright head and neck position has been frequently applied as baseline for diagnosis of neck problems. However, the variance of the position after cervical motions has never been demonstrated. Thus, it is unclear if the baseline position varies evenly across the cervical joints. The purpose was to assess reposition errors of upright cervical spine.Methods: Cervical reposition errors were measured in twenty healthy subjects (6 females) using video-fluoroscopy. Two flexion movements were performed with a 20 s interval, the same was repeated for extension, with an interval of 5 min between flexion and extension movements. Cervical joint positions were assessed with anatomical landmarks and external markers in a Matlab program. Reposition errors were extracted in degrees (initial position minus reposition) as constant errors (CEs) and absolute errors (AEs).Results: Twelve of twenty-eight CEs (7 joints times 4 repositions) exceeded the minimal detectable change (MDC), while all AEs exceeded the MDC. Averaged AEs across the cervical joints were larger after 5 min' intervals compared to 20 s intervals (p < 0.05).Conclusions: This is the first study to demonstrate single joint reposition errors of the cervical spine. The cervical spine returns to the upright positions with a 2° average absolute difference after cervical flexion and extension movements in healthy adults. [ABSTRACT FROM AUTHOR]

Background Diagnosis and treatment of patellofemoral disorders including osteoarthritis are currently often based on imaging and clinical assessment with patients in the supine position. Purpose To evaluate differences in patellar position in the trochlear groove and to assess the detection of medial and lateral patellofemoral (PF) osteoarthritis (OA) on axial radiographs in supine and standing positions, respectively. Material and Methods Thirty-five women and 23 men (mean age, 56 years; age range, 18-87 years) referred for routine radiographic examinations of the knees were included. Axial radiographs of the PF joint in both supine non-weight-bearing and standing weight-bearing position in 30° knee flexion were obtained of 111 knees. Measurements performed on the radiographs: patellar tilt, patellar displacement, joint space width, and grade of OA according to Ahlbäck. Results From supine to standing position the patella moved medially and medial joint space width and lateral patellar tilt angle decreased ( P < 0.0001 for the three measured parameters). In the standing position, medial PF OA was observed in 19 knees compared to three knees in the supine position. Fourteen knees had lateral PF OA with almost unchanged grade of OA irrespective of position. Conclusion In weight-bearing positions, the patella is positioned medially in the trochlear groove compared to supine non-weight-bearing positions. Therefore, this study suggests that the common occurrence of medial PF OA can generally not be detected on axial radiographs in supine non-weight-bearing positions and confirms the importance of imaging the PF joint in standing weight-bearing positions. [ABSTRACT FROM AUTHOR]

Purpose Conventionally in radiotherapy, a very heavy beam forming apparatus (gantry) is rotated around a patient. From a mechanical perspective, a more elegant approach is to rotate the patient within a stationary beam. Key obstacles to this approach are patient tolerance and anatomical deformation. Very little information on either aspect is available in the literature. The purpose of this work was therefore to design and test an MRI-compatible patient rotation system such that the feasibility of a patient rotation workflow could be tested. Methods A patient rotation system (PRS) was designed to fit inside the bore of a 3T MRI scanner (Skyra, Siemens) such that 3D images could be acquired at different rotation angles. Once constructed, a pelvic imaging study was carried out on a healthy volunteer. T2-weighted MRI images were taken every 45° between 0° and 360°, (with 0° equivalent to supine). The prostate, bladder, and rectum were segmented using atlas-based auto contouring. The images from each angle were registered back to the 0° image in three steps: (a) Rigid registration was based on MRI visible markers on the couch. (b) Rigid registration based on the prostate contour (equivalent to a rigid shift to the prostate). (c) Nonrigid registration. The Dice similarity coefficient (DSC) and mean average surface distance (MASD) were calculated for each organ at each step. Results The PRS met all design constraints and was successfully integrated with the MRI scanner. Phantom images showed minimal difference in signal or noise with or without the PRS in the MRI scanner. For the MRI images, the DSC (mean ± standard deviation) over all angles in the prostate, rectum, and bladder was 0.60 ± 0.11, 0.56 ± 0.15, and 0.76 ± 0.06 after rigid couch registration, 0.88 ± 0.03, 0.81 ± 0.08, and 0.86 ± 0.03 after rigid prostate guided registration, and 0.85 ± 0.03, 0.88 ± 0.02, 0.87 ± 0.02 after nonrigid registration. Conclusions An MRI-compatible patient rotation system has been designed, constructed, and tested. A pelvic study was carried out on a healthy volunteer. Rigid registration based on the prostate contour yielded DSC overlap statistics in the prostate superior to interobserver contouring variability reported in the literature. [ABSTRACT FROM AUTHOR]

Purpose This study aimed to investigate the breast dose reduction potential of a breast-positioning ( BP) technique for thoracic CT examinations with organ-based tube current modulation ( OTCM). Methods This study included 13 female anthropomorphic computational phantoms ( XCAT, age range: 27-65 y.o., weight range: 52-105.8 kg). Each phantom was modified to simulate three breast sizes in standard supine geometry. The modeled breasts were then morphed to emulate BP that constrained the majority of the breast tissue inside the 120° anterior tube current ( mA) reduction zone. The OTCM mA value was modeled using a ray-tracing program, which reduced the mA to 20% in the anterior region with a corresponding increase to the posterior region. The organ doses were estimated by a validated Monte Carlo program for a typical clinical CT system ( SOMATOM Definition Flash, Siemens Healthcare). The simulated organ doses and organ doses normalized by CTDIvol were used to compare three CT protocols: attenuation-based tube current modulation ( ATCM), OTCM, and OTCM with BP (OTCMBP). Results On average, compared to ATCM, OTCM reduced breast dose by 19.3 ± 4.5%, whereas OTCMBP reduced breast dose by 38.6 ± 8.1% (an additional 23.8 ± 9.4%). The dose saving of OTCMBP was more significant for larger breasts (on average 33, 38, and 44% reduction for 0.5, 1, and 2 kg breasts, respectively). Compared to ATCM, OTCMBP also reduced thymus and heart dose by 15.1 ± 7.4% and 15.9 ± 6.2% respectively. Conclusions In thoracic CT examinations, OTCM with a breast-positioning technique can markedly reduce unnecessary exposure to radiosensitive organs in anterior chest wall, specifically breast tissue. The breast dose reduction is more notable for women with larger breasts. [ABSTRACT FROM AUTHOR]

Triple-frequency signals of China's BeiDou navigation satellite system (BDS) are now accessible in the Asia-Pacific region. It is well understood that the third frequency signal will improve the navigation performance. Some literatures have described several navigation methods by using triple-frequency signals, and evaluated the performance. However the experiments were mostly implemented on simulated or semi-simulated observations. In this paper we investigate the navigation performance using real BDS triple-frequency observations. Apart from the pseudorange observations, carrier observations are also used, since the extra-wide-lane and wide-lane ambiguities can be reliably resolved with a single epoch. Several single-epoch navigation methods using BDS triple-frequency observations are described and the corresponding navigation accuracy and reliability are assessed. Results show that P3 has the highest accuracy among the three pseudorange observations. For carriers, the wide-lane and extra-wide-lane observations can be used to obtain much higher navigation precision compared with pseudorange observations. Besides, the two ambiguity-fixed extra-wide-lane and wide-lane observations can also be combined to ionosphere-free form, which can still obtain sub-decimetre and decimetre navigation accuracy in horizontal and vertical directions respectively. [ABSTRACT FROM AUTHOR]

Background: Incidental renal cysts are a very common finding in routine lumbar spine magnetic resonance imaging (MRI). However, there is no report of the renal cyst detection rate on routine lumbar spine MRI.Purpose: To determine the renal cyst detection rate in routine lumbar spine MRI based on findings of abdominal computed tomography (CT), and to investigate if the largest renal cyst seen by abdominal CT could be also detected by routine lumbar spine MRI.Material and Methods: A retrospective study was conducted of 70 patients who underwent both routine lumbar spine MRI and abdominal CT between December 2011 and January 2014. The detection rate of all renal cysts>5 mm as well as the largest renal cyst seen by abdominal CT were assessed in routine lumbar spine MRI.Results: On routine lumbar spine MRI, the detection rate of renal cysts was 46.5% (73/157) for>5-mm renal cysts and 68.0% (34/50) for>10-mm renal cysts, correlating with abdominal CT. The detection rate of the largest renal cyst seen by abdominal CT was 60.0% (27/45). Non-detection of the largest renal cyst could be caused by upper positioning (n = 7), lateral positioning (n = 6), or relatively small cyst size (n = 5).Conclusion: Approximately half of renal cysts>5 mm and two-thirds of renal cysts>10 mm were detected on routine lumbar spine MRI. However, radiologists should be aware that kidney lesions may not be included in the scan coverage of routine lumbar spine MRI. [ABSTRACT FROM AUTHOR]

Background: Radiographic imaging is a valuable tool in clinical practice for quick anatomical assessment. We aimed to radiographically assess (A) the anterior cruciate ligament (ACL) graft tunnel location after anatomic single-bundle (SB) reconstruction and (B) the effects of extremity positioning on the localization of the orifice of the tunnel in the distal femur in comparison with Blumensaat's line (BL). Methods: Three-dimensional computed tomography (3D CT) scan examinations of 22 knees of 22 subjects were evaluated. The 3D CT scan data was used to digitally reconstruct the true lateral radiographs. Graft tunnel location on the distal femoral shaft along the Blumensaat's line and perpendicular to it were assessed on these radiographs. The femur was digitally rotated to simulate varus, valgus, internal rotation and external rotation in 5-degree increments from 0 to 20-degree. At each incremental rotated position of the femur, position of the ACL graft tunnel was calculated relative to BL and the difference from the true lateral x-ray was estimated. Results: The position of the tunnel in the distal femur was 30.6 (±4.4) % along BL and 33.1 (±5.4) % perpendicular to BL. Ten and more degree of external, internal, valgus and varus rotations significantly affected the estimates of tunnel position (P < 0.05). Conclusions: Femoral tunnel location can be reliably estimated from lateral radiographs after anatomic SB ACL reconstruction. Although, ten or more degree of rotations can introduce significant inaccuracies in tunnel location estimates, our study suggests that BL is overall reliable for assessing location of the distal femoral tunnel. Level of evidence: Level 2b (Retrospective Cohort Study). [ABSTRACT FROM AUTHOR]

Dental panoramic radiograph, in addition to clinical examination, is a valuable diagnostic tool for the dentist to obtain information. Quality of each radiograph is of supreme importance. Unsatisfactory quality of radiograph can lead to misinterpretation that may result in inadequate diagnosis and treatment plan. Good quality radiograph will avoid any further need of repeating radiograph, thus reducing any unnecessary exposure of ionizing radiation to the patient. The objective of this study was to determine the relative frequency of common preparation and positioning errors observed on dental panoramic radiographs & to assess quality of radiographs as well. Dental panoramic radiographs were obtained from pretreatment records of patient undergoing orthodontic treatment & each radiograph was assessed for preparation and positioning errors. A three point quality scale proposed by National Radiological Protection Board was used by the examiner to rate each radiograph as being excellent, diagnostically acceptable or diagnostically unacceptable. Out of 480 panoramic radiographs examined, 100 (21%) radiographs were free from any type of preparation or positioning error while 380 (79%) radiographs had some preparation or positioning errors. The most frequent preparation error observed was patient wearing nose pin (8.3%). While the most common positioning error observed was patient's failure to position tongue against the palate (62.5%). More than one positioning or preparation error was found in 41.6% of the faulty radiographic films. Only 21% of radiographs were rated excellent, 64.5% were diagnostically acceptable, and 14.5% were unacceptable. Quality of panoramic radiograph must be assessed regularly making sure that they are free of any preparation or positioning error. All dental professionals must identify patient preparation and positioning errors and must understand consequence of these errors on diagnostic yield of radiograph. [ABSTRACT FROM AUTHOR]

Background: Reference values and physiological measurements of intracranial pressure (ICP) are primarily reported in the supine position, while reports of ICP in the vertical position are surprisingly rare considering that humans maintain the vertical position for the majority of the day. In order to distinguish normal human physiology from disease entities such as idiopathic intracranial hypertension and normal pressure hydrocephalus, we investigated ICP in different body postures in both normal and ill subjects. Methods: Thirty-one patients were included: four normal patients following complete removal of a solitary clearly demarcated small brain tumour and fitted with a telemetric ICP monitoring device for long-term ICP monitoring; 27 patients requiring invasive ICP monitoring as a part of their diagnostic work-up or monitoring of shunt treatment effect. ICP was recorded in the following body positions: upright standing, sitting in a chair, supine and right lateral lumbar puncture position. Results: Linear regression of median ICP based on patient posture, group, and purpose of monitoring presented a significant model ( p < 0.001), but could not distinguish between patient groups ( p = 0.88). Regression of differences in median ICP between body postures and supine ICP as the baseline, presented a highly significant model ( p < 0.001) and adjusted R = 0.86. Both body posture ( p < 0.001) and patient group ( p < 0.001) were highly significant factors. Conclusions: Differences in ICP between body postures enabled us to distinguish the normal group from patient groups. Normal patients appear able to more tightly regulate ICP when switching body postures. [ABSTRACT FROM AUTHOR]

The highly programmable positioning of molecules (biomolecules, nanoparticles, nanobeads, nanocomposites materials) on surfaces has potential applications in the fields of biosensors, biomolecular electronics, and nanodevices. However, the conventional techniques including self-assembled monolayers fail to position the molecules on the nanometer scale to produce highly organized monolayers on the surface. The present article elaborates different techniques for the immobilization of the biomolecules on the surface to produce microarrays and their diagnostic applications. The advantages and the drawbacks of various methods are compared. This article also sheds light on the applications of the different technologies for the detection and discrimination of viral/bacterial genotypes and the detection of the biomarkers. A brief survey with 115 references covering the last 10 years on the biological applications of microarrays in various fields is also provided. [ABSTRACT FROM AUTHOR]

Introduction: Poor long-term results of total hip arthroplasty (THA) can result from femoral component misalignment. There are few reports that discuss the effectiveness of intraoperative radiographs for placing femoral components. This study is a retrospective review to find out the usefulness of intraoperative radiographs in detecting and improving the femoral component misalignment in posterior-approached primary THA. Materials and methods: The study group included 150 primary THAs performed between September 2009 and April 2012. After the trial component insertion in lateral decubitus position, intraoperative radiography was performed. The surgeon assessed the femoral component position in three aspects: alignment, leg length, and offset. If it is not following the preoperative template, the surgeon makes the intraoperative adjustments to change the femoral component position. After the operation, postoperative radiograph was taken; the same parameters were measured and were compared to intraoperative findings. The changes in each parameter were classified into three categories: satisfactory, no change, and unsatisfactory. Among the three parameters, if one is satisfactory and the others are not unsatisfactory, we defined it as accurate positioning of the femoral component. Results: Intraoperative adjustments were made in 122 cases (81.3 %). The adjustments included changes in the component size (35.3 %), component alignment (38.6 %), femoral offset (14.0 %), and additional femoral neck cuts (56.0 %). As a result, accurate positioning was successfully achieved in 112 cases (91.8 %) by taking intraoperative radiographs. Conclusion: Our data suggest that intraoperative radiography is a useful method for detecting the errors of placing the femoral components, and the success of a surgeon to correct those errors after detecting them intraoperatively. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the frequency and severity of positioning errors in panoramic radiography in general dentistry. A total of 1904 digital panoramic radiographs, taken by the Public Dental Service in the county of Sörmland, Sweden, were analysed retrospectively. The study population consisted of all patients who underwent a panoramic examination during the year 2011. One experienced oral radiologist evaluated all radiographs for 10 common errors. Of the 1904 radiographs examined, 79 per cent had errors. The number of errors varied between 1-4 errors per image. No errors were found in 404 images (21%). Fifty-five images (3%) had severe errors, which made it impossible to make correct diagnostics. The most common error was the tongue not being in contact with the hard palate during exposure. However, this did not greatly affect the diagnostic usefulness of the image due to the ability to enhance the image.The patient's head was tilted too far upwards in 23 per cent of the images and the patient's head was rotated during exposure in 15 per cent. The least common error was due to patient movement during exposure (1%). Panoramic radiographs taken in general dental clinics in a Swedish county show several errors. Proper positioning of the patient is necessary to achieve panoramic images with good image quality. Some of the errors could be adjusted with the digital technique used.This allowed assessment of the images, which reduces radiation dose by avoiding retakes. [ABSTRACT FROM AUTHOR]

Professionals performing radiographic examinations are responsible for maintaining optimal image quality for accurate diagnoses. These professionals must competently execute techniques such as film manipulation and processing to minimize patient exposure to radiation. Improper performance by the professional and/or patient may result in a radiographic image of unsatisfactory quality that can also lead to a misdiagnosis and the development of an inadequate treatment plan. Currently, the most commonly performed extraoral examination is panoramic radiography. The invention of panoramic radiography has resulted in improvements in image quality with decreased exposure to radiation and at a low cost. However, this technique requires careful, accurate positioning of the patient's teeth and surrounding maxillofacial bone structure within the focal trough. Therefore, we reviewed the literature for the most common types of positioning errors in panoramic radiography to suggest the correct techniques. We would also discuss how to determine if the most common positioning errors occurred in panoramic radiography, such as in the positioning of the patient's head, tongue, chin, or body. [ABSTRACT FROM AUTHOR]

Purpose: This study was performed to evaluate the position of impacted mandibular third molars in different skeletal facial types among a group of Iranian patients. Materials and Methods: A total of 400 mandibular third molars in 200 subjects with different types of facial growth were radiographically investigated for their positions according to their types of facial growth on the basis of the β angle. The subjects were divided into three groups (class I, II, and III) according to ANB angle, representing the anteroposterior relationship of the maxilla to the mandible. Meanwhile, the subjects were also divided into three groups (long, normal, and short face) according to the angle between the stella-nasion and mandibular plane (SNGoGn angle). ANOVA was used for statistical analysis. Results: The mean β angle showed no significant difference among class I, II, and III malocclusions (df=2, F=0.669, p=0.513). The same results were also found in short, normal, and long faces (df=1.842, F=2, p=0.160). The mesioangular position was the most frequent one in almost all of the facial growth patterns. Distoangular and horizontal positions of impaction were not found in the subjects with class III and normal faces. In the long facial growth pattern, the frequency of vertical and distoangular positions were not different. Conclusion: In almost all of the skeletal facial types, the mesioangular impaction of the mandibular third molar was the most prevalent position, followed by the horizontal position. In addition, β angle showed no significant difference in different types of facial growth. [ABSTRACT FROM AUTHOR]

Observational studies suggest that combined spinal-epidural analgesia ( CSE) is associated with more reliable positioning, lower epidural catheter replacement rates, and a lower incidence of unilateral block compared with epidural analgesia. However, evidence from high-quality trials still needs to be assessed systematically. We performed a systematic review that included 10 randomised controlled trials comparing CSE and epidural analgesia in 1722 labouring women in labour. The relative risk of unilateral block was significantly reduced after CSE vs epidural analgesia (0.48, 95% CI 0.24-0.97), but significant between-study heterogeneity was present (I2 = 69%, p = 0.01). No differences were found for rates of epidural catheter replacement, epidural top-up, and epidural vein cannulation. On the basis of current best evidence, a consistent benefit of CSE over epidural analgesia cannot be demonstrated for the outcomes assessed in our review. A large randomised controlled trial with adequate power is required. [ABSTRACT FROM AUTHOR]

The SonixGPS™ needle guidance positioning system provides navigation assistance to facilitate needle handling during ultrasound-guided procedures. Each of 20 inexperienced nurse anaesthetists performed 12 different ultrasound-guided tasks in a porcine phantom. Using both in-plane and out-of-plane approaches, they inserted a needle and made contact with metal rods at depths of 2, 4 and 6 cm. We compared their performances without and with navigation as paired observations. Using the out-of-plane approach, navigation yielded shorter execution times (26 s vs 14 s, respectively; p = 0.01) and fewer needle repositionings (8 vs 3, respectively; p = 0.001). Using the in-plane approach, the needle was more visible with navigation assistance: 24% vs 52% of execution time, respectively (95% CI: 44%-12%; p = 0.0025). Better needle visibility was associated with shorter execution times and fewer needle repositionings. Combining ultrasound-guided techniques with the needle guidance positioning system may reduce tissue manipulation, thus improving patient comfort and safety. [ABSTRACT FROM AUTHOR]

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Pain and tenderness of the upper trapezius are the major complaints among people with chronic neck and shoulder disorders. Hyper-activation and increased muscle tension of the upper trapezius during arm elevation will cause imbalance of the scapular muscle force and contribute to neck and shoulder disorders. Assessing the elasticity of the upper trapezius in different arm positions is therefore important for identifying people at risk so as to give preventive programmes or for monitoring the effectiveness of the intervention programmes for these disorders. This study aimed to establish the reliability of supersonic shear imaging (SSI) in quantifying upper trapezius elasticity/shear elastic modulus and its ability to measure the modulation of muscle elasticity during arm elevation. Twenty-eight healthy adults (15 males, 13 females; mean age = 29.6 years) were recruited to participate in the study. In each participant, the shear elastic modulus of the upper trapezius while the arm was at rest and at 30° abduction was measured by two operators and twice by operator 1 with a time interval between the measurements. The results showed excellent within- and between-session intra-operator (ICC = 0.87–0.97) and inter-observer (ICC = 0.78–0.83) reliability for the upper trapezius elasticity with the arm at rest and at 30° abduction. An increase of 55.23% of shear elastic modulus from resting to 30° abduction was observed. Our findings demonstrate the possibilities for using SSI to quantify muscle elasticity and its potential role in delineating the modulation of upper trapezius elasticity, which is essential for future studies to compare the differences in shear elastic modulus between normal elasticity and that of individuals with neck and shoulder disorders. [ABSTRACT FROM AUTHOR]

An xyz-measuring table with a modular design has been developed for the determination of the individual 3D dose rate distributions of different brachytherapy sources requiring a high spatial resolution and reproducibility. The instrumental setup consists of a plastic scintillator detector system and the xyz-measuring table for guiding the detector across the radioactive sources. For this purpose, a micro positioning system with piezo inertial drives is chosen, providing a step width of 450 nm. To ensure a high reproducibility and accuracy better than 1 μm, an exposed linear encoder controls the positioning. The successful operation of the xyz-measuring table is exemplarily shown by measurements of dose profiles of two brachytherapy sources, an ophthalmic plaque and a radioactive seed. The setup allows a fully automated quality assurance of ophthalmic plaques and radioactive seeds under clinical conditions and can be extended to other (brachytherapy) sources of similar dimensions [ABSTRACT FROM AUTHOR]

Abstract: Background: Misplacement of right precordial electrocardiogram (ECG) electrodes superiorly is a prevalent procedural error that may lead to false findings of T-wave inversion or QS complexes in V2—possibly triggering wasteful utilization of health care resources. Standard technique for proper placement of V1–V2 entails initial palpation for the sternal angle, pointing to the second intercostal space (ICS), followed by lead fixation at the fourth ICS. Study Objective: Because adherence to this approach may be limited by lack of a visual landmark for the second ICS, we assessed an alternative technique. Methods: The evaluated technique involved placement of the patient’s hand up against the base of his/her neck (H→N maneuver) to help demarcate visually a specific point “X” on the chest. Results: Of 112 patients studied, “X” landed on the first rib in 2.7%, first ICS in 7.1%, second rib in 56.3%, second ICS in 33.0%, and third rib in 0.9%. Thus, in 89.3% (95% confidence interval 83.6–95.0%) of cases (93.3% of men, 84.6% of women; p =0.13), the second ICS could be identified by H→N via the following simple rule: Utilize “X” if it overlies an ICS; or the immediately subjacent ICS if “X” overlies a rib. Conclusion: The H→N maneuver provides a primarily visual approach to identifying the second ICS and, thereby, the fourth ICS for affixing V1–V2. If the present initial experience is confirmed, H→N might merit consideration as an educational tool to promote anatomically correct placement of these precordial leads, a prerequisite to diminishing the incidence of ECG procedure-related “septal ischemia/infarction.” [Copyright &y& Elsevier]

Purpose: To investigate the accumulated dose deviations to tumors and normal tissues in liver stereotactic body radiotherapy (SBRT) and investigate their geometric causes. Methods and Materials: Thirty previously treated liver cancer patients were retrospectively evaluated. Stereotactic body radiotherapy was planned on the static exhale CT for 27–60 Gy in 6 fractions, and patients were treated in free-breathing with daily cone-beam CT guidance. Biomechanical model-based deformable image registration accumulated dose over both the planning four-dimensional (4D) CT (predicted breathing dose) and also over each fraction’s respiratory-correlated cone-beam CT (accumulated treatment dose). The contribution of different geometric errors to changes between the accumulated and predicted breathing dose were quantified. Results: Twenty-one patients (70%) had accumulated dose deviations relative to the planned static prescription dose >5%, ranging from −15% to 5% in tumors and −42% to 8% in normal tissues. Sixteen patients (53%) still had deviations relative to the 4D CT–predicted dose, which were similar in magnitude. Thirty-two tissues in these 16 patients had deviations >5% relative to the 4D CT–predicted dose, and residual setup errors (n = 17) were most often the largest cause of the deviations, followed by deformations (n = 8) and breathing variations (n = 7). Conclusion: The majority of patients had accumulated dose deviations >5% relative to the static plan. Significant deviations relative to the predicted breathing dose still occurred in more than half the patients, commonly owing to residual setup errors. Accumulated SBRT dose may be warranted to pursue further dose escalation, adaptive SBRT, and aid in correlation with clinical outcomes. [Copyright &y& Elsevier]

Abstract: Volume visualization is a difficult three-dimensional task and a significant amount of research is devoted to the development of a suitable computer input device for it. Most of the proposed models use fixed displays, thus rendering extracted slices in orientations unrelated to their real locations within the volume. We present a new device which takes a different approach, as it leaves the volume in a fixed location and demands the user to change his or her posture to explore it from different angles. To implement this, we built a prototype based on a mobile display equipped with sensors that allows it to track its position, which is related to the location of the slice plane within the volume. Therefore, the user can manipulate this plane by displacing and rotating the display, which is a very intuitive method with minimum learning time. Furthermore, the postural changes required to use the device add a new channel of feedback, which effectively helps to reduce the cognitive load imposed on the user. We built a prototype device and tested it with two groups of volunteers who were asked to use it in a medical imaging application. Statistical analysis of the results shows that explorations made with the proposed device were considerably faster with no penalty in precision. We believe that, with further work, the proposed device can be developed into an useful tool for radiology and neurosurgery. [Copyright &y& Elsevier]

Purpose: To evaluate the setup, interfraction, and intrafraction organ motion error distributions and simulate intrafraction intervention strategies for prostate radiotherapy. Methods and Materials: A total of 17 patients underwent treatment setup and were monitored using the Calypso system during radiotherapy. On average, the prostate tracking measurements were performed for 8 min/fraction for 28 fractions for each patient. For both patient couch shift data and intrafraction organ motion data, the systematic and random errors were obtained from the patient population. The planning target volume margins were calculated using the van Herk formula. Two intervention strategies were simulated using the tracking data: the deviation threshold and period. The related planning target volume margins, time costs, and prostate position “fluctuation” were presented. Results: The required treatment margin for the left–right, superoinferior, and anteroposterior axes was 8.4, 10.8, and 14.7 mm for skin mark-only setup and 1.3, 2.3, and 2.8 mm using the on-line setup correction, respectively. Prostate motion significantly correlated among the superoinferior and anteroposterior directions. Of the 17 patients, 14 had prostate motion within 5 mm of the initial setup position for ≥91.6% of the total tracking time. The treatment margin decreased to 1.1, 1.8, and 2.3 mm with a 3-mm threshold correction and to 0.5, 1.0, and 1.5 mm with an every-2-min correction in the left–right, superoinferior, and anteroposterior directions, respectively. The periodic corrections significantly increase the treatment time and increased the number of instances when the setup correction was made during transient excursions. Conclusions: The residual systematic and random error due to intrafraction prostate motion is small after on-line setup correction. Threshold-based and time-based intervention strategies both reduced the planning target volume margins. The time-based strategies increased the treatment time and the in-fraction position fluctuation. [Copyright &y& Elsevier]

Purpose: To determine the advantages and disadvantages of daily online adaptive image-guided radiotherapy (RT) compared with conventional RT for muscle-invasive bladder cancer. Methods and Materials: Twenty-seven patients with T2–T4 transitional cell carcinoma of the bladder were treated with daily online adaptive image-guided RT using cone-beam computed tomography (CBCT). From day 1 daily soft tissue–based isocenter positioning was performed using CBCT images acquired before treatment. Using a composite of the initial planning CT and the first five daily CBCT scans, small, medium, and large adaptive plans were created. Each of these adaptive plans used a 0.5-cm clinical target volume (CTV) to planning target volume expansion. For Fractions 8–32, treatment involved daily soft tissue–based isocenter positioning and selection of suitable adaptive plan of the day. Treating radiation therapists completed a credentialing program, and one radiation oncologist performed all the contouring. Comparisons were made between adaptive and conventional treatment on the basis of CTV coverage and normal tissue sparing. Results: All 27 patients completed treatment per protocol. Bladder volume decreased with time or fraction number (p < 0.0001). For the adaptive component (Fractions 8–32) the small, medium, large, and conventional plans were used in 9.8%, 49.2%, 39.5%, and 1.5% of fractions, respectively. For the adaptive strategy, 2.7% of occasions resulted in a CTV V95 <99%, compared with 4.8% of occasions for the conventional approach (p = 0.42). Mean volume of normal tissue receiving a dose >45 Gy was 29% (95% confidence interval, 24–35%) less with adaptive RT compared with conventional RT. The mean volume of normal tissue receiving >5 Gy was 15% (95% confidence interval, 11–18%) less with adaptive RT compared with conventional RT. Conclusions: Online adaptive radiotherapy is feasible in an academic radiotherapy center. The volume of normal tissue irradiated can be significantly smaller without reducing CTV coverage. [Copyright &y& Elsevier]

Purpose: To evaluate the position and shape of the originally defined clinical target volume (CTV) over the treatment course, and to assess the impact of gross tumor volume (GTV)–based online computed tomography (CT) guidance on CTV localization accuracy. Methods and Materials: Weekly breath-hold CT scans were acquired in 17 patients undergoing radiotherapy. Deformable registration was used to propagate the GTV and CTV from the first weekly CT image to all other weekly CT images. The on-treatment CT scans were registered rigidly to the planning CT scan based on the GTV location to simulate online guidance, and residual error in the CTV centroids and borders was calculated. Results: The mean GTV after 5 weeks relative to volume at the beginning of treatment was 77% ± 20%, whereas for the prescribed CTV, it was 92% ± 10%. The mean absolute residual error magnitude in the CTV centroid position after a GTV-based localization was 2.9 ± 3.0 mm, and it varied from 0.3 to 20.0 mm over all patients. Residual error of the CTV centroid was associated with GTV regression and anisotropy of regression during treatment (p = 0.02 and p = 0.03, respectively; Spearman rank correlation). A residual error in CTV border position greater than 2 mm was present in 77% of patients and 50% of fractions. Among these fractions, residual error of the CTV borders was 3.5 ± 1.6 mm (left–right), 3.1 ± 0.9 mm (anterior–posterior), and 6.4 ± 7.5 mm (superior–inferior). Conclusions: Online guidance based on the visible GTV produces substantial error in CTV localization, particularly for highly regressing tumors. The results of this study will be useful in designing margins for CTV localization or for developing new online CTV localization strategies. [ABSTRACT FROM AUTHOR]

Abstract: Volumetric discrepancies between cone-beam computed tomography (CBCT) and planning CT image sets were investigated for both prone and supine breast radiotherapy. A phantom study was performed in order to examine the artefacts’ dependency on CBCT acquisition parameters and to minimize their effect on patient set-up accuracy. [Copyright &y& Elsevier]

Abstract: Purpose: To test a prone position against the international-standard supine position in women undergoing whole-breast-radiotherapy (WBRT) after wide-local-excision (WLE) of early breast cancer (BC) in terms of feasibility, set-up errors, and respiratory motion. Methods: Following WLE of BC with insertion of tumour-bed clips, patients underwent 4D-CT for WBRT-planning in supine and prone positions (the latter using an in-house-designed platform). Patients were randomised to undergo WBRT fractions 1–7 in one position, switching to the alternate position for fractions 8–15 (40Gy/15-fractions total). Cone-beam CT-images (CBCT) were acquired prior to fractions 1, 4, 7, 8, 11 and 14. CBCT data were matched to planning-CT data using (i) chest-wall and (ii) clips. Systematic and random errors were calculated. Maximal displacement of chest-wall and clips with respiration was measured on 4D-CT. Clinical- to planning-target-volume (CTV–PTV) margins were calculated. Patient-comfort-scores and treatment-times were evaluated. Results: Twenty-five patients were randomized. 192/192 (100%) planned supine fractions and 173/192 (90%) prone fractions were completed. 3D population systematic errors were 1.3–1.9mm (supine) and 3.1–4.3mm (prone) (p =0.02) and random errors 2.6–3.2mm (supine) and 3.8–5.4mm (prone) (p =0.02). Prone positioning reduced chest-wall and clip motion (0.5±0.2mm (prone) versus 2.7±0.5mm (supine) (p <0.001)) with respiration. Calculated CTV–PTV margins were greater for prone (12–16mm) than for supine treatment (10mm). Patient-comfort-scores and treatment times were comparable (p =0.06). Conclusions: Set-up errors were greater using our prone technique than for our standard supine technique, resulting in the need for larger CTV–PTV margins in the prone position. Further work is required to optimize the prone treatment-platform and technique before it can become a standard treatment option at our institution. [Copyright &y& Elsevier]

The deformity in idiopathic scoliosis (IS) is three dimensional in nature and effective correction involves all three planes. Even though the vertebral translation (VT) is an accepted element in the deformity along with vertebral rotation(VR) as reported by Asher and Cook (Spine (Phila Pa 1976) 20(12):1386-1391, ), Kotwicki et al. (Study Health Technol Inf 123:164-168, ) and Kotwicki and Napiontek (Pediatr Orthop 28(2):225-229, ), rib hump (rib hump index (RI)) and Cobb angle as reported by Aaro and Dahlborn (Spine (Phila Pa 1976) 6(6):567-572, ), it was assumed that VT was represented by adequately by Cobb angle and it was not analysed individually. We hypothesized that the Cobb angle and the VT measured in axial plane on CT scan and may not represent the same measurement and factors like coronal plane vertebral tilt,VR and vertebral deformation might affect them in different ways. Hence, VT should be considered as a separate variable and its relationship with VR, RI and Cobb angle should be investigated. Since the newer implants depend on curve translation and derotation for correction studying the role of VT and the relationships is important. VT, VR and RI were measured in CT scans of 75 patients with IS and correlated with Cobb angle. Regression analysis was used to identify the influence of the variables on each other. All the variables significantly correlated with one another but the correlation of Cobb and VT is not perfectly linear and it cannot be used to represent VT. VT influences RI much more than Cobb angle or VR. VT, therefore, merits further study treating it as an independent variable. [ABSTRACT FROM AUTHOR]

Abstract: We wanted to investigate whether using an endorectal balloon (ERB) in lieu of image guidance is reasonable. We compared daily prostate motion in 2 cohorts of patients with fiducial markers implanted in the prostate, one group with the ERB and the other without. Twenty-nine patients were treated using intensity-modulated radiation therapy: 14 with an ERB, and 15 without. All had fiducial markers placed in the prostate. We reviewed the daily displacements necessary to place the isocenter on the prostate as determined by portal imaging. In addition, we used the data to determine whether there is a change in prostate motion over the treatment course. The average prostate displacement for patients treated without an ERB was slightly greater than the average displacement for patients treated with the ERB. However, the difference observed with the ERB was not statistically significant (p > 0.05). The margins necessary to encompass the prostate 95% of the time for the patients treated without an ERB in the lateral, cranio/caudal, and anterior/posterior dimensions would be 4.8, 12.1, and 15.2 mm, respectively. When using the ERB, the margins necessary would be 4.1, 10.4, and 11 mm, respectively. Prostate motion in the anterior-posterior direction actually increased over the course of treatment in patients without an ERB. This increase was prevented by use of the ERB. Day-to-day variability of the position of the prostate is reduced in all dimensions with the water-filled ERB, but not significantly statistically. Use of the water-filled ERB did not obviate performing some form of image guidance daily. [Copyright &y& Elsevier]

Objective: Superimposition of frontal cephalograms cannot be performed when the cephalograms are taken with different vertical head rotations. The purpose of the present study was to evaluate the validity of correcting the positional change of frontal cephalometric landmarks caused by vertical head rotation. Methods: In 30 adult individuals, frontal and lateral cephalograms were taken at a 90° angle. Geometric principles of radiography were used to calculate the possible vertical and horizontal landmark changes if the head should be rotated down 5° about an ear rod axis. The calculated changes were then compared with cephalometric changes measured on frontal cephalogram actually taken with the head rotated down 5°. Results: When the frontal cephalograms were taken with the head rotated down 5° about an ear rod axis, significant changes in the vertical position of the landmarks occurred, particularly in the landmarks located farther anteriorly from the ear rod axis. The comparison of calculated changes and real cephalometric changes showed that the differences were less than 0.4 mm in the vertical direction and less than 0.2 mm in the horizontal direction. The differences between calculated and real changes were smaller in the landmarks less affected by vertical head rotation. Conclusions: Even when frontal cephalograms are taken at different vertical head rotations, the concomitant changes in the position of the landmarks can be corrected through calculation using the geometric principle of radiography as long as frontal and lateral cephalograms are taken perpendicular to each other. (Korean J Orthod 2011;41(2):98-111) [ABSTRACT FROM AUTHOR]

The aim of this study is to describe the radiological changes in rib-vertebral angles (RVAs), rib-vertebral angle differences (RVADs), and rib-vertebral angle ratios (RVARas) in patients with untreated right thoracic adolescent idiopathic scoliosis and to compare with the normal subjects. The concave and convex RVA from T1 to T12, the RVADs and the RVARas were measured on AP digital radiographs of 44 female patients with right convex idiopathic scoliosis and 14 normal females. Patients were divided into three groups: normal subjects (group 1), scoliotic patients with Cobb's angle equal or <30° (group 2) and scoliotic patients with Cobb's angle over 30° (group 3). Overall values (mean ± SD) of the RVAs on the concave side were 90.5° ± 17° in group 1, 90.3° ± 15.8° in group 2 and 88.8° ± 15.4° in group 3. On the convex side, values were 90.0° ± 17.3° in group 1, 86.3° ± 13.7° in group 2 and 80.7° ± 14.4° in group 3. Overall values (mean ± SD) of the RVADs at all levels were 0.5° ± 0.7° in group 1, 4.0° ± 4.8° in group 2 and 8.0° ± 4.0° in group 3. The RVARa values (mean ± SD) at all levels was 1.008° ± 0.012° in group 1, 1.041° ± 0.061° in group 2 and 1.102° ± 0.151° in group 3. RVAD and RVARa values in the scoliotic segment were greater in patients with untreated scoliosis over 30° than in patients with an untreated deformity of <30° or normal subjects. A significant effect between groups was observed for the RVA, RVAD and RVARa variables. Measurement of RVA, RVAD and RVARa should not only be performed at and around the apex of a thoracic spinal deformity, but also extended to the whole thoracic spine. [ABSTRACT FROM AUTHOR]

Purpose: NYU 05-181 protocol compared the CT simulation in both supine and prone positions for 400 patients with breast cancer (200 left-breast and 200 right-breast) to identify which setup is better at sparing heart and lung involvement in the treatment process. The results demonstrated that all right-breast patients benefited from the prone treatment position, while for left-breast patients, 85% were better treated prone and 15% were better treated supine. Using the clinical data collected from this protocol, the authors aimed at developing an automated tool capable of identifying which of the left-breast cancer patients are better treated supine without obtaining a second CT scan in the supine position. Methods: Prone CT scans from 198 of the 200 left-breast cancer patients enrolled in NYU 05-181 protocol were deidentified and exported to a dedicated research planning workstation. Three-dimensional geometric features of the organs at risk and tumor bed were extracted. A two-stage classifier was used to classify patients into the prone class or the supine class. In the first stage, the authors use simple thresholding to divide the patients into two groups based on their in-field heart volume. For patients with in-field heart volume ≤0.1 cc, the prone position was chosen as the preferred treatment position. Patients with in-field heart volume >0.1 cc will be further classified in the second stage by a weighted support vector machine (SVM). The weight parameters of the SVM were adjusted to maximize the specificity [true-supine/(true-supine+false-prone)] at the cost of lowering but still maintaining reasonable sensitivity [true-prone/(true-prone+false-supine)]. The authors used K-fold cross validations to test the performance of the SVM classifier. A feature selection algorithm was also used to identify features that give the best classification performance. Results: After the first stage, 49 of the 198 left-breast cancer patients were found to have >0.1 cc of in-field heart volume. The three geometric features of heart orientation, distance between heart and tumor, and in-field lung were selected by the feature selection algorithm in the second stage of the two-stage classifier to give the best predefined weighted accuracy. The overall sensitivity and specificity of the proposed method were found to be 90.4% and 99.3%, respectively. Using two-stage classification, the authors reduced the proportion of prone-treated patients that need a second supine CT scan down to 16.3/170 or 9.6%, as compared to 21/170 or 12.4% when the authors use only the first stage (thresholding) for classification. Conclusions: The authors' study showed that a feature-based classifier is feasible for predicting the preferred treatment position, based on features extracted from prone CT scans. The two-stage classifier achieved very high specificity at an acceptable expense of sensitivity. [ABSTRACT FROM AUTHOR]

Purpose: In circular cone-beam microcomputed tomography (micro-CT), it is likely that the length of the Field of View (FOV) of a single acquisition is shorter than the total length of the object to be imaged, such as a rat in the case of preclinical application of micro-CT. This leads to multiple acquisitions using different bed positions with bed translations in between, which can be automated using a motorized bed stage. However, subtle mechanical inaccuracies can cause undesired effects when the reconstructed volumes of the different acquisitions are combined into one larger volume. In this paper, we develop an automated method for accurately stitching 3D computed tomography (CT) data using an image registration scheme, and validate this technique in a circular cone-beam micro-CT scanner. Methods: The approach is based on precalculated spatial transformation matrices acquired by a calibration phantom with point markers at stitching positions. The spatial transformation between two adjacent subvolumes was calculated only once with a rigid-body matching algorithm. Once all transformation matrices are obtained, all subsequent reconstructed subvolumes imaged at these fixed positions can be stitched accurately, and efficiently using these precalculated matrices. Results: We applied this method to real object/animal imaging in circular cone-beam micro-CT and compared the result with that obtained by stitching method calculated only by translation distances and CT voxel size. Both stitching errors calculated using point markers and stitched volumes of rigid object (a syringe) and small animal (a rat) illustrated the success of our proposed approach. Conclusions: Preliminary experimental results demonstrate that "3D data stitching" using an image registration scheme provides a good solution to the voxel mismatch caused by limited FOV length in circular cone-beam micro-CT. This method can be extended to other tomography techniques which need to acquire data at fixed scanning positions. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this study was to determine the accuracy and efficiency of a custom-designed immobilization device for patients with extremity soft-tissue sarcoma. The custom device consisted of a thermoplastic shell, vacuum pillow, and adaptable baseplate. The study included patients treated from January 2005 to March 2007, with 92 patients immobilized with the custom device and 98 with an established standard. Setup times for these cohorts were analyzed retrospectively for conformal and intensity modulated radiotherapy techniques (IMRT). Thigh tumor setup times were analyzed independently. A subset of patients treated with IMRT was analyzed for setup error using the radiographically verified isocenter position measured daily with electronic portal imaging and cone-beam computed tomography. Mean setup time was reduced by 2.2 minutes when using the custom device for conformal treatment (p = 0.03) and by 5.8 min for IMRT of thigh tumors (p = 0.009). All other setup time comparisons were not significant. A significant systematic error reduction was seen in all directions using the custom device. Random error standard deviations favored the custom device. The custom device offers immobilization advantages. Patient setup time was reduced for conformal techniques and IMRT of thigh tumors. Positioning uncertainty was improved, permitting a reduction of the planning target volume margin by 2 to 4 mm. [Copyright &y& Elsevier]

Abstract: To investigate the unexpected skin dose increase from intensity-modulated radiation therapy (IMRT) on vacuum cushions and carbon-fiber couches and then to modify the dosimetric plan accordingly. Eleven prostate cancer patients undergoing IMRT were treated in prone position with a vacuum cushion. Two under-couch beams scattered the radiation from the vacuum cushion and carbon-fiber couch. The IMRT plans with both devices contoured were compared with the plans not contouring them. The skin doses were measured using thermoluminescent dosimeters (TLDs) placed on the inguinal regions in a single IMRT fraction. Tissue equivalent thickness was transformed for both devices with the relative densities. The TLD-measured skin doses (59.5 ± 9.5 cGy and 55.6 ± 5.9 cGy at left and right inguinal regions, respectively) were significantly higher than the calculated doses (28.7 ± 4.7 cGy; p = 2.2 × 10−5 and 26.2 ± 4.3 cGy; p = 1.5 × 10−5) not contouring the vacuum cushion and carbon-fiber couch. The calculated skin doses with both devices contoured (59.1 ± 8.8 cGy and 55.5 ± 5.7 cGy) were similar to the TLD-measured doses. In addition, the calculated skin doses using the vacuum cushion and a converted thickness of the simulator couch were no different from the TLD-measured doses. The recalculated doses of rectum and bladder did not change significantly. The dose that covered 95% of target volume was less than the prescribed dose in 4 of 11 patients, and this problem was solved after re-optimization applying the corrected contours. The vacuum cushion and carbon-fiber couch contributed to increased skin doses. The tissue-equivalent-thickness method served as an effective way to correct the dose variations. [Copyright &y& Elsevier]