Alignment Discrepancies Research Articles

SU-E-J-60: Comparison of CT-On-Rails and a 3D Surface Imaging System for Image Guided Pelvic Radiation Therapy for Both Supine and Prone Patient Positions.

We investigate the feasibility of using AlignRT for pelvic radiation image guidance. The uniqueness of our study is that all patients have multiple CT-on-rails (CTOR) scans to compare corresponding AlignRT images to. Ten patients receiving pelvic radiation were enrolled in this study. Two simulation CT scans were performed in supine and prone positions for each patient. Body surface contours were generated in treatment planning system and exported to AlignRT to serve as reference images. The patient was aligned to treatment isocenter with room lasers, and then scanned with both CTOR and AlignRT in both supine and prone positions. Image guidance shifts were calculated for both modalities by comparison to the simulation CT and the differences between them were analyzed. These procedures were performed for each patient once per week for five weeks. The average and maximum difference of displacement between AlignRT and CTOR were calculated for each patient. For supine position, there are 4 patients who had the average difference of displacement between AlignRT and CTOR along any direction (vertical, longitudinal, and lateral) greater than 0.5cm, and 1 patient greater than 1cm. For prone position, there are 7 patients who had the average difference greater than 0.5cm, and 3 patients greater than 1cm. For supine position, there are 4 patients who had the maximum difference great than 1cm. For prone position, there are 9 patients who had the maximum difference greater than 1 cm. The difference of displacement between AlignRT and CTOR is greater for prone position than for supine position. AlignRT does not appear to be an advisable image guidance approach for pelvic radiation therapy for patients with either supine or prone position. There appears to be a potential for large alignment discrepancies (up to 2.25 cm) between AlignRT and CTOR.

A practical method of comparing luminous intensity distributions

In the field of goniophotometry, as in many other measurement disciplines, there is an increasing need for laboratories to become ISO-17025 accredited. This involves, amongst other things, characterisation of the goniophotometric measurement for uncertainty analysis and laboratory intercomparisons. Simple comparison of the luminous intensity measurements, however, can lead to large errors where there is a steep luminous intensity gradient when the only difference between the two sets of measurements is a small discrepancy in alignment. Given the difficulty in mounting and aligning some types of luminaires, this makes uncertainty analysis and intercomparisons difficult. Furthermore, the work of several CIE Division 2 Technical Committees (e.g. TC2-62) highlights the need to compare the measurements made on both far-field and near-field goniophotometers. This paper introduces a metric for comparison of two luminous intensity distributions that isolates and removes discrepancies that arise both from misalignment and also the difference in absolute calibration scales or the luminous flux output of the source. Moreover, these discrepancies are reported as part of the metric, so that a complete comparison of the sets of measurements is possible.

Mathematical Reasoning Requirements in Swedish Upper Secondary Level Assessments

We investigate the mathematical reasoning required to solve the tasks in the Swedish national tests and a random selection of Swedish teacher-made tests. The results show that only a small proportion of the tasks in the teacher-made tests require the students to produce new reasoning and to consider the intrinsic mathematical properties involved in the tasks. In contrast, the national tests include a large proportion of tasks for which memorization of facts and procedures are not sufficient. The conditions and constraints under which the test development takes place indicate some of the reasons for this discrepancy and difference in alignment with the reform documents.

Use of Intraoperative Computed Tomography in Complex Facial Fracture Reduction and Fixation

Using conventional complex facial fracture management principles, confirmation of adequate facial fracture reduction can be achieved only by obtaining a postoperative computed tomography (CT) scan. If the CT scan revealed any discrepancy in fracture alignment, additional procedures for correction may be required. The concept of intraoperative CT scanning provides immediate postreduction or intraoperative information that orients the surgeon to the potential need for additional maneuvers for improved fracture reduction and osseous fixation. We assessed the early technical feasibility of real-time intraoperative CT scanning using the xCAT ENT (Xoran Technologies, Inc, Ann Arbor, MI), for monitoring of fracture reduction with the possibility of immediate intraoperative revision if needed, potentially obviating the need for revision procedures. Three adult patients were studied who were admitted from the emergency department. During their respective reconstructive procedures, the xCAT ENT was used to provide images: Axial, coronal, sagittal, and three-dimensional reformatted images with segmentation of the CT data set and mirroring of the reconstructed side to the unaffected side were used for precise measurement and comparison of the reconstruction. The scans were examined by the operating surgeon and an intraoperative decision was made as to whether immediate revision was required. Facial fracture management with intraoperative CT monitoring was changed in 2 of the 3 cases. One patient who underwent immediate revision had an open reduction-internal fixation after cranialization. The second patient who had a revision had a persistent subcondylar fracture that was found not amenable to closed reduction. The intraoperative CT scan may positively change the outcome of facial fracture reduction especially when dealing with complex fractures. Additional studies are needed for studying its potential impact in monitoring reduction of facial fractures.

Hybrid PET/CT of the Thorax

To determine if computer registration improves the image fusion of hybrid positron emission tomography (PET)/computed tomography (CT) data sets in the thorax acquired during different breathing maneuvers. Hybrid PET/CT scans were acquired with varying CT respiratory instructions. The scans of 64 patients with 5 different breathing maneuvers were reviewed, including expiration, suspended breath hold, quiet breathing, small breath in, and regular breath in. The PET/CT data sets were reviewed before registration, after linear registration, and combined linear/nonlinear registration. Each PET/CT data set was graded for the quality of alignment at 5 anatomical locations (diaphragm, aortic arch, heart, thoracic spine, and lung apices) and rated from 1 (very poor) to 5 (excellent). The Kruskal-Wallis test was used to compare alignment between the breathing protocols, and Wilcoxon signed rank test was used to compare the registration techniques. The quality of anatomical alignment between superimposed (nonregistered) PET and attenuation correction CT (CTAC) acquired during expiration, suspended breath hold, and quiet breathing was excellent, with no significant changes in alignment following registration. The quality of anatomical alignment between superimposed (nonregistered) PET and CTAC acquired during inspiration showed significant misalignment at the heart (P = 0.001, P < 0.0001) and diaphragm (P = 0.0001, P < 0.0001) which did not correct with linear registration. Alignment significantly improved with additional nonlinear registration at the diaphragm (P = 0.008, P = 0.0002), although cardiac misalignment remained. With hybrid PET/CT, excellent anatomical alignment between PET and CTAC scans can be achieved with CT acquisition during expiration, suspended breath hold, or quiet breathing, and additional software registration is not necessary. Nonlinear registration significantly improves alignment discrepancies at the diaphragm if inspiratory methods are used, however, cardiac misalignment remains.

Interface characteristics of (Zn,Mn)O/ZnO grown on ZnO substrate

ZnO single layer and (Zn,Mn)O/ZnO hetero-structure were fabricated on an O-face ZnO substrate. Both surfaces were very smooth, consisting of steps and terraces, and were very similar. These results suggest that the interface between the ZnO and (Zn,Mn)O layers is very smooth. The temperature dependence of the electron mobility indicates the existence of accumulated electrons beside the interface. However, the electron mobility was lower than that of the two-dimensional electron gas (2DEG) beside the (Zn,Mn)O/ZnO hetero-interface reported in our previous paper. In addition, the electron mobility at room temperature suggests that the electrons are confined in the (Zn,Mn)O layer, although the 2DEG observed in the previous study was confined in the ZnO layer. Therefore, the band alignments of the hetero-structures of the present study are expected to be very different from those reported in the previous study. In order to confirm the band alignment with confined electrons in the (Zn,Mn)O layer, an electron-supplying layer was fabricated in the ZnO layer. The resulting change in the electron mobility supports the band alignment. Enlargement of the energy band gap of (Zn,Mn)O was carried out by Mg doping. The results for the electron transport properties also support the band alignment. All of the present results support the band alignment having confined electrons in the (Zn,Mn)O side of the hetero-interface, although, in our previous study, the 2DEG was confirmed to be in the ZnO layer. The discrepancy in band alignment was assumed to be caused by the unintentional change in Mn concentration related to the parameters defining the band alignment, such as the energy band gap, electron affinity and Fermi level of the (Zn,Mn)O layer.

Secondary correction of malocclusion after treatment of maxillofacial trauma

d alocclusion after primary treatment of maxillofaial trauma is not frequently reported in the literaure. Despite many developments in the treatment f facial fractures, the most common hard tissue omplications after maxillofacial trauma are temoromandibular joint (TMJ) dysfunction, followed y infections and malocclusions. When rigid meallic plates and screws became available, the reuirements for accuracy in surgery increased, as ven a mild discrepancy in alignment of bony fragents and osteosynthesis can have a severe effect n occlusion. As with all surgery, the rate of comlications decreases with the greater experience of he operating surgeon. Maxillofacial trauma patients frequently have ther injuries, most often neurologic or orthopedic. f emergency surgery must be carried out, the facial ractures will usually be operated on at the same ime. Emergency situations may lead to poor preperative imaging and inadequate preoperative reatment planning of maxillofacial injuries. On the

Prosthetic alignment effects on gait symmetry: a case study

The loss of a significant portion of a lower extremity causes changes in the usual pattern of human ambulation. These changes have been documented kinematically, kinetically and metabolically, giving insight into the costs of limb amputation relative to ambulatory efforts. The role of the prosthetist is to provide a limb substitute to achieve the best gait performance, while assuring maximum comfort for the patient. This case study examined the effects of antero-posterior alignment of a below-knee prosthesis on sagittal plane gait kinematics by comparing the anatomical side with the prosthetic side. The greatest changes due to variations of alignment were found during the prosthetic stance phase; knee angles showed the greatest asymmetry between anatomical and prosthetic sides. The stance phase on the prosthetic side was reduced with anterior socket displacement due to early knee flexion and toe-off. Posterior socket displacement caused a greater maximum centre of gravity height, but anterior socket displacement caused greater knee flexion which decreased the maximum centre of gravity height. Asymmetries in temporal and other kinematic parameters were not always minimal at the optimal alignment subjectively selected by a certified prosthetist. Comparisons of asymmetry ratios with prosthetic side data revealed the subclinical sensitivity of this amputee to antero-posterior alignment discrepancies.

Cranking-HFB calculations of the yrastline for the nuclei232Th,234,236,238U,248Cm

The CHFB method is applied to actinide nuclei. The calculated neutron alignment agrees with the experimental data, but for the proton alignment discrepancies are observed. The reliability of our approach and the information from measured odd-mass-actinide spectra are discussed. It is concluded that the experimental even-even spectra might have to be interpreted as bands in which the lowest excitation of two (651, 3/2) protons is not populated.