Head Supports Research Articles

Overcoming a 'forbidden phenotype': the parrot's head supports, propels and powers tripedal locomotion.

No vertebrate, living or extinct, is known to have possessed an odd number of limbs. Despite this 'forbidden phenotype', gaits that use odd numbers of limbs (e.g. tripedalism or pentapedalism) have evolved in both avian and mammalian lineages. Tripedal locomotion is commonly employed by parrots during climbing, who use their beaks as an additional support. However, it is unclear whether the beak functions simply as a stabilizing hook, or as a propulsive limb. Here, we present data on kinetics of tripedal climbing in six rosy-faced lovebirds (Agapornis roseicollis). Our findings demonstrate that parrots use cyclical tripedal gaits when climbing and the beak and hindlimbs generate comparable propulsive and tangential substrate reaction forces and power. Propulsive and tangential forces generated by the beak are of magnitudes equal to or greater than those forces generated by the forelimbs of humans and non-human primates during vertical climbing. We conclude that the feeding apparatus and neck flexors of parrots have been co-opted to function biomechanically as a propulsive third limb during vertical climbing. We hypothesize that this exaptation required substantive alterations to the neuromuscular system including enhanced force-generating capabilities of the neck flexors and modifications to locomotor central pattern generators.

Head and neck positioning for out-of-theatre intubation during the COVID-19 pandemic.

The COVID-19 pandemic has brought with it a large number of challenges for healthcare professionals including intubation safety in out-of-theatre environments. An important aspect of this topic is the optimisation of a patient’s head and neck position prior to laryngoscopy which can be challenging when a pillow cannot be located. As a result, the authors compared how well the sniffing position (35o neck flexion and 15o head extension) could be reached using pillows or other novel head supports. The resulting data demonstrated that a 1-litre pressure bag and two 1-litre saline bags achieved the most accurate position.

Eliminating computed tomography imaging artifacts through 3D printed radiotherapy head supports.

PurposeThe geometry of an immobilization device such as a headrest can cause undesired computed tomography (CT) artifacts that may affect both volume definition and dosimetry in radiotherapy of the brain. The purpose of this work was to reduce CT artifacts caused by a standard hard plastic hollow radiotherapy headrest. This was to be achieved through design and prototyping of a custom‐made head support.MethodsA series of CT scans were acquired of both a water phantom and an anthropomorphic head phantom which were resting on custom‐made three‐dimensional (3D) printed supports. All custom‐made supports were made of polylactic acid (PLA) plastic filament and printed by fused deposition modeling (FDM) 3D printing technology. Initial designs were studied with a water phantom using a simplified support with straight and curved shapes both at the edges and as infill patterns. Imaging of a 3D printed clinical prototype was then compared to our standard headrest using an anthropomorphic head phantom.ResultsThe presence of dark streaks inside both phantoms was seen on the CT images for headrests involving supports with straight shapes at the edges or as infill patterns. Such artifacts were ascribed to the exponential edge‐gradient effect (EEGE). No such artifact was observed when the support was designed with a combination of curved edges and infill patterns.ConclusionWhen developing immobilization accessories for use in CT scanners, more attention could be paid to artifact attenuating design elements. This work illustrates the usefulness of 3D printing in prototyping radiotherapy accessories and solving concrete clinical problems.

A parametric investigation on seat/occupant contact forces and their relationship with initially perceived discomfort using a configurable seat

The present work investigates the contact forces between sitters and seat as well as their correlations with perceived discomfort. Twelve different economy class aeroplane seat configurations were simulated using a multi-adjustable experimental seat by varying seat pan and backrest angles, as well as seat pan compressed surface. Eighteen males and 18 females, selected by their body mass index and stature, tested these configurations for two sitting postures. Perceived discomfort was significantly affected by seat parameters and posture and correlated both with normal force distribution on the seat-pan surface and with normal forces at the lumbar and head supports. Lower discomfort ratings were obtained for more evenly distributed normal forces on the seat pan. Shear force at the seat pan surface was at its lowest when sitters were allowed to self-select their seat-pan angle, supporting that a shear force should be reduced but not zeroed to improve seating comfort. Practitioner Summary: The effects of seat-pan and backrest angle, anthropometric dimensions and sitting posture on contact forces and perceived discomfort were investigated using a multi-adjustable experimental seat. In addition to preferred seat profile parameters, the present work provides quantitative guidelines on contact force requirement for improving seating comfort.

Comparison of Skull Motions in Six Degrees of Freedom Between Two Head Supports During Frameless Radiosurgery by CyberKnife.

Introduction: Maintaining immobilization to minimize skull motion is important during frameless radiosurgery. This study aimed to compare the intrafractional skull motions between two head supports.Methods: With 6D skull tracking system, 4,075 image records from 45 patients receiving radiosurgery by CyberKnife were obtained. Twenty-three patients used TIMO head supports (CIVCO) (Group A) and twenty-two patients used Silverman head supports (CIVCO) with MoldCare cushions (ALCARE) (Group B). The skull motions in X (superior-inferior), Y (right-left), Z (anterior-posterior) axes, 3D (three-dimensional) vector, Roll, Pitch and Yaw between the two groups were compared and the margins of planning target volume were estimated.Results: The translational motions in Group A were similar in three axes at initial but became different after 10 min, and those in Group B were less prominent in the Y axis. The rotational errors in Group A were most obvious in Yaw, but those in Group B were stationary in three axes. The motions in the X axis, 3D vector, Pitch and Yaw in Group B were significantly smaller than those in Group A; conversely, the motions in the Z axis in Group B were larger. To cover the 95% confidence intervals, margins of 0.77, 0.79, and 0.40 mm in the X, Y, and Z axes, respectively, were needed in Group A, and 0.69, 0.50, and 0.51 mm were needed in Group B.Conclusions: Both head supports could provide good immobilization during the frameless radiosurgery. Silverman head support with MoldCare cushion was better than TIMO head support in the superior-inferior direction, 3D vector, Pitch and Yaw axes, but worse in the anterior-posterior direction.

Repetition of Examination Due to Motion Artifacts in Horizontal Cone Beam CT: Comparison among Three Different Kinds of Head Support.

Aims and Objectives:The aim of this study was to evaluate the repetition rate of examination due to motion artifacts in horizontal cone beam computed tomography, using three different kinds of head support, with reference to the patient's age. Further purpose was to evaluate how comfortable head supports were.Materials and Methods:Seven hundred and fifty patients underwent a maxillofacial/dental arches volumetric imaging scan. They were divided into three groups depending on the head support used: foam headrest, foam headrest with head strap, and head restraint helmet. Each group was subdivided into three age groups: ≤18-year-old, 19–65-year-old, and ≥66-year-old patients. A severity index of motion artifacts, divided into four tiers from absence to remarkable artifacts, was adopted. Finally, each patient gave their judgment about the head support comfort by a questionnaire including ten yes/no questions. A three-score scale (insufficient, sufficient, and good) was used to judge the comfort. Collected data were analyzed using the SPSS® version 23.0 statistical analysis software.Results:Forty-one patients (5.4%) repeated the examination. In 16 (2.1%), 15 (2.0%), and 10 (1.3%) of them, foam headrest, foam headrest with head strap, and head restraint helmet were used, respectively. Examination was repeated in 5.3%, 3.8%, and 10.6% in ≤18-year-old, 19–65-year-old, and ≥66-year-old patients, respectively. Patients almost always judged good the comfort for each kind of support. The lowest percentage of satisfaction was observed for the headrest with head strap and was judged good in 78% of the cases.Conclusions:The repetition rate of examination showed similar values among the foam headrest, foam headrest with head strap, and head restraint helmet in under 66-year-old patients. In over 65-year-old patients, the head restraint helmet obviously decreased the repetition rate of examination. All three head supports were good comfort, especially the foam headrest.

Parameter identification for a low-density-foam material model using numerical optimisation procedures

Purpose – In the event of a crash involving a car, its seats, together with their backrests and head supports, ensure the safety of the passengers. The filling material used for such a car seat is normally made of polyurethane foam. To simulate the behaviour of the seat assembly during a crash, the material characteristics of the seat-filling foam should be appropriately modelled. The purpose of this paper is to present a method, with which the proper parameter values of the selected material model for the seat-filling foam can be easily determined. Design/methodology/approach – In the study, an experiment with the specimen from seat-filling foam was carried out. The results from this experiment were the basis for the determination of the parameter values of the low-density-foam material model, which is often used in crash-test simulations. Two different numerical optimisation algorithms – a genetic algorithm and a gradient-descent algorithm – were coupled with LS-DYNA explicit simulations to identify the material parameters. Findings – The paper provides comparison of two optimisation algorithms and discusses the engineering applicability of the results. Originality/value – This paper presents an approach for the identification of the missing parameter values of the highly non-linear material model, if these cannot be easily determined directly from experimental data.

Assessment of Fiducial-based 2D kV Orthogonal Imaging, Fiducial-based CBCT, and Soft-tissue-based CBCT for Prostate Cancer Patients With Implanted Fiducial Markers

Purpose/Objective(s): To assess the geometric accuracy and imaging performance of a newly developed phased array coil system optimized for MR imaging of patients immobilized with the type S frame for head and neck radiation therapy. Materials/Methods: Protocol optimization for the novel coil was undertaken using a GE Optima450-GEM 70cm wide bore unit adapted for radiation therapy MR-SIM localization. Pulse sequence parameters for T1FSE, T2 FRFSE and T1 and T2 CUBE (including matrix, slice thickness, bandwidth) were optimized to maximize SNR while minimizing the effect of chemical shift. Phantom measurements were then performed to quantify system related residual geometric distortions after application of a 3D commercial gradient distortion correction algorithm for the effective FOV and the pulse sequences utilized. The optimized protocols were used to image seven volunteers positioned using an MR compatible type S system with neutral head supports. MRI images (from the base of brain to below the clavicles) were acquired using the novel phased array coil combination placed over the head, neck and thoracic region. The volunteers were re-imaged without immobilization in a standard diagnostic head coil, which served as the benchmark for image quality. Signal to noise, image homogeneity and image artifacts were compared between the two image datasets in a blinded study. Visibility of ten anatomical structures was evaluated. For statistical analysis, Cohen’s kappa, Wilcoxon matched pairs and t-testing were utilized. Results: A geometrically accurate, high resolution MR-SIM imaging protocol (T1/T2CUBE. 2D T1/T2 FSE) was developed with 3mm slice thickness/no gap that provides excellent image quality from the base of brain to below the clavicles in the treatment position. From phantom studies, residual distortions were found to be 1.0mm within a 10 cm radius and < 1.5 mm within a 15 cm radius of the scan centre. Using a RBWof 50-62.5 minimized chemical shift (<1mm within a 10cm radius) at 1.5T while providing acceptable SNR. The coil provided higher SNR values in all anatomical structures, but less uniformity than the standard diagnostic head coil (full comparative SNR/CNR/geometric data will be presented). No significant difference for image quality and artifacts were demonstrated between the coils in the blinded study. Conclusions: The novel open architecture purpose built phased coil array provides unparalleled coverage and good image quality of the subject immobilized for head and neck radiation therapy and is a promising solution for MR-SIM in the head and neck region. Author Disclosure: G. Perkins: None. R. Hammoud: None. S. Pienaar: None. S. Paloor: None. N. Al Hammadi: None.

Flow-induced vibration of a steam control valve

Main steam control valves in power plants are required to operate underwide ranges of valve openings and pressure ratios. In the present paper, experimental and numerical investigations are conducted using rigid and flexible valve head supports to clarify the mechanisms of valve head vibrations that are caused by unsteady flows around the valve. The results obtained using the rigid support without valve head vibration show that the unsteady flow around the valve head causes pressure fluctuations on the valve head surface with random and impulsive wave forms. When using the flexible support, the valve head vibrates near the natural frequency of the valve head support system, and vibrations are excited around the operating conditions where the pressure fluctuation becomes greater when using the rigidly supported valve head. When the valve head vibration increases, the pressure fluctuation becomes periodic with the same frequency as the valve head vibration. The numerical results show that the response of the separated jet lags behind the valve head motion. As a result, the lateral fluid force adds negative damping on the vibration on the valve head.

Design of a Mobile Head Support Based on a Compliant Mechanism

In the Netherlands, approximately 100,000 people have a muscle disease. Often this disease is progressive, so patients’ disabilities get worse over time. They end up in a wheelchair and will be dependent on technical supports. Head supports are often not used because of bad cosmetics, comfort, and control. This paper presents a slim, disguisable, and body supported innovative head rest. The prototype is tested in two ways: by tilting the setup to simulate accelerations and observing it during a car drive. It proved to withstand accelerations varying up to around 5 m/s2, comparable to normal driving conditions in a bus. While there remains scope for improvement, the prototype was appreciated by the patient. A company is willing to further develop the design.

Flow-Induced Vibration of Valve Head of Steam Control Valve

Main steam control valves in power plants are required to operate under wide ranges of valve openings and pressure ratios. In the present paper, experimental and numerical investigations are conducted with rigid and flexible valve head supports in order to clarify mechanisms of valve head vibrations caused by unsteady flows around the valve. Results obtained with the rigid support without valve head vibration show that the unsteady flow around the valve head causes pressure fluctuations on the valve head surface with random and impulsive wave forms. With flexible support, the valve head vibrates at near the natural frequency of the valve head support system and the vibrations are excited around the operation condition where the pressure fluctuation becomes large with rigid support valve head. When the valve head vibration becomes large, the pressure fluctuation becomes periodic with the same frequency of the valve head vibration. The numerical result shows that the response of the separated jet delays behind the valve head motion. As a result, the lateral fluid force fluctuations on the valve head provide negative damping on the vibration.

Evaluation of the Flow Distortion around the Campbell Scientific CSAT3 Sonic Anemometer Relative to Incident Wind Direction

Abstract In June 2002, a high-frequency air–sea momentum system was deployed in the surf zone for 3 days as part of an experiment to quantify air–sea momentum transfer when the wind and wave direction were at angles. The system obtained measurements in the nearshore via a high-resolution Campbell Scientific CSAT3 3D sonic anemometer and five high-frequency saltwater wave staffs. An advantage of the air–sea momentum system is that direct measurements of the atmospheric turbulent fluctuations can be obtained and applied to the calculation of momentum transfer at the air–sea interface. The Campbell Scientific CSAT3 sonic anemometer was postcalibrated under turbulent wind conditions to determine incident wind direction measurements influenced by the geometry of the instrument. Measurement results are compared to a pre-established benchmark, constant tow speed; and the mean wind speed, incident wind direction, and spectral density characteristics are evaluated to resolve specific instrument orientations in which the measurements are corrupted by the head and probe supports of the sonic anemometer. Calibration testing of the sonic anemometer determined that the mean wind speeds are reduced by 16% over a 40° range for incident wind angles of 160°–200° relative to the head of the anemometer. Tilting the anemometer is found to decrease mean wind speed reduction influenced by the geometry of the anemometer. Variations in the measured wind directions were found to be greater than 1° for incident wind angles between 160° and 200° for 0° and 10° of tilt. Spectral characteristics were highly repeatable for all wind angles except for incident wind angles of 180° for 0° and 10° of tilt.

Comparison of geometric uncertainties using electronic portal imaging device in focal three-dimensional conformal radiation therapy using different head supports

To study the geometric uncertainties in the treatment and evaluate the adequacy of the margins employed for planning target volume (PTV) generation in the treatment of focal conformal radiotherapy (CRT) for patients with brain tumors treated with different head support systems. The study population included 11 patients with brain tumors who were to be treated with CRT. Contrast-enhanced planning CT scan (5-mm spacing and reconstructed to 2 mm) of brain were performed. Five patients were immobilized using neck support only (NR-only) and six patients had neck support with flexion (NRF), the form of immobilization being decided by the likely beam arrangements to be employed for that particular patient. The data was transferred to the planning system (CadPlan) where three-dimensional conformal radiation therapy was planned. Digitally reconstructed radiographs (DRRs) were created for the orthogonal portals with the fixed field sizes of 10 x 10 taken at the isocenter. Treatment verification was done using an amorphous silicon detector portal imaging device for using orthogonal portals and the DRR was used as a reference image. An image matching software was used to match the anatomical landmarks in the DRR and the portal imaging and the displacement of the portals in x, y axis and rotation were noted in the anteroposterior (AP) and lateral images. Electronic portal imaging was repeated twice weekly and an average of 8-14 images per patient was recorded. The mean deviation in all the directions was calculated for the each patient. Comparison of setup errors between the two head support systems was done. A total 224 images were studied in anterior and lateral portals. The patient group with NR-only had 100 images, while the NRF group had 124 images. The mean total error in all patients, NR-only group, and NRF group was 0.33 mm, 0.24 mm, and 0.79 mm in the mediolateral (ML) direction; 1.16 mm, 0.14 mm, and 2.22 mm in the AP direction; and 0.67 mm, 0.31 mm, and 0.96 mm in the superoinferior (SI) direction, respectively. The systematic error (S) in all patients, NR-only group, and NRF group in the ML direction was 0.31 mm, 0.28 mm, and 0.78 mm; 1.29 mm, 0.1 mm, and 2.24 mm in the AP direction; and 0.75 mm, 0.52 mm, and 0.94 mm in the SI direction, respectively. Random error (s) in all patients, NR-only group, and NRF group in the ML direction was 1.25 mm, 1.04 mm, and 1.41 mm; 1.31 mm, 1.36 mm, and 1.28 mm in the AP direction; 1.38 mm, 1.37 mm, and 1.39 mm in the SI direction, respectively. In all patients, the PTV margin with Stroom's formula in the NR-only and NRF group was 1.29 mm and 2.55 mm in the ML, 1.15 mm and 5.38 mm in the AP, and 2.0 mm and 2.85 mm in the SI directions, respectively. A PTV margin of 5 mm appears to be adequate; further reduction to 3 mm may be considered based on our results. Errors were significantly higher in the AP direction with NRF when compared to NR-only. Differential PTV margin may therefore be considered, with more margin in the AP and less in other directions, especially with the use of flexion devices.

Feasibility of radiosurgery for malignant brain tumors in infants by use of image-guided robotic radiosurgery: preliminary report.

The benefits of radiation therapy are generally denied to infants with malignant brain tumors because of the risk of devastating cognitive decline. Efforts to limit this morbidity with radiosurgical techniques have not been feasible for infants because of the dual requirements of rigid head fixation and high precision. We report the radiosurgical treatment of five infants by use of a robotically controlled system without rigid head fixation. Five infants with malignant brain tumors received radiosurgical treatment with a robotically driven linear accelerator. Immobilization was aided by general anesthesia, form-fitting head supports, face masks, and body molds. The average marginal dose was 17 +/- 2 Gy, and the average treatment volume was 18 +/- 22 ml. X-rays obtained during treatment revealed acceptable agreement with preoperative computed tomographic scans in all patients. In one patient, the lesion did not progress, but a distant recurrence occurred 15 months after radiosurgery and also was treated with radiosurgery. In another patient, tumor in the treated region did not progress, but recurrence elsewhere led to death 7 months after treatment. Tumor enlargement occurred in Patient 3 at 3 months posttreatment, leading to death 2 months later. Tumor size was smaller in the remaining two patients at 9 and 11 months after treatment. There has been no toxicity attributed to treatment. Radiosurgery with minimal toxicity can be delivered to infants by use of a robotically controlled system that does not require rigid fixation. A formal dose-escalation trial is under way to address dose and toxicity for infants more thoroughly.

Positioning For Anesthetic Induction Of Neonates With Encepalocele

This is to describe a method of building a platform for positioning and intubation of a neonate with a large posteriorly-located encepalocele. INTRODUCTION Encephalocele, midline defect of cranial bone fusion, occurs most frequently in the occipital region. In those presenting with an intact encephalocele sac every measure should be applied to prevent rupture, and so preventing infection [1]. When the anesthesiologist is faced with a large posterior located encephalocele, endotracheal intubation becomes a challenge [2]. This is mostly related to difficulty in positioning the neonate on the back without pressing on the delicate encephalocele sac. CASE Our patient presented with a large encephalocele for anesthesia and surgical repair. Figure 1 Figure 1: Encephalocele A method for positioning this neonate for intubation is described. In this method (figure 2) the available cushions, headrests, donut head support or blankets may be used. In our case a blanket and bed cover were put down on top of each other under the neonate body until the height matched that of the encephalocele sac. The neonate was put in the supine position with the body on the platform while an assistant temporarily supported the head. The encephalocele is then circled by a “C” shaped gel foam donut. Under the donut a hollow head cushion, or if not available rolled soft towels, is inserted to build the same height as the platform. By doing so the encephalocele sac should be hanging freely in between the edges of the gel foam and towels, and just touching the table mattress, thus preventing pressure on it and possible rupture. Figure 2 Figure 2: Positioning for intubation The platform method is a great help to anesthesiologists and neurosurgeons especially when dealing with a large posterior located encephalocele. The same method may be applied for patients with meningocele [3]. This method may be well known to the practicing senior anesthesiologists and Positioning For Anesthetic Induction Of Neonates With Encepalocele 2 of 3 neurosurgeons. This communication is mainly directed to the resident in training in both branches to reinforce the need of such methods to protect encephalocele sac. Medical equipment companies may also construct a ready-made platforms and head supports for use by neurosurgical centers.

Positioning For Anesthetic Induction Of Neonates With Encepalocele

This is to describe a method of building a platform for positioning and intubation of a neonate with a large posteriorly-located encepalocele. INTRODUCTION Encephalocele, midline defect of cranial bone fusion, occurs most frequently in the occipital region. In those presenting with an intact encephalocele sac every measure should be applied to prevent rupture, and so preventing infection [1]. When the anesthesiologist is faced with a large posterior located encephalocele, endotracheal intubation becomes a challenge [2]. This is mostly related to difficulty in positioning the neonate on the back without pressing on the delicate encephalocele sac. CASE Our patient presented with a large encephalocele for anesthesia and surgical repair. Figure 1 Figure 1: Encephalocele A method for positioning this neonate for intubation is described. In this method (figure 2) the available cushions, headrests, donut head support or blankets may be used. In our case a blanket and bed cover were put down on top of each other under the neonate body until the height matched that of the encephalocele sac. The neonate was put in the supine position with the body on the platform while an assistant temporarily supported the head. The encephalocele is then circled by a “C” shaped gel foam donut. Under the donut a hollow head cushion, or if not available rolled soft towels, is inserted to build the same height as the platform. By doing so the encephalocele sac should be hanging freely in between the edges of the gel foam and towels, and just touching the table mattress, thus preventing pressure on it and possible rupture. Figure 2 Figure 2: Positioning for intubation The platform method is a great help to anesthesiologists and neurosurgeons especially when dealing with a large posterior located encephalocele. The same method may be applied for patients with meningocele [3]. This method may be well known to the practicing senior anesthesiologists and Positioning For Anesthetic Induction Of Neonates With Encepalocele 2 of 3 neurosurgeons. This communication is mainly directed to the resident in training in both branches to reinforce the need of such methods to protect encephalocele sac. Medical equipment companies may also construct a ready-made platforms and head supports for use by neurosurgical centers.

Ancillary equipment to increase quality and reduce radiation exposure in the equine nuclear medicine laboratory.

The construction of ancillary equipment used to improve image quality and reduce personnel radiation exposure in the equine nuclear medicine laboratory is illustrated. The devices include a self supporting lead sheet for shielding the distal limb or limb pair, a hanging lead sheet for shielding the proximal limb, a lead square for shielding the urinary bladder or jugular catheter, a restraining board for acquiring a palmar view of the foot, a head support to stabilize the head for imaging and a head support for stabilizing the neck for imaging. The restraining board and head supports decrease patient motion, improve image quality, and decrease the number of repeat acquisitions so that the time to perform the complete study is shortened. The self supporting shielding device allows the handlers to increase their distance from the horse which enhances radiation safety.

Conformal radiation therapy with fixed shaped coplanar or noncoplanar radiation beam bouquets: A possible alternative to radiosurgery

Three-dimensional (3D) geometric conformation of the therapeutic dose volume to the shape of a target tissue volume is the motivation for both conformal radiotherapy and radiosurgery. Although noncoplanar arcs have a clear physical and geometric advantage over fixed fields for small spherical targets, those advantages are reduced for large or irregularly shaped targets where static fields can be individually shaped. We have developed a system that allows efficient and flexible design and reliable delivery of customized "bouquets" of fixed nonopposed coplanar or noncoplanar shaped fields, resulting in highly uniform dose distributions. This report describes our initial experience using beam bouquets to treat intracranial lesions. Patients with primary (11) or metastatic (4) intracranial lesions with a maximum diameter less than approximately 6 cm, most of whom candidates for single-fraction radiosurgery, were treated with beam bouquets of four to eight nonopposed coplanar or noncoplanar beams. Doses ranged from 16-20 Gy in four fractions for recurrent lesions (8) to 45 to 68 Gy in 25 to 34 fractions for primary lesions (7). The patients were immobilized with custom foam head supports and face masks attached to a fixed base plate. Planning computed tomography scans were acquired, from which the physician developed the custom beam bouquet using 3D treatment-planning tools. The bouquet was designed based primarily on geometric concerns. The bouquet was subsequently modified to add wedge filters chosen by vector analysis of dose gradients to achieve uniform dose over the volume of beam crossfire. At the time of treatment, the isocenter was placed using the instructions provided by the treatment-planning system and pretreatment orthogonal port films were compared to digitally reconstructed radiographs (DRR) to assure proper isocenter placement. For several situations, the 3D dose distributions resulting from alternative coplanar and noncoplanar plans were compared. Each patient was treated without incident. Daily pretreatment port films showed excellent reproducibility of isocenter placement in 87% of setups. With short follow-up (0-12 months), two patients with recurrent glioblastoma experienced clinical deterioration 2 to 4 weeks following treatment. One had increased edema on scans and responded to steroids. Six patients clinically improved following radiation therapy. Review of alternative treatment plans reveals that the relative utility of coplanar vs. noncoplanar beams is likely dependent on the location of the lesion. Noncoplanar beam bouquets are likely preferable to coplanar beams when the target is located in the central regions of the head. Coplanar beams are likely adequate, and possibly preferable, for peripherally located targets. The biological advantages of fractionation and the physical advantages of radiosurgery are exploited with this approach. The use of multiple nonopposed coplanar or noncoplanar conformal wedged fields provides a uniform dose to the target and acceptable dose gradient at the target edge. This technique may prove to be an alternative to arc-based radiosurgery in some settings and has the potential advantages that fractionation should improve the therapeutic ratio, and each beam can be individually shaped to conform to irregularly shaped targets. Additional studies are underway to improve this system and better define its utility.

A customized head and neck support system

Purpose : To describe a customized head and neck immobilization system for patients receiving radiotherapy including a head support that conforms to the posterior contour of the head and neck. Methods: The system includes a customized headrest to support the posterior head and neck. This is fixed to a thermoplastic face mask that molds to the anterior head/face contours. The shape of these customized head and neck supports were compared to ‘standard” supports. Results : This system is comfortable for the patients and appears to be effective in reproducing the setup of the treatment. Conclusions : The variability in the size and shape of the customized posterior supports exceeded that of ‘standard” headrests. It is our clinical impression that the customized supports improve reproducibility and are now a standard part of our immobilization system. The quantitative analysis of the customized headrests and some commonly used ‘standard” headrests suggests that the customized supports are better able to address variabilities in patient shape.

顎関節の経頭蓋撮影法に関する基礎的研究 Ｘ線入射角度に関する検討

There are many studies in the literature of temporomandibular joint (TMJ) roentgenography which reported various methods. Schuller's method is one of the routine techniques in TMJ roentgenography, but it was designed for otological diseases rather than for TMJ. The purpose of my study is the determination of a suitable angle of X-ray incidence in lateral oblique transcranial projection (LOTP) that indicates the normal rest position in between the codyle and articular fossa. Thirty five dry skulls were examined in various angles of X-ray incidence in LOTP and the film images were analysed by computer and visual evaluation. The results showed that an angulation of 15 degrees with LOTP of TMJ was more suitable than the 25 degree angle which is ordinarily used. This method produced the obvious images of the shapes of articular condyle and condylar fossa, and also the reproducibility of TMJ position was improved when head supports were used. The coincidence was recognized in images of both tomography and LOTP for the relationship of condyle and fossa, but the method was unable to exhibit obviously the internal surface of condylar head, which should be given particular attention. I believe that this method is useful as the bases of TMJ roentgenography on the screening of the clinical diagnosis of TMJ disorders, since the disease of TMJ disorders is usually recognized on the external surface of the temporomandibular joint.