Performance of a linear accelerator couch positioning quality control task using an electronic portal imaging device.

Short and semi-automated quality assurance (QA) programs are becoming one of the most popular and highly demanding tasks in radiotherapy. The current research investigates the accuracy of a four degrees of freedom (4DoF) medical linear accelerator couch positioning with a fast and accurate method based on images acquired using an electronic portal imaging device (EPID). An accurate EPID QA phantom and a proper in-house code were used. A Siemens medical linear accelerator equipped with an a-Si EPID was used to acquire portal images. For verifying the mechanical performance of the EPID positioning, EPID sensitivity, and accuracy of the code response from the image processing point of view were investigated. To characterize the results, three deviations in the phantom positioning were deliberately created. The translational and rotational displacements of the treatment couch were then evaluated. The loading effect on the treatment couch was then investigated. The results of prerequisite tests, including the mechanical performance of the EPID, and the sensitivity and accuracy of the recognition codes, were assessed. The results were found to be within the tolerance range reported at AAPM TG-142. The mean deviations of the tests between expected and measured displacements by 4DoF treatment couch were found to be 0.13° ± 0.11°, 0.12 ± 0.17 mm, 0.17 ± 0.13 mm, and 0.04 ± 0.09 mm for rotational, longitudinal, lateral, and vertical shifts, respectively. The results showed that the proposed method is a reliable and fast approach to find the uncertainties occurring intreatment couch positioning.

Benchmarking of Siemens Linac in Electron Modes: 8-14 MeV Electron Beams.

BACKGROUND: Radiation therapy using electron beams is a promising method due to its physical dose distribution. Monte Carlo (MC) code is the best and most accurate technique for forespeaking the distribution of dose in radiation treatment of patients. MATERIAL AND METHODS: We report an MC simulation of a linac head and depth dose on central axis, along with profile calculations. The purpose of the present research is to carefully analyze the application of MC methods for the calculation of dosimetric parameters for electron beams with energies of 8-14 MeV at a Siemens Primus linac. The principal components of the linac head were simulated using MCNPX code for different applicators. RESULTS: The consequences of measurements and simulations revealed a good agreement. Gamma index values were below 1 for most points, for all energy values and all applicators in percent depth dose and dose profile computations. A number of states exhibited rather large gamma indices; these points were located at the tail of the percent depth dose graph; these points were less used in in radiotherapy. In the dose profile graph, gamma indices of most parts were below 1. The discrepancies between the simulation results and measurements in terms of Zmax, R90, R80 and R50 were insignificant. The results of Monte Carlo simulations showed a good agreement with the measurements. CONCLUSION: The software can be used for simulating electron modes of a Siemens Primus linac when direct experimental measurements are not feasible.

127I NMR calculations in binary metal iodides by PBE-GGA, YS-PBE0 and mBJ exchange correlation potentials.

We have calculated Nuclear Magnetic Resonance (NMR) spectroscopy for 127I (quadrupolar nuclei I=5/2) in binary metal iodides XI (X=Li, Na, K, Rb and Cs) by using PBE- GGA, YS- PBE0 and mBJ exchange correlation potentials. The results show that the nature of bonds between Iodine and metal atoms are ionic. The main contribution in NMR spectroscopy is related to the induced current inside the atomic sphere and the remainder of the unit cell volume contributes only a few ppm. Obtained NMR shifts are compared with the NMR shielding data and the NMR shielding for metal-p band varies across the series about 221ppm. Density of states results indicate that the largest contribution in the shielding comes from the I-core electrons (1s and 4d). The NMR shielding graphs show that there are negative linear correlation with slope -1.18, -1.16 and -1.01 by PBE- GGA, YS- PBE0 and mBJ, respectively. The computed results by mBJ are in good agreement with the experimental values.

Monte Carlo Simulation of Siemens Primus plus Linac for 6 and 18 MV Photon Beams.

OBJECTIVE: The aim of the present study is to simulate 6 MV and 18 MV photon beam energies of a Siemens Primus Plus medical linear accelerator (Linac) and to verify the simulation by comparing the results with the measured data. METHODS: The main components of the head of Siemens Primus Plus linac were simulated using MCNPX Monte Carlo (MC) code. To verify the results, experimental data of percentage depth dose (PDD) and beam dose profile for 5 × 5 cm2, 10 × 10 cm2 and 20 × 20 cm2 field sizes were measured and compared with simulation results. Moreover, gamma function was used to compare the measurement and simulation data. RESULTS: The results show a good agreement, within 1%, was observed between the data calculated by the simulations and those obtained by measurement for 6 MV photon beam, while it was within 2% for 18 MV photon beam, except in the build-up region for both beams. Gamma index values were less than unity in most data points for all the mentioned energies and fields. To calculate the dose in the phantom, cells were selected in different modes, one of the modes due to the lack of dose gradient and overlapping, produced better results than others produce. CONCLUSION: There was good settlement between measured and MC simulation values in this research. The simulation programs can be used for photon modes of Siemens Primus Plus linac in conditions in which it is not possible to perform experimental measurements.

Impact of Various Beam Parameters on Lateral Scattering in Proton and Carbon-ion Therapy.

BACKGROUND: In radiation therapy with ion beams, lateral distributions of absorbed dose in the tissue are important. Heavy ion therapy, such as carbon-ion therapy, is a novel technique of high-precision external radiotherapy which has advantages over proton therapy in terms of dose locality and biological effectiveness. METHODS: In this study, we used Monte Carlo method-based Geant4 toolkit to simulate and calculate the effects of energy, shape and type of ion beams incident upon water on multiple scattering processes. Nuclear reactions have been taken into account in our calculation. A verification of this approach by comparing experimental data and Monte Carlo methods will be presented in an upcoming paper. RESULTS: Increasing particle energies, the width of the Bragg curve becomes larger but with increasing mass of particles, the width of the Bragg curve decreases. This is one of the advantages of carbon-ion therapy to treat with proton. The transverse scattering of dose distribution is increased with energy at the end of heavy ion beam range. It can also be seen that the amount of the dose scattering for carbon-ion beam is less than that of proton beam, up to about 160mm depth in water. CONCLUSION: The distortion of Bragg peak profiles, due to lateral scattering of carbon-ion, is less than proton. Although carbon-ions are primarily scattered less than protons, the corresponding dose distributions, especially the lateral dose, are not much less.

Effectiveness Evaluation of Skin Covers against Intravascular Brachytherapy Sources Using VARSKIN3 Code.

BACKGROUND AND OBJECTIVE: The most common intravascular brachytherapy sources include (32)P, (188)Re, (106)Rh and (90)Sr/(90)Y. In this research, skin absorbed dose for different covering materials in dealing with these sources were evaluated and the best covering material for skin protection and reduction of absorbed dose by radiation staff was recognized and recommended. METHOD: Four materials including polyethylene, cotton and two different kinds of plastic were proposed as skin covers and skin absorbed dose at different depths for each kind of the materials was calculated separately using the VARSKIN3 code. RESULTS: The results suggested that for all sources, skin absorbed dose was minimized when using polyethylene. Considering this material as skin cover, maximum and minimum doses at skin surface were related to (90)Sr/(90)Y and (106)Rh, respectively. CONCLUSION: polyethylene was found the most effective cover in reducing skin dose and protecting the skin. Furthermore, proper agreement between the results of VARSKIN3 and other experimental measurements indicated that VRASKIN3 is a powerful tool for skin dose calculations when working with beta emitter sources. Therefore, it can be utilized in dealing with the issue of radiation protection.

Dorsalis pedis arterial pulse: palpation using a bony landmark.

INTRODUCTION: The unreliability of the pulse examination of the foot has primarily been due to variability of technique between examiners. Whereas the groove between the medial malleolus and the Achilles tendon more readily defines the location of the posterior tibial pulse, the location of the dorsalis pedis pulse remains vague. In this paper a novel method of locating the dorsalis pedis pulse by physical examination is described. METHODS: Forty one consecutive patients admitted to a general surgery service of a tertiary medical centre within a two month period were examined. Using the dorsal most prominence of the navicular bone as a landmark, the distance to the dorsalis pedis pulse in bilateral lower extremities was measured by palpation and compared to Doppler ultrasound. Measurements were confirmed by two separate examiners blinded to each others' results. RESULTS: The dorsalis pedis artery was palpable in 78% of extremities and present by Doppler ultrasound in 95%. The location of the left dorsalis pedis artery was a mean (SD) 9.8 (1.4) mm by palpation and 11.1 (2.1) mm by Doppler ultrasound from the dorsal most prominence of the navicular bone. The right dorsalis pedis artery was 10.4 (3.4) mm by palpation and 11.5 (0.7) mm from the dorsal most prominence of the navicular bone. No significant differences in location of the dorsalis pedis artery were observed bilaterally between Doppler ultrasound and palpation; No significant differences were observed comparing contralateral dorsalis pedis arteries nor any differences between the examiners' results. CONCLUSION: The dorsal most prominence of the navicular bone provides a bony landmark to readily locate the dorsalis pedis artery. Reliability of the examination may be increased as to the patency of the dorsalis pedis artery by using this dependable anatomic landmark.

Upper blepharoplasty with bony anatomical landmarks to avoid injury to trochlea and superior oblique muscle tendon with fat resection.

The trochlea and superior oblique muscle tendon separate the medial and central fat compartments in the upper lid. The purpose of this study was to determine anatomical landmarks to predict the location of and avoid injuring the trochlea and superior oblique muscle tendon with orbital fat resection during upper blepharoplasty. The trochlea and superior oblique muscle tendon were identified in 14 cadaver heads. Bony anatomical landmarks were identified to predict the oblique vector along which the trochlea and superior oblique tendon lie. The trochlea was measured in millimeters from the palpable superior orbital foramen. The oblique course of the superior oblique muscle tendon was measured from its medial location in the lateral direction in millimeters from the frontozygomatic suture. These measurements were obtained with 4.0-power loupe magnification. The trochlea was identified 10.0 +/- 0.9 mm inferior to the palpable superior orbital foramen. The superior oblique muscle tendon coursed laterally along an oblique vector to within 1 mm of the frontozygomatic suture for all 14 dissections. The vertical vector of the superior orbital foramen was measured 15.9 +/- 1.1 mm lateral to the medial canthus. The width of the bony orbit measured 42.2 +/- 1.6 mm. In two dissections, the superior orbital foramen could not be palpated, and the latter measurements were used to predict the superior orbital foramen. This anatomical study showed that when performing orbital fat resection with upper blepharoplasty, the trochlea and superior oblique muscle tendon can be identified and avoided with the above-described bony landmarks.

Transplantation of tracheal epithelial cells onto a prefabricated capsule pouch with fibrin glue as a delivery vehicle.

OBJECTIVE: The purpose of this study was to investigate whether in vitro cultured tracheal epithelial cells can be transplanted onto a prefabricated capsule surface in vivo for possible use in tracheal reconstruction. METHODS: Tracheal epithelial cells from 12 donor inbred rats were harvested for culture and expansion. In 16 recipient inbred rats, 2 sterile cylinders made of silicone rubber were implanted in each rat bilaterally in the folds of both the left and right anterior rectus sheath by wrapping the sheaths around the cylinders to induce a capsule formation. Ten days later, the cell cultures were divided and suspended in 1 of 2 delivery vehicles (standard culture medium or fibrin glue) and implanted onto the capsule surface. To compare the 2 delivery vehicles, we used fibrin glue on one side and the standard culture medium on the other. RESULTS: After 2 (group 1, n = 8) and 4 (group 2, n = 8) weeks, histologic findings, immunohistochemical staining, and electron microscopy demonstrated the capsule to be covered with a tracheal neoepithelium in group 1 and additional ciliated cells and secretory cells in a confluent layer in group 2 but only on the side with fibrin glue as the delivery vehicle. No viable epithelial cells were identified on the side with the standard culture medium in either group. CONCLUSION: We conclude that cultured epithelial cells can be successfully transplanted onto a prefabricated capsule surface with fibrin glue, which will differentiate into morphologic, nearly normal epithelium, showing potential for tracheal reconstruction.

Effects of liposome-mediated gene transfer of VEGF in ischemic rat gracilis muscle.

The purpose of the current study was to determine the effects of vascular endothelial growth factor (VEGF) on muscle flap survival and vascularity in a rat gracilis ischemia-reperfusion model. A total of 12 adult male Wistar rats were divided into two groups (n = 6). The experimental group received the plasmid encoding VEGF(165) cDNA plus lipofectamine (cationic liposome) injected directly to the gracilis muscle following 4 h of ischemia. The control group received lipofectamine only. The viability and vascularity of the flaps were evaluated after 7 days of reperfusion. The data demonstrated that the VEGF plasmid- and lipofectamine-treated muscle flaps had significantly greater total survival and capillary count 7 days after reperfusion compared with the flaps treated only with lipofectamine. These results indicate that VEGF exerts a protective effect on ischemic skeletal muscle flaps.

Histomorphologic and volumetric analysis of implanted autologous preadipocyte cultures suspended in fibrin glue: a potential new source for tissue augmentation.

Previous efforts to use adipocyte transplants for tissue augmentation have been limited by high and unpredictable resorption rates. Preadipocytes are precursor cells that are capable of replication and differentiation into mature adipocytes. Furthermore, they are more resilient to ischemia, making them a desirable transplant media. Utilizing fibrin glue as a transport vehicle and a prefabricated intramuscular capsule pouch as the recipient site, we have demonstrated the successful transplantation of cultured preadipocytes without the previously presented resorption sequelae. Histological analysis at 2 weeks has demonstrated establishment of vascular supply and the complete resorption of fibrin glue. Most importantly, using planimetric analysis, volume retention has been demonstrated in implanted areas up to 1 year following implantation. Finally, BrdU labeling has been utilized to demonstrate the lack of increased and uncontrolled replication rate, an index of potentially tumorigenic tissue. In conclusion, we have demonstrated a potentially new and safe source of tissue augmentation in the rat model.

Limited use of cyclosporin A in skeletal muscle ischemia--reperfusion injury.

Reperfusion injury is propagated by an inflammatory-mediated tissue edema and damage after reestablishment of vascular flow following an initial ischemic insult. In the field of transplantation, cyclosporin A(CsA) provides protection against chronic graft rejection through lymphocyte immunosuppression. Evidence for an independent protective effect of CsA against ischemia-reperfusion (IR) injury during organ transfer has prompted studies showing the benefit of CsA in various ischemia-exposed visceral organs. The authors hypothesized that CsA administration may similarly benefit IR injury after skeletal muscle amputations. To determine the effects of CsA on IR injury the authors induced 4 hours of ischemia on the gracilis muscle in a rat model. CsA (15 mg per kilogram orally) was administered in two experimental groups: (1) preischemic (N = 6): 48, 24, and 3 hours before ischemia; and (2) postischemic (N = 6): 30 minutes after induction of ischemia. The effects of CsA on IR muscle injury were observed in each of the experimental groups as well as a control group (N = 6) exposed to similar ischemia and administered a saline vehicle. Muscle viability (nitro blue tetrazolium staining) and muscle edema (wet-to-dry weight ratio) were assessed 24 hours after reperfusion. The preischemic CsA-treated gracilis muscle group demonstrated improved muscle viability (39.1 +/- 4.8%) when compared with the ischemic control muscle group (23.8 +/- 7.1%; p = 0.039). Furthermore, the preischemic CsA-treated muscle group demonstrated decreased edema (1.137 +/- 0.095 times the contralateral nonischemic muscle) when compared with the control ischemic muscle group (1.248 +/- 0.045 times the contralateral nonischemic muscle; p = 0.011). Although a trend toward improved muscle viability (32.1 +/- 4.2%) and decreased edema formation (1.200 +/- 0.062 times the contralateral nonischemic muscle) was observed in the peri-ischemic CsA-treated group when compared with the control ischemic muscle group, these differences were not significant. These observations confirm the beneficial effects of preischemic CsA therapy observed in organ transplantation research and suggest limited clinical use of peri-ischemic CsA therapy for patients with musculoskeletal amputations.

Inhibition of the initial wave of NF-kappaB activity in rat muscle reduces ischemia/reperfusion injury.

Nuclear factor kappaB (NF-kappaB) is thought to play an important role in the expression of genes expressed in response to ischemia/reperfusion (I/R) injury. In this report, the activation of NF-kappaB in rat skeletal muscle during reperfusion following a 4-h ischemic period was studied. NF-kappaB activation displayed a biphasic pattern, showing peak activities from 30 min to 3 h postperfusion and 6 h to 16 h postperfusion, with a decline to baseline binding activity levels between 3 h and 6 h. Inhibition of NF-kappaB activation was investigated using proline dithiocarbamate (Pro-DTC). NF-kappaB binding activity during reperfusion was significantly reduced by intravenous administration of Pro-DTC. Additionally, Pro-DTC resulted in decreased muscle edema and neutrophil activity, with an increased percentage of muscle survival compared with vehicle controls. These results demonstrate that NF-kappaB is activated during reperfusion in a biphasic manner and that the regulation of the initial phase of NF-kappaB activation affords physiological protection against a severe ischemic stress. Selective inhibition of NF-kappaB during early reperfusion may therefore be a therapeutic intervention for I/R injury.

The effects of hyperglycemia on skin graft survival in the burn patient.

The authors elected to determine the relative effects of hyperglycemia and/or elevated wound Gram-positive bacterial counts on success of skin graft survival in 74 burn patients. Results of serum glucose and quantitative wound biopsies on the day of admission and on postoperative day 4 were charted. Cases were separated into the following groups for analysis: normoglycemia plus normal bacterial counts, elevated bacterial counts only, hyperglycemia only, and hyperglycemia plus elevated bacterial counts. Successful graft "take" was defined as survival of 80% to 100% of the grafted area as assessed on postoperative day 4. Significant results included decreased incidence of graft take for groups with hyperglycemia only (62.5%), elevated bacterial counts only (63.3%), as well as hyperglycemia plus elevated bacterial counts (54.5%) when compared with the group with normoglycemia plus normal bacterial counts (92.8%; p = 0.020, p = 0.042, p = 0.012 respectively) for physiological parameters measured on postoperative day 4 only. Additionally, incidence of graft take was reassessed and found to be decreased significantly in groups with hyperglycemia (60.0%) vs. groups with normoglycemia (84.6%), regardless of Gram-positive bacterial counts (p = 0.034).

The management of cubital tunnel syndrome: a meta-analysis of clinical studies.

Despite extensive clinical experience in treating cubital tunnel syndrome, optimal surgical management remains controversial. A meta-analysis of 30 studies with accurate preoperative and postoperative staging was undertaken. Patients were staged preoperatively into minimum, moderate, and severe groups on the basis of clinical presentation. Treatment modalities included nonoperative management, surgical decompression, medial epicondylectomy, anterior subcutaneous transposition, and anterior submuscular transposition. Statistical analysis using a standard SAS database with analysis of variance and chi-square tests was used to assess the efficacy of each therapeutic modality. For minimum-staged patients, all modalities produced similar degrees of satisfaction. However, total relief occurred most after medial epicondylectomy and least after anterior subcutaneous transposition. Patients treated nonoperatively had the highest rate of recurrence. For moderate-staged patients, submuscular transposition was most efficacious, whereas patients with nonoperative management fared the worst. Finally, for severe-staged patients, current therapeutic modalities were not consistently effective, with medial epicondylectomy producing the poorest operative result. This article reveals statistically significant differences in outcomes among therapeutic modalities, which may assist in treatment planning; it introduces standardized methods to aid in determining, analyzing, and communicating treatment outcomes.

The youthful forehead: placement of skin incisions in hidden furrows.

BACKGROUND: Attaining good aesthetic results remains a primary goal in removal of benign cutaneous facial lesions. OBJECTIVE: Strategic planning of the incision is perhaps the most critical step in excision of such a lesion. METHODS: A study of one case of epidermoid cyst excision from a youthful forehead was undertaken. RESULTS: Poor surgical planning of a simple cyst excision from the forehead resulted in placement of the incision inferior to a natural furrow and within the basin defect, producing a noticeable scar. Facial animation accentuates the aesthetically poor placement of the surgical incision. CONCLUSION: The detection of hidden furrows through facial animation during preoperative planning, especially in the youthful forehead, is imperative for achievement of an optimal aesthetic result. When possible, incisions should be concealed within natural furrows.

Psychiatric patients who desire aesthetic surgery: identifying the problem patient.

Plastic surgeons are often confronted with psychiatric patients seeking aesthetic surgery. It is imperative for surgeons to recognize underlying psychiatric illnesses and to acknowledge their influence over patient motives and judgment. It is the goal of this paper to present the defining characteristics of the major psychiatric disorders as illustrated in the Diagnostic and Statistical Manual of Mental Disorders, fourth edition, in a manner that will allow plastic surgeons to incorporate and utilize this information in daily practice. It is the authors' hope that this paper will assist plastic surgeons in ultimately preventing patient dissatisfaction within the population of patients with psychiatric disorders.