Patient Surface Research Articles

Technical Tips: Methods of Warming and Maintaining Limb Temperature during Nerve Conduction Studies

ABSTRACT.Many physiologic and nonphysiologic factors contribute to performing correct or incorrect nerve conduction studies. Nonphysiologic factors such as filter settings, averaging techniques, stimulus artifact, and supramaximal Stimulation are just a few of the ones encountered during the nerve conduction study examination. Physiologie factors such as muscle atrophy, tremors and spasticity, edema, and profuse sweating are physical conditions that may pose technical Problems during the study. Other general physiologic conditions such as height, aging and nerve maturation, Variation between various nerve segments, and temperature may also contribute to the obtaining an accurate and correct nerve conduction study, as well as the electromyogram (EMG) itself. Obtaining and keeping the patient's surface temperature between 31 to 34 or 33 to 34 degrees Celsius, depending on which literature you read, is essential to obtaining and presenting correct nerve conduction studies. Cold limb temperature results in discrepancies in basic nerve conduction values such as amplitude, distal latency, conduction velocity, and duration in both motor and sensory studies. Cold to cool temperature also adversely affects the EMG. Repetitive Stimulation studies for neuromuscular junction disease are greatly affected by decreasing the limb temperature. How to warm these patients and maintain a desirable temperature throughout the examination is vitally important. Methods of warming patients may vary from inexpensive to expensive in cost and simple to complex in nature.

SU-E-T-320: Low Dose Rate Pediatric Total Body Irradiation (TBI) Using TrueBeam

Purpose: To develop a Low Dose Rate Pediatric Total Body Irradiation (TBI) methodology using a linear accelerator with dose rates less than 100 MU/min (TrueBeam), specifically, using this feature to deliver an Anterior-to-Posterior beam and a Posterior-to-Anterior beam, i.e. AP-PA treatment, with a delivered dose rate < 10 cGy/min for thin pediatric patients (< 14 cm). Methods: A raised platform was constructed to sit approximately 6 cm off of the floor (approximately 2 meters from the source), the patient positioned supine with head turned for the AP beam and supine with head turned the same direction for the PA beam. A scattering plate was placed on foam pillars approximately 20 cm from the patient's surface. This also used to hold custom organ blocks and/or compensators. Output, percent depth dose, surface dose, block transmission, and off axis measurements were taken using solid water slabs, ion chambers, and film. From these measurements the optimal dose rate and number of monitor units could be selected for a given patient thickness. Results: Depth dose and off axis measurements confirmed a dose distribution within ±5% of the central axis dose at all positions for an open field. Dose measurements taken at 3 mm depth with varied scattering plate distance indicated that a 20 cm distance would allow quick access to the patient as they would be under anesthesia and not compromise surface dose coverage. Conclusions: This work has shown that for certain patients, particularly pediatric patients, linear accelerators that allow the user more low dose rate options can be used to deliver low dose rate TBI (< 10 cGy/min) without the need to construct heavy beam attenuators placed above the patient. This allows greater flexibility and increased patient safety.

Projection-based visual guidance for robot-aided RF needle insertion

The use of projector-based augmented reality (AR) in surgery may enable surgeons to directly view anatomical models and surgical data from the patient's surface (skin). It has the advantages of a consistent viewing focus on the patient, an extended field of view and augmented interaction. This paper presents an AR guidance mechanism with a projector-camera system to provide the surgeon with direct visual feedback for supervision of robotic needle insertion in radiofrequency (RF) ablation treatment. The registration of target organ models to specific positions on the patient body is performed using a surface-matching algorithm and point-based registration. An algorithm based on the extended Kalman filter and spatial transformation is used to intraoperatively compute the virtual needle's depth in the patient's body for AR display. Experiments of this AR system on a mannequin were conducted to evaluate AR visualization and accuracy of virtual RF needle insertion. The average accuracy of 1.86mm for virtual needle insertion met the clinical requirement of 2mm or better. The feasibility of augmented interaction with a surgical robot using the proposed open AR interface with active visual feedback was demonstrated. The experimental results demonstrate that this guidance system is effective in assisting a surgeon to perform a robot-assisted radiofrequency ablation procedure. The novelty of the work lies in establishing a navigational procedure for percutaneous surgical augmented intervention integrating a projection-based AR guidance and robotic implementation for surgical needle insertion.

TOPOS: A new topometric patient positioning and tracking system for radiation therapy based on structured white light

A patient positioning system for radiation therapy based on structured white light and using off-the-shelf hardware components for flexibility and cost-effectiveness has been developed in house. Increased accuracy, patient comfort, abandonment of any skin marks, accelerated workflow, objective reading/recording, better usability and robust sensor design, compared to other positioning approaches, were the main goals of this work. Another aim was the application of a 6 degrees of freedom tracking system working without dose deposition. Two optical sensors are the main parts of the TOPOS® system (Topometrical Positioning, cyberTECHNOLOGIES, Germany). The components: cameras, projectors, and computers are commercial off-the-shelf products, allowing for low production costs. The black/white cameras of the prototype are capable of taking up to 240 frames per second (resolution: 640 × 488 pixels). The projector has a resolution of 1024 × 768 and a refresh rate of 120 Hz. The patient's body surface is measured continuously and registered to a reference surface, providing a transformation to superimpose the patient's surface to the reference (planning CT) surface as best as possible. The execution of the calculated transformation provides the correct patient position before the treatment starts. Due to the high-speed acquisition of the surfaces, a surveillance of the patient's (respiration) motion during treatment is also accomplished. The accuracy of the system was determined using a male mannequin. Two treatment sites were evaluated: one simulating a head and neck treatment and the other simulating a thoracic wall treatment. The mannequin was moved to predefined positions, and shift vectors given by the surface registration were evaluated. Additionally manual positioning using a color-coding system was evaluated. Two prototypes have been developed, each allowing a continuous high density scan of a 500 × 500 × 400 mm(3) (L × W × D) large volume with a refresh rate of 10 Hz (extendible to 20 Hz for a single sensor system). Surface and position correction display, as well as respiratory motion, is shown in real-time (delay < 200 ms) using present graphical hardware acceleration. For an intuitive view of the patient's misalignment, a fast surface registration algorithm has been developed and tested and a real-time color-coding technique is proposed and verified that allows the user to easily verify the position of the patient. Using first the surface registration and then the color coding the best results were obtained: for the head and neck case, the mean difference between the actual zero position and the final match was 0.1 ± 0.4, -0.2 ± 0.7, and -0.1 ± 0.3 mm in vertical, longitudinal, and lateral direction. For the thoracic case, the mean differences were 0.3 ± 0.5, -0.6 ± 1.9, 0.0 ± 0.4 mm. The presented system copes with the increasing demand for more accurate patient positioning due to more precise irradiation technologies and minimizes the preparation times for correct patient alignment, therefore optimizing the treatment workflow. Moreover, TOPOS is a versatile and cost effective image guided radiation therapy device. It allows an objective rating of the patient's position before and during the irradiation and could also be used for respiratory gating or tracking.

On the significance of density‐induced speed of sound variations on US‐guided radiotherapy

To show the effect of speed of sound (SOS) aberration on ultrasound guided radiotherapy (US-gRT) as a function of implemented workflow. US systems assume that SOS is constant in human soft tissues (at a value of 1540 m∕s), while its actual nonuniform distribution produces small but systematic errors of up to a few millimeters in the positions of scanned structures. When a coregistered computerized tomography (CT) scan is available, the US image can be corrected for SOS aberration. Typically, image guided radiotherapy workflows implementing US systems only provide a CT scan at the simulation (SIM) stage. If changes occur in geometry or density distribution between SIM and treatment (TX) stage, SOS aberration can change accordingly, with a final impact on the measured position of structures which is dependent on the workflow adopted. Four basic scenarios were considered of possible changes between SIM and TX: (1) No changes, (2) only patient position changes (rigid rotation-translation), (3) only US transducer position changes (constrained on patient's surface), and (4) patient tissues thickness changes. Different SOS aberrations may arise from the different scenarios, according to the specific US-gRT workflow used: intermodality (INTER) where TX US scans are compared to SIM CT scans; intramodality (INTRA) where TX US scans are compared to SIM US scans; and INTERc and INTRAc where all US images are corrected for SOS aberration (using density information provided by SIM CT). For an experimental proof of principle, the effect of tissues thickness change was simulated in the different workflows: a dual layered phantom was filled with layers of sunflower oil (SOS 1478 m∕s), water (SOS 1482 m∕s), and 20% saline solution (SOS 1700 m∕s). The phantom was US scanned, the layer thicknesses were increased and the US scans were repeated. The errors resulting from the different workflows were compared. Theoretical considerations show that workflows implementing SOS correction based on SIM-CT scan (INTERc, INTRAc) give null errors in all scenarios except when tissues thickness changes, where an error proportional to the degree of change in SOS maps between SIM and TX (ΔSOS) occurs. An uncorrected workflow such as INTER produces in all scenarios a pure SOS error, while uncorrected INTRA produces a null error for rotation-translation of the patient, a ΔSOS error for changing tissues thickness and an error proportional to the degree of SOS distribution change along the different lines of view when shifting the transducer. The dual layered phantom demonstrated experimentally that the effect of SOS change between SIM and TX is clinically nonrelevant, being less than the intrinsic resolution of imaging systems, even when a substantial change in thicknesses is applied, provided that a SIM-CT-based SOS aberration correction is applied. Noncorrected workflows produce errors up to 4 mm for INTER and to 3 mm for INTRA in the phantom test. A SOS correction is advantageous for all US-gRT workflows and clinical cases, where the effect of SOS change can be considered a second order effect.

Surface dose reduction from bone interface in kilovoltage X‐ray radiation therapy: a Monte Carlo study of photon spectra

This study evaluated the dosimetric impact of surface dose reduction due to the loss of backscatter from the bone interface in kilovoltage (kV) X‐ray radiation therapy. Monte Carlo simulation was carried out using the EGSnrc code. An inhomogeneous phantom containing a thin water layer (0.5–5 mm) on top of a bone (thickness=1 cm) was irradiated by a clinical 105 kVp photon beam produced by a Gulmay D3225 X‐ray machine. Field sizes of 2, 5, and 10 cm diameter and source‐to‐surface distance of 20 cm were used. Surface doses for different phantom configurations were calculated using the DOSXYZnrc code. Photon energy spectra at the phantom surface and bone were determined according to the phase‐space files at the particle scoring planes which included the multiple crossers. For comparison, all Monte Carlo simulations were repeated in a phantom with the bone replaced by water. Surface dose reduction was found when a bone was underneath the water layer. When the water thickness was equal to 1 mm for the circular field of 5 cm diameter, a surface dose reduction of 6.3% was found. The dose reduction decreased to 4.7% and 3.4% when the water thickness increased to 3 and 5 mm, respectively. This shows that the impact of the surface dose uncertainty decreased while the water thickness over the bone increased. This result was supported by the decrease in relative intensity of the lower energy photons in the energy spectrum when the water layer was with and over the bone, compared to without the bone. We concluded that surface dose reduction of 7.8%–1.1% was found when the water thickness increased from 0.5–5 mm for circular fields with diameters ranging from 2–10 cm. This decrease of surface dose results in an overestimation of prescribed dose at the patient's surface, and might be a concern when using kV photon beam to treat skin tumors in sites such as forehead, chest wall, and kneecap.PACS number: 87.55.K‐; 87.55.ne; 87.57.uq

Effect of the bone heterogeneity on the dose prescription in orthovoltage radiotherapy: A Monte Carlo study

BackgroundIn orthovoltage radiotherapy, since the dose prescription at the patient's surface is based on the absolute dose calibration using water phantom, deviation of delivered dose is found as the heterogeneity such as bone present under the patient's surface. AimThis study investigated the dosimetric impact due to the bone heterogeneity on the surface dose in orthovoltage radiotherapy. Materials and methodsA 220kVp photon beam with field size of 5cm diameter, produced by a Gulmay D3225 orthovoltage X-ray machine was modeled by the BEAMnrc. Phantom containing water (thickness=1–5mm) on top of a bone (thickness=1cm) was irradiated by the 220kVp photon beam. Percentage depth dose (PDD), surface dose and photon energy spectrum were determined using Monte Carlo simulations (the BEAMnrc code). ResultsPDD results showed that the maximum bone dose was about 210% higher than the surface dose in the phantoms with different thicknesses of water. Surface dose was found to be increased in the range of 2.5–3.7%, when the distance between the phantom surface and bone was increased in the range of 1–5mm. The increase of surface dose was found not to follow the increase of water thickness, and the maximum increase of surface dose was found at the thickness of water equal to 3mm. ConclusionsFor the accepted total orthovoltage radiation treatment uncertainty of 5%, a neglected consideration of the bone heterogeneity during the dose prescription in the sites of forehead, chest wall and kneecap with soft tissue thickness=1–5mm would cause more than two times of the bone dose, and contribute an uncertainty of about 2.5–3.7% to the total uncertainty in the dose delivery.

SU-GG-T-610: Skin Dose during Radiotherapy: A Summary and General Estimation Technique

Purpose: The skindose associated with radiotherapy is often of interest for clinical evaluation or examining the risk of late effects. Because the skindose is difficult to measure, it is of interest to have a general dosimetry system for estimating the skindose based on treatment parameters. Our objectives were to review the literature, conduct measurements to supplement the literature, and develop a general dosimetry system suitable for estimating the skindose for clinical situations or epidemiologic evaluation. Methods: The literature was supplemented with measurements and Monte Carlo simulations. In particular, the impact of a block tray on skindoses from a cobaltbeam was evaluated with TLD measurements. The skindose outside of the treatment field for MV beams as a function of field size and distance from the edge of the treatment field was examined with Monte Carlo. Using the entirety of available data, a general dosimetry system was developed in the form of a series of equations to evaluate the skindose based on treatment parameters including the Dmaxdose,treatment modality, and field size.Results: While there was little difference in skindose between MV beam energies, cobalt,electron beams, and orthovoltage produced substantially different skindoses. Within the treatment field, it was found that the skindose increased with field size, the presence of a block tray, and the obliquity of the incident beam to the patient's surface. Outside the treatment field, the skindose was highly elevated relative to the dose at depth, increasing with increasing field size and distance from the field edge to as much as a factor of 7. Conclusions: On the basis of the literature and the findings of this study we developed a set of general rules and equations that estimate the skindose for patients receiving radiotherapy.

MO‐E‐204B‐04: Interventional Fluoroscopy Procedure Skin Dose Assessment Using DICOM Dose Structured Reports

Purpose: Patient skin injury due to radiation exposure during interventional fluoroscopy procedures is a concern. The FDA has recommended dose be monitored, along with the dose distribution on the patient's skin. Modern fluoroscopy equipment provides a readout of the accumulated reference point air kerma. However, this parameter is a poor estimate of localized skin dose since it does not take into account beam movement. Acquisition information needed to calculate skin dose can be recorded as a DICOM Dose Structured Report (Dose SR), which has recently become available on new fluoroscopy equipment. We have developed a system that uses the Dose SR to produce a skin dose map, along with determination of the peak skin dose. Method and Materials: The Dose SR provides data for each irradiation event (fluoroscopy footswitch or acquisition): kerma‐area‐product, reference point air kerma, C‐arm angulation and table position. Using the position of the patient on the table, backscatter and table attenuation, the air kerma to 1‐cm2 regions on the patient's surface is calculated. The patient surface is approximated as a mathematical model using SolidWorks simulation software, with model size varied based on patient parameters. Results: The method was validated using a Siemens Axiom Artis angiography system. Measurements made with an ionization chamber and lucite phantom were compared to calculated skin dose values for a range of C‐arm angles, table positions and exposure levels. Errors ranged from 2–10% with higher errors corresponding to increased C‐arm angulation. Conclusion: A system has been developed to estimate skin dose and generate skin dose maps from an interventional procedure Dose SR. The system allows for a more precise determination of localized skin dose and assists with planning appropriate entry ports for future procedures to minimize skin injury. Application to any vendor platform providing a Dose SR is possible.

TH‐C‐BRB‐04: In Vivo Measurements for Proton Therapy Using a Glass Dosimeter

Purpose: The purpose of this study was to measure the dose distributions near the superficial using a glass dosimeter for proton therapy plans with a varying separation between the target volume and the surface of 3 patients. Method and Materials: All measurements were performed in clinical proton beam at National Cancer Center in Korea. The proton therapy test cases were planned using the Varian Eclipse proton treatment planning system. In vivo surface dosimetry for proton therapy was performed for 3 patients. For all patients the surface doses were measured for delivers using dosimeters (glass dosimeter TLD) placed on the patient's surface. A model GD‐301 glass dosimeter and FGD‐1000 automatic reader were used. In the one case of our patient that GTV was defined from the superficial the surface dose was 189 cGy and the case that GTV was defined by the expansion from the surface by 5 mm it was 138 cGy. Results: The results of glass dosimeter were substantially higher than the TLD result. The doses measured by the glass dosimeter indicated that the proton therapy Eclipse treatment planning system overestimates superficial doses by 7.4±1.9%. The TLD dose test case was 168±2.44 cGy as compared to the calculated dose of 190±4.54 cGy. The calculated and measured doses for the clinical cases where the target volume extends to the surface of the patient indicate that the target will be underdosed without the use of bolus. Conclusion: Given the results of the glass dosimeter and TLD‐100 measurements the calculated doses on the surface of the patient are typically overestimated between 4% and 15%. As such it is recommended that bolus be added for these clinical cases. We also believe that the glass dosimeter has considerable potential to be used for in vivo patient proton dosimetry.

TU‐C‐BRA‐03: Skin Toxicity in Stereotactic Body Radiation Therapy — Improving the Treatment Planning and Delivery Process

Purpose: Stereotactic body radiation therapy is delivered using high doses, specialized immobilization and careful treatment planning. Although more centers now offer SBRT treatments, little data regarding toxicity and doses are available. We have previously reported increased skin toxicity with hypofractionated SBRT and correlated toxicity to tumor‐skin proximity, beam arrangement and buildup dose calculation inaccuracies. The purpose of this study was to determine the accuracy of our buildup region doses through correlation with in‐vivo measurements. Method and Materials: Surface doses were measured on 30 patients receiving single fraction 18–24 Gy SBRT. Patients were supine and immobilized with an Alpha Cradle and custom SBRT cradle. IMRT planning with approximately seven posterior, 6 or 15 MV x‐rays beams was done using an in‐house planning system (TPS) and delivered on Varian accelerators. Buildup region doses were measured with thermoluminescent (TLD) or optically stimulated luminescent (OSLD) dosimeters. An 5–10 dosimeter array was positioned on the patient's surface during treatment. Dosimeter positioning was verified by KV imaging. Calculations at corresponding points at depths 1 and 2 mm were done using both our TPS (pencil beam algorithm) and Monte Carlo and compared to measurements. For six patients the TPS calculations were also done including the immobilization equipment. Results: In vivo dosimetry showed patient surface dose could be 50% higher than that calculated by the TPS. Factors contributing to higher measured doses were: tumor proximity to surface, immobilization device thickness, beam angular segmentation, and beam energy. Calculations including the immobilization device greatly improved correlation with measurements. Conclusion: To limit skin toxicity, SBRT treatments require awareness of beam placement, energy selection and immobilization devices. At these high single fraction doses it is necessary to carefully consider immobilization devices as well as to reanalyze and improve treatment planning beam data in the buildup region.

Measuring Interfractional and Intrafractional Motion With Cone Beam Computed Tomography and an Optical Localization System for Lower Extremity Soft Tissue Sarcoma Patients Treated With Preoperative Intensity-Modulated Radiation Therapy

To evaluate inter- and intrafractional motion and rotational error for lower extremity soft tissue sarcoma patients by using cone beam computed tomography (CBCT) and an optical localization system. Thirty-one immobilized patients received CBCT image-guided intensity-modulated radiation therapy. Setup deviations of >3 mm from the planned isocenter were corrected. A second CBCT acquired before treatment delivery was registered to the planning CT to estimate interfractional setup error retrospectively. Interfractional error and rotational error were calculated in the left-right (LR), superoinferior (SI), and anteroposterior (AP) dimensions. Intrafractional motion was assessed by calculating the maximum relative displacement of optical localization system reflective markers placed on the patient's surface, combined with pre- and postfraction CBCT performed for 17 of the 31 patients once per week. The overall systematic error (SE) and random error (RE) were calculated for the interfractional and intrafractional motion for planning target volume margin calculation. The standard deviation (SD) of the interfractional RE was 1.9 mm LR, 2.1 mm SI, and 1.8 mm AP, and the SE SD was 0.6 mm, 1.2 mm, and 0.7 mm in each dimension, respectively. The overall rotation (inter- and intrafractional) had an RE SD of 0.8° LR, 1.7° SI, and 0.7° AP and an SE SD of 1.1° LR, 1.3° SI, and 0.3° AP. The SD of the overall intrafractional RE was 1.6 mm LR, 1.6 mm SI, and 1.4 mm AP, and the SE SD was 0.7 mm AP, 0.6 mm SI, and 0.6 mm AP. A uniform 5-mm planning target volume margin was quantified for lower extremity soft tissue sarcoma patients and has been implemented clinically for image-guided intensity-modulated radiation therapy.

Image-guided Stereotactic Radiotherapy for Peripheral Lung Tumors: Gating vs. Motion Encompassing Approaches

Image-guided Stereotactic Radiotherapy for Peripheral Lung Tumors: Gating vs. Motion Encompassing Approaches

A Method for Correcting IMRT Optimizer Heterogeneity Dose Calculations

Radiation therapy treatment planning for volumes close to the patient's surface, in lung tissue and in the head and neck region, can be challenging for the planning system optimizer because of the complexity of the treatment and protected volumes, as well as striking heterogeneity corrections. Because it is often the goal of the planner to produce an isodose plan with uniform dose throughout the planning target volume (PTV), there is a need for improved planning optimization procedures for PTVs located in these anatomical regions. To illustrate such an improved procedure, we present a treatment planning case of a patient with a lung lesion located in the posterior right lung. The intensity-modulated radiation therapy (IMRT) plan generated using standard optimization procedures produced substantial dose nonuniformity across the tumor caused by the effect of lung tissue surrounding the tumor. We demonstrate a novel iterative method of dose correction performed on the initial IMRT plan to produce a more uniform dose distribution within the PTV. This optimization method corrected for the dose missing on the periphery of the PTV and reduced the maximum dose on the PTV to 106% from 120% on the representative IMRT plan.

SU-GG-T-376: Feasibility of MRI Guided Proton Therapy: Magnetic Field Dose Effects

Modern radiotherapy aims to escalate the dose to the tumour while minimising the dose to the surrounding organs at risk. This requires two major steps: 1) bringing radiotherapy fully under image guidance by using anatomical images in the whole radiotherapy cycle: treatment preparation, treatment delivery, treatment response assessment and treatment follow up. 2) Optimise the spatial dose distribution using IMRT or protons.Proton therapy leads to a lower integral dose and is especially advantegeous for small tumours and tumours close to critical organs. However, it still requires imaging for the whole cycle of radiotherapy. One may even argue that image guidance is more important when the Bragg peak of proton therapy is maximally exploited to generate high dose gradients. Then the actual depth of the tumour relative to the patient's surface is crucial since small deformations in the anatomy can lead to large dose differences. MRI offers optimal soft‐tissue contrast for guidance. Clearly, integrating a proton accelerator and MRI faces technical hurdles. From preceeding research on combining a 1.5 T MRI and a conventional accelerator we know that the impact of the magnetic field on the dose distribution is one of the hurdles to take. This paper addresses the magnetic fielddoseeffects for proton irradiation in the presence of a 0.5T transverse magnetic field. Geant4 simulations show that the dose distribution at 0.5 T is not affected seriously. In homogeneous tissue, the beam is tilted slightly, due to the Lorentz force on protons. At tissue‐air interfaces, returning secondary electrons cause a major doseeffect for photon therapy. However, for protons, this effect does not exist due to the very low (<2 keV) energy of the secondary electrons. In summary, proton therapy can benefit from MRI guidance and the dosedistribution is not seriously hampered by the magnetic field.

SU‐GG‐T‐266: Implementation of Total Skin Electron Irradiation (TSEI) Using High Dose Rate Mode at Siriraj Hospital

Purpose: To implement and commissioning of applied Stanford total skin electron irradiation (TSEI) technique using standard linear accelerator at our institute. Method and Materials: Patient was treated in six different upright patient positions using dual angle fields. This study was carried out on Varian 23EX linear accelerator with 6 MeV, 36×36 cm2 field size at collimator in HDTSe mode at a SSD of 400 cm behind a beam degrader. The dosimetric characteristics were verified experimentally using a parallel plate ion chamber, electron diodes, and TLD‐100 chip and rod types. The delivered dose is 36 Gy in 9 weeks. The basic dosimetric parameter consists of beam profile, depth dose curve and electron beam output in the treatment plane. The output and depth dose curve was measured by PTW23343 Markus chamber in solid phantom. Delivered dose from six dual fields technique in treatment position was verified on round phantom by TLD‐100. Results: The uniform vertical profile was obtained for gantry angulations of ± 17.5 degree above and below horizontal within 10% of the prescribed dose. The depth dose curve shows maximum dose at skin surface. The mean energy is 2.09 MeV with beam degrader 1 cm thick. The dose uniformity from six dual fields on round phantom is within 10%. The average measured skin dose in the anterior and posterior at the level of head, chest and pelvis on rando phantom is within 10% of prescribed point. Total X‐ray contamination in the rando phantom is about 1.35% of the delivered dose. Conclusion: The TSEI technique using six dual fields applied Stanford technique produced a uniformity at the whole patient's surface cannot be better than 15% of the prescribed dose because of variable skin distance, self‐shielding, and differences in curvature.

Radiation safety issues with positron‐emission/computed tomography simulation for stereotactic body radiation therapy

Stereotactic body radiation therapy (SBRT) simulations using a Stereotactic Body Frame (SBF: Elekta, Stockholm, Sweden) were expanded to include 18F‐deoxyglucosone positron‐emission tomography (FDG PET) for treatment planning. Because of the length of time that staff members are in close proximity to the patient, concerns arose over the radiation safety issues associated with these simulations. The present study examines the radiation exposures of the staff performing SBRT simulations, and provides some guidance on limiting staff exposure during these simulations. Fifteen patients were simulated with PET/CT using the SBF. Patients were immobilized in the SBF before the FDG was administered. The patients were removed from the frame, injected with FDG, and allowed to uptake for approximately 45 minutes. After uptake, the patients were repositioned in the SBF. During the repositioning, exposure rates were recorded at the patient's surface, at the SBF surface, and at 15 cm, 30 cm, and 1 m from the SBF. Administered dose and the approximate time spent on patient repositioning were also recorded. The estimated dose to staff was compared with the dose to staff performing conventional diagnostic PET studies. The average length of time spent in close proximity (<50 cm) to the patient after injection was 11.7 minutes, or more than twice the length of time reported for diagnostic PET staff. That time yielded an estimated average dose to the staff of 26.5mSv per simulation. The annual occupational exposure limit is 50 mSv. Based on dose per simulation, staff would have to perform nearly 1900 SBRT simulations annually to exceed the occupational limit. Therefore, at the current rate of 50–100 simulations annually, the addition of PET studies to SBRT simulations is safe for our staff. However, ALARA (“as low as reasonably achievable”) principles still require some radiation safety considerations during SBRT simulations. The PET/CT‐based SBRT simulations are safe and important for treatment planning that optimizes biologic dose distribution with highly accurate and reproducible target definition.PACS numbers: 87.57.uk, 87.59.bd

Evidence and Mechanism of External Qi in Chinese Medicine

Background: There are 2 kinds of Qi: Internal Qi is what circulates inside a human body while External Qi is what an experienced practitioner could emit and could be felt by a receiver. The healer's body will emit electromagnetic waves of low oscillating frequency from 0.1–100 Hz. Objective: To document the existence of External Qi using infrared imaging to detect changes in body surface temperature. Design, Setting, and Patient: A man in his 40s had been in a car crash at the age of 18 that permanently injured his neck. He was told to sit or lie down and relax, close his eyes, and prepare to accept treatment. During the healing session, the author put his hands several inches from the patient's head, neck, or body but never touched. Infrared images were taken before and after each healing session with External Qi, which typically lasts about 10 minutes. The patient was treated with External Qi once a week from May to August 2005. Main Outcome Measure: Documented infrared images of change in body surface temperature. Results: The patient reported continuous and steady improvement in the 3-month period. Significant changes in the maximum temperature were observed at some parts of the body before and after each healing session. The largest differences were 6.7°F in the back region, 1.14°F in the lower back region, 0.97°F in the front region, 3.83°F in the upper back region, and 2.11°F in the face. Conclusions: Significant changes in the patient's surface body temperature through the effect of External Qi were demonstrated without the patient feeling any pain or discomfort.

SU-FF-T-376: SBRT Simulations Using PET/CT: Radiation Safety Concerns

Purpose:SBRT simulations using a Stereotactic Body Frame (SBF — Elekta) were expanded to include a PET study. Because of the time that staff are in close proximity to the patient, some concerns arose over the radiation safety issues associated with these simulations. This study examines the radiation exposures of the staff performing SBRT simulations and provides some guidance on limiting staff exposure during these simulations. Methods and Materials: Fifteen patients were simulated with PET/CT using the SBF. Patients were immobilized in the SBF prior to the administration of FDG (18F‐fluoro‐deoxy‐glucose). The patients were removed from the frame, injected with FDG, and allowed to uptake for 45 minutes. After uptake, the patients were repositioned in the SBF. During the repositioning, exposure rates were recorded at the patient's surface, at the SBF surface, and at 15cm, 30cm, and 1m from the SBF, along with administered dose and the approximate time spent on patient repositioning. Comparisons of the estimated dose to the staff were performed with staff performing conventional diagnostic PET studies. Results: The average time spent in close proximity to the patient after injection was 11.4 minutes, or over twice that reported for diagnostic PET staff. This time yielded an estimated average dose to the staff of 26.5 μSv per simulation. Conclusions: Occupational exposure limits are 50 mSv per year. Based on the dose per simulation, the staff would have to perform nearly 1900 SBRT simulations per year to exceed the occupational limit. Therefore, at the current rate of 50–100 simulations per year, the addition of PET studies to the SBRT simulations is safe for our staff. However, ALARA principles still require some radiation safety considerations during the SBRT simulations. PET/CT‐based SBRT simulations are safe and important for treatment planning that optimizes biologic dose‐distribution with highly accurate and reproducible target definition.

Proton therapy is the best radiation treatment modality for prostate cancer

Proton therapy is the best radiation treatment modality for prostate cancer