Accuracy Of Treatment Planning Research Articles

Assessing the Impact of AI-Enhanced Diagnostic Tools on the Treatment Planning of Orthodontic Cases: An RCT

ABSTRACT Background: Orthodontic treatment planning involves the precise assessment of dental and skeletal anomalies, which can be facilitated by AI-enhanced diagnostic tools. Materials and Methods: A total of 100 orthodontic cases were included in this RCT. Patients were randomly assigned to two groups: an AI-enhanced diagnostic group and a traditional diagnostic group. The AI-enhanced diagnostic group underwent orthodontic assessment with the aid of AI-powered software, which provided automated cephalometric analysis, 3D model evaluations, and treatment suggestions. The traditional diagnostic group received conventional diagnostic assessments by orthodontists. The primary outcome measures included treatment planning accuracy, treatment time, and patient satisfaction. Secondary outcomes included the number of appointments required and treatment cost. Results: The AI-enhanced diagnostic group demonstrated a significantly higher accuracy in treatment planning compared to the traditional diagnostic group (P < 0.05). The AI group also required fewer appointments (mean ± SD: 10.2 ± 2.1 vs. 12.8 ± 3.4) and had a shorter treatment time (mean ± SD: 14.6 ± 3.2 months vs. 18.9 ± 4.5 months) (P < 0.001 for both comparisons). Additionally, patient satisfaction scores were higher in the AI group (mean ± SD: 9.2 ± 0.6 vs. 8.1 ± 0.8) (P < 0.001). However, the AI-enhanced diagnostic group had a slightly higher treatment cost. Conclusion: AI-enhanced diagnostic tools significantly enhance the accuracy of treatment planning in orthodontic cases, leading to reduced treatment time, fewer appointments, and increased patient satisfaction.

Novel Intrafraction Motion Tracking During Postoperative Spine Stereotactic Irradiation for a Patient With Carbon Fiber Fixation Hardware

Carbon-fiber reinforced (CFR) polyetheretherketone hardware is an alternative to traditional metal hardware used for spinal fixation surgeries before postoperative radiation therapy for patients with spinal metastases. CFR hardware's radiolucency decreases metal artifact, improving visualization and accuracy of treatment planning. We present the first clinical use and proof of principle of CFR spinal hardware with tantalum markers used for successful tracking of intrafraction motion (IM) using Varian TrueBeam IMR (Intrafraction Motion Review) software module during postoperative spine stereotactic radiation. A 63-year-old woman with history of endometrial cancer presented with acute back pain. Imaging demonstrated pathologic T12 vertebral fracture with cord compression. She underwent T12 vertebrectomy with circumferential decompression and posterior instrumented T10-L2 fusion at our facility using CFR-polyetheretherketone hardware with tantalum screw markers followed by postoperative stereotactic body radiation therapy to 3000 cGy in 5 fractions delivered to T11-T12. Tantalum screw markers were used for IMR tracking. During irradiation, 260 kV images were acquired, and IMR software was able to identify and track markers. During the entire treatment, the IM motions were less than 3 mm. This is the first presented case of CFR spinal hardware with tantalum markers used for successful IMR tracking of IM during daily spine stereotactic treatment. Future work will be needed to improve workflow and create a spine-specific IMR protocol.

Automated Segmentation of Sacral Chordoma and Surrounding Muscles Using Deep Learning Ensemble

The manual segmentation of organ structures in radiation oncology treatment planning is a time-consuming and highly skilled task, particularly when treating rare tumors like sacral chordomas. This study evaluates the performance of automated deep learning (DL) models in accurately segmenting the gross tumor volume (GTV) and surrounding muscle structures of sacral chordomas. An expert radiation oncologist contoured 5 muscle structures (gluteus maximus, gluteus medius, gluteus minimus, paraspinal, piriformis) and sacral chordoma GTV on computed tomography images from 48 patients. We trained 6 DL auto-segmentation models based on 3-dimensional U-Net and residual 3-dimensional U-Net architectures. We then implemented an average and an optimally weighted average ensemble to improve prediction performance. We evaluated algorithms with the average and standard deviation of the volumetric Dice similarity coefficient, surface Dice similarity coefficient with 2- and 3-mm thresholds, and average symmetric surface distance. One independent expert radiation oncologist assessed the clinical viability of the DL contours and determined the necessary amount of editing before they could be used in clinical practice. Quantitatively, the ensembles performed the best across all structures. The optimal ensemble (volumetric Dice similarity coefficient, average symmetric surface distance) was (85.5 ± 6.4, 2.6 ± 0.8; GTV), (94.4 ± 1.5, 1.0 ± 0.4; gluteus maximus), (92.6 ± 0.9, 0.9 ± 0.1; gluteus medius), (85.0 ± 2.7, 1.1 ± 0.3; gluteus minimus), (92.1 ± 1.5, 0.8 ± 0.2; paraspinal), and (78.3 ± 5.7, 1.5 ± 0.6; piriformis). The qualitative evaluation suggested that the best model could reduce the total muscle and tumor delineation time to a 19-minute average. Our methodology produces expert-level muscle and sacral chordoma tumor segmentation using DL and ensemble modeling. It can substantially augment the streamlining and accuracy of treatment planning and represents a critical step toward automated delineation of the clinical target volume in sarcoma and other disease sites.

The Role of Cone-Beam Computed Tomography in the Imaging Guided Implantology with Surgical Stent for Dental Implants Placement _ a Case Report

Three-dimensional imaging, particularly cone-beam computed tomography (CBCT), has made significant contributions to the planning and placement of implants of missing tooth or at immediately removed tooth. The accuracy of CBCT data can be used to fabricate a surgical guide that transfers the implant planning information to the surgical site to facilitate implant placement. Prosthetically driven implant prosthesis assures good aesthetics, function and more importantly hygiene maintenance enabling long time success. Accuracy in treatment planning and implementation of planned treatment is vital for this success. Here we describe a method for applying CBCT data to aid in the planning and placement of implant using CBCT data to aid in planning and placement of Missing and immediate extracted tooth implant.

The Fundus Structural and Functional Predictions of DME Patients After Anti-VEGF Treatments.

Diabetic retinopathy (DR) is an important complication with a high incidence of 34.6% in the diabetic populations. DR could finally lead to vision impairment without effective interventions, during which, diabetic macular edema (DME) is a key phase causing visual loss. Up to date, antivascular endothelial growth factor (anti-VEGF) therapy is the first-line treatment for DME which has achieved relatively better clinical outcomes than traditional treatments. However, there are several kinds of anti-VEGF medicines, and patients are sensitive to different anti-VEGF treatments. In addition, its effectiveness is unstable. Considering the patients’ need to accept continual anti-VEGF treatments and its price is comparatively high, it is clinically important to predict the prognosis after different anti-VEGF treatments. In our research, we used the demographic and clinical data of 254 DME patients and 2,763 optical coherence tomography (OCT) images from three countries to predict the fundus structural and functional parameters and treatment plan in 6 months after different anti-VEGF treatments. Eight baseline features combined with 11 models were applied to conduct seven prediction tasks. Accuracy (ACC), the area under curve (AUC), mean absolute error (MAE), and mean square error (MSE) were respectively used to evaluate the classification and regression tasks. The ACC and AUC of structural predictions of retinal pigment epithelial detachment were close to 1.000. The MAE and MSE of visual acuity predictions were nearly 0.3 to 0.4 logMAR. The ACC of treatment plan regarding continuous injection was approaching 70%. Our research has achieved great performance in the predictions of fundus structural and functional parameters as well as treatment plan, which can help ophthalmologists improve the treatment compliance of DME patients.

The role of novel imaging in prostate cancer focal therapy: treatment and follow-up.

Multiparametric magnetic resonance imaging (mpMRI) has fundamentally changed how intraprostatic lesions are visualized, serving as a highly sensitive means for detecting clinically significant prostate cancer (csPCa) via image-targeted biopsy. However, limitations associated with mpMRI have led to the development of new imaging technologies with the goal of better characterizing intraprostatic disease burden to more accurately guide treatment planning and surveillance for prostate cancer focal therapy. Herein, we review several novel imaging modalities with an emphasis on clinical data reported within the past two years. 7T MRI, artificial intelligence applied to mpMRI, positron emission tomography combined with either computerized tomography or MRI, contrast-enhanced ultrasound, and micro-ultrasound are novel imaging modalities with the potential to further improve intraprostatic lesion localization for applications in focal therapy for prostate cancer. Many of these technologies have demonstrated equivalent or favorable diagnostic accuracy compared to contemporary mpMRI for identifying csPCa and some have even shown improved capabilities to define lesion borders, to provide volumetric estimates of lesions, and to assess the adequacy of focal ablation of planned treatment zones. Novel imaging modalities with capabilities to better characterize intraprostatic lesions have the potential to improve accuracy in treatment planning, real-time assessment of the ablation zone, and posttreatment surveillance; however, many of these technologies require further validation to determine their clinical utility.

Enhancing benefits of bolus use through minimising the effect of air-gaps on dose distribution in photon beam radiotherapy

AbstractIntroduction:Bolus material is frequently used on patient’s skin during radiation therapy to reduce or remove build-up effect for high-energy beams. However, the air-gaps formed between the bolus and the skin’s irregular surface reduce the accuracy of treatment planning. To achieve a good treatment outcome using bolus, experimental investigations are required to choose its thickness and to quantify the air-gap effect.Material and methods:Measurements for a 6 MV photon beam with a fixed source surface distance were carried out using the 31021 Semiflex 3D chamber into the water phantom. Firstly, the depth of maximum dose (R100) and the dose value at surface (Ds) were evaluated as a function of bolus thickness for some square fields. Secondly, to test the effect of the air-gaps ranged from 5 to 30 mm with a step of 5 mm between the bolus and the phantom surface, a water-equivalent RW3 (Goettingen White Water) slab form of 10 mm thickness was considered as a bolus.Results:We observed that the linear behaviour of R100 in terms of the bolus thickness makes the choice of this parameter more convenient depending on field size. In addition, increasing the air-gaps widens the penumbra and created electrons that have a greater probability to quit the radiation field borders before reaching the surface. The dose spread of the off-field area could have a significant influence on the patient treatment.Conclusion:Based on dose distribution comparisons between the measurements with and without air-gaps for the field size of 100 mm × 100 mm, it has been demonstrated that a maximum air-gap value lower than 5 mm would be desirable for an efficient use of the bolus technique.

Generic and robust method for automatic segmentation of PET images using an active contour model.

Although positron emission tomography (PET) images have shown potential to improve the accuracy of targeting in radiation therapy planning and assessment of response to treatment, the boundaries of tumors are not easily distinguishable from surrounding normal tissue owing to the low spatial resolution and inherent noisy characteristics of PET images. The objective of this study is to develop a generic and robust method for automatic delineation of tumor volumes using an active contour model and to evaluate its performance using phantom and clinical studies. MASAC, a method for automatic segmentation using an active contour model, incorporates the histogram fuzzy C-means clustering, and localized and textural information to constrain the active contour to detect boundaries in an accurate and robust manner. Moreover, the lattice Boltzmann method is used as an alternative approach for solving the level set equation to make it faster and suitable for parallel programming. Twenty simulated phantom studies and 16 clinical studies, including six cases of pharyngolaryngeal squamous cell carcinoma and ten cases of nonsmall cell lung cancer, were included to evaluate its performance. Besides, the proposed method was also compared with the contourlet-based active contour algorithm (CAC) and Schaefer's thresholding method (ST). The relative volume error (RE), Dice similarity coefficient (DSC), and classification error (CE) metrics were used to analyze the results quantitatively. For the simulated phantom studies (PSs), MASAC and CAC provide similar segmentations of the different lesions, while ST fails to achieve reliable results. For the clinical datasets (2 cases with connected high-uptake regions excluded) (CSs), CAC provides for the lowest mean RE (-8.38% ± 27.49%), while MASAC achieves the best mean DSC (0.71 ± 0.09) and mean CE (53.92% ± 12.65%), respectively. MASAC could reliably quantify different types of lesions assessed in this work with good accuracy, resulting in a mean RE of -13.35% ± 11.87% and -11.15% ± 23.66%, a mean DSC of 0.89 ± 0.05 and 0.71 ± 0.09, and a mean CE of 19.19% ± 7.89% and 53.92% ± 12.65%, for PSs and CSs, respectively. The authors' results demonstrate that the developed novel PET segmentation algorithm is applicable to various types of lesions in the authors' study and is capable of producing accurate and consistent target volume delineations, potentially resulting in reduced intraobserver and interobserver variabilities observed when using manual delineation and improved accuracy in treatment planning and outcome evaluation.

Overview of surgical guides for implant therapy

Prosthetically driven implant prosthesis assures good aesthetics, function and more importantly hygiene maintenance enabling long time success. Accuracy in treatment planning and implementation of planned treatment is vital for this success. Following advancements that have occurred in treatment planning (virtual software) for implant prosthesis; an equal rise is to be expected in transferring the planned therapy to surgical fruition. In this regard, surgical templates have enabled clinician to deliver predictable surgical & prosthetic rehabilitation. Surgical guides have not only decreased the chances of iatrogenic damage of critical anatomic structures; they also increase the esthetic and functional advantages of prosthodontic-driven implant. Within the constraints of this article, the authors describes an over view of use of surgical guides in clinical situation. If clinician is considered a pilot, then surgical guide is his navigator.

Surgiguide used for a minimally Invasive Flapless Surgery and Precise Placement of Eight Nobel Biocare (Select) Implants

Implant dentistry has always the final prosthesis in mind. The prosthetically driven implant prosthesis will assure good esthetics, function, and also hygiene. This will give long-time success. The use of medical imaging and software planning has resulted in a marked improvement in treatment planning. The virtual software helps in accuracy in treatment planning. Surgical guides can be fabricated from a computed tomography scan. A surgical guide is used to assist in proper surgical placement and angulation of the implants. A guide also increases the esthetic and functional aspect of prosthetically driven implant treatment.

TH‐A‐BRF‐10: Quantification of Subject‐Specific Susceptibility‐Related Geometric Distortion in Clinical Liver MRI for Radiation Therapy

Purpose:Subject‐specific susceptibility‐induced B0 inhomogeneity affects the geometric accuracy of MRI images, with potential impact on the accuracy of treatment planning and image guidance. This study quantifies individual distortions for patients with intrahepatic tumors.Methods:Liver MRI scans of 13 patients who were enrolled in an IRB approved study were acquired on a 3T scanner (Skyra, Siemens). Clinical contrast‐enhanced images were acquired by a 3D Volume Interpolated Breath‐Hold Examination (VIBE) sequence with TE/TR =1.65/4.3ms, voxel size = 2.5×2.5×3mm (axial sets) or 3.5×3.5×5mm (coronal sets), and frequency‐encoding (FE) bandwidth of 440Hz/pixel. B0 inhomogeneity was evaluated by acquisition of dual gradient echoes (GRE) with TE1/TE2/TR =4.92/7.38/106ms, a voxel size of 3.5×3.5×3.75mm, a FE bandwidth of 290Hz/pixel and breath‐hold. The phase difference maps from the two echoes were unwrapped using a quantitative MRI analysis software package (FSL, FMRIB, Oxford, UK). The resulting calculated B0 inhomogeneity maps (ΔB0 in Hz) were converted to voxel distortion maps in the FE direction (ΔX in mm) corresponding to the VIBE images.Results:Maximum susceptibility‐induced distortions were observed in the liver dome near the diaphragm. Using results from coronal VIBE images in this study as examples, we observed clusters of voxels displaced close to or greater than ΔX=3.5mm (440 Hz in ΔB0) in the VIBE images of the liver in 3 patients, and greater than 2 mm but less than 3.5 mm in 12 patients. On average, approximately 14% of imaged liver voxels had distortions ΔX>±1mm (ΔB0>±125Hz) and 1% of the voxels had ΔX>±2mm (ΔB0>±250Hz).Conclusion:Although advanced MRI techniques, like VIBE, permit faster acquisitions allowing for breath‐held examinations with limited motion‐induced artifacts, this study suggests that localized distortions due to subject‐specific susceptibility variations can occur and require additional advanced corrections based on measuring patient‐specific B0 inhomogeneity maps.The authors would like to acknowledge funding support from NIH R01EB016079 and NIH/NCI RO1 CA132834.

Effects of CBL mode on making treatment plan among orthodontic postgraduates

Objective To study the effects of CBL teaching mode on treatment plan making process among orthodontic postgraduates. Methods Totally 42 junior and senior orthodontic post- graduates were randomly divided into 2 groups （21 per group） named as experimental group and test group. Each group was further divided in to 3 teams involved in CBL and traditional teaching. Six cases of the same type malocclusion were selected each time; after 4 teaching cycle, test scores of two groups were analyzed with SPSS 19.0. Results were shown as mean ＋ standard deviation and t test and χ2 test were applied to evaluate the rationality and accuracy of treatment plan made by students. Survey questionnaire were issued to teachers and students after class and the assessment results of CBL teaching mode were summed up. Results Test scores were （88.61± 8.34） in experimental group and （76.13 ± 8.59） in control group with significant differences （t=3.16,P=0.01）. Pass rate of two groups were96.12% and 87.51% with significant differences （χ2=4.76,P=0.02）. During the first teaching program, accurate rates of experimental group and control group were respectively 31.00% and 36.70% and ra- tionality were 33.31% and 33.30%. During the second teaching program, accurate rates of experimen- tal group and eontrot group were 68.80% and 45.70% and rationality were 62.72% and 43.37%. During the third teaching program, accurate rates of experimental group and control group were 89.70% and 51.20%, and rationality were 95.00% and 66.70%. During the fourth program, accurate rates of ex- perimental group and control group were respectively 97.80% and 55.30% and rationality were 98.30% and 75.60%. Conclusions CBL teaching mode is helpful to improve the students＇ ability of analyzing clinical eases and making more accurate and rational treatment plan, however the increasing teaching cost and the course load are also involved. Key words: Orthodontics; Case-based learning; Treatment plans

SU-E-J-97: Evaluation of Multi-Modality (CT/MR/PET) Image Registration Accuracy in Radiotherapy Planning.

Evaluate accuracy of multi-modality image registration in radiotherapy planning process. A water-filled anthropomorphic head phantom containing eight 'donut-shaped' fiducial markers (3 internal + 5 external) was selected for this study. Seven image sets (3CTs, 3MRs and PET) of phantom were acquired and fused in a commercial treatment planning system. First, a narrow slice (0.75mm) baseline CT scan was acquired (CT1). Subsequently, the phantom was re-scanned with a coarse slice width = 1.5mm (CT2) and after subjecting phantom to rotation/displacement (CT3). Next, the phantom was scanned in a 1.5 Tesla MR scanner and three MR image sets (axial T1, axial T2, coronal T1) were acquired at 2mm slice width. Finally, the phantom and center of fiducials were doped with 18F and a PET scan was performed with 2mm cubic voxels. All image scans (CT/MR/PET) were fused to the baseline (CT1) data using automated mutual-information based fusion algorithm. Difference between centroids of fiducial markers in various image modalities was used to assess image registration accuracy. CT/CT image registration was superior to CT/MR and CT/PET: average CT/CT fusion error was found to be 0.64 ± 0.14 mm. Corresponding values for CT/MR and CT/PET fusion were 1.33 ± 0.71mm and 1.11 ± 0.37mm. Internal markers near the center of phantom fused better than external markers placed on the phantom surface. This was particularly true for the CT/MR and CT/PET. The inferior quality of external marker fusion indicates possible distortion effects toward the edges of MR image. Peripheral targets in the PET scan may be subject to parallax error caused by depth of interaction of photons in detectors. Current widespread use of multimodality imaging in radiotherapy planning calls for periodic quality assurance of image registration process. Such studies may help improve safety and accuracy in treatment planning.

MO‐D‐BRB‐11: Evaluation of the Accuracy of Eclipse AAA Modeling for Flatten Filter Free Beam Used for SBRT

Purpose: To evaluate the Eclipse analytical anisotropic algorithm (AAA) modeling of flattening filter free (FFF) megavoltage photon beams for a new Varian linear accelerator, TruebeamSTx, TM, used for Gated SBRT. Materials and Methods: With the new Varian TruebeamSTx, Eclipse AAA was configured by using the measured dosimetric data. The TruebeamSTx can operate 6 and 10 MV photon beams free of the flattening filter (FFF). FFF photon beams are especially suitable for use of SBRT since they can operate at high dose rate (1400MU/min for 6MVFFF, 2400MU/min for 10MVFFF). Gated IMRT, RapidArc and gated RapidArc have routinely been used for SBRT, using the FFF photon beams. The accuracy of treatment plans with field sizes as small as 1×1 sq. cm are evaluated by measurement performed using films, ion chamber, and also with a Delta4 measurement system (ScandiDos). For gated treatments, measurements were done on a Respiratory Gating Platform (Standard Imaging) with motion simulating the actual patient breathing pattern. Results: The dosimetric leaf gap of the HD120MLC was adjusted to 1.7 mm with leaf transmission set to 0.015 so the calculated isodose distribution has the best fit with the measurement. The comparison between Eclipse and measured isodose distribution show an agreement of better than 95% using a gamma index of (3%/3mm). For gated RapidArc, the difference of FWHM of the measured and calculated profiles is found to be less than 0.2 mm with target size larger than 3 cm in diameter, and less than 1 mm for 1 cm diameter target size. Conclusions: The Eclipse AAA (V8.9) is found to be within 1mm accuracy for target volume as small as 1 cm in diameter. No major difference of the isodose distribution produced between the WFF and the FFF beams.

Geometrical optimization of a particle tracking system for proton computed tomography

Abstract Proton computed tomography (pCT) is currently being developed as an imaging modality for improving the accuracy of treatment planning in proton therapy. A tracking telescope comprising eight planes of single-sided silicon strip detectors (SSDs) forms an integral part of our present pCT design. Due to the currently maximum available Si wafer size, the sensitive area of 9 cm × 18 cm of the pCT tracker requires each tracking plane to be composed of two individual SSDs, which creates potential reconstruction problems due to overlap or gaps of the sensitive SSD areas. Furthermore, the spacing of the tracking planes creates competing design requirements between compactness and spatial resolution. Two Monte Carlo simulations were performed to study the effect of tracking detector location on pCT image quality. It was found that a “shingled” detector design suppressed reconstruction artefacts and, for the spatial resolution of the current detector hardware, reconstructed spatial resolution was not improved with a tracking separation of greater than 8 cm.

Geometrical modeling of H&N cancer tumor

PurposeMost of the current radiation treatment planning systems use pre‐treatment computed tomography (CT) images to detect the tumor location and then plan the radiation therapy to be delivered during the treatment period. It is assumed that the tumor geometry will not change throughout the treatment course; however, tumor geometry is shown to be changing over time. The purpose of this paper is to present results of an ongoing research in 3‐D modeling and reconstruction of head and neck cancer tumors. The results from this phase of the project will be used in developing a prediction model for tumor deformation during radiation treatment of cancer patients.Design/methodology/approachBy using CT scan data in the 3‐D ASCII format, the tumor's progressive geometric changes during the treatment period are quantified. After constructing slice contours, both triangular and rectangular patch approaches are applied to map and analyze the tumor surface and volume. The changes in tumor location are calculated based on a reference feature on the top of the spine canal. MATLAB routines are developed to perform the required calculations. A set of prototype mockups of different stages are used for the purpose of validation and verification of the proposed methodology.FindingsThe proposed method is applied to calculate volume, surface, and displacement of the tumor, using patients’ data obtained from the University of Texas‐MD Anderson Cancer Center. The results are consistent with the actual data.Originality/valueThe proposed methodology increases the accuracy of treatment planning by predicting the changes in tumor geometry. The literature survey reveals that no work has been devoted to mathematically model the geometrical changes that a tumor might go through after each radiation.

SU‐FF‐T‐332: The Effect of Metal Implants On Proton Transport

Purpose: Proton therapy treatment planning in the presence of high‐density metal implants has considerable uncertainty. This uncertainty arises from artifacts produced through the imaging process, uncertainty in the CT density of the implant itself and the effect which both of these have on the range of protons. Because of this uncertainty, beam directions which pass through such implants are avoided if possible. However, in some cases such beams are unavoidable in order to preserve normal tissue and treat the tumor volume effectively. The goal of this ongoing project is to investigate proton transport through high‐density implants and to determine the accuracy of treatment planning software in reproducing isodose distributions when such materials are present. Methods and Materials: We have constructed a phantom with titanium and medical grade stainless steel plates of 1–4 mm thickness embedded within polystyrene. The phantom has been CT‐scanned and then planned using the Odyssey treatment planning system (PerMedics Medical Systems), which is used in routine treatment planning at Loma Linda University Medical Center. The plan generated will be compared to physical dose measurements using ion chambers inserted into the polystyrene phantom. In addition, GEANT4 Monte Carlo simulations of the experimental setup will be completed using CT data as the basis for geometry and material definitions. Additional simulations will be performed with geometry defined based on manufacturers' specifications. Results: Treatment plans of the experimental setup provide an indication of the perturbation of the proton radiation field caused by the metallic implants and indicate areas where measurements and comparisons with GEANT4 should be completed. Conclusions: This study will provide useful data on the accuracy in treatment planning in the presence of metallic implants in proton therapy, and may indicate areas in which improvements to current treatment planning methods can be made.

Radiation-based quantitative bioimaging at the national institute of standards and technology

Building on a long history of providing physical measurements and standards for medical X rays and nuclear medicine radionuclides, the laboratory has expanded its focus to better support the extensive use of medical physics in the United States today, providing confidence in key results needed for drug and device development and marketing, therapy planning and efficacy and disease screening. In particular, to support more quantitative medical imaging, this laboratory has implemented a program to provide key measurement infrastructure to support radiation-based imaging through developing standard, benchmark phantoms, which contain radioactive sources calibrated to national measurement standards, to allow more quantitative imaging through traceable instrument calibration for clinical trials or patient management. Working closely with colleagues at the National Institutes of Health, Rensselaer Polytechnic Institute, the Food and Drug Administration and Cornell University, this laboratory has taken the initial steps in developing phantoms, and the protocols to use them, for more accurate calibration of positron emission tomography (PET) or single-photon emission computed tomography (SPECT) cameras, including recently standardizing 68Ge. X-ray measurements of the laboratory's recently developed small, resilient and inexpensive length standard phantom have shown the potential usefulness of such a “pocket” phantom for patient-based calibration of computed tomography (alone or with PET) systems. The ability to calibrate diagnostic imaging tools in a way that is traceable to national standards will lead to a more quantitative approach; both physician and patient benefit from increased accuracy in treatment planning, as well as increased safety for the patient.

SU‐FF‐T‐381: Real‐Time Treatment Planning System for Prostate Photodynamic Therapy

Purpose: To develop a real‐time treatment planning system for prostate photodynamic therapy (PDT). Method and Materials: A real‐time treatment planning system has been developed for prostate PDT, which is composed of two sub‐systems, i.e., image acquisition and light fluence rate calculation engine. The whole system is built in a personal computer. The image acquisition is implemented using an image frame grabber (DT‐3120, Data Translation, Inc., MA) to acquire ultrasound images from a transrectal ultrasound unit in real time during a treatment. The software converts information about the organ geometries and the actual locations of the light sources on a template with 0.5‐cm grids. These data are then input into the calculation system for prediction of light fluence rate distribution. The three‐dimensional (3D) geometry of the prostate and the actual source arrangements are reconstructed and are used in the calculation, which takes into account the effect of optical heterogeneity. Treatment planning is accomplished with the prediction of 3D light fluence rate distribution. Results: The system has been tested in experiments. In a phantom experiment, transrectal ultrasound images of the prostate phantom during treatment were acquired and the actual locations of the linear sources were recorded. The geometry of the phantom was reconstructed and light fluence rate was calculated in the geometry with the accurate source locations. The capability of calculating light fluence rate distribution in a heterogeneous phenomenon was tested in a patient prostate. The reconstructed prostate geometry, actual source strengths, and measured heterogeneous optical properties, were used in the calculation. The predicted light fluence rate distribution showed the effect of heterogeneous distribution of optical properties. Conclusion: The real‐time treatment planning system provides an efficient tool for prostate PDT, which improves accuracy in treatment planning.

Extracranial frameless stereotactic radiosurgery with multi-modal imaging and opto-electronic position verification

The purpose of the present work is to investigate the feasibility and develop the methods for a clinical protocol of frameless extracranial stereotactic hypo-fractioned radiotherapy and radiosurgery, for the treatment of small secondary tumours. The main concept relies on the exploitation of opto-electronic technologies and multi-modal imaging to increase the target localization accuracy in treatment planning and dose delivery. Preliminary results show that the combined use of PET/CT imaging and opto-electronic respiratory gating is a promising technique for the reduction of localization uncertainties in extracranial stereotactic irradiation. The application of moderate deep inspiration breath-hold manoeuvres, guided by an opto-electronic localizer, can provide an effective improvement in localization accuracy.