In this study we estimated a geometric correlation among digitally reconstructed radiographic image (DRRI), kV x-ray image (kVXI) from the On-Board Imager (OBI) and electric portal image (EPI). To verify geometric correspondence of DRRI, kVXI and EPI, specially designed phantom with indexed 6 ball bearings (BBs) were employed. After accurate setup of the phantom on a treatment couch using orthogonal EPIs, we acquired set of orthogonal kVXIs and EPIs then compared the absolute positions of the center of the BBs calculated at each phantom plane for kVXI and EPI respectively. We also checked matching result for obliquely incident beam (gantry angle of 315 degrees) after 2D-2D matching provided by OBI application. A reference EPI obtained after initial setup of the phantom was compared with 10 series of EPIs acquired after each 2D-2D matching. Imaginary setup errors were generated from -5 mm to 5 mm at each couch motion direction. Calculated positions of all center positions of the BBs at three different images were agreed with the actual points within a millimeter and each other. Calculated center positions of the BBs from the reference and obtained EPIs after 2D-2D matching agreed within a millimeter. We could tentatively conclude that the OBI system was mechanically quite reliable for image guided radiation therapy (IGRT) purpose.
Radiotherapy, Image-Guided

High precision radiotherapy has been a hot issue to radiation oncologists for the last 100 years. Introduction of mega volt machine with linear accelerators changed the paradigm of radiotherapy, and development of computers and three-dimensional treatment opened the new era of high tech radiotherapy. However, the change and development in high tech radiotherapy for the last 10 years was much bigger than those of previous century, and it seems that we are very close to the finish line of high precision radiotherapy. Linear accelerator has been a firm base for such an evolution to high tech radiotherapy. It is the machine which is used most frequently for stereotactic radiosurgery, image-guided and respiratory gated radiotherapy and this review will introduce the basic concepts of this linac-based high precision radiotherapy.
Particle Accelerators ; Radiosurgery ; Radiotherapy, Image-Guided

Cone-beam digital tomosynthesis (CBDT) has greatly been paid attention in the image-guided radiation therapy because of its attractive advantages such as low patient dose and less motion artifact. Image quality of tomograms is, however, dependent on the imaging conditions such as the scan angle (beta(scan)) and the number of projection views. In this paper, we describe the principle of CBDT based on filtered-backprojection technique and investigate the optimization of imaging conditions. As a system performance, we have defined the figure-of-merit with a combination of signal difference-to-noise ratio, artifact spread function and floating-point operations which determine the computational load of image reconstruction procedures. From the measurements of disc phantom, which mimics an impulse signal and thus their analyses, it is concluded that the image quality of tomograms obtained from CBDT is improved as the scan angle is wider than 60 degrees with a larger step scan angle (Delta beta). As a rule of thumb, the system performance is dependent on . If the exact weighting factors could be assigned to each image-quality metric, we would find the better quantitative imaging conditions.
Artifacts ; Humans ; Image Processing, Computer-Assisted ; Radiotherapy, Image-Guided ; Thumb

Technological advances that have been achieved over the last two decades in the area of treatment planning and sophisticated and complicated hardware capabilities, such as computer-controlled treatments, multileaf collimators, and incorporating imaging devices into treatment machines, enable clinical implementation of high-precision radiotherapy in field of radiation oncology. High-precision radiotherapy allows the delivery of increased tumor doses with relative sparing of normal tissues compared to 3 -dimensional radiotherapy and conventional techniques. Preliminary clinical experiences of high precision radiation therapy have been encouraging by high rates of local control and decrease of toxicity. This article provides an overview of high precision radiotherapy such as intensity-modulated radiotherapy, stereotactic radiation therapy, image-guided radiotherapy, and charged particle therapy.
Proton Therapy ; Radiation Oncology ; Radiotherapy, Image-Guided ; Radiotherapy, Intensity-Modulated

PURPOSE: On-line image guided radiation therapy (on-line IGRT) and (kV X-ray images or cone beam CT images) were obtained by an on-board imager (OBI) and cone beam CT (CBCT), respectively. The images were then compared with simulated images to evaluate the patient's setup and correct for deviations. The setup deviations between the simulated images (kV or CBCT images), were computed from 2D/2D match or 3D/3D match programs, respectively. We then investigated the correctness of the calculated deviations. MATERIALS AND METHODS: After the simulation and treatment planning for the RANDO phantom, the phantom was positioned on the treatment table. The phantom setup process was performed with side wall lasers which standardized treatment setup of the phantom with the simulated images, after the establishment of tolerance limits for laser line thickness. After a known translation or rotation angle was applied to the phantom, the kV X-ray images and CBCT images were obtained. Next, 2D/2D match and 3D/3D match with simulation CT images were taken. Lastly, the results were analyzed for accuracy of positional correction. RESULTS: In the case of the 2D/2D match using kV X-ray and simulation images, a setup correction within 0.06degrees for rotation only, 1.8 mm for translation only, and 2.1 mm and 0.3degrees for both rotation and translation, respectively, was possible. As for the 3D/3D match using CBCT images, a correction within 0.03degrees for rotation only, 0.16 mm for translation only, and 1.5 mm for translation and 0.0degrees for rotation, respectively, was possible. CONCLUSION: The use of OBI or CBCT for the on-line IGRT provides the ability to exactly reproduce the simulated images in the setup of a patient in the treatment room. The fast detection and correction of a patient's positional error is possible in two dimensions via kV X-ray images from OBI and in three dimensions via CBCT with a higher accuracy. Consequently, the on-line IGRT represents a promising and reliable treatment procedure.
Cone-Beam Computed Tomography ; Humans ; Radiotherapy, Image-Guided

OBJECTIVETo discuss the influence of setup errors on the accuracy of pelvic cancer in IGRT, analysis setup errors and determine the CTV-to-PTV margins.

METHODS60 pelvic cancer patients treated with Varian 23IX, all of them were performed by CBCT before and after-correction three times in the first week and after that once a week. Then, to measure the setup errors at X(left-right), Y(superior-inferior), Z(anterior-posterior) axis and E(coronal), F(sagittal), G(axial) rotation directions.

RESULTS530 scans obtained in all, the setup errors in X, Y, Z, E, F, G were (-0.52 ± 4.18) mm, (0.73 ± 4.86) mm, (-0.36 ± 3.62) mm, (0.14 ± 1.20)degrees, (0.13 ± 1.34)degrees, (0.21 ± 1.73)degrees respectively and were much lower after correction at X, Y, Z axis, besides, CTV-to-PTV margins decrease a lot.

CONCLUSIONThe accuracy of radiotherapy can be highly increased with the use of IGRT in pelvic cancer.

Humans ; Pelvic Neoplasms ; radiotherapy ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; Radiotherapy, Image-Guided

With increasing clinical use, radiotherapy (RT) has been considered reliable and effective method for hepatocellular carcinoma (HCC) treatment, depending on extent of disease and patient characteristics. RT for HCC can improve therapeutic outcomes through excellent local control, downstaging, conversion from unresectable to resectable status, and treatments of unresectable HCCs with vessel invasion or multiple intrahepatic metastases. In addition, further development of modern RT technologies, including image-guided radiotherapy (IGRT), intensity-modulated radiotherapy (IMRT), and stereotactic body radiotherapy, has expanded the indication of RT. An essential feature of IGRT is that it allows image guidance therapy through in-room images obtained during radiation delivery. Compared with 3D-conformal RT, distinctions of IMRT are inverse treatment planning process and use of a large number of treatment fields or subfields, which provide high precision and exquisitely conformal dose distribution. These modern RT techniques allow more precise treatment by reducing inter- and intra-fractional errors resulting from daily changes and irradiated dose at surrounding normal tissues. More recently, particle therapy has been actively investigated to improve effectiveness of RT. This review discusses modern RT strategies for HCC, as well as optimal selection of RT in multimodal approach for HCC.
Carcinoma, Hepatocellular* ; Humans ; Methods ; Neoplasm Metastasis ; Radiosurgery ; Radiotherapy* ; Radiotherapy, Image-Guided ; Radiotherapy, Intensity-Modulated

OBJECTIVETo validate the efficiency of an improved Demons deformable registration algorithm and evaluate its application in registration of the treatment image and the planning image in image-guided radiotherapy (IGRT).

METHODSBased on Brox's gradient constancy assumption and Malis's efficient second-order minimization algorithm, a grey value gradient similarity term was added into the original energy function, and a formula was derived to calculate the update of transformation field. The limited Broyden-Fletcher-Goldfarb-Shanno (L-BFGS) algorithm was used to optimize the energy function for automatic determination of the iteration number. The proposed algorithm was validated using mathematically deformed images, physically deformed phantom images and clinical tumor images.

RESULTSCompared with the original Additive Demons algorithm, the improved Demons algorithm achieved a higher precision and a faster convergence speed.

CONCLUSIONDue to the influence of different scanning conditions in fractionated radiation, the density range of the treatment image and the planning image may be different. The improved Demons algorithm can achieve faster and more accurate radiotherapy.

Algorithms ; Humans ; Liver Neoplasms ; radiotherapy ; Radiotherapy Dosage ; Radiotherapy Planning, Computer-Assisted ; methods ; Radiotherapy, Conformal ; methods ; Radiotherapy, Image-Guided ; methods

Image-guided radiation therapy using magnetic resonance imaging (MRI) is a new technology that has been widely studied and developed in recent years. The technology combines the advantages of MRI imaging, and can offer online real-time tracking of tumor and adjacent organs at risk, as well as real-time optimization of radiotherapy plan. In order to provide a comprehensive understanding of this technology, and to grasp the international development and trends in this field, this paper reviews and summarizes related researches, so as to make the researchers and clinical personnel in this field to understand recent status of this technology, and carry out corresponding researches. This paper summarizes the advantages of MRI and the research progress of MRI linear accelerator (MR-Linac), online guidance, adaptive optimization, and dosimetry-related research. Possible development direction of these technologies in the future is also discussed. It is expected that this review can provide a certain reference value for clinician and related researchers to understand the research progress in the field.
Magnetic Resonance Imaging ; Particle Accelerators ; Radiometry ; Radiotherapy Planning, Computer-Assisted ; Radiotherapy, Image-Guided

PURPOSE: The aim of this study was to identify volume changes and dose variations of rectum and bladder during radiation therapy in prostate cancer (PC) patients. MATERIALS AND METHODS: We analyzed 20 patients with PC treated with helical tomotherapy. Daily image guidance was performed. We re-contoured the entire bladder and rectum including its contents as well as the organ walls on megavoltage computed tomography once a week. Dose variations were analyzed by means of Dmedian, Dmean, Dmax, V₁₀ to V₇₅, as well as the organs at risk (OAR) volume. Further, we investigated the correlation between volume changes and changes in Dmean of OAR.
Humans ; Organs at Risk ; Prostate ; Prostatic Neoplasms ; Radiotherapy, Image-Guided ; Radiotherapy, Intensity-Modulated ; Rectum ; Urinary Bladder