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PURPOSE: We developed a novel automated estimation method for patient setup errors based on simulated and real portal images for prostate cancer radiotherapy. METHODS: The estimation of patient setup errors in this study was based on a template matching technique with a cross-correlation coefficient and Sobel filter between the real portal image and localized pelvic template of reference image, which were DRR (digitally reconstructed radiography) images and simulated portal images. The simulated portal image was derived by projecting a CT image according to an inverse exponential power law of x-ray attenuation for a water-equivalent path length of each voxel of the CT image on each ray from a source to each pixel on the EPID (electric portal imaging device). A localized pelvic template of each patient in AP (anterior-posterior) or lateral view was automatically extracted from the DRR or simulated portal images by cropping a rectangular region, which was determined by using the mean pelvic template and four anatomical feature points. We applied the proposed method to three prostate cancer cases, and evaluated it using the residual error between the patient setup error obtained by proposed method and the gold standard setup error determined by two radiation oncologists. RESULTS: The average residual errors of the patient setup error for the DRR and simulated portal images were 0.79 and 1.26 mm in the left-right (LR) direction, 3.17 and 2.05 mm in the superior-inferior (SI) direction, 1.69 and 5.82 mm in the anterior-posterior (AP) direction, 3.84 and 6.94 mm in Euclidean distance (ED), respectively. If we used the simulated portal image for LR and SI directions and the DRR image for AP direction, the Euclidean distance was 3.22 mm. CONCLUSIONS: The proposed method has a potential to correctly estimate patient setup errors for prostate cancer radiotherapy.
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PURPOSE: Microsoft Kinect has potential for use in real-time patient position monitoring in diagnostic radiology and radiotherapy. We evaluated the accuracy of depth image data and the device-to-device variation in various conditions simulating clinical applications in a hospital. METHODS: Kinect sensor consists of infrared-ray depth camera and RGB camera. We developed a computer program using OpenNI and OpenCV for measuring quantitative distance data. The program displays depth image obtained from Kinect sensor on the screen, and the cartesian coordinates at an arbitrary point selected by mouse-clicking can be measured. A rectangular box without luster (300 × 198 × 50 mm3 ) was used as a measuring object. The object was placed on the floor at various distances ranging from 0 to 400 cm in increments of 10 cm from the sensor, and depth data were measured for 10 points on the planar surface of the box. The measured distance data were calibrated by using the least square method. The device-to-device variations were evaluated using five Kinect sensors. RESULTS: There was almost linear relationship between true and measured values. Kinect sensor was unable to measure at a distance of less than 50 cm from the sensor. It was found that distance data calibration was necessary for each sensor. The device-to-device variation error for five Kinect sensors was within 0.46% at the distance range from 50 cm to 2 m from the sensor. The maximum deviation of the distance data after calibration was 1.1 mm at a distance from 50 to 150 cm. The overall average error of five Kinect sensors was 0.18 mm at a distance range of 50 to 150 cm. CONCLUSIONS: Kinect sensor has distance accuracy of about 1 mm if each device is properly calibrated. This sensor will be useable for positioning of patients in diagnostic radiology and radiotherapy.
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PURPOSE: Radiographic simulator system is useful for learning radiographic techniques and confirmation of positioning before x-ray irradiation. Conventional x-ray simulators have drawbacks in cost and size, and are only applicable to situations in which position of the object does not change. Therefore, we have developed a new radiographic simulator system using an infrared-ray based three-dimensional shape measurement device (Microsoft Kinect). METHODS: We made a computer program using OpenCV and OpenNI for processing of depth image data obtained from Kinect, and calculated the exact distance from Kinect to the object by calibration. Theobject was measured from various directions, and positional relationship between the x-ray tube and the object was obtained. X-ray projection images were calculated by projecting x-rays onto the mathematical three-dimensional CT data of a head phantom with almost the same size. The object was rotated from 0 degree (standard position) through 90 degrees in increments of 10 degrees, and the accuracy of the measured rotation angle values was evaluated. In order to improve the computational time, the projection image size was changed (512*512, 256*256, and 128*128). RESULTS: The x-ray simulation images corresponding to the radiographic images produced by using the x-ray tube were obtained. The three-dimensional position of the object was measured with good precision from 0 to 50 degrees, but above 50 degrees, measured position error increased with the increase of the rotation angle. The computational time and image size were 30, 12, and 7 seconds for 512*512, 256*256, and 128*128, respectively. CONCLUSIONS: We could measure the three-dimensional position of the object using properly calibrated Kinect sensor, and obtained projection images at relatively high-speed using the three-dimensional CTdata. It was suggested that this system can be used for obtaining simulated projection x-ray images before x-ray exposure by attaching this device onto an x-ray tube.
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PURPOSE: The quality of a treatment plan for stereotactic body radiotherapy (SBRT) depends on an experience of each treatment planner. Therefore, the treatment plans are subjectively determined by comparison of several treatment plans developed by time consuming iterative manners, while considering the benefit to a tumor and the risk to the surrounding normal tissues. The aim of our study was to develop an automated optimization method for beam arrangements based on similar cases in a database including plans designed by senior experienced treatment planners. METHODS: Our proposed method consists of three steps. First, similar cases were automatically selected based on image features from the treatment planning point of view. We defined four types of image features relevant to planning target volume (PTV) location, PTV shape, lung size, and spinal cord positional features. Second, the beam angles of the similar case were registered to the objective case with respect to lung regions using a linear registration technique. Third, the beam direction of the objective case was locally optimized based on the cost function considering radiation absorption in normal tissues and organs at risk. The proposed method was evaluated with 10 test cases and a treatment planning database including 81 cases by using eight planning evaluation indices such as D95, lung V20, and maximum spinal cord dose. RESULTS: The proposed method may provide usable beam directions, which have no statistically significant differences with the original beam directions (P > 0.05) in terms of the seven planning evaluation indices. Moreover, the mean value of D95 for 10 test cases was improved with a statistically significant difference by using the proposed method, compared with the original beam directions (P = 0.03). CONCLUSIONS: The proposed method could be used as a computer-assisted treatment planning tool for determination of beam directions in SBRT.
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PURPOSE: The three-dimensional (3D) dose distribution covering a tumor region tends to be more breakable if the beam's eye view (BEV) of the 3D electron density (ED) map in a beam direction changes more abruptly with large fluctuations. Our aim of this study was to develop an automated determination method of robust beam directions against the patient setup error based on the ED-based BEV in the beam direction in the particle therapy. METHODS: The basic idea of our proposed method was to find the robust beam directions, whose the ED-based BEV has the spatial fluctuations with low special frequency and small amplitude. For evaluation of the spatial fluctuation in the ED-based BEV in a beam direction, we obtained power spectra of the ED-based BEVs in all directions, i.e., 0 to 355 degree, with an interval of 5 degree. It was assumed that as the average spatial frequency and amplitude of the fluctuation in the ED-based BEV in a beam direction is lower and smaller, respectively, the absolute value of a gradient of the power spectrum becomes larger. Therefore the gradient of the power spectrum was calculated for determination of the robust beam direction. The ED-based BEV was produced by projecting a 3D electron density map derived from the computed tomography (CT) image from a beam source to the distal end of a planning target volume (PTV). Four cases of head and neck cancer patients were selected for evaluation of the proposed method. RESULTS: As a preliminary result, radiation oncologists agreed with most beam directions, which seem to be robust against patient setup errors, suggested by the proposed method. CONCLUSIONS: Our proposed method could be feasible to suggest the robust beam directions against patient setup errors in hadron particle therapy.
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PURPOSE: The accumulated dose distributions during the course of radiation treatment are substantially important for verifying whether treatment dose distributions are produced according to planned dose distributions. The purpose of this study was to develop a computer-assisted verification method of accumulated dose distribution during the irradiation of a tumor based on estimation of four-dimensional (4D) dose distribution using an electronic portal imaging device (EPID). METHODS: The 4D 'treatment' computed tomography (CT) images during the irradiation were estimated based on affine transformations including respiratory motions, which were derived by registration between a planning portal dose image and treatment portal dose dynamic image. Planning portal dose images were calculated from planning CT images and an algorithm for calculation of dose spatial distribution. Treatment portal dose images were estimated from EPID dynamic images obtained during a treatment time. The planning portal dose images were registered to the treatment portal dose images to obtain the affine transformation, which could include respiratory motion in a patient body. The CT images at a treatment time were determined by deforming the planning CT images using the affine transformation matrix. 4D dose distributions during a treatment delivery were obtained by applying a dose calculation algorithm to the 4D treatment CT images. Finally, accumulated dose distributions during the course of radiation treatment were verified with planned dose distributions. RESULTS: We applied the proposed method to EPID dynamic images of 2 lung cancer patients, and evaluated the difference in accumulated dose distribution between the plan and treatment using a gamma evaluation (3mm/3%). The average pass rate for 2 cases was 78.2%. CONCLUSIONS: The proposed method can be used for adaptively modifying the plan based on the dose discrepancy between the plan and treatment. This work was partially supported by Grant-in-Aid for Scientific Research (C) (22611011) and Okawa Foundation for Information and Telecommunications.
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The purpose of this study was to develop a computerized method for estimation of the location of a lung tumor in cine images on an electronic portal imaging device (EPID) without implanted markers during stereotactic body radiotherapy (SBRT). Each tumor region was segmented in the first EPID cine image, i.e., reference portal image, based on a multiple-gray level thresholding technique and a region growing technique, and then the image including the tumor region was cropped as a 'tumor template' image. The tumor location was determined as the position in which the tumor template image took the maximum cross-correlation value within each consecutive portal image, which was acquired in cine mode on the EPID in treatment. EPID images with 512 x 384 pixels (pixel size: 0.56 mm) were acquired at a sampling rate of 0.5 frame s(-1) by using energies of 4, 6 or 10 MV on linear accelerators. We applied our proposed method to EPID cine images (226 frames) of 12 clinical cases (ages: 51-83, mean: 72) with a non-small cell lung cancer. As a result, the average location error between tumor points obtained by our method and the manual method was 1.47 +/- 0.60 mm. This preliminary study suggests that our method based on the tumor template matching technique might be feasible for tracking the location of a lung tumor without implanted markers in SBRT.
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Algoritmos , Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/cirurgia , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Radiocirurgia/métodos , Técnica de Subtração , Cirurgia Assistida por Computador/métodos , Ecrans Intensificadores para Raios X , Inteligência Artificial , Humanos , Reconhecimento Automatizado de Padrão/métodos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
The role of lead foil in protecting film from image degradation due to back-scattered radiation was studied. The effects of low-scattering (polystyrene foam) and tissue-equivalent (Lucite) materials on relative speed and modulation transfer factor (MTF) of the front and back films from Kodak DF-57 double film packets were evaluated. The relative speed of the back film with polystyrene foam behind the film was about 10% faster with lead foil. However, when Lucite was placed behind the film, lead foil eliminated the effect of scattered radiation on film density, MTF, was decreased by the presence of lead foil when polystyrene foam was placed behind the film. With Lucite, however, lead foil improved the MTF value, which was decreased by the scattered radiation at spatial frequencies over 5 cycle mm-1. These results suggest that lead foil itself causes scattered or secondary radiation and affects film speed and resolution. However, it also protects the film from scattered radiation from tissue behind the film and results in improvement in resolution.
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Chumbo , Radiografia Dentária/normas , Filme para Raios X , Análise de Variância , Humanos , Metilmetacrilato , Metilmetacrilatos , Poliestirenos , Garantia da Qualidade dos Cuidados de Saúde , Radiografia Dentária/instrumentação , Análise de Regressão , Reprodutibilidade dos Testes , Espalhamento de RadiaçãoRESUMO
Quantitative image analysis of mouse parotid gland sialograms was achieved by conversion of the digital image to a histogram. The relationships between histogram pattern, microsialographic appearance and the amount of contrast medium infused were compared in normal glands and in experimentally induced sialoadenitis. Differences in the pattern enabled a distinction to be drawn between poor sialographic technique and genuine pathology.
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Doenças Parotídeas/diagnóstico por imagem , Doenças das Glândulas Salivares/diagnóstico por imagem , Sialadenite/diagnóstico por imagem , Sialografia/métodos , Animais , Meios de Contraste , Estudos de Avaliação como Assunto , Camundongos , Intensificação de Imagem RadiográficaRESUMO
Synchrotron radiation available at the Photon Factory, National Laboratory for High Energy Physics, provides a new X-ray source which is highly suitable for K-edge subtraction. This is due to its high intensity, its parallelism and its monochromaticity, available in a monochromator system. Experiments were performed using wiggler synchrotron radiation. Since the beam size is relatively-small for in-vivo imaging, a phantom coupled with a detector was moved horizontally using a scanning table. K-edge subtraction was successfully applied both to the coronary artery phantom filled with barium sulphate, and to rat angiography using iodine contrast material. The potential use and value of energy subtraction was successfully demonstrated.
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Angiografia Coronária , Técnica de Subtração , Animais , Humanos , Iodo , Métodos , Modelos Estruturais , RatosRESUMO
The escape phenomenon is characteristic of osteoclastic bone resorption in organ cultures, and calcitonin only transiently inhibits parathyroid hormone (PTH)-stimulated resorption. The present study demonstrated that the transient inhibition of osteoclastic bone resorption, a phenomenon reminiscent of escape, occurs in the bones of calcitonin (ECT)-treated rats and that whole-body irradiation inhibits this escape. Rats were treated with daily subcutaneous injections of ECT for 72 h. At 24 h ECT decreased the incidence of osteoclast profiles with ruffled borders both in the growth plate-metaphysis junction (GPMJ) and the metaphyseal trabecular bone region (MT). However, by 72 h the incidence in the MT had been restored to the level of the control. The trabecular bone volume in the ECT-treated bone did not differ significantly from the control value. Whole-body irradiation (600 rad) before the first injections of ECT prevented the re-activation of the ruffled border formation and increased the trabecular bone volume at 72 h. Irradiation diminished the number of osteoclasts in the ECT-treated bones to the level of the control. ECT-treated bones contained a greatly increased number of macrophage-like cells (MO). Irradiation prevented this ECT-induced increase in the number of MO. These results strongly suggest that the escape phenomenon in vivo involves the calcitonin-induced proliferation of cells in the mononuclear phagocyte system, with resultant increases in the number of osteoclasts and in the bone resorption activity of osteoclasts.
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Reabsorção Óssea/efeitos da radiação , Calcitonina/farmacologia , Osteoclastos/efeitos da radiação , Irradiação Corporal Total , Animais , Reabsorção Óssea/efeitos dos fármacos , Diferenciação Celular/efeitos dos fármacos , Diferenciação Celular/efeitos da radiação , Lâmina de Crescimento/citologia , Hipocalcemia/fisiopatologia , Macrófagos/ultraestrutura , Masculino , Osteoclastos/efeitos dos fármacos , Osteoclastos/ultraestrutura , Hormônio Paratireóideo/fisiologia , Ratos , Ratos Endogâmicos LewRESUMO
A method of externally observing the stop-region of pi- meson for monitoring during exposure to a patient is discussed. Negative pi mesic X-rarys, gamma-rays and neutrons are emitted from the region where pi- mesons stop and produce stars. These radiations can be detected outside the exposed patient. Water phantom as normal tissue equivalent material was exposed by pi- mesons at various depths. The resulting gamma-ray yields were determined by counting the gamma-rays in coincidence with incident pi- mesons using a sodium iodide (NaI) detector. This type of gamma-ray measuring system is useful to make sure that the peak position of the depth-dose distribution in the patient is exactly situated at the desired one during exposure. It is suggested that the scintillation camera with a multiholecollimator is a powerful and convenient tool for the two dimensional peak positioning.
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Nêutrons , Monitoramento de Radiação/métodos , Contagem de Cintilação/métodos , Raios gama , Humanos , Neoplasias/radioterapia , Monitoramento de Radiação/instrumentação , Dosagem Radioterapêutica , Contagem de Cintilação/instrumentação , Raios XAssuntos
Osso e Ossos/análise , Minerais/análise , Espectrometria por Raios X , Humanos , MatemáticaRESUMO
Microdosimetry of in-flight pi-beams was performed at the T1 channel of National Laboratory for High Energy Physics (KEK), Tsukuba, Japan. Distributions of lineal energy (y) in-flight pi-beams having six momentum values from 120 MeV/c to 1000 MeV/c were measured with an LET counter which simulates 2 micron sphere of soft tissue filled with the methane base tissue equivalent gas. Frequency spectra were obtained in the range of 1.6 less than y less than 430 keV/micron. Fractional dose y . d(y), cumulative dose D(y), and mean lineal energy were calculated from these spectra; then momentum dependences were investigated. These absolute values have little physical application because of the lack of data for y less than 1.6 keV/micron. However, the general trends of y distribution in momentum dependence were found, qualitatively. As the momentum becomes smaller, the rate of high y component in the dose increased.