RESUMO
PURPOSE: The purpose of the work is to describe a new algorithm for the automatic detection of implanted radioactive seeds within the prostate. The algorithm is based on the traditional Hough transform. A method of quality assurance is described as well as a quantitative phantom study to determine the accuracy of the algorithm. METHODS AND MATERIALS: An algorithm is described which is based on the Hough transform. The Hough transform is a well known transform traditionally used to automatically segment lines and other well defined geometric objects from images. The traditional Hough transform is extended to three-dimensions and applied to CT images of seed implanted prostate glands. A method based on digitally reconstructed radiographs is described to quality assure the determined three-dimensional positions of the detected seeds. Two phantom studies utilizing eight seeds and nine seeds are described. All eight seeds form a contiguous a square while the nine seed phantom describes seeds which are placed side-by-side in groups of two and three. The algorithm is applied to the CT scans of both phantoms and the seed positions determined. RESULTS: The algorithm has been commercially developed and used to perform postsurgical dosimetric assessment on approximately 1000 patients. Using the described quality assurance tool it was determined that the algorithm accurately determined the seed positions in all 1000 patients. The algorithm was also applied to the eight seed phantom. The algorithm successfully found all eight seeds as well as their seed coordinates. The average radial error was determined to be 0.9 mm. For the nine seed phantom, the algorithm correctly identified all nine seeds, with an average radial error of 3 mm. CONCLUSIONS: The described algorithm is a robust, accurate, automatic, three-dimensional application for CT based seed determination.
Assuntos
Algoritmos , Braquiterapia/métodos , Imageamento Tridimensional/métodos , Reconhecimento Automatizado de Padrão/métodos , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Próteses e Implantes , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Braquiterapia/instrumentação , Cateterismo/métodos , Humanos , Masculino , Imagens de Fantasmas , Garantia da Qualidade dos Cuidados de Saúde/métodos , Intensificação de Imagem Radiográfica/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Processamento de Sinais Assistido por Computador , Tomografia Computadorizada por Raios X/métodosRESUMO
Our purpose in this study is to describe an algorithm for the automatic detection of linear artifacts in medical images. Linear artifacts arise as a result of many different forms of tissues and tissue boundaries within the imaging volume. Additionally, linear artifacts can arise for artificial structures such as radioactive seeds and radioactive linear sources. It is the purpose of the described algorithm to automatically detect linear artifacts of a certain length and diameter. The algorithm was written and compiled on a Pentium-4 based computer in the Microsoft Visual C/C++ language. Inert coils supplied by Radiomed Inc. were implanted into a standard prostate ultrasound phantom. Transaxial ultrasound images of the implanted phantom were obtained at 2 mm increments. The coded algorithm was then applied to the ultrasound imaging volume to automatically segment out the implanted coils. Thirteen coils were implanted in the prostate phantom. Thirteen coils were automatically identified in the imaging volume. An algorithm was developed to automatically determine the position and orientation of radioactive coils within an imaging volume. The algorithm successfully identified thirteen coils implanted in an ultrasound prostate phantom.
Assuntos
Algoritmos , Artefatos , Braquiterapia/métodos , Interpretação de Imagem Assistida por Computador/métodos , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Implantação de Prótese/métodos , Cirurgia Assistida por Computador/métodos , Humanos , Interpretação de Imagem Assistida por Computador/instrumentação , Masculino , Reconhecimento Automatizado de Padrão/métodos , Imagens de Fantasmas , Próteses e Implantes , Garantia da Qualidade dos Cuidados de Saúde/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Ultrassonografia/instrumentação , Ultrassonografia/métodosRESUMO
We describe a procedure for intraoperative treatment planning for seed implantation. One hundred seven treatment plans have been analyzed at the Beth Israel Deaconess Medical Center and affiliated hospitals. The average time for the intraoperative procedure was 1. 74 hours. No significant difference in dose coverage to the prostate or normal tissues was evident.
Assuntos
Braquiterapia/métodos , Radioisótopos do Iodo/uso terapêutico , Neoplasias da Próstata/radioterapia , Humanos , Período Intraoperatório , Masculino , Salas Cirúrgicas , Neoplasias da Próstata/cirurgia , Dosagem RadioterapêuticaRESUMO
The goal of radioactive seed implantation in prostate cancer is to treat the tumor to the necessary dose while minimizing the dose to adjacent normal structures. The uniform and peripheral loading schemes used in the past have serious limitations. However, with the availability of three-dimensional treatment-planning systems, it has become possible to do custom volume loading based on volumetric ultrasound imaging of the gland. As a result, the dose distributions are more uniform, and the doses to the urethra and rectum are maintained in a safe range.
Assuntos
Braquiterapia/métodos , Neoplasias da Próstata/radioterapia , Humanos , Masculino , Planejamento de Assistência ao Paciente/normas , Planejamento de Assistência ao Paciente/tendências , Próstata/diagnóstico por imagem , Radiometria , UltrassonografiaRESUMO
PURPOSE: To determine whether real-time ultrasound imaging and targeting system for the treatment of prostate cancer was feasible. The initial phase of this project included a study to develop and determine (a) software for the fusion of ultrasound images to standard x-rays obtained during simulation, and (b) the potential reduction in field size with real-time imaging. METHODS AND MATERIALS: During 13 patient simulations a transrectal ultrasound image was obtained. Orthogonal x-ray films were acquired with the rectal probe in place. Both the x-ray and ultrasound images were digitized and a fusion image was created of the prostate position in relation to the probe, bladder, and rectum. The two-dimensional area of the rectum, bladder, and prostate was determined in the lateral projection. Potential conformal blocks were designed for the lateral portals in a four-field treatment technique. RESULTS: The transrectal ultrasound probe enabled real-time prostate imaging. The lateral field size can be reduced to 6.08 x 5.68 cm2 +/- 0.62 x 0.48 cm2 from the standard 8 x 8 cm2 field. The posterior rectal wall was physically displaced out of the lateral field. The area of the rectum included in the lateral field is 1.75 cm2 +/- 0.85 cm2. CONCLUSION: The prostate position can be determined with certainty on a regular basis with transrectal ultrasonography. The amount of normal tissue in the high dose volume can be reduced. This approach may reduce acute and chronic morbidity and allow further dose escalation.
Assuntos
Sistemas Computacionais , Neoplasias da Próstata/diagnóstico por imagem , Radioterapia Assistida por Computador/métodos , Estudos de Viabilidade , Humanos , Masculino , Próstata/diagnóstico por imagem , Neoplasias da Próstata/radioterapia , Radiografia , Ultrassonografia de IntervençãoRESUMO
Distortions of the magnetic field, such as those caused by susceptibility artifacts and peripheral magnetic field warping, can limit geometric precision in the use of magnetic resonance (MR) imaging in stereotactic procedures. The authors have routinely found systematic error in MR stereotactic coordinates with a median of 4 mm compared to computerized tomography (CT) coordinates. This error may place critical neural structures in jeopardy in sme procedures. A description is given of an image fusion technique that uses a chamfer matching algorithm; the advantages of MR imaging in anatomical definition are combined with the geometric precision of CT, while eliminating most of the anatomical spatial distortion of stereotactic MR imaging. A stereotactic radiosurgical case is presented in which the use of MR localization alone would have led to both irradiation of vital neural structures outside the desired target volume and underdose of the intended target volume. The image fusion approach allows for the use of MR imaging, combined with stereotactic CT, as a reliable localizing technique for stereotactic neurosurgery and radiosurgery.
Assuntos
Encéfalo/cirurgia , Aumento da Imagem/métodos , Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética , Radiocirurgia , Técnicas Estereotáxicas , Tomografia Computadorizada por Raios X , Algoritmos , Cerebelo/cirurgia , Feminino , Humanos , Pessoa de Meia-Idade , Neuroma Acústico/cirurgia , Ponte/cirurgia , Radiologia Intervencionista , Processamento de Sinais Assistido por ComputadorRESUMO
PURPOSE: We describe an image fusion application that addresses two basic problems that previously limited the use of magnetic resonance imaging (MRI) for geometric localization in stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT). The first limitation is imposed by the use of a relocatable, MRI-incompatible, stereotactic frame for stereotactic radiotherapy. The second limitation is an inherent lack of geometric fidelity in current MRI scanners that invalidates the use of MRI for stereotactic localization. METHODS AND MATERIALS: We recently developed and implemented a novel automated method for fusing computerized tomography (CT) and MRI volumetric image studies. The method is based on a chamfer matching algorithm, and provides a quality assurance procedure to verify the accuracy of the fused image set. The image fusion protocol removes the need for stereotactic fixation of the patient for the MRI study. RESULTS: The image fusion protocol significantly improves on the spatial accuracy of the MRI study. We demonstrate the effect of distortion and the effectiveness of the fusion with a phantom study. We present two case studies, an acoustic neurinoma treated with SRS, and a pilocytic astrocytoma treated with SRT. CONCLUSION: The image fusion protocol significantly improves our logistical management of treating patients with radiosurgery and makes conformal therapy practical for treating patients with SRT. The image fusion protocol demonstrates both the superior diagnostic quality and the poor geometric fidelity of MRI. MRI is a required imaging modality in stereotactic therapy. Image fusion combines the superior MRI diagnostic quality with the superior CT geometric definition, and makes the use of MRI in stereotactic therapy possible and practical.
Assuntos
Astrocitoma/diagnóstico , Neoplasias Encefálicas/diagnóstico , Neuroma Acústico/diagnóstico , Radiocirurgia , Astrocitoma/radioterapia , Neoplasias Encefálicas/radioterapia , Criança , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Pessoa de Meia-Idade , Neuroma Acústico/cirurgia , Tomografia Computadorizada por Raios XRESUMO
PURPOSE: The effect of systematic and stochastic setup error on the dose delivered to the gap region for the three field radiation treatment of medulloblastoma is studied. The consequences of such setup error is discussed. METHODS AND MATERIALS: The treatment of medulloblastoma is typically a 3 field technique, in which two lateral cranial fields are matched with a spine field. The x-ray dose delivered to the region between the matched fields depends upon the gap size. The choice of the gap width between the cranial and spinal fields is controversial. It is currently a compromise between minimizing the risk of dose hot spots to the spine, and the associated clinical complications, as well as the magnitude of cold spots (underdosing) across the gap, with the associated risk of disease recurrence. In this paper, we examine the effect of gap width with a moving junction, referred to as "field feathering", on the dose across the field junction for a 6MV photon beam. In addition, we have studied 129 portal films and 40 simulation films to assess the accuracy and precision of patient setup during treatment with a plan involving feathered fields. Selected landmarks observable on both portal and simulation films were identified and the variation in the distances to the field edges measured. The distribution of patient setup error was convoluted with the beam profiles for a 6MV linac. These convoluted field edges were used obtain dose profiles across the gap region as a function of gap separation. The consequences for therapy are discussed. In addition, analysis of patient setup error on an alternative treatment involving beam modifiers to broaden the beam penumbra is discussed. RESULTS: The magnitude of the spatial stochastic and systematic setup error was determined to be approximately three and two millimeters respectively. The dosimetric consequences of patient setup error lead to over and under dosing in the spinal gap region for the three field technique. The degree of under or over dose depends on the nature and magnitude of the patient setup error. CONCLUSIONS: The effect of patient setup error can lead to significant dosimetric errors in the dose to the gap region depending on the magnitude of the setup errors. The effective over and under dose can be compensated by the use beams modifiers such as a beam spoiler or vibrating jaws.
Assuntos
Neoplasias Cerebelares/radioterapia , Meduloblastoma/radioterapia , Modelos Biológicos , Dosagem Radioterapêutica/normas , Neoplasias da Coluna Vertebral/radioterapia , Calibragem , HumanosRESUMO
An automatic image correlation algorithm is discussed for the cranial region which is based on the geometric properties of the second moment tensor associated with a volume. The second moment tensor of two identical volumes represented in two different coordinate frames is evaluated to obtain the set of translations, rotations, and anisotropic scaling operators which relate the two coordinate frames. The theory is presented along with a discussion of quantitative error analysis to measure the usefulness of such an algorithm in the clinical setting.
Assuntos
Algoritmos , Diagnóstico por Imagem , Humanos , MatemáticaRESUMO
Stereotactic radiosurgery of intra-cranial lesions is a treatment modality where a well defined target volume receives a high radiation dose in a single treatment. Our technique delivers this dose using a set of non-coplanar arcs and small circular collimators. We use a standard linear accelerator in our treatments, and the adjustable treatment parameters are: isocenter location, gantry arc rotation interval, couch angle, collimator field size, and dose. The treatment planning phase of the treatment determines these parameters such that the target volume is sufficiently irradiated, and dose to surrounding healthy tissue and critical, dose-limiting structures is minimized. The attachment of a BRW localizing frame to the patient's cranium combined with CT imaging (and optionally MRI or angiography) provides the required accuracy for localizing individual structures in the treatment volume. The treatment is fundamentally 3-dimensional and requires a volumetric assessment of the treatment plan. The selection of treatment arcs relies primarily on geometric constraints and the beam's eye view concept to avoid irradiating critical structures. The assessment of a treatment plan involves isodose distributions throughout the volume and integral dose-volume histograms. We present the essential concepts of our treatment planning approach, and illustrate these in three clinical cases.
Assuntos
Neoplasias Encefálicas/radioterapia , Planejamento da Radioterapia Assistida por Computador , Técnicas Estereotáxicas , Adolescente , Adulto , Pré-Escolar , Feminino , Humanos , Masculino , Aceleradores de Partículas , Radioterapia de Alta EnergiaRESUMO
A three-dimensional analytical technique for the representation of the cranial surface based on a spherical harmonic expansion is presented. The analytical surface representation is used in conjunction with a sample iterative ray-intersection algorithm to compute the dose calculation depth. The technique is compared to other conventional techniques and it is determined that the spherical harmonic approach of approximating the cranial surface decreases the depth calculation time by approximately a factor of 60.