ABSTRACT
BACKGROUND: To evaluate the daily total error shift patterns on post-prostatectomy patients undergoing image guided radiotherapy (IGRT) with a diagnostic quality computer tomography (CT) on rails system. METHODS: A total of 17 consecutive post-prostatectomy patients receiving adjuvant or salvage IMRT using CT-on-rails IGRT were analyzed. The prostate bed's daily total error shifts were evaluated for a total of 661 CT scans. RESULTS: In the right-left, cranial-caudal, and posterior-anterior directions, 11.5%, 9.2%, and 6.5% of the 661 scans required no position adjustments; 75.3%, 66.1%, and 56.8% required a shift of 1 - 5 mm; 11.5%, 20.9%, and 31.2% required a shift of 6 - 10 mm; and 1.7%, 3.8%, and 5.5% required a shift of more than 10 mm, respectively. There was evidence of correlation between the x and y, x and z, and y and z axes in 3, 3, and 3 of 17 patients, respectively. Univariate (ANOVA) analysis showed that the total error pattern was random in the x, y, and z axis for 10, 5, and 2 of 17 patients, respectively, and systematic for the rest. Multivariate (MANOVA) analysis showed that the (x,y), (x,z), (y,z), and (x, y, z) total error pattern was random in 5, 1, 1, and 1 of 17 patients, respectively, and systematic for the rest. CONCLUSIONS: The overall daily total error shift pattern for these 17 patients simulated with an empty bladder, and treated with CT on rails IGRT was predominantly systematic. Despite this, the temporal vector trends showed complex behaviors and unpredictable changes in magnitude and direction. These findings highlight the importance of using daily IGRT in post-prostatectomy patients.
Subject(s)
Prostatic Neoplasms/radiotherapy , Radiotherapy Planning, Computer-Assisted/methods , Tomography, X-Ray Computed/methods , Aged , Algorithms , Humans , Male , Middle Aged , Postoperative Period , Prostate/radiation effects , Prostatectomy/methods , Reproducibility of Results , Software , Treatment OutcomeABSTRACT
Since its discovery, ionizing radiation has been a cornerstone of cancer treatment. In step with technological advances, radiation therapy has strived to increase its therapeutic ratio. With the advent of 3D and cross-sectional imaging, and the ability to modulate the radiation beam, the current age of radiation oncology was initiated, promising better tumor control rates with fewer side effects. However, these ever more precise and conformal treatments have also revealed the importance of accounting for organ and tumor motion. Efforts to understand and compensate for the uncertainties caused by movement are required to ensure accurate conformal radiation therapy. This review will explore the current and future directions of image-guided radiation therapy, whose goal is to increase the accuracy of radiotherapy.
Subject(s)
Neoplasms/radiotherapy , Radiotherapy, Computer-Assisted/methods , Humans , Image Processing, Computer-Assisted/instrumentation , Image Processing, Computer-Assisted/methods , Radiotherapy, Computer-Assisted/instrumentationABSTRACT
Nos tratamentos por radiaçäo, nos quais a regiäo ocular é exposta ao campo de tratamento, uma proteçäo é colocada entre a pálpebra e o globo ocular para proteger as estruturas oculares mais sensíveis à radiaçäo. Isto é importante, pois uma dose de 500 cGy na córnea pode provocar catarata. A efetividade de uma proteçäo ocular construida em chumbo e uma outra proteçäo comercial (Ace Medical Supply Co., New York) foi avaliada para feixes de elétrons de 5,4 MeV e 3,7 MeV. Na avaliaçäo do efeito de concavidade, verificou-se que o formato côncavo desse tipo de proteçäo permite que o dobro de radiaçäo seja transmitida, comparada a uma proteçäo plana. A proteçäo comercial testada apresentou proteçäo suficiente para o feixe de 3,7 MeV/ entretanto, para o feixe de 5,4 MeV a dose na interface proteçäo-material absorvedor foi 56 por cento da dose na profundidade de dose máxima, dmax, sem a proteçäo. A espessura encontrada para uma dose transmitida de aproximadamente 5 por cento da dose em dmax`, para uma proteçäo desse tipo, para este último feixe, foi de 3mm em chumbo. Um aumento significativo da dose na interface externa da proteçäo ocorre devido ao efeito de retroespalhamento dos elétrons. Para que este efeito seja reduzido a um nível de dose próximo à dose em dmax, espessura mínima de 3mm de poliestireno é necessária para ambos os feixes testados
Subject(s)
Eye Protective Devices/classification , Electrons , Whole-Body Irradiation/adverse effects , RadiationABSTRACT
Este trabalho apresenta os resultados da determinação experimental dos coeficientes de conversão da grandeza de calibração kerma no ar para a nova grandeza da ICRU de monitoração de área, H*(d). As medidas foram realizadas nas profundidades 10, 50 e 60 mm de uma esfera de PMMA de 30 cm de diâmetro em feixes de raios-X de radiodiagnóstico.
