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1.
Pract Radiat Oncol ; 5(6): e689-95, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26209122

RESUMO

PURPOSE: Stereotactic radiation therapy is an established treatment technique for intracranial malignancies. We evaluated a new intracranial immobilization system with an emphasis on determining the intrafraction motion and the correlation of this motion with treatment time. METHODS AND MATERIALS: Patients were immobilized using the trUpoint ARCH fixation system (CIVCO Medical Solutions). We collected data from 85 lesions in 73 patients treated between November 2011 and December 2013. Sixty-nine of 73 patients (95%) used the complete mask system; for the remaining 4 patients, the system had to be adapted. Patients were treated using volumetric modulated arc therapy stereotactic radiation therapy on a TrueBeam linear accelerator (Varian Medical Systems, Palo Alto, CA). Fraction doses of 2-8 Gy were applied in 4-30 fractions. Daily cone beam computed tomography imaging was performed before the treatment and was matched to the reference computed tomography using a 6-degrees-of-freedom automatching procedure. Additionally, posttreatment cone beam computed tomography scans were performed to assess intrafraction motion for 67 patients (375 fractions). RESULTS: The average 3-dimensional setup error was 2.1 ± 2.9 mm. The mean pitch and roll was -0.1 ± 0.7° and 0.2 ± 0.7°. A total of 98.0% of the pitch values and 98.9% of the roll values were <1.5°. Mean intrafractional motion was 0.51 mm (±0.27) and mean treatment time was 10.1 minutes (±1.4). The maximum intrafractional motion was 2.0 mm in the longitudinal direction; 95% of the total shifts were <1.4 mm. The linear regression showed a weak but significant influence (R(2) = 0.26, P = .01) of the treatment time on the total intrafractional shift. CONCLUSIONS: The new intracranial immobilization system appears to be robust in terms of setup accuracy, intrafraction motion, and repositioning of the mask system.


Assuntos
Neoplasias Encefálicas/radioterapia , Imobilização/métodos , Neoplasias/radioterapia , Posicionamento do Paciente , Radiocirurgia , Erros de Configuração em Radioterapia/prevenção & controle , Adulto , Idoso , Idoso de 80 Anos ou mais , Neoplasias Encefálicas/secundário , Fracionamento da Dose de Radiação , Humanos , Pessoa de Meia-Idade , Neoplasias/patologia , Aceleradores de Partículas , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem , Radioterapia de Intensidade Modulada , Respiração , Carga Tumoral
2.
Radiat Oncol ; 9: 229, 2014 Nov 11.
Artigo em Inglês | MEDLINE | ID: mdl-25384898

RESUMO

PURPOSE: To evaluate PTV margins for hypofractionated IGRT of prostate comparing kV/kV imaging or CBCT. PATIENTS AND METHODS: Between 2009 and 2012, 20 patients with low- (LR), intermediate- (IR) and high-risk (HR) prostate cancer were treated with VMAT in supine position with fiducial markers (FM), endorectal balloon (ERB) and full bladder. CBCT's and kV/kV imaging were performed before and additional CBCT's after treatment assessing intra-fraction motion. CTVP for 5 patients with LR and CTVPSV for 5 patients with IR/HR prostate cancer were contoured independently by 3 radiation oncologists using MRI. The van Hark formula (PTV margin =2.5Σ +0.7σ) was applied to calculate PTV margins of prostate/seminal vesicles (P/PSV) using CBCT or FM. RESULTS: 172 and 52 CBCTs before and after RT and 507 kV/kV images before RT were analysed. Differences between FM in CBCT or in planar kV image pairs were below 1 mm. Accounting for both random and systematic uncertainties anisotropic PTV margins were 5-8 mm for P (LR) and 6-11 mm for PSV (IR/HR). Random uncertainties like intra-fraction and inter-fraction (setup) uncertainties were of similar magnitude (0.9-1.4 mm). Largest uncertainty was introduced by CTV delineation (LR: 1-2 mm, IR/HR: 1.6-3.5 mm). Patient positioning using bone matching or ERB-matching resulted in larger PTV margins. CONCLUSIONS: For IGRT CBCT or kV/kV-image pairs with FM are interchangeable in respect of accuracy. Especially for hypofractionated RT, PTV margins can be kept in the range of 5 mm or below if stringent daily IGRT, ideally including prostate tracking, is applied. MR-based CTV delineation optimization is recommended.


Assuntos
Tomografia Computadorizada de Feixe Cônico/métodos , Fracionamento da Dose de Radiação , Marcadores Fiduciais , Neoplasias da Próstata/patologia , Neoplasias da Próstata/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Seguimentos , Humanos , Masculino , Posicionamento do Paciente , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/metabolismo , Radioterapia de Intensidade Modulada
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