RESUMEN
PURPOSE: There are several potential advantages of using 18-fluor-fluorodeoxiglucose (18F-FDG) PET for target volume contouring, but before PET-based gross tumor volumes (GTVs) can reliably and reproducibly be incorporated into high-precision radiotherapy planning, operator-independent segmentation tools have to be developed and validated. The purpose of the present work was to apply the adaptive to the signal/background ratio (R(S/B)) thresholding method for head and neck tumor delineation, and compare these GTV(PET) to reference GTV(CT) volumes in order to assess discrepancies. MATERIALS AND METHODS: A cohort of 19 patients (39 lesions) with a histological diagnosis of head and neck cancer who would undergo definitive concurrent radiochemotherapy or radical radiotherapy with intensity-modulated radiotherapy technique (IMRT), were enrolled in this prospective study. Contouring on PET images was accomplished through standardized uptake value (SUV)-threshold definition. The threshold value was adapted to R(S/B). To determine the relationship between the threshold and the R(S/B), we performed a phantom study. A discrepancy index (DI) between both imaging modalities, overlap fraction (OF) and mismatch fraction (MF) were calculated for each lesion and imaging modality. RESULTS: The median DI value for lymph nodes was 2.67 and 1.76 for primary lesions. The OF values were larger for CT volumes than for PET volumes (p < 0.001), for both types of lesions. The MF values were smaller for CT volumes than for PET volumes (p < 0.001), for both types of lesions. The GTV(PET) coverage (OF(PET)) was strongly correlated with the lesion volume (GTV(CT)) for metastatic lymph nodes (Pearson correlation = 0.665; p < 0.01). For smaller lesions, despite the GTV volumes were relatively larger on PET than in CT contours, the coverage was poorer. Accordingly, the MF(PET/CT) was negatively correlated with the lesion volume for metastatic lymph nodes. CONCLUSIONS: The present study highlights the considerable challenges involved in using FDG PET imaging for the delineation of GTV in head and neck neoplasms. The methods that rely mainly on SUV(max) for thresholding, as the RS/B method, are very sensitive to partial volume effects and may provide unreliable results when applied on small lesions.
Asunto(s)
Carcinoma/diagnóstico por imagen , Carcinoma/patología , Fluorodesoxiglucosa F18 , Neoplasias de Cabeza y Cuello/diagnóstico por imagen , Neoplasias de Cabeza y Cuello/patología , Planificación de la Radioterapia Asistida por Computador/métodos , Carcinoma/radioterapia , Estudios de Cohortes , Femenino , Neoplasias de Cabeza y Cuello/radioterapia , Humanos , Ganglios Linfáticos/diagnóstico por imagen , Ganglios Linfáticos/patología , Metástasis Linfática , Masculino , Imagen Multimodal , Fantasmas de Imagen , Tomografía de Emisión de Positrones/métodos , Dosificación Radioterapéutica , Radioterapia Guiada por Imagen/métodos , Tomografía Computarizada por Rayos X , Carga TumoralRESUMEN
Over the past two decades radiation oncology has evolved into a high-technology, multi-disciplinary field of medicine which requires not only the command of highly complex modes of treatment but also the grouping together of skilled teams of medical professionals who are able to provide individualized assistance to the cancer patient. Supportive care in Radiation Oncology integrates key aspects of diagnosis and treatment with the objective of alleviating physical and psycho-social co-morbidities inherent in the disease, as well as the treatment of the cancer. This article addresses the impact of treatment on the individual and the issues facing health-provision professionals who provide clinical and supportive care. Future directions for clinical development are discussed.