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Análise da exposição de planeamento e verificação em radioterapia em doentes com carcinoma da cabeça e pescoço
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Abstract(s)
Introdução: A radioterapia (RT) é uma das principais modalidades escolhidas para o tratamento radical, adjuvante ou neoadjuvante dos tumores de células escamosas da cabeça e pescoço (HNSCC, do inglês Head and Neck Squamous Cell Carcinoma). Durante o tratamento de RT o doente passa por várias etapas, desde a definição do posicionamento à entrega da dose de tratamento. Apesar da dose de tratamento ser bastante superior à dose cumulativa do planeamento e da verificação, estas exposições deverão ser contabilizadas para que se possa cumprir o princípio de manter a dose “tão baixa quanto razoavelmente possível”. Surge assim a necessidade e importância dos valores de dose da tomografia computorizada de planeamento (CTp) e do cone beam computorized tomography (CBCT) serem avaliados e ainda, à semelhança do que já existe para os exames de diagnóstico, serem definidos níveis de referência de diagnóstico (DRLs, do inglês, diagnostic reference levels) para RT.
Objetivo: Avaliar os valores de dose da CTp e do CBCT de doentes com HNSCC no serviço de RT da Unidade Local de Saúde do São João (ULSSJ) e estabelecer DRLs para o serviço.
Metodologia: Foram incluídos doentes adultos com diagnóstico de HNSCC que realizaram tratamento de RT a título radical no serviço de RT da ULSSJ, tendo sido realizada caracterização clínica e dos procedimentos realizados (CTp e CBCT). Foram obtidos os valores do índice volumétrico de dose de CT (CTDIvol, do inglês volumetric CT dose index) e o produto dose-comprimento (DLP do inglês, dose lenght-product) para a CTp e CBCT, CBCT, com cálculo do percentil 75 (P75th) e do percentil 50 (P50th), e comparação com os valores descritos na literatura. Foi ainda avaliada a qualidade de imagem de forma objetiva, com definição de regiões de interesse (ROI, do inglês Region Of Interess) nas imagens de CTp e análise de valores de sinal e de ruído.
Resultados: Foram incluídos 35 doentes diagnosticados com HNSCC com média de idade de 63,3±10 anos, dos quais 87,5% eram do sexo masculino. Obteve-se um CTDIvol mediano de 9,46mGy e um DLP mediano de 341,01 mGy.cm; o terceiro quartil foi de 11,3mGy e 499,825mGy.cm, respetivamente. O valor de CTDIvol mediano foi significativamente inferior às DRLs reportadas na literatura p<0,001. A mediana de DLP foi também significativamente inferior às reportadas p<0,001. Quanto à qualidade de imagem, foi possível verificar
diferenças estatisticamente significativas entre o ruído obtido para as diferentes estruturas (F (1,24;42,15) = 702,1; p<0,001; p2=0,95).
Conclusão: Os valores do serviço da ULSSJ foram significativamente inferiores aos valores encontrados na literatura. Pela escassez de dados quer a nível de DRLs do CBCT quer a nível da qualidade de imagem, serão necessários estudos futuros que permitam a sua quantificação e otimização.
Introduction: Radiotherapy (RT) is one of the main modalities chosen for the radical, adjuvant or neoadjuvant treatment of head and neck squamous cell tumours (HNSCC). During RT treatment, the patient goes through several stages, from the definition of positioning to the delivery of the treatment dose. Although the treatment dose is much higher than the cumulative dose from planning and verification, these exposures must be accounted for in order to fulfil the principle of keeping the dose ‘as low as reasonably achievable’. This raises the need and importance of evaluating the dose values of planning computed tomography (CTp) and cone beam computed tomography (CBCT) and, similarly to what already exists for diagnostic exams, defining diagnostic reference levels for RT. Objective: Evaluate the dose values of CTp and CBCT of patients with HNSCC in the RT department of the Unidade Local de Saúde do São João (ULSSJ) and to establish diagnostic reference levels (DRLs) for the department. Methodology: Adult patients with a diagnosis of HNSCC who underwent radical RT treatment at the ULSSJ RT department were included, clinical and procedural (CTp and CBCT) characterisation was performed. The volumetric CT dose index (CTDIvol) and the dose-length product (DLP) were obtained for CTp and CBCT, 75th percentile (P75th) and the 50th percentile (P50th) were calculated and then comparing them with the values described in the literature. Image quality was also objectively assessed by defining regions of interest (ROI) in the CTp images and analysing signal and noise values. Results: This study included 35 patients diagnosed with HNSCC with a mean age of 63.3±10 years, 87.5% of whom were male. A median CTDIvol of 9.46mGy and a median DLP of 341.01 mGy.cm were obtained; the third quartile was 11.3mGy and 499.825mGy.cm, respectively. The median CTDIvol value was significantly lower than the DRLs reported in the literature p<0.001. The median DLP was also significantly lower than the DRLs reported p<0.001. As for image quality, statistically significant differences were found between the noise obtained for the different structures (F(1.24;42.15)=702.1; p<0.001; p2=0.95). Conclusion: The ULSSJ service values were significantly lower than those found in the literature. Due to the scarcity of data on both CBCT DRLs and image quality, future studies will be needed to quantify and optimise them.
Introduction: Radiotherapy (RT) is one of the main modalities chosen for the radical, adjuvant or neoadjuvant treatment of head and neck squamous cell tumours (HNSCC). During RT treatment, the patient goes through several stages, from the definition of positioning to the delivery of the treatment dose. Although the treatment dose is much higher than the cumulative dose from planning and verification, these exposures must be accounted for in order to fulfil the principle of keeping the dose ‘as low as reasonably achievable’. This raises the need and importance of evaluating the dose values of planning computed tomography (CTp) and cone beam computed tomography (CBCT) and, similarly to what already exists for diagnostic exams, defining diagnostic reference levels for RT. Objective: Evaluate the dose values of CTp and CBCT of patients with HNSCC in the RT department of the Unidade Local de Saúde do São João (ULSSJ) and to establish diagnostic reference levels (DRLs) for the department. Methodology: Adult patients with a diagnosis of HNSCC who underwent radical RT treatment at the ULSSJ RT department were included, clinical and procedural (CTp and CBCT) characterisation was performed. The volumetric CT dose index (CTDIvol) and the dose-length product (DLP) were obtained for CTp and CBCT, 75th percentile (P75th) and the 50th percentile (P50th) were calculated and then comparing them with the values described in the literature. Image quality was also objectively assessed by defining regions of interest (ROI) in the CTp images and analysing signal and noise values. Results: This study included 35 patients diagnosed with HNSCC with a mean age of 63.3±10 years, 87.5% of whom were male. A median CTDIvol of 9.46mGy and a median DLP of 341.01 mGy.cm were obtained; the third quartile was 11.3mGy and 499.825mGy.cm, respectively. The median CTDIvol value was significantly lower than the DRLs reported in the literature p<0.001. The median DLP was also significantly lower than the DRLs reported p<0.001. As for image quality, statistically significant differences were found between the noise obtained for the different structures (F(1.24;42.15)=702.1; p<0.001; p2=0.95). Conclusion: The ULSSJ service values were significantly lower than those found in the literature. Due to the scarcity of data on both CBCT DRLs and image quality, future studies will be needed to quantify and optimise them.
Description
Keywords
Radioterapia Tomografia computorizada de feixe cónico Níveis de referência de diagnóstico Qualidade de imagem Neoplasias de cabeça e pescoço Radiotherapy Head and neck neoplasms Cone-beam computed tomography Diagnostic reference levels Image Quality