Prospective evaluation of the setup errors and its impact on safety margin for cervical cancer pelvic conformal radiotherapy.
Rep Pract Oncol Radiother
; 25(2): 260-265, 2020.
Article
en En
| MEDLINE
| ID: mdl-32140083
ABSTRACT
AIM:
The primary objective was to assess set-up errors (SE) and secondary objective was to determine optimal safety margin (SM).BACKGROUND:
To evaluate the SE and its impact on the SM utilizing electronic portal imaging (EPI) for pelvic conformal radiotherapy. MATERIAL ANDMETHODS:
20 cervical cancer patients were enrolled in this prospective study. Supine position with ankle and knee rest was used during CT simulation. The contouring was done using consensus guideline for intact uterus. 50â¯Gy in 25 fractions were delivered at the isocenter with ≥95% PTV coverage. Two orthogonal (Anterior and Lateral) digitally reconstructed radiograph (DRR) was constructed as a reference image. The pair of orthogonal [Anterior-Posterior and Right Lateral] single exposure EPIs during radiation was taken. The reference DRR and EPIs were compared for shifts, and SE was calculated in the X-axis, Y-axis, and Z-axis directions.RESULTS:
320 images (40 DRRs and 280 EPIs) were assessed. The systematic error in the Z-axis (AP EPI), X-axis (AP EPI), and Y-axis (Lat EPI) ranged from -12.0 to 11.8â¯mm, -10.3 to 7.5â¯mm, and -8.50 to 9.70â¯mm, while the random error ranged from 1.60 to 6.15â¯mm, 0.59 to 4.93â¯mm, and 1.02 to -4.35â¯mm. The SM computed were 7.07, 6.36, and 7.79â¯mm in the Y-axis, X-axis, and Z-axis by Van Herk's equation, and 6.0, 5.51, and 6.74â¯mm by Stroom's equation.CONCLUSION:
The computed SE helps defining SM, and it may differ between institutions. In our study, the calculated SM was approximately 8â¯mm in the Z-axis, 7â¯mm in X and Y axis for pelvic conformal radiotherapy.
Texto completo:
1
Banco de datos:
MEDLINE
Tipo de estudio:
Observational_studies
Idioma:
En
Revista:
Rep Pract Oncol Radiother
Año:
2020
Tipo del documento:
Article
País de afiliación:
India