Introduction: During free-breathing arbitrary phase, a mean motion reconstruction is acquired using not gated CT. The lack of knowledge of the tumor and organs at risk (OAR) location can generate possible random/systematic errors during RT treatment. A home-made anthropomorphic dynamic phantom was developed to assess, by TLD, the breathing of the lung district and to quantify the dose variation due to intra-fraction motion. Materials and Methods: Respiratory motion was simulated by a LEGO Mindstorms phantom, programmed in LabVIEW and equipped by 8 ribs, 1 OAR and 1 target with 4 degree of freedom. Within a treatment of 40 cGy, 3 planning strategies were compared. Static (S): CT acquired and plan delivered with phantom in static mode. Static-Real (SR): equal to the S condition but plan delivered with human breathing condition. Dynamic (D): 4DCT with breathing phantom and plan based on Maximum Intensity Projection (MIP) and the ITV generated by the junction of the target contoured in each phases. For each CT were planned and delivered an IMRT, VMAT and Helical plan to uniformly irradiate the target. Dosimetry was made using TLD GR-200 (LiF:Mg,Cu,P). Results: For each technique, data were normalized to the S IMRT plan. In SR condition, the dose delivered to the target was 89.2 ± 6.6%. Due to the motion of the target, TLD measure confirms the uncorrected dose distribution related with the plan. Between the 3 techniques, the Helical plan allows reaching a greater coverage probably due to the kinetic behavior with slow machine rotation. In D condition, the dose delivered to the target was 93.5 ± 5.1%. The internal motion was partially accounted with ITV density re-assignment. Conclusions: Respiratory motion is often assumed to be the same during CT and RT cycles. However, due to contraction of the thoracic diaphragm muscle, it can be slightly different. In this study, a dynamic phantom and TLD measures have quantified the error and dose distribution in a simulated lung treatment.
Maffei, N., Guidi, G., Ciarmatori, A., Mistretta, G.M., Ceroni, P., Bruni, A., et al. (2016). Intra-fraction motion in IMRT, VMAT and helical tomotherapy: In vivo dosimetry using TLD and LEGO phantom. PHYSICA MEDICA, 32, 38-41 [10.1016/j.ejmp.2016.01.133].
Intra-fraction motion in IMRT, VMAT and helical tomotherapy: In vivo dosimetry using TLD and LEGO phantom
GUIDI, GABRIELEProject Administration
;CIARMATORI, ALBERTOInvestigation
;BALDAZZI, GIUSEPPEProject Administration
;COSTI, TIZIANAProject Administration
2016
Abstract
Introduction: During free-breathing arbitrary phase, a mean motion reconstruction is acquired using not gated CT. The lack of knowledge of the tumor and organs at risk (OAR) location can generate possible random/systematic errors during RT treatment. A home-made anthropomorphic dynamic phantom was developed to assess, by TLD, the breathing of the lung district and to quantify the dose variation due to intra-fraction motion. Materials and Methods: Respiratory motion was simulated by a LEGO Mindstorms phantom, programmed in LabVIEW and equipped by 8 ribs, 1 OAR and 1 target with 4 degree of freedom. Within a treatment of 40 cGy, 3 planning strategies were compared. Static (S): CT acquired and plan delivered with phantom in static mode. Static-Real (SR): equal to the S condition but plan delivered with human breathing condition. Dynamic (D): 4DCT with breathing phantom and plan based on Maximum Intensity Projection (MIP) and the ITV generated by the junction of the target contoured in each phases. For each CT were planned and delivered an IMRT, VMAT and Helical plan to uniformly irradiate the target. Dosimetry was made using TLD GR-200 (LiF:Mg,Cu,P). Results: For each technique, data were normalized to the S IMRT plan. In SR condition, the dose delivered to the target was 89.2 ± 6.6%. Due to the motion of the target, TLD measure confirms the uncorrected dose distribution related with the plan. Between the 3 techniques, the Helical plan allows reaching a greater coverage probably due to the kinetic behavior with slow machine rotation. In D condition, the dose delivered to the target was 93.5 ± 5.1%. The internal motion was partially accounted with ITV density re-assignment. Conclusions: Respiratory motion is often assumed to be the same during CT and RT cycles. However, due to contraction of the thoracic diaphragm muscle, it can be slightly different. In this study, a dynamic phantom and TLD measures have quantified the error and dose distribution in a simulated lung treatment.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
