Volume : VII, Issue : XI, November - 2018

Inter fraction set up errors and organ motion in Carcinoma Rectum- Role of Image Guidance

Dr Shailley A S

Abstract :

 Introduction- New technological advances in radiation have its own limitations. We give large Planning Target Volume (PTV) margins to overcome set up errors and organ motion which in turn lead to more organs at risk toxicity. If there is quantification of set up errors and organ motion PTV margins can be reduced accordingly which is possible with image guidance. Here we are evaluating the role of image guidance by assessing bone shifts and interfraction urinary bladder motion in pelvic radiotherapy for Carcinoma Rectum.

Material and methods- Six patients of Carcinoma Rectum from December, 2014 to June, 2015 who gave consent for treatment with Image Guided Radiotherapy were taken for interfraction set up errors. 10 pre treatment CBCT scans per patient were analyzed. Values were registered on three principal axes, left-right(x), supero-inferior (y) and antero posterior (z) axes values for inter-fraction set up errors. Amongst organs at risk we have evaluated urinary bladder and assessed interfraction motion by the differences in bladder volume and translation of the bladder wall in three dimensions in comparison to the baseline PCT.

Results- Mean (standard deviation) bone shifts noted were 0.34± 0.26 cm, 0.34± 0.13 cm and 0.22 ± 0.10 cm in x, y and z axis respectively. There was an overall decrease in mean CBCT bladder volume compared to PCT bladder volume. However the difference between PCT mean (214.42±84.17) and CBCT mean (203.80±83.71) was not statistically significant (p=0.706). Maximum movements were seen in superior direction of bladder wall.

Conclusion- Prescribed PTV margins are able to cover set up errors and organ motion, however exceptional errors need to be addressed on time.

·         During treatment patient should be periodically followed up and patients’ dietary, bowel and bladder habits and weight loss should be observed and noted.

·         Alternate day CBCT is a good option especially patient with frequent change in bowel and bladder habits.

·         Adaptive strategies based on first and second week CBCTs should be undertaken.

The effect of organ motion on adjacent organs warrants further studies. 

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Article: Download PDF    DOI : https://www.doi.org/10.36106/gjra  

Cite This Article:

Inter fraction set up errors and organ motion in Carcinoma Rectum- Role of Image Guidance , Dr Shailley A S , GLOBAL JOURNAL FOR RESEARCH ANALYSIS : Volume-7 | Issue-11 | November-2018

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