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Evaluation of a Tattoo-Less Setup with Surface Guidance On Breast Radiation Therapy -- A Single Institution Study

L Zhuang1*, C Breit2, (1) Northwestern Medicine Mchenry Hospital, Mchenry, IL, (2) Northwestern Medicine Lake Forest Hospital,Lake Forest, IL

Presentations

PO-GePV-M-214 (Sunday, 7/10/2022)   [Eastern Time (GMT-4)]

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Purpose: To develop a tattoo-less(TL) setup with surface guidance(SG) on breast radiation therapy (BRT) and evaluate the accuracy of the TLSG using post SG imaging shift (PSGIS).

Methods: Sixteen breast patients’ data (6 LTDIBH and 10 RT breast cases) from a community hospital were evaluated in this study. All patients were simulated without tattoo, while immobilization device was indexed on table and sharpie was utilized to mark the BB position on patient body post CT scan. Patient was asked to keep the mark till 1st fraction to confirm SG positioning and treatment couch position were acquired then. In subsequent fractions, Patient was setup against SG with couch in recorded position and translation & rotation were adjusted to within 1.0cm & 3° through re-positioning followed by applying shifts provided by SG. 2D image pair were then taken to apply 3D shifts if any. PSGIS were evaluated among directions and the effect of patient age and weight were evaluated using two-way ANOVA.PSGIS of LTDIBH and RTBRT were evaluated using paired t-test. Early indicators of large PSGIS were investigated with ROC analysis.

Results: The mean±sd of PSGIS in SI/RL/AP directions were 0.0 ± 0.4cm/0.0 ± 0.3cm/0.0 ± 0.3cm indicating a good agreement between imaging and SG setup. No statistical significant difference were found in shifts of 3 directions (p= 0.56). LTDIBH setup accuracy is comparable to that of RTBRT (p=0.33). Age (p=0.13) and weight (p=0.98) were not found to be an indicator for large PSGIS. The magnitude of PSGIS vector (MPSGISV) from the first 3 fractions were identified as an indicator for large MPSGISV through entire treatment(AUC=0.9). Therapists favored the proposed TLSG which significantly reduced the time of repetitive imaging.

Conclusion: Tattoo-less setup could efficiently setup BRT and early indicator was identified to potentially reduce the frequency of post SG imaging.

Keywords

Surface Matching

Taxonomy

Not Applicable / None Entered.

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