Tattoo free setup for partial breast irradiation: A feasibility study

Abstract

Purpose Patients undergoing external beam accelerated partial breast irradiation (APBI) receive permanent tattoos to aid with daily setup alignment and verification. With the advent of three‐dimensional (3D) body surface imaging and two‐dimensional (2D) x‐ray imaging‐based matching to surgical clips, tattoos may not be necessary to ensure setup accuracy. We compared the accuracy of conventional tattoo‐based setups to a patient setup without tattoos. Materials/methods Twenty consecutive patients receiving APBI at our institution from July 10, 2017 to February 13, 2018 were identified. All patients received tattoos per standard of care. Ten patients underwent setup using tattoos for initial positioning followed by surface imaging and 2D matching of surgical clips. The other ten patients underwent positioning using surface imaging followed by 2D matching without reference to tattoos. Overall setup time and orthogonal x‐ray‐based shifts after surface imaging per fraction were recorded. Shift data were used to calculate systematic and random error. Results Among ten patients in the “no tattoo” group, the average setup time per fraction was 6.83 min vs 8.03 min in the tattoo cohort (P < 0.01). Mean 3D vector shifts for patients in the “no tattoo” group were 4.6 vs 5.9 mm in the “tattoo” cohort (P = NS). Mean systematic errors in the “no tattoo” group were: 1.2 mm (1.5 mm SD) superior/inferior, 0.5 mm (1.6 mm SD) right/left, and 2.3 mm (1.9 mm SD) anterior/posterior directions. Mean systematic errors in the “tattoo” group were: 0.8 mm (2.2 mm SD) superior/inferior, 0.3 mm (2.5 mm SD) right/left, and 1.4 mm (4.4 mm SD) anterior/posterior directions. The random errors in the “no tattoo” group ranged from 0.6 to 0.7 mm vs 1.2 to 1.7 mm in the “tattoo” group. Conclusions Using both surface imaging and 2D matching to surgical clips provides excellent accuracy in APBI patient alignment and setup verification with reduced setup time relative to the tattoo cohort. Skin‐based tattoos may no longer be warranted for patients receiving external beam APBI.

Recent advances in Surface Guided Radiation Therapy

“…There is a broad agreement on the supremacy of SGRT over 3-point laser-based patient setup, when the surface serves as a surrogate for the target positioning, i.e. breast and other skin-near targets [13,16,[21][22][23][24][25][26][27][28][29][30]. For deeper situated targets, surface imaging should be used with caution [13,22,31,32].…”

“…In a recent study, the target registration error (TRE) for a SGRT system agreed with the kV clip-based TRE within less than 3 mm. Furthermore, the combination of SGRT and 2D X-ray matching to surgical clips allowed for accurate alignment and setup verification without the need for skin-based tattoos [26]. In the absence of surgical clips in the lumpectomy area, SGRT still appears to be a potentially valuable image guidance approach for patients treated with APBI when they experience < 10% changes in surgical cavity volume between computed tomography (CT) simulation and treatment [21].…”

“…Regarding setup of breast cancer patients, studies comparing laser alignment with surface imaging report a reduction of positioning errors for skin and clip alignment [ 23 – 26 ] by around 40% on average, with absolute errors (1SD) for all studies being smaller than 4 mm, verified with kV orthogonal imaging [ 29 , 30 , 33 , 34 ], portal imaging [ 16 , 27 , 30 ], or cone-beam computed tomography (CBCT) [ 13 ]. In addition to accurate isocenter positioning, the surface imaging provides guidance for correcting patient posture, i.e.…”

“…The SGRT workflow within an NAL (No Action Level) imaging protocol has shown the potential to reduce the frequency of IGRT, and thus spare additional imaging dose [ 16 , 30 , 31 ]. Advances in surface imaging for positioning of breast cancer patients have recently led to a tattoo-free workflow and reduced time for patient setup compared to laser alignment [ 26 ].…”

Accuracy of surface‐guided patient setup for conventional radiotherapy of brain and nasopharynx cancer

“…Most clinical applications involve patient setup and motion monitoring either for rigid anatomy with a fixed relationship between the skin surface and deep-seated lesions, such as brain cancer, [4][5][6][7] or for superficial lesions, such as breast cancer. [8][9][10][11] For patient setup, the external body contour from the planning CT is mostly used as the reference, while for motion monitoring, an on-site surface reference is usually captured, excluding the residual setup error. The OSI has recently been applied to achieve tattoo-free SGRT patient setup and motion monitoring as a replacement of conventional tattoo-laser alignment setup.…”