Techniques to verify the correct skin areas for biopsy, treatment, recurrence and in-vivo dosimetry using an A4 plastic sheet as template

Introduction Radiotherapy (RT) is a precise treatment usually given over multiple sessions with millimetre accuracy to the planned target. Patients undergoing RT require verification of the target area prior each treatment. Imaging with kilovoltage X-rays is usually used to verify the treatment volumes of solid internal tumours, but this process is unsuitable for skin cancers as it cannot visualise skin marks. When biopsying or treating skin cancers, there is a chance that other nearby benign skin structures can be confused with the lesion of concern. Templates using transparent sheets have been used to verify the treatment area. We present a series of cases to demonstrate our skin cancer verification technique using the humble A4 plastic sheet protector. Case series: Case 1 details the use of a plastic sheet template to correctly identify lesions that require biopsy. Cases 2 and 3 describe how templates are used for in-field verification prior to electron and superficial RT treatment, respectively. Case 4 shows how stored templates can be used to quantify recurrence. Conclusion: For skin cancer planning and verification, the A4 plastic sheet protector is easy to use, reproducible, economical and storable. It serves multiple purposes: to delineate areas of biopsy and treatment, to discover whether a recurrence is in-field or not, and to also verify where in vivo dosimetry should be measured.