Inaccuracies during the planning process can lead to dose inaccuracies during treatment. Despite technological advancements over the years, the increasing complexity of these technologies and the potential for human error throughout the treatment process can still result in mistakes.
The primary goal of radiation therapy is to target the tumor or tumor bed while sparing nearby healthy tissue and the organs at risk. This requires the radiation oncologist to define the treatment area and determine the total dose. The radiation therapist acquires the CT simulation that dosimetry uses to plan the treatment which is then verified by physics. All of this occurs before the first day of treatment when the treatment therapist ensures precise patient positioning and delivers the prescribed dose of radiation.
Before the CT simulation, a radiation therapist utilizes various tools to ensure treatment accuracy. They position the patient on the CT couch in a way that can be reproduced exactly on the treatment table. This is done using immobilization devices, thermoplastic masks, and skin markers that can be aligned with lasers on the walls and ceiling. The skin markers are used to outline field borders, breast tangents, scars, as well as isocenters and 3-point setups.
Distinguishing skin marker from skin line
However, because these skin markers lie flat on the skin, they are included within the automatic body contour established at the start of treatment planning. When the treatment dose is calculated, the density of the markers is incorrectly factored into the plan, potentially leading to dose calculation errors.
To compensate for this, the dosimetrist must contour the skin marker and override the density to the density of air. If the skin marker is not perfectly contoured, dose perturbation will occur, especially with electron plans. This process can be extremely time-consuming and may introduce another source of dose inaccuracy. This can occur when the marker is not completely contoured, or the contour includes skin or a portion of a thermoplastic mask.
Raised to be excluded from the automatic body contour
Beekley Medical’s RT-SPOT® family of skin markers for radiation oncology are elevated from the skin line on a radiolucent foam backing. This foam backing raises the imaging portion of the linear marker away from the skin, keeping it outside the automatic body contour.
A physicist from Northfield, Minnesota, commented that they love the spacing between the body tissue and the radiopaque line, as it allows for a clean auto-contour of the body without artifacts. They went on to say, “They save time for dosimetry and physicians in contouring and are helpful for surface image guidance fidelity.”
A dosimetrist from Bloomington, Indiana, values how RT-SPOTs save time for the entire treatment planning team, reduce the need for plan rework, and enhance overall accuracy. “It has saved the dosimetrists a lot of contouring time, and RT-SPOT line is very flexible, so it allows the physicians to shape the targeted area more easily.”
To learn more about RT-SPOTs including our new RT-SPOT Pellets and RT-SPOT Crosshair, contact your Radiation Oncology Account Manager at 1.800.233.5539 or email info@beekley.com.
Megan Sargalski
Marketing Communications Specialist
