In radiation oncology, delivering an accurate dose to the tumor while sparing healthy tissue is essential. One often overlooked but increasingly important factor in achieving this goal is Linear Energy Transfer (LET). LET describes how radiation energy is deposited in tissue, and it plays a significant role in treatment planning for advanced modalities such as proton therapy and carbon ion therapy.
This blog explores how LET affects modern radiation therapy techniques and highlights how clinical tools like Beekley Medical’s InkRight® semi-permanent tattoos and RT- SPOT® elevated skin markers support precision in CT simulation, reduce dose distortion, and streamline the treatment planning process.
What Is LET and Why Should We Care?
LET stands for Linear Energy Transfer, and it measures the amount of energy that ionizing radiation deposits per unit length as it travels through matter, typically expressed in kiloelectron volts per micrometer (keV per micrometer).
Low LET radiation, such as X-rays and gamma rays, spreads energy over a longer path. High LET radiation, like alpha particles or heavy ions such as carbon, concentrates energy deposition in a very short distance, creating dense ionization tracks that can cause irreparable DNA damage.
In modern radiation therapy, LET has become a key consideration in emerging and advanced modalities:
- Proton therapy and carbon ion therapy feature variable LET along the particle path, with a peak at the Bragg peak where therapeutic energy is deposited.
- Steoreotactic Body Radiation Therapy (SBRT) and Stereotactic Radiosurgery (SRS) use low LET beams, but the biological effect
Understanding and accounting for LET is essential not only for effective tumor control but also for protecting adjacent healthy tissues. That means setup accuracy, marking reliability, and reproducible imaging are essential every single day.
How InkRight and RT- SPOT Fit Into LET-Aware Precision
While InkRight® semi-permanent tattoos and RT SPOT® elevated skin markers for CT simulation don’t influence LET directly, they play an important role in supporting the precision and consistency needed for LET-informed treatment plans.
As radiation therapy continues to evolve with advanced modalities and biologically optimized approaches, these tools help ensure that the dose and its biological impact are delivered exactly as planned.
InkRight® Semi-Permanent Tattoos
Tattooing remains one of the most reliable methods of permanent skin marking in radiation therapy. These small but critical marks provide consistent visual reference points throughout the entire treatment course.
Why it matters in LET-aware therapy:
In proton therapy, dose gradients near the Bragg peak are steep. A small setup deviation, even just a few millimeters, can shift a high LET region from tumor to healthy tissue.
InkRight® helps ensure stable patient positioning by offering reference points that remain visible up to 14 days, even with skin changes, washing, or movement. They minimize the need for remarking and help align daily treatment with the original simulation setup, reducing the risk of cumulative positioning drift.
In LET-aware treatments where biological impact depends on precise delivery, InkRight® semi-permanent tattoos provide a simple, yet dependable foundation for reproducibility.
RT - SPOT®: Elevated Marking That Supports Clean Dose Planning
RT SPOT® is the only elevated skin marker designed specifically for CT simulation. Its raised design helps prevent the marker from being automatically included in the body contour, a common challenge with skin markers that are not elevated. This unique feature reduces the need for manual contouring edits, which can be time-consuming and introduce variability in treatment planning.
Why it matters in LET-aware therapy:
In high LET therapies like proton or carbon ion treatment, precise dose distribution is critical. Manual contouring of markers inside the automatic body contour can introduce inaccuracies that disrupt dose calculations, especially near regions with steep dose gradients. This can be the result of not contouring the entire mark or by contouring and over-riding skin.
RT- SPOT® elevated skin markers will minimize artifact-related dose distortion due to the decreased density of the marker. They also maintain excellent visibility for image registration without compromising the integrity of dose plans. This is particularly helpful when working with multimodality image fusion and biologically optimized techniques.
RT-SPOT® helps clinicians maintain clean, efficient, and accurate treatment planning in LET-aware protocols by reducing workflow burden and supporting dose accuracy.
Precision Tools for a Biologically Complex Landscape
Radiation therapy is becoming more biologically informed with LET playing a growing role in treatment planning and outcome modeling. As planning systems and delivery techniques evolve, so must the supportive clinical tools that uphold the accuracy of those treatments.
InkRight® semi-permanent tattoos and RT - SPOT® elevated skin markers for CT simulation may seem like small components of the workflow, but they play an important role in making sure what is planned is what gets delivered. That is especially important when the biological effects of radiation vary with location and dose concentration.
Ready to Strengthen Your LET-Aware Protocols?
Whether you're implementing proton therapy, carbon ion therapy, or biologically guided radiation planning, precision tools can make a significant difference. If you're looking to improve CT simulation accuracy, reduce dose planning errors, and streamline your workflow, InkRight® and RT SPOT® offer practical solutions that support consistent and accurate treatment delivery.
Connect with us today to learn more about how these tools can make your workflow smoother and your treatments more reliable. We're here to help you get the most out of your technology and support your team's goals.
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Megan Sargalski
Marketing Communications Specialist
