Coding Radiation Treatment Modality - 1st Course Therapy (Archived)
FCDS has been working diligently to remind registrars to document the Phase I Treatment Modality (source of radiation) in the Treatment Text for Radiation for a number of years – even before the new radiation modality codes were introduced along with coding of 3 phases of radiation therapy at CoC Accredited Cancer Programs.
The new radiation modality codes ‘fixed’ some of the previous misclassification. The biggest problem with the old codes is that they mixed radiation techniques (how radiation is delivered) with the modality (the source of the radiation). Since the new modality codes were introduced there has also been a lot of confusion over presumptive modalities (source of radiation) based only on the Megavoltage rate (MV). This presumptive radiation source is not 100% accurate. And, registrars mix MV with MeV which are abbreviated different things.
The energy of diagnostic and therapeutic gamma- and X-rays is expressed in kilovolts or megavolts (kV or MV), while the energy of therapeutic electrons is expressed in terms of mega-electron volts (MeV). The current convention is to use MV for photons and MeV for electrons. Orthovoltage is usually expressed in kV or kVp.
External beam radiation therapy usually is classified as orthovoltage or megavoltage radiotherapy, based on the energy of the photon. Orthovoltage machines produce x-rays with an energy of 150 to 500 kVp; megavoltage radiation emits photons with an average energy greater than 1 million electron volts (1 MeV).
Radiation may come from a unit (external radiation, teletherapy, beam radiation), may be placed inside or next to the tumor site (internal radiation, brachytherapy), or may use unsealed radioactive materials that go throughout the body (systemic radiation therapy). These are techniques that use various modalities (sources).
X-rays are created by units called linear accelerators. Electrons are produced by linear accelerators, without the xray target in place. Electron beams are commonly used to treat superficial tumors and special skin cancers.
Megavoltage Radiation Therapy (MRT) is a modality in which radiation is delivered by an MRT unit. An MRT unit can be a linear accelerator, cobalt unit, particle accelerator or other piece of medical equipment operating at an energy level equal to or greater than 1.0 million electron volts (megavolts or MeV). Some MRT units are multipurpose and can deliver radiation in multiple techniques such as IORT, Stereotactic Radiosurgery or standard linear accelerator. Some units are designed to emit only electrons – use in operating rooms (IORT) for example.
Megavoltage x-rays have lower biological effectiveness than Orthovoltage x-rays. And Photons are attenuated higher than Megavoltage x-rays. So, Megavoltage x-rays are preferred for treatment of deep tumors than lower energy photons. The Megavoltage penetrates further with a lower skin dosage. This keeps surrounding tissue from being damaged while delivering the highest possible dose to the target tumor, tumor bed or metastasis.
Lower levels of MV or Megavoltage in the ranges noted for presumed Photon source therapies particularly in the 2MV-10MV range can be reached without the use of photons. These ranges can be reached using conventional electrons depending on the make and model of linear accelerator and its calibration.
Adding to the frustration is that it is often impossible to find the radiation source in the radiation summary report and records – was the source of radiation electrons, photons, protons, orthovoltage or some mixed modality? And what is the difference between modality and technique?
High-Energy Photon Beam is the most common method for delivery of radiation to treat cancer – primary tumor or metastatic site(s). But External Beam Radiation can come from several different sources; Cobalt, Cesium, Orthovoltage, Electrons, Photons, Neutrons, and Gamma Knife or Stereotactic Radiotherapy. Sometimes there is even a mix of electrons and photons.
There is even a new ‘technique’ not a new modality but a new technique, called FLASH-RT that delivers ultra-high dose radiation to a target with a single ultra-high dose of radiation therapy in one visit.
The dose-rate of deliver of radiation is 400-times more rapid than conventional radiation therapy. Delivery is measured in microseconds not minutes or seconds. This new technique is expected to revolutionize radiation therapy.
All said and done, FCDS has decided that it is best for all of us to just go along with the guidelines the CoC has promoted for presumptive photon modality based on range of MV rather than trying to get registrars to document the radiation source (modality) more clearly in text – especially when it is often not available.
Therefore, FCDS would like registrars to use the below table to determine modality using photons and MV so we are in synch with the CoC and because this is a CoC data item. Further clarifications may come at a later date. Text documentation using the specified MV rate in the below table is sufficient. When other sources are used, please be sure to apply the correct Radiation Modality Code in accordance with the Radiation Regional Radiation Modality Codes published in the FCDS DAM and in Appendix R of the 2023 STORE Manual.
Here is another table that may be of some help for folks who have annotation of devices, machines, products or techniques that are not modality. Here is the conversion to modality for some common devices, techniques.
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