Oncology & Hematology Coding Alert

The emergence of intensity modulated radiation therapy (IMRT) has resulted in the need for more dosimetry calculations 77300 (Basic radiation dosimetry calculation) and 77331 (Special dosimetry).
 
Radiation oncology practices should code dosimetry calculations based on the number of ports and fields. Dosimetry is used to determine the amount of radiation that needs to be administered to a specific area, including beam or implant orientations and exposures, tissue inhomogeneities, isodose strength, and distribution. It is part of the overall preparation prior to the delivery of radiation, which also includes simulations. Unlike simulations, dosimetry may be repeated during the course of treatment because of changes in tumor volume, for example, and each calculation may be paid separately.
 
Code 77300 is used more often because it represents a more typical calculation than 77331, which uses special radiation measuring and monitoring devices.
 
Basic dosimetry includes eight types of dose calculations:
  

Central axis depth dose
  

Time dose factor
  

Nominal standard dose
  

Gap calculation
  

Off-axis factor
  

Tissue inhomogeneity factors
  

Monitor unit calculation for electron field
  

Breast angle calculation.

 
Some payers reimburse for 77300 each time the calculation is performed, while others will pay only once per area treated. For example, if two dosimetry calculations are performed on the same port, a payer may allow 77300 to be reported twice.
 
Generally, however, payers (including Medicare) will reimburse for dosimetry calculations once per port, per treatment setup, says Jim Hugh, vice president of AMAC, a coding consulting firm in Atlanta.
 
Some practices may cap the number of dosimetry calculations reported to avoid payer scrutiny, but this is not advisable. "The number of times 77300 is performed is the number of times it should be reported, with few exceptions," says Carl Bogardus, MD, president of the Cancer Care Network, an oncology practice management consulting firm in Midwest City, Okla.
 
To illustrate, dosimetry calculations performed on a brain tumor with nine ports will result in reporting 77300 nine times. In the case of a patient with prostate cancer (185) where two ports are used to deliver radiation, you would report two dosimetry calculations. However, if the ports represent mirror images, such as anterior/posterior, only one can be reported because the images are calculations of the same size field, shape and depth. 
 
If further treatment was required, for instance, after the volume of the tumor had changed, and the same nine ports were used, bill for nine additional basic dosimetry calculations, Hugh says.
 
Medicare considers 77300 reasonable and necessary for each treatment port. It is also appropriate to report if a patient has off-axis calculations, calculations for different depth doses, different volumes of interest, secondary film dosimetry, abutting volumes of interest, or any other situation requiring individual point calculations of radiation dosage.

 
Note: The typical course of radiation therapy requires one to six calculations, depending on the complexity of the patient's problem.

 
Special dosimetry is medically necessary when the radiation oncologist determines that a measurement of radiation to a specific area is needed the results of which are used to accept or modify a current treatment plan.
 
It is important to note that 77331 is not routinely performed. According to Bogardus, you should not report it as often as 77300. The ratio should be 77331 once for every two times 77300 is reported. "If you have a diode dosimetry unit, you may perform 77331 more often," he adds.
 
The following must be present for special dosimetry to be medically necessary:
 

 Thermoluminescent dosimetry, microdosimetry, film dosimetry, solid-state diode, or other methods of measuring specific dosage
 

 Documentation for the special radiation measuring and monitoring devices used, such as solid-state diode probes
 

 Hard-copy documentation of the measurements with additional notes regarding the measuring devices used, which must be signed by the physicist and radiation oncologist
 

Written request by the radiation oncologist for the special dosimetry.
 
 
Reporting special dosimetry is similar to reporting simple dosimetry. The number of times 77331 is reported depends on the number of ports used to deliver radiation. Special dosimetry should be reserved for complex clinical treatment planning where it is important to measure the amount of radiation a patient has received. The results determine whether to continue with a treatment plan or to modify it. In the case of a patient with a brain tumor (191.0-191.9) where it is important to protect surrounding tissue, it may be necessary to use thermoluminescent dosimeters, solid-state diode probes, special dosimetry probes, or film dosimetry services to measure radiation at any point of treatment.
 
Individual payer policies may vary regarding proper coding and reimbursement for special dosimetry. Some Medicare carriers allow 77331 to be reported for each field monitored, while others reimburse 77331 once per course of treatment.
 
Some payers may also request documentation of the calculations with the diagnosis information. Documentation should clearly explain how special dosimetry will impact the patient's current treatment plan.
 
Note: Radiation oncology practices cannot report special dosimetry calculations (77331) with 77301 (Intensity modulated radiotherapy plan, including dose volume histograms for target and critical structure partial tolerance specifications).