Medicare Compliance & Reimbursement

The descriptor for 77300 says it's appropriate for a required calculation prescribed by the treating physician -- but after a few denials, you might start thinking that payers have their own definition of "required."

Here's a rundown of the service -- and the trouble you might run into when reporting multiple units.

What it is: Before coding for dosimetry, you need to know exactly what the service entails. According to AMA's CPT Assistant (October 1997), "Dosimetry requires the physician to select from the available inventory of photon or electron beams and that the proper energy and modality is used for each of the simulated treatment portals. There are four parts to dosimetry: 1) basic time dose relationships, 2) isodosimetry, 3) beam shaping and organ protection, and 4) special physics services."

The calculation of the dose within the tumor or treatment site is often performed by computer and checked by manual calculation. The computer's dose calculation is a billable service, but the double-check is part of quality assurance and is not billable.

The appropriate code for basic dosimetry is 77300 (Basic radiation dosimetry calculation, central axis depth dose calculation, TDF, NSD, gap calculation, off axis factor, tissue inhomogeneity factors, calculation of nonionizing radiation surface and depth dose, as required during course of treatment, only when prescribed by the treating physician).

Service run-down: Basic dosimetry calculation includes any of the following, according to Lashelle Walker, CPC, CPC-I, in her American Academy of Professional Coders Las Vegas 2009 conference presentation,

"You Don't Have to be Einstein to Understand Radiation Oncology Billing":

• Central axis depth dose

• Time dose factor (TDF)

• Nominal standard dose (NSD)

• Tissue inhomogeneity factors as required during a course of treatment prescribed by the treating physician

• Gap calculation

• Off-axis factor.

Term tip: Calculating a gap in distance between ports at skin-level to separate two overlapping beams is a gap calculation. If you see a calculation of a dose at a point other than the port's central axis, this is an off-axis calculation.

Be sure the documentation supports medical necessity for these calculations, and that the radiation oncologist gives specific orders for these particular calculations for the patient.

Clearly document: The team should document all calculations in the chart, Walker says. The physics employee should date and sign them on the date she performs the service. And the physician must also sign and date each charged calculation, she says.

Each port typically requires a calculation. Gap and off-axis calculations also merit their own 77300 charge.

And if the patient requires a new calculation during treatment (such as because of weight change), you may code 77300 again.

But two parallel opposed ports with the same parameters may require one calculation for both, says Cindy Parman, CPC, CPC-H, RCC, principal with Coding Strategies Inc. in Powder Springs, Ga.

Medicare may expect one to eight calculations during the initial course of a patient's therapy, Walker says. You may charge additional calculations for each boost (conedown).

Payers may deny charges that exceed this number, Walker warns.

Caution: Some coders report having to appeal any claim for more than four calculations. Others have gotten word from their contractor to bill up to 10 units on a single line and put additional units on a separate line with modifier 76 (Repeat procedure or service by same physician).

You may also find some payers who allow you to bill only one service per treatment area (such as the pelvis) regardless of the number of ports.

If you're receiving denials for multiple units, be sure to ask your payer for its policy -- in writing -- on reporting multiple 77300 services. If your payer has a frequency/medically unlikely edit in place, be sure you find out how to override the edit for medically necessary services. Some payers may ask for modifier 76, modifier 59 (Distinct procedural service), or modifier GD (Units of service exceeds medically unlikely edit value and represents reasonable and necessary services).

Assuming your payer allows you to report each necessary calculation, decide how many times you would report 77300 for these examples. Note that "MU" stands for "monitor units" -- the time the treatment unit is in "beam on" mode.

Example 1: The patient requires treatment for his pelvis with four fields per day: anterior, posterior, right lateral, and left lateral. The parameters for the AP and PA pelvis are the same. You are reporting the professional service only.

AP Pelvis: 90 MU

PA Pelvis: 90 MU

RT Lat Pelvis: 57 MU

LT Lat Pelvis: 59 MU

Solution: Report 77300-26 (Professional component) three times -- once for the right lateral, once for the left lateral, and once total for the AP and PA pelvis. (When two parallel opposed ports have the same parameters -- "mirror image" calculations -- you should report only one 77300 service for both ports, says Parman.)

Example 2: A stereotactic radiosurgery patient requires six treatment fields and all six have different monitor units calculated. (You are reporting the professional service only.)

Field 1: 77 MU

Field 2: 75 MU

Field 3: 90 MU

Field 4: 85 MU

Field 5: 72 MU

Field 6: 70 MU

Solution: Bill six 77300-26 charges (77300-26 x 6, for example), says Walker.