Table 3.
Example 3 – HDR 192Ir BT source for breast balloon applicator.
| Category | Typical level (%) | Assumptions |
|---|---|---|
| Source strength | 2 | PSDL traceable calibrations |
| Treatment planning | 3 | Reference data with the appropriate bin width |
| Medium dosimetric corrections | 3 | Balloon filled with standard level of contrast agent, no consideration or composition of chestwall, lung, or breast |
| Scatter dosimetric corrections | 7 | A non-scalar correction for skin dose (and at points in proximity to the surface near the balloon) is needed, and will require an advanced dose calculation formalism to properly account for radiation scatter conditions in the patient. Use of a single prescription point might be not sufficient |
| Dose delivery including registration of applicator geometry to anatomy | 7 | Accurate QA concept for commissioning and constancy checks, especially for source positioning and applicator/ source path geometry, appropriate imaging techniques (either small slice thickness, 3D sequences or combination of different slice orientations), applicator characterization |
| Interfraction/Intrafraction changes between imaging and dose delivery | 7⁎ | For one treatment plan per applicator insertion and measures to detect major variations for subsequent fractions |
| Total dosimetric uncertainty (k = 1) | 13 | For treatment delivered with the same BT source |
⁎
Estimated value based on expert discussion.