Table 1.
A qualitative analysis of effectiveness of QA techniques to catch some potential discrepancy or error that could happen in an IMRT treatment. Note: only a few are mentioned here and only pretreatment QA techniques are analyzed.
| Data Transfer, Delivery Error, Planning Error Type | Point Dose Measurement a | Field‐by‐Field Planar Dose QA b | Composite Planar Dose QA c | DynaLog QA d | Independent Dose Calculation QA e |
|---|---|---|---|---|---|
| Beam Parameters Discrepancy | |||||
| During Data Transfer or Machine Delivery | |||||
| Gantry Angle | 3 | 5 | 4 | 1 | 5 |
| Collimator Jaw Setting | 3 | 3 | 3 | 1 | 5 |
| Collimator Angle | 3 | 3 | 3 | 1 | 5 |
| MLC Positioning Error | 4 | 3 | 3 | 1 | 5 |
| MUs | 1 | 1 | 3 | 5 | 5 |
| Couch Angle Error | 2 | 5 | 2 | 5 | 5 |
| Machine Issues/Data Transfer Issues | |||||
| Dosimetry Characteristic – | |||||
| Energy Change, Symmetry and | 4 | 4 | 4 | 5 | 5 |
| Flatness Off | |||||
| Absolute Dose Output Calibration | 5 | 5 | 5 | 5 | 5 |
| Relative Dose Output – Small Field Output Off | 1 | 1 | 1 | 5 | 5 |
| One Segment Dropped Out or Not Transferred Properly | 4 | 3 | 4 | 1 | 5 |
| One Field Not Transferred Correctly | 4 | 2 | 3 | 1 | 5 |
| Demanding MLC Sequence or MLC Positioning Issues – Beam Hold Off | 4 | 4 | 4 | 1 | 5 |
| TPS Beam Modeling Issues | |||||
| Small Field Out Prediction Issue | 2 | 2 | 2 | 5 | 1 |
| Heterogeneity Correction Issues | 5 | 5 | 5 | 5 | 1 |
| Wrong CT to ED | 5 | 5 | 5 | 5 | 2 |
| DVH Calculation Discrepancy | 5 | 5 | 5 | 5 | 1 |
| In vivo Changes | |||||
| Beam Data Modification After | |||||
| Pretreatment QA and Other Machine Issues During Each Fraction | 5 | 5 | 5 | 5 | 5 |
| IGRT Issues | |||||
| Anatomy Changes, localization Issues, Setup Issues | 5 | 5 | 5 | 5 | 5 |
| Treatment Planning | |||||
| Isocenter Placement, Prescription, Wrong CT Voxel Size, Plan Quality | 5 | 5 | 5 | 5 | 5 |
Note: 1 is most effective, 4 is least effective, and 5 is not possible to find from QA test results.
Point dose measurement refers to ion chamber measurement with one or two points in a composite fashion (i.e., all beam delivered to a water equivalent phantom as it would be delivered to the patient).
Field‐by‐field planar dose measurement: all beams delivered from AP direction with gantry and could reset to default position.
Composite planar dose QA refers to measuring a plane using a 2D detector embedded in a phantom and the QA is performed with actual beam parameters as it will be delivered to the patients.
DynaLog QA: analysis of machine log file collected by delivering the actual plan to air or during composite point or planar dose measurement, as explained in a) and c).
Independent dose calculation is verifying the dose distribution of the planning system by recalculating in an independent dose calculation by exporting DICOM RT files (Plan, Dose, Images, Structure set) and any POIs.