Table 1.
Quality Assurance Summary From In Vivo EPID Dosimetry on 10 Patients With Rectal Cancer.a
| Patient | No. Imaged Fields (Total: 164) | Soft Tissue Changes in Belly Board Opening | Belly Board Positioning Errors ≥ 1.5 cm | Bowel Gas | Patient Setup Errors ≥ 1 cm (Bony Anatomy) | Other |
|---|---|---|---|---|---|---|
| 1 | 8 (4 fields, 2 fx) | |||||
| 2 | 17 (3 fields, 6b fx) | Board misaligned by 2 cm S-I (AP field, fx 5) | Persistent gas (LAT fields, fx 2, 5, 6; Figure 4) | 1 cm S-I setup error (AP field, fx 4) | ||
| 3 | 12 (2 fields, 6 fx) | Stretched soft tissue caused +8% AP field dose (both fields, all fx; Figure 2) | Board misaligned by 2 cm S-I (both fields, fx 2, 5) | |||
| 4 | 20 (4 fields, 5 fx) | Stretched soft tissue caused +4% AP field dose (AP field, all fx) | Tissue reduction in posterior region (LAT fields, all fx; Figure 5). Unexplained +10%-15% dose areas (PA field, all fx) | |||
| 5 | 12 (2 fields, 6 fx) | Board misaligned by 2 cm S-I (both fields, fx 1) | ||||
| 6 | 16 (4 fields, 4 fx) | Board misaligned by 2 cm S-I (AP, PA fields, fx 3; Figure 3) | 1.5 cm L-R setup error (AP field, fx 2), probable VRT setup error (LAT fields, fx 2) | |||
| 7 | 21 (3 fields, 7 fx) | Stretched soft tissue caused +3% AP field dose (AP field, all fx) | ||||
| 8 | 16 (4 fields, 4 fx) | |||||
| 9 | 18 (3 fields, 6 fx) | |||||
| 10 | 24 (3 fields, 8 fx) | Genitals placed differently (AP field, all fx) |
Abbreviations: AP, antero-posterior; fx, fraction(s); LAT, lateral; L-R, left-right; PA, postero-anterior; S-I, superior-inferior; VRT, vertical.
aIn brackets are the imaged fields and fractions in which the dose discrepancy was visible (columns 3-7).
bAntero-posterior field fraction 6 is not usable due to imager misplacement.