Abstract
Purpose/Objective: The main objectives were to explore the intermodality and intra-observer variations of anal cancer GTV delineations on CT, MRI and PET images.
Materials and Methods: 22 patients with biopsy-proven anal carcinoma scheduled for curative RT underwent FDG-PET/contrast enhanced CT and MRI. The delineations of GTV were done twice for each imaging modality with a minimum of 3 months in between. Delineations on the CT and MRI were done by routine methods. For the PET part three different cut-off values were used: SUV 2.5, 40% and 50% of maximum SUV, respectively. The GTVs were compared for: size, volume changes, center-of-mass (COM) and non-overlapping regions, regarding inter-modality and intra-observer variations. Wilcoxon rank sum test and ANOVA analysis were used, where p < 0.05 was considered significant.
Results: 1. Volume size: The mean GTV-CT of the 1st and 2nd delineation was significantly larger compared to the mean GTV-MRI and the median GTVs from the different PET cut-offs (33.9 cm3, 18.0 cm3, 15.6 cm3, 14.8 cm3 and 10.3 cm3, respectively). The intraobserver differences in voluma size were small and non-significant. It was additionally found that the mean GTV-CT increased when overlaying either mean GTV-MRI or one of the three mean GTV-PETs (17%, 24%, 56% and 36 %, respectively). 2. COM: The inter-modality differences in COM were found to be > 1cm between CT-MRI, CT-PET2.5 and MRI-PET2.5. However, the intraobserver differences in COM were found to be minor. 3. Non-overlap: There were significant differences in mean of the non-overlapping regions using the CT or MRI (20.5% and 22.5%) compared to the different PET cut-offs (5.5%, 6.4% and 5.8%), respectively.
Conclusions: Delineations of anal tumors are difficult. GTV-CT was the largest compared to GTV-MRI and the different GTV-PETs. Although the GTV-CT were larger, it did not always cover the GTVs of MRI and PET. The GTV-CT increased if overlaying GTV-MRI or one of the GTV-PETs. Based on our study, our recommendations are not to use CT solely for delineating anal tumors; MRI or PET should be considered as a second imaging modality.
Materials and Methods: 22 patients with biopsy-proven anal carcinoma scheduled for curative RT underwent FDG-PET/contrast enhanced CT and MRI. The delineations of GTV were done twice for each imaging modality with a minimum of 3 months in between. Delineations on the CT and MRI were done by routine methods. For the PET part three different cut-off values were used: SUV 2.5, 40% and 50% of maximum SUV, respectively. The GTVs were compared for: size, volume changes, center-of-mass (COM) and non-overlapping regions, regarding inter-modality and intra-observer variations. Wilcoxon rank sum test and ANOVA analysis were used, where p < 0.05 was considered significant.
Results: 1. Volume size: The mean GTV-CT of the 1st and 2nd delineation was significantly larger compared to the mean GTV-MRI and the median GTVs from the different PET cut-offs (33.9 cm3, 18.0 cm3, 15.6 cm3, 14.8 cm3 and 10.3 cm3, respectively). The intraobserver differences in voluma size were small and non-significant. It was additionally found that the mean GTV-CT increased when overlaying either mean GTV-MRI or one of the three mean GTV-PETs (17%, 24%, 56% and 36 %, respectively). 2. COM: The inter-modality differences in COM were found to be > 1cm between CT-MRI, CT-PET2.5 and MRI-PET2.5. However, the intraobserver differences in COM were found to be minor. 3. Non-overlap: There were significant differences in mean of the non-overlapping regions using the CT or MRI (20.5% and 22.5%) compared to the different PET cut-offs (5.5%, 6.4% and 5.8%), respectively.
Conclusions: Delineations of anal tumors are difficult. GTV-CT was the largest compared to GTV-MRI and the different GTV-PETs. Although the GTV-CT were larger, it did not always cover the GTVs of MRI and PET. The GTV-CT increased if overlaying GTV-MRI or one of the GTV-PETs. Based on our study, our recommendations are not to use CT solely for delineating anal tumors; MRI or PET should be considered as a second imaging modality.
| Original language | English |
|---|---|
| Journal | Radiotherapy & Oncology |
| Volume | 103 |
| Issue number | Supplement 1 |
| Pages (from-to) | S305 |
| ISSN | 0167-8140 |
| DOIs | |
| Publication status | Published - 2012 |
| Event | ESTRO 31 - Barcelona, Spain Duration: 9 May 2012 → 13 May 2012 http://www.estro-events.org/pages/estro31.aspx |
Conference
| Conference | ESTRO 31 |
|---|---|
| Country/Territory | Spain |
| City | Barcelona |
| Period | 09/05/2012 → 13/05/2012 |
| Internet address |
