In the realm of personalized radionuclide therapy, the accuracy of patient-specific dosimetry is paramount to achieving optimal treatment outcomes. However, when it comes to lesions, particularly in hepatocellular carcinoma (HCC), challenges arise due to the inherent uncertainties in the dosimetry process. A recent study delved into the intra- and inter-operator variability in manually delineated HCC lesion contours on MRIs and its consequential impact on dosimetry, specifically focusing on radioembolization (RE) dosimetry.
Quantifying Variability:
The study involved ten patients with HCC lesions treated with Y-90 RE, where three radiologists manually contoured 20 lesions on baseline MRIs, with two radiologists re-contouring the lesions in subsequent sessions. The aim was to assess the uncertainty in segmented volume and mean absorbed dose, shedding light on how this uncertainty affects tumor control probability (TCP) in dosimetry-guided treatments. The findings revealed a notable range in lesion volume and absorbed doses, with inter-observer variability being significantly higher than intra-observer variability, emphasizing the importance of consistency in contouring for accurate dosimetry.
The Dosimetry Process:
Dosimetry in radionuclide therapy involves multiple steps, each contributing to uncertainties in the final absorbed dose estimation. From quantitative imaging and volume delineation to absorbed dose calculations, uncertainties can arise at various points. Even with advancements like voxel-level dosimetry using Monte Carlo radiation transport, the accuracy of lesion contouring remains crucial as it directly impacts the absorbed dose calculation. Moreover, the use of partial volume correction (PVC) further underscores the significance of precise segmentation in dosimetry.
Challenges in Segmentation:
While automated segmentation methods are increasingly available, manual contouring remains a common practice for tumor delineation due to the variability in lesion characteristics. Manual segmentation on anatomical images such as MRIs offers higher resolution but is susceptible to inter- and intra-observer variability, as demonstrated in the study. The variability in delineating lesion boundaries can propagate into uncertainties in dose metrics, influencing treatment decisions and outcomes.
Implications for Treatment Efficacy:
The study’s findings highlight the impact of segmentation uncertainty on dose metrics and subsequent tumor control probability. By quantifying the relationship between volume and uncertainty in dose estimation, the study provides insights into how variability in contouring can affect treatment efficacy. The propagation of segmentation uncertainty to TCP underscores the need for robust and consistent contouring practices to enhance the accuracy of dosimetry-guided treatments.
Future Directions:
Moving forward, addressing segmentation variability through more standardized and reproducible contouring methods could enhance the reliability of dosimetry in radionuclide therapy. Additionally, exploring strategies to minimize the impact of segmentation uncertainties on treatment outcomes, such as dose escalation planning and refined PVC techniques, may offer avenues for improving therapeutic efficacy. Integrating the insights from this study with other sources of uncertainty along the dosimetry chain could pave the way for comprehensive approaches to enhance treatment precision and patient outcomes.
Key Takeaways:
– Inter-observer variability in manual segmentation of HCC lesions can significantly impact dosimetry accuracy.
– Uncertainties in segmented volume and absorbed dose play a crucial role in predicting tumor control probability.
– Consistency in lesion contouring is essential for reducing uncertainties in dose metrics and optimizing treatment efficacy.
– Future research should focus on standardizing segmentation methods and exploring innovative strategies to mitigate the effects of variability on dosimetry outcomes.
In conclusion, the study sheds light on the intricate interplay between manual segmentation variability and dosimetry accuracy in HCC lesion treatments, emphasizing the need for meticulous contouring practices to enhance therapeutic precision in radionuclide therapy. By quantifying the uncertainties in segmentation and their implications on dose metrics, the study offers valuable insights for refining dosimetry-guided treatments and improving patient outcomes in the realm of personalized cancer therapy.
Read more on pmc.ncbi.nlm.nih.gov
