Page 117 - 18F-FDG PET as biomarker in aggressive lymphoma; technical and clinical validation

Workflow optimization of MTV in DLBCL
medicine physician or radiologist is necessary if a semi-automated method is applied, as was illustrated by the outliers in this pilot study. For example, patient 10 showed a large difference between the three workflows (Figs. 1 to 3). It appeared that the decision whether the liver was involved or not was the main reason for the large differences in the assessments. Both the observers and the NM physicians did not agree on the question of whether the liver was involved or not. In clinical practice, access to additional clinical information (e.g., physical examination or lab results) may help to support the decision whether a site is involved or not. This situation illustrates the importance of the development of clear clinical criteria, definitions, and guidelines for lesion selection in PET/CT studies of patients with different lymphoma types [25].
We also compared the results of the observers (who were clinicians, but not NM physicians) before and after the check of the NM physician. It appeared that only small lesions were added, and in a few patients, physiological uptake was erroneously included in MTV, again supporting the need for checking of results by a NM physician.
This study has strengths and limitations that should be taken into account when interpreting the results. First, we deliberately selected patients with a large variation in number and size of lesions. This might be a strength because it represents examples of different challenges that can occur when analyzing MTV in lymphoma, but this could give a higher prevalence of difficult cases compared with the general DLBCL cohort. However, according to the three experienced nuclear medicine physicians, the dataset was representative of a general DLBCL cohort, even though we selected a relatively small number of patients.
Another strength is the comparison of different workflows for MTV and TLG assessment and their impact on interobserver reliability. Most studies acknowledge the difficulties in the assessment of multiple lymphoma lesions. Some used boxes or VOIs to constrain individual tumors [6,8,12], or limited segmentation to a representative maximum of 5 lymphoma lesions [26], but none of these studies compared such strategies with another workflow.
A limitation is the dependency of the ICC values on the range of MTV values in the population [21]. This is present in other MTV studies as well and hampers
115
5