Background:
BSI calculated from bone scintigraphy using 99mtechnetium-methylene
diphosphonate (99mTc-MDP) is used as a quantitative indicator of metastatic bone
involvement in bone metastasis diagnosis, therapeutic effect assessment, and prognosis
prediction. However, the BONE NAVI, which calculates BSI, only supports bone
scintigraphy using 99mTc-MDP.
Aims:
We developed a method in collaboration with the Tokyo University of
Agriculture and Technology to calculate bone scan index (BSI) employing deep
learning algorithms with bone scintigraphy images using 99mtechnetiumhydroxymethylene diphosphonate (99mTc-HMDP). We used a convolutional neural
network (CNN) enabling the simultaneous processing of anterior and posterior bone
scintigraphy images named CNNapis.
Objectives:
The purpose of this study is to investigate the usefulness of the BSI
calculated by CNNapis as bone imaging and bone metabolic biomarkers in patients with
bone metastases from prostate cancer.
Methods:
At our hospital, 121 bone scintigraphy scans using 99mTc-HMDP were
performed and analyzed to examine bone metastases from prostate cancer, revealing the
abnormal accumulation of radioisotope (RI) at bone metastasis sites. Blood tests for
serum prostate-specific antigen (PSA) and alkaline phosphatase (ALP) were performed
concurrently. BSI values calculated by CNNapis were used to quantify the metastatic
bone tumor involvement. Correlations between BSI and PSA and between BSI and ALP
were calculated. Subjects were divided into four groups by BSI values (Group 1, 0 to <1; Group 2, 1 to <3; Group 3, 3 to <10; Group 4, >10), and the PSA and ALP values in
each group were statistically compared.
Results:
Patients diagnosed with bone metastases after bone scintigraphy were also
diagnosed with bone metastases using CNNapis. BSI corresponding to the range of
abnormal RI accumulation was calculated. PSA and BSI (r = 0.2791) and ALP and BSI
(r = 0.6814) correlated positively. Significant intergroup differences in PSA between
Groups 1 and 2, Groups 1 and 4, Groups 2 and 3, and Groups 3 and 4 and in ALP
between Groups 1 and 4, Groups 2 and 4, and Groups 3 and 4 were found.
Conclusion :
BSI calculated using CNNapis correlated with ALP and PSA values and is
useful as bone imaging and bone metabolic biomarkers, indicative of the activity and
spread of bone metastases from prostate cancer.