TY - JOUR
T1 - Delineation of prostatic calcification using quantitative susceptibility mapping
T2 - Spatial accuracy for magnetic resonance-only radiotherapy planning
AU - Kan, Hirohito
AU - Tsuchiya, Takahiro
AU - Yamada, Masato
AU - Kunitomo, Hiroshi
AU - Kasai, Harumasa
AU - Shibamoto, Yuta
N1 - Publisher Copyright:
© 2021 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, LLC on behalf of The American Association of Physicists in Medicine
PY - 2022/2
Y1 - 2022/2
N2 - To investigate the spatial accuracy of delineating prostatic calcifications by quantitative susceptibility mapping (QSM) in comparison with computed tomography (CT), we conducted phantom and human studies. Five differently-sized spherical hydroxyapatites mimicking prostatic calcification (pseudo-calcification) were arranged in the order of their sizes at the center of a plastic container filled with gelatin. This calcification phantom underwent magnetic resonance (MR) imaging, including the multiple spoiled gradient-echo sequences (SPGR) for the QSM and CT as a reference. The volume of each pseudo-calcification and center-to-center distance between the pseudo-calcifications delineated by QSM and CT were measured. In the human study, eight patients with prostate cancer who underwent radiation therapy and had some prostatic calcifications were included. The patients underwent CT and SPGR and modified DIXON sequence for MR-only simulation. The hybrid QSM processing combined with the complex signals in the SPGR and water and fat fraction maps estimated from the modified DIXON sequence were used to reconstruct the pelvic susceptibility map in humans. The threshold of CT numbers was set at 130 HU, while the QSM images were manually segmented in the calcification phantom and human studies. In the phantom study, there was an excellent agreement in the pseudo-calcification volumes between QSM and CT (y = 1.02x – 7.38, R2 = 0.99). The signal profiles had similar trends in CT and QSM. The center-to-center distances between the pseudo-calcifications in the phantom were also identical in QSM and CT. The calcification volumes were almost identical between the QSM and CT in the human study (y = 0.95x – 9.32, R2 = 1.00). QSM can offer geometric and volumetric accuracies to delineate prostatic calcifications, similar to CT. The prostatic calcification delineated by QSM may facilitate image-guided radiotherapy in the MR-only simulation workflow.
AB - To investigate the spatial accuracy of delineating prostatic calcifications by quantitative susceptibility mapping (QSM) in comparison with computed tomography (CT), we conducted phantom and human studies. Five differently-sized spherical hydroxyapatites mimicking prostatic calcification (pseudo-calcification) were arranged in the order of their sizes at the center of a plastic container filled with gelatin. This calcification phantom underwent magnetic resonance (MR) imaging, including the multiple spoiled gradient-echo sequences (SPGR) for the QSM and CT as a reference. The volume of each pseudo-calcification and center-to-center distance between the pseudo-calcifications delineated by QSM and CT were measured. In the human study, eight patients with prostate cancer who underwent radiation therapy and had some prostatic calcifications were included. The patients underwent CT and SPGR and modified DIXON sequence for MR-only simulation. The hybrid QSM processing combined with the complex signals in the SPGR and water and fat fraction maps estimated from the modified DIXON sequence were used to reconstruct the pelvic susceptibility map in humans. The threshold of CT numbers was set at 130 HU, while the QSM images were manually segmented in the calcification phantom and human studies. In the phantom study, there was an excellent agreement in the pseudo-calcification volumes between QSM and CT (y = 1.02x – 7.38, R2 = 0.99). The signal profiles had similar trends in CT and QSM. The center-to-center distances between the pseudo-calcifications in the phantom were also identical in QSM and CT. The calcification volumes were almost identical between the QSM and CT in the human study (y = 0.95x – 9.32, R2 = 1.00). QSM can offer geometric and volumetric accuracies to delineate prostatic calcifications, similar to CT. The prostatic calcification delineated by QSM may facilitate image-guided radiotherapy in the MR-only simulation workflow.
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U2 - 10.1002/acm2.13469
DO - 10.1002/acm2.13469
M3 - Article
C2 - 34726833
AN - SCOPUS:85118458707
SN - 1526-9914
VL - 23
JO - Journal of applied clinical medical physics
JF - Journal of applied clinical medical physics
IS - 2
M1 - e13469
ER -