PMC8281898_01
Multiparametric MRI at 3T before and 3 months after treatment. The liver metastasis (arrow) was hyperintense relative to adjacent liver parenchyma on HASTE imaging (TR/TE/FA = 1100 ms/95 ms/160 degree) (A); T1 times of the tumor (arrow) were shorter than those of adjacent liver parenchyma on quantitative T1 mapping (B); Three months after MRI-guided SABR, the tumor volume reduced significantly on HASTE imaging (arrow) (C); Quantitative T1 map imaging (arrow) (D). HASTE : half-flourier-acquired single-shot turbo spin echo; TR : repetition time; TE : echo time; FA : flip angle; SABR : stereotactic ablative radiation therapy
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T1 times of the tumor were substantially shorter than those of adjacent liver parenchyma on quantitative T1 mapping (qT1) reflecting cancer cell viability (Fig. 1B). Then, the patient underwent MRI simulation on 0.35T MRI-guided radiotherapy system (MRIdian  System, ViewRayTM Inc, Oakwood Village, Ohio, USA) with surface coils on the abdomen using true fast imaging with steady-state free precession (true FISP) images (3.33 ms TR, 1.43 ms TE, 60 flip angle, 3 mm slice thickness, 40 cm x 40 cm x 43 cm field of view) (Fig. 2A-C).
Plain and SPIO-enhanced true FISP images at 0.35T. Liver metastasis is barely visible on non-contrast enhanced true FISP images consisting of axial (A), coronal (B) and sagittal (C) planes. After SPIO administration, liver metastasis (arrows) is clearly visualized on true FISP images consisting of axial (D), coronal (E) and sagittal (F) planes; SPIO : superparamagnetic iron oxide; FISP : fast imaging with steady-state free precession
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T1 times of the tumor were substantially shorter than those of adjacent liver parenchyma on quantitative T1 mapping (qT1) reflecting cancer cell viability (Fig. 1B). Then, the patient underwent MRI simulation on 0.35T MRI-guided radiotherapy system (MRIdian  System, ViewRayTM Inc, Oakwood Village, Ohio, USA) with surface coils on the abdomen using true fast imaging with steady-state free precession (true FISP) images (3.33 ms TR, 1.43 ms TE, 60 flip angle, 3 mm slice thickness, 40 cm x 40 cm x 43 cm field of view) (Fig. 2A-C). One hour after the administration of ferucarbotran, the lesion of liver metastasis was clearly visualized on true FISP image (Fig. 2D-F).
MRI-guided SABR isodose line distribution. Isodose lines are displayed on axial (A), coronal (B), and sagittal (C) true FISP images. Isodose lines with corresponding actual radiation dose were given over 5 fractions. SABR : stereotactic ablative radiation therapy; FISP : fast imaging with steady-state free precession
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The prescribed dose to the D95% of the PTV (the dose covering 95% of the PTV) was 40 Gy in 5 fractions over 5 days (Fig. 3A-C).