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Introduction: Bone metastasis is the third most common metastasis in cancer patients, causing intractable pain and debilitating complications. However, studies have shown that conventional single-energy computed tomography (SECT) has limitation in detecting subtle bone metastases without obvious osteolysis/osteosclerosis. We hypothesize that dual-energy computed tomography (DECT) can distinguish different composition in tumors and in healthy bone marrow, facilitating the detection of bone marrow metastases.Methods: We constructed 51 semi-anthropomorphic lumbar spine phantoms embedded with 75 simulated tumors (25 mild lytic, 25 isodense, and 25 mild sclerotic). These phantoms were initially scanned without outer torso phantom encasement, and then scanned again with outer torso phantom encasement under the same machine setting in a rapid-kilovoltage-switching DECT scanner. Two radiologists independently reviewed the virtual monochromatic reconstruction in 70 keV and material decomposition images (hydroxyapatite-water, water-hydroxyapatite, cortical bone-water, water-cortical bone). We recorded reviewer’s response regarding the presence of tumors, tumor conspicuity score and image quality using 3-point Likert scales. The sensitivity and specificity of different reconstruction algorithms were evaluated with McNemar test. Wilcoxon signed rank test was used to evaluate the tumor conspicuity and image quality of different algorithms. Then we validate our testing algorithms by retrospectively reviewing patients’ images in our institution.Results: Hydroxyapatite-Water material decomposition algorithm achieved higher sensitivity in detecting isodense lesions as compared to the 70 keV reconstruction (without torso phantom encasement: 94% vs 82%, p=0.031; with torso phantom encasement: 38% vs 18%, p=0.013). Hydroxyapatite-Water material decomposition algorithms also possessed higher tumor conspicuity score (p<0.0001) compared to 70 keV reconstruction, and was less affected b

Introduction: Bone metastasis is the third most common metastasis in cancer patients, causing intractable pain and debilitating complications. However, studies have shown that conventional single-energy computed tomography (SECT) has limitation in detecting subtle bone metastases without obvious osteolysis/osteosclerosis. We hypothesize that dual-energy computed tomography (DECT) can distinguish different composition in tumors and in healthy bone marrow, facilitating the detection of bone marrow metastases.Methods: We constructed 51 semi-anthropomorphic lumbar spine phantoms embedded with 75 simulated tumors (25 mild lytic, 25 isodense, and 25 mild sclerotic). These phantoms were initially scanned without outer torso phantom encasement, and then scanned again with outer torso phantom encasement under the same machine setting in a rapid-kilovoltage-switching DECT scanner. Two radiologists independently reviewed the virtual monochromatic reconstruction in 70 keV and material decomposition images (hydroxyapatite-water, water-hydroxyapatite, cortical bone-water, water-cortical bone). We recorded reviewer’s response regarding the presence of tumors, tumor conspicuity score and image quality using 3-point Likert scales. The sensitivity and specificity of different reconstruction algorithms were evaluated with McNemar test. Wilcoxon signed rank test was used to evaluate the tumor conspicuity and image quality of different algorithms. Then we validate our testing algorithms by retrospectively reviewing patients’ images in our institution.Results: Hydroxyapatite-Water material decomposition algorithm achieved higher sensitivity in detecting isodense lesions as compared to the 70 keV reconstruction (without torso phantom encasement: 94% vs 82%, p=0.031; with torso phantom encasement: 38% vs 18%, p=0.013). Hydroxyapatite-Water material decomposition algorithms also possessed higher tumor conspicuity score (p<0.0001) compared to 70 keV reconstruction, and was less affected b

IntroductionStereotactic body radiotherapy (SBRT) planning for spinal metastases is a challenging task that involves complex target shapes and steep dose gradients proximal to the spinal cord. The aim of the present study is to investigate dosimetric variability among delivery systems and institutions doing spine SBRT.Materials and Methods: Three institutions (in Japan, Canada, and the USA) participated in this retrospective treatment planning study. Computed tomography (CT) datasets for three patients including fully delineated targets and organs-at-risk (OAR) were distributed to all three institutions for planning. Delivery systems included the Clinac 21EX, Vero4DRT, Synergy S, and CyberKnife. All treatment plans were generated using a prescribed dose of 24 Gy in 2 fractions and met the following objectives: the evaluated planning target volume (PTVevl, defined as the PTV minus spinal cord) should receive greater than 16.8 Gy in at least 95% of the volume (D95 > 16.8 Gy) and a maximum dose to the less than 140% of the prescribed dose (Dmax < 33.6 Gy). The maximum dose of planning risk volume (PRV) cord or thecal sac was limited to 0.035 cm3 receiving less than 17 Gy. Aside from minimum and maximum dose objectives for the PTVevl, there were no criteria regarding the shape of the PTVevl dose-volume histogram (DVH). For each completed treatment plan, the following DVH parameters were evaluated for the PTVevl: D95, D80, D50, D2 and sigma-index (S-index, standard deviation of the differential DVH).ResultsThe PTVevl and OAR dose volume constraints were satisfied in all treatment plans. For Case 1, the mean PTVevl D50 was 25.4 ± 1.5 Gy (range: 23.7 - 27.8 Gy), for Case 2 it was 26.7 ± 2.0 Gy (23.6 - 28.6 Gy), and for Case 3 it was 26.0 ± 1.3 Gy (24.1 - 27.3 Gy). The mean PTVevl D2 was 27.3 ± 2.2 Gy (24.4 - 30.2 Gy), 28.9 ± 3.0 Gy (24.5 - 31.4 Gy) and 28.7 ± 2.7 Gy (25.2 - 31.6 Gy) for Cases 1, 2, and 3, respectively. However, there were statistically significant va