Spectral ct

All CT studies were acquired in treatment positions on a Spectral CT (IQon, Philips Healthcare, Cleveland, Ohio) with 120 kVp, 0.36 pitch, 0.625-mm collimation, autoexposure control, and a 50 cm field of view. The images were reconstructed with an iterative algorithm (iDose4, level 2) to yield a pixel size of 0.98 by 0.98 mm² and a slice thickness of 1 to 2 mm. The T1W MRI_tx images were acquired in treatment position using a Turbo Field Echo sequence on 1.5T or 3T MRI systems (Ingenia, Philips Healthcare, Gainesville, Florida). To replicate treatment position, flexible-loop coils and a head-positioning overlay board were used to accommodate face masks and other immobilization devices, as described previously [10 (link)].

For Hounsfield unit (HU) measurements, a mid-line 15 mm MPR section in sagittal reformations was created with a PACS tool (IDS7, Sectra). Then, cylindrical volumes of interest were manually positioned in three non-fractured thoracolumbar vertebrae (ideally, L1–3) by one radiologist (YL), and mean HU was noted (Figure 1) (14 (link)). Fractured or otherwise altered vertebrae (e.g., vertebrae with severe degenerative changes, vertebrae after vertebro-/kyphoplasty) were not used for HU measurements. The HU values were then converted into BMD using HU-to-BMD conversion as previously described: (i) 0.928 × HU + 4.5 mg/cm³ for the IQon Spectral CT, (ii) 0.855 × HU + 1.172 mg/cm³ for the Philips iCT 256, (iii) 0.778 × HU − 4.693 mg/cm³ for the Philips Brilliance 64, (iv) 1.011 × HU − 3.385 mg/cm³ for the Siemens Somatom Definition AS+, and (v) 0.985 × HU + 15.516 mg/cm³ for the Siemens Somatom Definition (12 (link), 15 (link)). A BMD correction offset for contrast-enhanced CT scans with arterial (-8.6 mg/cm³) and portal venous contrast phase (-15.8 mg/cm³) was added (16 (link)). Osteoporosis was defined as BMD < 80 mg/cm³ and osteopenia as 80 ≤ BMD ≤ 120 mg/cm³ (17 ).

For contrast-enhanced CT scanning, the following scanners were used: 128-channel CT (IQon Spectral CT), 256-channel CT (Philips Brilliance iCT 256), 256-channel CT (Siemens Healthcare) and 128-channel CT (Siemens Healthcare). The scanning specifications were as follows: a tube voltage range of 80 to 120 kVp, a tube current range of 120 to 300 mAs, a pitch range of 0.6 to 1.25 mm, an image matrix of 512×512, and a reconstruction slice thickness range of 1 or 2 mm. Before having an abdominal contrast-enhanced CT, each patient had an intramuscular injection of 20 mg of Racanisodamine Hydrochloride and drank 1,000-2,000 mL of water. Following intravenous injection of contrast media (1.5mL/kg, at a rate of 3.0-3.5mL/s), the arterial phase and portal venous phase were recorded in 25-30 seconds and 65-70 seconds, respectively.