The accuracy of computed tomography number to electron density (CT‐ED) calibration is a key component for dose calculations in an inhomogeneous medium. In a previous work, it was shown that the tolerance levels of CT‐ED calibration became stricter with an increase in tissue thickness and decrease in the effective energy of a photon beam. For the last decade, a low effective energy photon beam (e.g., flattening‐filter‐free (FFF)) has been used in clinical sites. However, its tolerance level has not been established yet. We established a relative electron density (ED) tolerance level for each tissue type with an FFF beam. The tolerance levels were calculated using the tissue maximum ratio (TMR) and each corresponding maximum tissue thickness. To determine the relative ED tolerance level, TMR data from a Varian accelerator and the adult reference computational phantom data in the International Commission on Radiological Protection publication 110 (ICRP‐110 phantom) were used in this study. The 52 tissue components of the ICRP‐110 phantom were classified by mass density as five tissues groups including lung, adipose/muscle, cartilage/spongy‐bone, cortical bone, and tooth tissue. In addition, the relative ED tolerance level of each tissue group was calculated when the relative dose error to local dose reached 2%. The relative ED tolerances of a 6 MVFFF beam for lung, adipose/muscle, and cartilage/spongy‐bone were ±0.044, ±0.022, and ±0.044, respectively. The thicknesses of the cortical bone and tooth groups were too small to define the tolerance levels. Because the tolerance levels of CT‐ED calibration are stricter with a decrease in the effective energy of the photon beam, the tolerance levels are determined by the lowest effective energy in useable beams for radiotherapy treatment planning systems.
Computed tomography (CT) data are required to calculate the dose distribution in a patient’s body. Generally, there are two CT number calibration methods for commercial radiotherapy treatment planning system (RTPS), namely CT number‐relative electron density calibration (CT‐RED calibration) and CT number‐mass density calibration (CT‐MD calibration). In a previous study, the tolerance levels of CT‐RED calibration were established for each tissue type. The tolerance levels were established when the relative dose error to local dose reached 2%. However, the tolerance levels of CT‐MD calibration are not established yet. We established the tolerance levels of CT‐MD calibration based on the tolerance levels of CT‐RED calibration. In order to convert mass density (MD) to relative electron density (RED), the conversion factors were determined with adult reference computational phantom data available in the International Commission on Radiological Protection publication 110 (ICRP‐110). In order to validate the practicability of the conversion factor, the relative dose error and the dose linearity were validated with multiple RTPSes and dose calculation algorithms for two groups, namely, CT‐RED calibration and CT‐MD calibration. The tolerance levels of CT‐MD calibration were determined from the tolerance levels of CT‐RED calibration with conversion factors. The converted RED from MD was compared with actual RED calculated from ICRP‐110. The conversion error was within ±0.01 for most standard organs. It was assumed that the conversion error was sufficiently small. The relative dose error difference for two groups was less than 0.3% for each tissue type. Therefore, the tolerance levels for CT‐MD calibration were determined from the tolerance levels of CT‐RED calibration with the conversion factors. The MD tolerance levels for lung, adipose/muscle, and cartilage/spongy‐bone corresponded to ±0.044, ±0.022, and ±0.045 g/cm3, respectively. The tolerance levels were useful in terms of approving the CT‐MD calibration table for clinical use.
The common carotid artery (CCA) usually divides into the internal carotid artery (ICA) and the external carotid artery (ECA). We present an extremely rare case of a non-bifurcating carotid artery through which intra-arterial chemotherapy for laryngeal cancer was administered. The CCA angiogram, as well as ultrasonographic evaluation of the carotid arteries, demonstrated a non-bifurcating CCA that subsequently constituted the ICA. Furthermore, several branches normally given off by the ECA arose directly from the single carotid artery. Superselective intra-arterial infusion of cis-diamminedichloroplatinum (II) (CDDP) was subsequently performed.
High levels of remnant lipoprotein, triglyceride (TG)-rich lipoprotein, are atherogenic and pose a high risk for cardiovascular diseases [1-4]. Although the beneficial effects of reducing lowdensity lipoprotein cholesterol (LDL-C) are known, residual risks remain after reduction of LDL-C in patients with high TG-rich lipoproteinemia [5-8]. We demonstrated that remnant lipoprotein, as assessed by measuring remnant-like lipoprotein particles cholesterol (RLP-C), was an independent predictor of cardiovascular events in patients with coronary artery disease and LDL-C <100 mg/dL after adjustment for known risk factors [1]. Statin therapy targets LDL-C, which is accompanied by low triglyceriderich lipoproteins levels [9-11]. Therefore, it is possible that the reduction of RLP-C in patients with combined hyperlipidemia mediates the beneficial effect of lowering of LDL-C levels by statins. However, it remains mostly unclear the extent to which lipoprotein
Background: This study assesses clinical outcomes after drug-eluting balloon treatment for recurrent in-stent restenosis lesions based on the number of metallic layers. Methods and Results: We enrolled 304 consecutive patients (333 lesions) treated with percutaneous coronary intervention using drug-eluting balloon for in-stent restenosis lesions between March 2014 and June 2015. Per the number of stent layers previously implanted to the lesion, the patients were categorized into 3 groups, 1 stent layer (1L), 166 patients; 2 stent layers (2L), 87 patients; and ≥3 stent layers (≥3L), 51 patients. The end points were major adverse cardiovascular events (MACE), including cardiac death, target lesion revascularization, myocardial infarction, and definite or probable stent thrombosis. No significant differences were observed in patients’ baseline characteristics among the groups. The 1-year MACE and target lesion revascularization rates were significantly higher in the ≥3L group than those in the 1L and 2L groups (MACE: 1L, 16.9%; 2L, 16.1%; and ≥3L, 43.1%, P <0.01; target lesion revascularization: 1L, 14.5%; 2L, 14.9%; and ≥3L, 41.2%, P <0.01). The multivariable Cox regression analysis revealed that the number of metallic layers (≥3L compared with 1L; hazard ratio, 3.17; [95% CI, 1.75–5.76]; P <0.01 and hemodialysis [hazard ratio, 2.21; (95% CI, 1.12–4.36); P =0.02]) were independent predictors for MACE. No significant differences were observed in the occurrence of cardiac death among the groups ( P =0.34). Conclusions: Seemingly, drug-eluting balloon is less effective for ≥3L in-stent restenosis lesions. Hemodialysis and in-stent restenosis with the number of metallic layers are independent predictors for MACE.
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