Purpose-To demonstrate the CT imaging, conformal irradiation and treatment planning capabilities of a small animal radiation research platform (SARRP).Methods-The SARRP employs a dual-focal spot, constant voltage x-ray source mounted on a gantry with a source-to-isocenter distance of 35 cm. Gantry rotation is limited to 120° from vertical. Eighty to 100 kVp x-rays from the smaller 0.4 mm focal spot are used for imaging. Both 0.4 mm and 3.0 mm focal spots operate at 225 kVp for irradiation. Robotic translate/rotate stages are used to position the animal. Cone-beam (CB) CT imaging is achieved by rotating the horizontal animal between the stationary x-ray source and a flat-panel detector. Radiation beams range from 0.5 mm in diameter to (60 × 60) mm 2 . Dosimetry is measured with radio-chromic films. Monte Carlo dose calculations are employed for treatment planning. The combination of gantry and robotic stage motions facilitate conformal irradiation.Results-The SARRP spans 3 ft × 4 ft × 6 ft (WxLxH). Depending on filtration, the isocenter dose outputs at 1 cm depth in water range from 22 to 375 cGy/min from the smallest to the largest radiation fields. The 20% to 80% dose fall-off spans 0.16 mm. CBCT with (0.6 × 0.6 × 0.6) mm 3 voxel resolution is acquired with less than 1 cGy. Treatment planning is performed at sub-mm resolution.Conclusions-The capability of the SARRP to deliver highly focal beams to multiple animal model systems provides new research opportunities that more realistically bridge laboratory research and clinical translation.

Small animal research allows detailed study of biological processes, disease progression, and response to therapy, with the potential to provide a natural bridge to the clinical environment. The Small Animal Radiation Research Platform (SARRP) is a portable system for precision irradiation with beam sizes down to approximately 0.5 mm and optimally planned radiation with on-board conebeam CT (CBCT) guidance. This paper focuses on the geometric calibration of the system for highprecision irradiation. A novel technique for calibration of the treatment beam is presented, which employs an x-ray camera whose precise positioning need not be known. Using the camera system we acquired a digitally reconstructed 3D "star shot" for gantry calibration, and then developed a technique to align each beam to a common isocenter with the robotic animal positioning stages. The calibration incorporates localization by cone-beam CT guidance. Uncorrected offsets of the beams with respect to the calibration origin ranged from 0.4 mm to 5.2 mm. With corrections, these alignments can be brought to within < 1 mm. The calibration technique was used to deliver a stereotactic-like arc treatment to a phantom constructed with EBT Gafchromic films. All beams were shown to intersect at a common isocenter with a measured beam (FWHM) of approximately 1.07 mm using the 0.5 mm collimated beam. The desired positioning accuracy of the SARRP is 0.25 mm and the results indicate an accuracy of 0.2 mm. To fully realize the radiation localization capabilities of the SARRP, precise geometric calibration is required, as with any such system. The x-ray camerabased technique presented here provides a straightforward and semi-automatic method for system calibration.

The aim of this study was to compare survival of childhood-onset systemic lupus erythematosus (c-SLE) and adult-onset SLE (a-SLE) according to initial manifestations. This was a retrospective cohort study. All patients were categorized into c-SLE (≤18 years) and a-SLE (>18 years). The clinical and serological data at the time of diagnosis were recorded and compared. Kaplan-Meier curves were used to compare survival rates between the two groups. Predictors of mortality were obtained by a backward Cox regression. One hundred eighty patients with c-SLE and 394 patients with a-SLE were enrolled. The female/male ratio was higher in c-SLE (P = 0.0001). Lupus nephritis (P = 0.002) and valvular heart disease (P = 0.025) were more common in c-SLE and a-SLE, respectively. In a 23-year follow-up, 20 patients (11.1%) with c-SLE and 35 patients (8.9%) with a-SLE died. Mortality was not significantly different between them (P = 0.4). The main causes of death were nephritis (50% in c-SLE vs. 29% in a-SLE), infections (40% in c-SLE vs. 29% in a-SLE), and circulatory disease (10% in c-SLE vs. 37% in a-SLE). The difference was not significant (P = 0.08). Cumulative survival rates after 5, 10, 15, and 20 years were 91, 87, 85, and 78% in c-SLE and 93, 90, 90, and 83% in a-SLE, respectively. By multivariate analysis, seizure, proteinuria, and nephritis in c-SLE and seizure, hematuria, and pericarditis in a-SLE had negative prognostic effect on survival. Both c-SLE and a-SLE patients with seizure or renal involvement should be monitored more carefully to prevent ominous outcomes.

Abstract. In cancer research, well characterized small animal models of human cancer, such as transgenic mice, have greatly accelerated the pace of development of cancer treatments. The goal of the Small Animal Radiation Research Platform (SARRP) is to make those same models available for the development and evaluation of novel radiation therapies. In combination with advanced imaging methods, small animal research allows detailed study of biological processes, disease progression, and response to therapy, with the potential to provide a natural bridge to the clinical environment. The SARRP will realistically model human radiation treatment methods in standard animal models. In this paper, we describe the mechanical and control structure of the system. This system requires accurate calibration of the x-ray beam for both imaging and radiation treatment, which is presented in detail in the paper.