IGRT is an integral aspect of spine SBRT treatment delivery, allowing for accurate patient positioning and high dose to tumor while sparing dose to critical nerves. Meanwhile, intrafraction imaging with kV CBCT introduces additional radiation dose to the peripheral tissues, bone, and spinal cord, which is unaccounted for in treatment planning, with implications particularly for pediatric patients or those at high risk of myelopathy in setting of reirradiation. IGRT to verify our institutional tolerance of 1 mm and 1° between arcs may prolong treatment time and introduce further setup uncertainty. To optimize the imaging workflow (prioritizing KV-2D-3D vs KV-CBCT if sufficient) for achieving practical set up accuracy while limiting the imaging dose received, the cumulative CBCT imaging dose to the spinal cord and the dose perturbation induced by patient setup error were investigated. CBCT imaging dose to spinal cord was derived by correlating our institutional CTDI QA assessment on 4 linear accelerators and 3 C-Series LINACs with the reference value provided in the current literature. The clinical pelvis protocol CTDI was measured with the ACR torso phantom with 10cm pencil chamber, 125kVp, 1080mAs on liner accelerators and 125kVp, 80mA, 13ms on C-Series, respectively. Dosimetry change from setup uncertainty was analyzed by shifting the VMAT plan isocenter by 1 mm in Y direction and 1° couch rotation from the original planning isocenter on 5 spine SBRT patients, prescribed a course of 30Gy in 5 fractions. Dose differences were evaluated in terms of the target volume coverage D95, the spinal cord D0.035cc, D0.1cc and Dmax by re-calculating the plan with the same beam geometry, MLC motion, and MUs as the original plans. Differences between measured and vendor specified CTDI was 14% ± 11%SD (n = 7). Correlating the CBCT imaging dose reference based on Rando phantom measurement and Monte Carlo simulation in the literature, imaging dose to the spinal cord in our clinic was estimated as 3 - 4cGy per pelvis protocol CBCT. Dosimetry change with respect to target D95 showed an average deviation of 0.2% prescription dose with 1mm and 1° positioning uncertainty from the planning intents (n = 5). In the worst-case, the spinal cord with 1mm expansion had a max dose (D0.035cc) increase by an average of 132cGy (4.4% Rx) and with a max of 245cGy (8.2% Rx). CBCT dose from multiple scans (conventionally initial, mid and post) contribute to the total dose of the spinal cord. Mid-CBCTs may also prolong the treatment and introduce additional uncertainty. Our current patient positioning accuracy, effectively achieved with use of multiple 2D-3D kV images and minimized CBCT verification scans per fraction, does not produce any significant change in patient dose distributions in the target or spinal cord. Customized CBCT protocols, optical monitoring system (OSMS), or use of MR-LINAC could potentially further reduce imaging dose related to intrafraction monitoring for spine SBRT.