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1.  Dose optimisation for intraoperative cone-beam flat-detector CT in paediatric spinal surgery 
Pediatric Radiology  2012;42(8):965-973.
Background
During surgery for spinal deformities, accurate placement of pedicle screws may be guided by intraoperative cone-beam flat-detector CT.
Objective
The purpose of this study was to identify appropriate paediatric imaging protocols aiming to reduce the radiation dose in line with the ALARA principle.
Materials and methods
Using O-arm® (Medtronic, Inc.), three paediatric phantoms were employed to measure CTDIw doses with default and lowered exposure settings. Images from 126 scans were evaluated by two spinal surgeons and scores were compared (Kappa statistics). Effective doses were calculated. The recommended new low-dose 3-D spine protocols were then used in 15 children.
Results
The lowest acceptable exposure as judged by image quality for intraoperative use was 70 kVp/40 mAs, 70 kVp/80 mAs and 80 kVp/40 mAs for the 1-, 5- and 12-year-old-equivalent phantoms respectively (kappa = 0,70). Optimised dose settings reduced CTDIw doses 89–93%. The effective dose was 0.5 mSv (91–94,5% reduction). The optimised protocols were used clinically without problems.
Conclusions
Radiation doses for intraoperative 3-D CT using a cone-beam flat-detector scanner could be reduced at least 89% compared to manufacturer settings and still be used to safely navigate pedicle screws.
doi:10.1007/s00247-012-2396-0
PMCID: PMC3414709  PMID: 22669457
O-arm; Paediatric spine; Preoperative CT scan; Radiation dose
2.  Microdialysis of paraspinal muscle in healthy volunteers and patients underwent posterior lumbar fusion surgery 
European Spine Journal  2009;18(11):1604-1609.
Paraspinal muscle damage is inevitable during conventional posterior lumbar fusion surgery. Minimal invasive surgery is postulated to result in less muscle damage and better outcome. The aim of this study was to monitor metabolic changes of the paraspinal muscle and to evaluate paraspinal muscle damage during surgery using microdialysis (MD). The basic interstitial metabolisms of the paraspinal muscle and the deltoid muscle were monitored using the MD technique in eight patients, who underwent posterior lumbar fusion surgery (six male and two female, median age 57.7 years, range 37–74) and eight healthy individuals for different positions (five male and three female, age 24.1 ± 0.8 years). Concentrations of glucose, glycerol, and lactate pyruvate ratio (L/P) in both tissues were compared. In the healthy group, the glucose and glycerol concentrations and L/P were unchanged in the paraspinal muscle when the body position changed from prone to supine. The glucose concentration and L/P were stable in the paraspinal muscle during the surgery. Glycerol concentrations increased significantly to 243.0 ± 144.1 μM in the paraspinal muscle and 118.9 ± 79.8 μM in the deltoid muscle in the surgery group. Mean glycerol concentration difference (GCD) between the paraspinal muscle and the deltoid tissue was 124.1 μM (P = 0.003, with 95% confidence interval 83.4–164.9 μM). The key metabolism of paraspinal muscle can be monitored by MD during the conventional posterior lumbar fusion surgery. The glycerol concentration in the paraspinal muscle is markedly increased compared with the deltoid muscle during the surgery. It is proposed that GCD can be used to evaluate surgery related paraspinal muscle damage. Changing body position did not affect the paraspinal muscle metabolism in the healthy subjects.
doi:10.1007/s00586-009-1021-x
PMCID: PMC2899392  PMID: 19418074
Glucose; Lactate pyruvate ratio; Glycerol; Paraspinal muscle; Microdialysis

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