HOW MANY DOSEMETERS ARE NEEDED FOR CORRECT MEAN ORGAN DOSE ASSESSMENT WHEN PERFOMING PHANTOM DOSIMETRY? A PHANTOM STUDY EVALUATING LIVER ORGAN DOSE AND INVESTIGATING TLD NUMBERS AND WAYS OF DOSEMETER PLACEMENT.

This study evaluated repeated mean organ dose measurements of the liver by phantom dosimetry and statistical modelling in order to find a way to reduce the number of dosemeters needed for precise organ dose measurements. Thermoluminescent dosemeters were used in an adult female phantom exposed to a biplanar x-ray source at three different axial phantom rotations. Generalised mixed linear effect modelling was used for statistical analysis. A subgroup of five to six organ-specific locations out of 28 yielded mean liver organ doses within 95% confidence intervals of measurements based on all 28 liver-specific dosemeter locations. No statistical difference of mean liver dose was observed with rotation of the phantom either 10° clockwise or counter-clockwise as opposed to the coronal plane. Phantom dosimetry handling time during organ dose measurements can be markedly reduced, in this case the liver, by 79% (22/28), while still providing precise mean organ dose measurements.

A Nano-Dose Protocol For Cobb Angle Assessment in Children With Scoliosis: Results of a Phantom-based and Clinically Validated Study.

STUDY DESIGN: This was a prospective validation study with technical notes. OBJECTIVE: This study aimed to validate a new ultra-low-dose full-spine protocol for reproducible Cobb angle measurements-the "nano-dose" protocol. SUMMARY OF BACKGROUND DATA: Scoliosis is a 3-dimensional (3D) deformity of the spine characterized by 3D clinical parameters. Nevertheless, 2D Cobb angle remains an essential and widely used radiologic measure in clinical practice. Repeated imaging is required for the assessment and follow-up of scoliosis patients. The resultant high dose of absorbed radiation increases the potential risk of developing radiation-induced cancer in such patients. Micro-dose radiographic imaging is already available in clinical practice, but the radiation dose delivered to the patient could be further reduced. METHODS: An anthropomorphic child phantom was used to establish an ultra-low-dose protocol in the EOS Imaging System still allowing Cobb angle measurements, defined as nano-dose. A group of 23 consecutive children presenting for scoliosis assessment, 12 years of age or younger, were assessed with standard-dose or micro-dose and additional nano-dose full-spine imaging modalities. Intraobserver and interobserver reliability of determining the reliability of 2D Cobb angle measurements was performed. The dosimetry was performed in the anthropomorphic phantom to confirm theoretical radiation dose reduction. RESULTS: A nano-dose protocol was established for reliable Cobb angle measurements. Dose area product with this new nano-dose protocol was reduced to 5 mGy×cm, corresponding to one sixth of the micro-dose protocol (30 mGy×cm) and <1/40th of the standard-dose protocol (222 mGy×cm). Theoretical dose reduction, for posteroanterolateral positioning was confirmed using phantom dosimetry. Our study showed good reliability and repeatability between the 2 groups. Cobb variability was <5 degrees from the mean using 95% confidence intervals. CONCLUSIONS: We propose a new clinically validated nano-dose protocol for routine follow-up of scoliosis patients before surgery, keeping the radiation dose at a bare minimum, while allowing for reproducible Cobb angle measurements.

EOS Micro-dose Protocol: First Full-spine Radiation Dose Measurements in Anthropomorphic Phantoms and Comparisons with EOS Standard-dose and Conventional Digital Radiology.

STUDY DESIGN: A comparative study of radiation dose measured in anthropomorphic phantoms. OBJECTIVES: The aim of this study was to first report the first organ dose and effective dose measurements in anthropomorphic phantoms using the new EOS imaging micro-dose protocol in full-spine examinations, and to compare these measurements of radiation dose to measurements in the EOS standard-dose protocol and conventional digital radiology (CR). SUMMARY OF BACKGROUND DATA: Few studies evaluating organ dose and effective dose for the EOS low-dose scanner exist, and mainly for the standard-dose protocol. To the best of our knowledge, no studies of effective dose based on anthropomorphic phantom measurements exist for the new micro-dose protocol. METHODS: Two anthropomorphic phantoms, representing a 5-year-old (pediatric) and a 15-year-old (adolescent). The phantoms were exposed to EOS micro-dose and standard-dose protocols during full-spine imaging. Additionally, CR in scoliosis settings was performed. For all modalities, organ doses were measured and effective doses were calculated using thermoluminescent dosimeters. RESULTS: We found a 17-fold reduction (94%) of effective dose in micro-dose protocol compared with our CR system in the adolescent phantom. Micro-dose versus standard-dose protocol, showed a 6-fold reduction (83%), and for standard-dose versus our CR system a 2.8-fold reduction (64%) reduction of effective dose was observed.For the pediatric phantom, a 5-fold reduction (81%) of effective dose in micro-dose protocol compared to our CR system was observed. Micro-dose versus standard-dose protocol, showed a seven-fold (86%) reduction. However, we observed an increase in absorbed dose of 38% when comparing the EOS standard-dose protocol with our CR system. CONCLUSION: The EOS imaging micro-dose option exposes patients to lower radiation doses than any currently available modality for full-spine examination. Expected reduction of dose was established for the adolescent phantom when comparing CR and standard-dose protocol. However, no reduction of effective dose with EOS standard-dose protocol compared to our reference CR system was observed in the pediatric phantom. LEVEL OF EVIDENCE: N/A.

Circumferential fusion is dominant over posterolateral fusion in a long-term perspective: cost-utility evaluation of a randomized controlled trial in severe, chronic low back pain.

STUDY DESIGN: Cost-utility evaluation of a randomized, controlled trial with a 4- to 8-year follow-up. OBJECTIVE: To investigate the incremental cost per quality-adjusted-life-year (QALY) when comparing circumferential fusion to posterolateral fusion in a long-term, societal perspective. SUMMARY OF BACKGROUND DATA: The cost-effectiveness of circumferential fusion in a long-term perspective is uncertain but nonetheless highly relevant as the ISSLS prize winner 2006 in clinical studies reported the effect of circumferential fusion superior to the effect of posterolateral fusion. A recent trial found no significant difference between posterolateral and circumferential fusion reporting cost-effectiveness from a 2-year viewpoint. METHODS: A total of 146 patients were randomized to posterolateral or circumferential fusion and followed 4 to 8 years after surgery. The mean age of the cohort was 46 years (range, 20-65 years); 61% were females, 49% were smokers, 30% had primary diagnosis of isthmic spondylolisthesis, 35% had disc degeneration and no previous surgery, and 35% had disc degeneration and previous surgery. Eighty-two percent of patients have had symptoms for more than 2 years and 50% were out of the labor market due to sickness. The EQ-5D instrument was applied for the measurement of health-related quality of life and costs (2004 U.S. dollars) were measured in a full-scale societal perspective. Productivity costs were valued by the Friction Cost method, and both costs and effects were discounted. Arithmetic means and 95% bias-corrected, bootstrapped confidence intervals were reported. Nonparametric statistics were used for tests of statistical significance. Comprehensive sensitivity analysis was conducted and reported using cost-effectiveness acceptability curves. RESULTS: The circumferential group demonstrated clinical superiority over the posterolateral fusion group in functional outcome (P < 0.01), fusion rate (P < 0.04), and number of reoperations (P < 0.01) among others. Cost-utility analysis demonstrated circumferential fusion dominant over posterolateral fusion, that is, for each QALY gained performing circumferential fusion, the incremental saving was estimated at U.S. $49,306 (95% confidence interval, $27,183-$2,735,712). Results proved to be strong to various sensitivity analyses; only a differentiated underestimation of patients' need for postoperative household help against the circumferential approach could alter the dominance; however, still the probability of cost-effectiveness was >0.85 given a threshold for willingness to pay of U.S. $50,000 per QALY. CONCLUSION: Circumferential fusion is dominant over instrumented posterolateral fusion, that is, both being significantly cheaper and significantly better in a long-term, societal perspective.

Circumferential lumbar spinal fusion with Brantigan cage versus posterolateral fusion with titanium Cotrel-Dubousset instrumentation: a prospective, randomized clinical study of 146 patients.

STUDY DESIGN: A prospective randomized clinical study with a 2-year follow-up period was conducted. OBJECTIVE: To analyze the effects of circumferential fusion using ALIF radiolucent carbon fiber cages and titanium posterior instrumentation on functional outcome, fusion rate, complications, and lumbar lordosis. SUMMARY OF BACKGROUND DATA: Circumferential fusion has become a common procedure in lumbar spine fusion, both as a primary and salvage procedure. However, the claimed advantages of ALIF plus PLF over conventional PLF lack scientific documentation. METHODS: From April 1996 through November 1999, a total of 148 patients with severe chronic low back pain were randomly selected for either posterolateral lumbar fusion with titanium CD-Horizon (posterolateral group) or circumferential fusion with a ALIF Brantigan cage plus posterior instrumentation. The Dallas Pain Questionnaire (DPQ), the Low Back Pain Rating Scale (LBPR), and a questionnaire concerning work status assessed their outcomes. RESULTS: Both groups showed highly significant improvement in all four categories of life quality (DPQ) as well as in the back pain and leg pain index (LBPR), as compared with preoperative status. There was a clear tendency toward better overall functional outcome for patients with the circumferential procedure ( < 0.08), and this patient group also showed significantly less leg pain at the 1-year follow-up evaluation ( < 0.03) and less peak back pain at 2 years ( < 0.04). Sagittal lordosis was restored and maintained in the circumferential group ( < 0.01). The circumferential fusion patients showed a higher posterolateral fusion rate (92%) than the posterolateral group (80%)( < 0.04). The repeat operation rate including implant removal was significantly lower in the circumferential group (7%) ( < 0.009) than in the posterolateral group (22%). CONCLUSIONS: Circumferential lumbar fusion restored lordosis, provided a higher union rate with significantly fewer repeat operations, showed a tendency toward better functional outcome, and resulted in less peak back pain and leg pain than instrumented posterolateral fusion. The clinical perspective of the current study implies a recommendation to favor circumferential fusion as a definitive surgical procedure in complex lumbar pathology involving major instability, flatback, and previous disc surgery in younger patients, as compared with posterolateral fusion with pedicle screws alone.