title: Estimated effective dose of CT-guided percutaneous cryoablation of liver tumors.
abstract: OBJECTIVE
  To estimate effective dose during CT-guided cryoablation of liver tumors, and to assess which procedural factors contribute most to dose.
  
  
  METHODS
  Our institutional review board approved this retrospective, HIPAA-compliant study. A total of 20 CT-guided percutaneous liver tumor cryoablation procedures were performed in 18 patients. Effective dose was determined by multiplying the dose length product for each CT scan obtained during the procedure by a conversion factor (0.015mSv/mGy-cm), and calculating the sum for each phase of the procedure: planning, targeting, monitoring, and post-ablation survey. Effective dose of each phase was compared using a repeated measures analysis. Using Spearman correlation coefficients, effective doses were correlated with procedural factors including number of scans, ratio of targeting distance to tumor size, anesthesia type, number of applicators, performance of ancillary procedures (hydrodissection and biopsy), and use of CT fluoroscopy.
  
  
  RESULTS
  Effective dose per procedure was 72±18mSv. The effective dose of targeting (37.5±12.5mSv) was the largest component compared to the effective dose of the planning phase (4.8±2.2mSv), the monitoring phase (25.5±6.8mSv), and the post-ablation survey (4.1±1.9mSv) phase (p<0.05). Effective dose correlated positively only with the number of scans (p<0.01).
  
  
  CONCLUSIONS
  The effective dose of CT-guided percutaneous cryoablation of liver tumors can be substantial. Reducing the number of scans during the procedure is likely to have the greatest effect on lowering dose.
authors.affiliation: Department of Radiology, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Republic of Korea. rapark@skku.edu
authors.forename: Byung Kwan
authors.initials: BK
authors.lastname: Park
authors.forename: Paul R
authors.initials: PR
authors.lastname: Morrison
authors.forename: Servet
authors.initials: S
authors.lastname: Tatli
authors.forename: Usha
authors.initials: U
authors.lastname: Govindarajulu
authors.forename: Kemal
authors.initials: K
authors.lastname: Tuncali
authors.forename: Phil
authors.initials: P
authors.lastname: Judy
authors.forename: Paul B
authors.initials: PB
authors.lastname: Shyn
authors.forename: Stuart G
authors.initials: SG
authors.lastname: Silverman
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001822:Body Burden; D017115:Catheter Ablation / Q000379:methods*; D005260:Female; D006801:Humans; D008113:Liver Neoplasms / Q000000981:diagnostic imaging* / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D011874:Radiometry / Q000379:methods*; D012062:Relative Biological Effectiveness; D025321:Surgery, Computer-Assisted / Q000379:methods*; D014057:Tomography, X-Ray Computed / Q000379:methods*