title: An alternative approach to account for patient organ doses from imaging guidance procedures.
abstract: OBJECTIVE
  To investigate the feasibility of an alternative method of accounting for additional organ doses resulting from image guidance procedures during patient treatment planning through tabulated values based on scan protocol and scan site.
  
  
  METHODS
  Patient-specific imaging dose to 30 patients resulting from Varian OBI kV-CBCT scans using the Standard Head (17 patients), Low-dose Thorax (8 patients), and Pelvic (5 patients) scan protocols were retrospectively calculated using Monte Carlo methods. Dose dependence on scan location and patient geometry was explored. Patient organ doses were analyzed by using dose-volume histograms and expressed by the mean, minimum dose delivered to 50% of the organ volume, D50. The reported doses are dose-to-medium instead of dose-to-water.
  
  
  RESULTS
  The organ doses from all patient-specific calculations show predictable and limited ranges across patients. For brain isocenters using Standard Head Scans: Bone: 0.7-1.1 cGy, Brain: 0.2-0.3 cGy, Brainstem: 0.2-0.3 cGy, Skin: 0.3-0.4 cGy, Eye: 0.03-0.3 cGy. For head and neck patients using the Standard Head Scan: Bone: 0.3-0.6 cGy, Parotids: 0.3-0.4 cGy, Spinal Cord: 0.15-0.25 cGy, Thyroid: 0.1-0.25 cGy, Skin: 0.2-0.3 cGy, Trachea-Esophagus: 0.1-0.2 cGy. For chest using Thorax Scans: Bone: 1.1-1.8 cGy, Soft tissue organs (Bowel, Lung, Heart, Kidney, Esophagus, and Spinal Cord): 0.3-0.6 cGy. For abdominal site using Pelvic Scans: Bone: 3.2-4.2 cGy. Soft tissue organs (Bladder, Bowel, Rectum, Prostate, and Skin) D50s fell between 1.2 and 2.2 cGy. Femoral Heads: 2.5-3.4 cGy.
  
  
  CONCLUSIONS
  It is adequate to estimate and account for organ dose by using tabulated values based on scan procedure and site because organ doses from imaging procedures are only modestly dependent upon scan location and body size. Considering the dose variation and magnitude of dose from each scan protocol in comparison to therapeutic doses, this approach provides a simple alternative to account for additional imaging guidance doses during patient treatment planning. Clinicians can use these tabulated values to make informed decisions in selecting the appropriate imaging procedures and imaging frequency during radiotherapy treatment.
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, USA.
authors.forename: Alan P
authors.initials: AP
authors.lastname: Nelson
authors.affiliation: Department of Radiation Oncology, Vanderbilt University School of Medicine, Nashville, USA; Department of Physics and Astronomy, Vanderbilt University, Nashville, USA. Electronic address: george.ding@vanderbilt.edu.
authors.forename: George X
authors.initials: GX
authors.lastname: Ding
mesh_terms: D054893:Cone-Beam Computed Tomography / Q000009:adverse effects*; D005240:Feasibility Studies; D005260:Female; D006257:Head / Q000000981:diagnostic imaging*; D006801:Humans; D008297:Male; D009010:Monte Carlo Method; D009369:Neoplasms / Q000532:radiotherapy; D010388:Pelvis / Q000000981:diagnostic imaging*; D011829:Radiation Dosage; D013902:Radiography, Thoracic / Q000009:adverse effects*; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects*; D012189:Retrospective Studies
keywords: Managing imaging dose; Method of accounting organ dose; kV–CBCT dose