title: CT-guided lumbar nerve root injections: are we using the correct radiation dose settings?
abstract: OBJECTIVE
  Selecting a lower tube current for CT fluoroscopic spine injections is a method of radiation dose reduction. Ideally tube current should be tailored to the patient's body habitus, but a greater influence on tube current may be the proceduralist's personal preference. The purpose of this study was to compare tube current and fluoroscopy time of different proceduralists for lumbar spine CT-guided selective nerve root blocks, and to correlate image quality to patient diameter and tube current.
  
  
  METHODS
  Eighty CT-guided SNRBs performed by 4 proceduralists were retrospectively reviewed for tube current and fluoroscopy time. Patient body habitus was evaluated by measuring anteroposterior diameters on scout images. Image quality was evaluated objectively and subjectively: noise was measured in the psoas muscle and images were graded on a 3-point scale.
  
  
  RESULTS
  The mean tube current was 59 ± 20 mA and mean fluoroscopy time was 10.4 ± 7.5 seconds. The mean tube current between proceduralists differed by almost 2-fold, and there was greater than 2-fold difference in mean fluoroscopy time (P < .0001 and .01, respectively). Mean AP body size was 27 ± 5 cm. When categoric data of tube current and AP diameter were analyzed, only AP diameter was a statistically significant variable influencing image noise (P = .009). Twenty of 23 patients with AP diameter ≤30 cm had adequate to excellent image quality, even with lower tube current of ≤40 mA.
  
  
  CONCLUSIONS
  Wide variability in tube current selection between proceduralists calls for a more objective method of selecting tube current to minimize radiation dose. Body size, measured by AP diameter, had the greatest influence on image quality. This could be used to identify patients for lower tube current selection.
authors.affiliation: Departments of Radiology, Duke University Medical Center, Durham, North Carolina 27710, USA.
authors.forename: J S
authors.initials: JS
authors.lastname: Schauberger
authors.forename: P G
authors.initials: PG
authors.lastname: Kranz
authors.forename: K R
authors.initials: KR
authors.lastname: Choudhury
authors.forename: J D
authors.initials: JD
authors.lastname: Eastwood
authors.forename: L
authors.initials: L
authors.lastname: Gray
authors.forename: J K
authors.initials: JK
authors.lastname: Hoang
mesh_terms: D000293:Adolescent; D000328:Adult; D000779:Anesthetics, Local / Q000008:administration & dosage*; D001822:Body Burden; D005260:Female; D006801:Humans; D007267:Injections; D008159:Lumbar Vertebrae / Q000187:drug effects / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000379:methods*; D011829:Radiation Dosage; D011835:Radiation Protection / Q000379:methods*; D015641:Radiography, Interventional; D011874:Radiometry; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013126:Spinal Nerve Roots / Q000000981:diagnostic imaging* / Q000187:drug effects; D014057:Tomography, X-Ray Computed; D055815:Young Adult
chemical_list: D000779:Anesthetics, Local