title: Computed tomography scan to detect intra-articular air in the knee joint: a cadaver study to define a low radiation dose imaging protocol.
abstract: OBJECTIVE
  To determine the lowest estimated radiation dose necessary to reproducibly detect intra-articular air in the knee joint of a cadaver model.
  
  
  METHODS
  Ten adult fresh-frozen cadaver knees with intact joint capsules were thawed and scanned at 5 decreasing radiation doses (decreasing by approximately half from 8.42 to 0.74 mGy) after introducing increasing volumes (0, 0.1, 0.3, 0.5, 0.7, and 0.9 cc) of intra-articular air. Scans were performed using 2.0-mm slice thickness from the distal one-third of the femur to the proximal one-third of the tibia. Sagittal and coronal reconstructions of each scan using 1.0-mm slice thickness were rendered. All scans were reviewed by (1) a single attending radiologist, (2) a single attending orthopedic surgeon, and (3) a single chief resident, for the presence of intra-articular air.
  
  
  RESULTS
  The sensitivity and specificity of computed tomography scan to detect intra-articular air at each volume of intra-articular air (0.1, 0.3, 0.5, 0.7, and 0.9 cc) was 100% at 0.74 mGy--the radiation threshold dose (scan parameters: voltage 80 kV, current: 33 mA, and scan time: 12.17 seconds). The effective radiation dose at 0.74 mGy for a CT scan of the knee is approximately 0.10 mSV.
  
  
  CONCLUSIONS
  Computed tomography scan to detect traumatic knee arthrotomies can be successfully accomplished at a threshold radiation dose of 0.74 mGy and for an intra-articular volume of 0.1 cc of air. This low radiation dose protocol and volume of intra-articular air should be taken into consideration with future studies evaluating the use of CT scan to detect traumatic arthrotomies.
authors.affiliation: Department of Orthopaedic Surgery, NYU Hospital for Joint Diseases, New York, New York 10003, USA.
authors.forename: Sanjit R
authors.initials: SR
authors.lastname: Konda
authors.forename: Daniel O
authors.initials: DO
authors.lastname: Howard
authors.forename: Soterios
authors.initials: S
authors.lastname: Gyftopoulos
authors.forename: Roy I
authors.initials: RI
authors.lastname: Davidovitch
authors.forename: Kenneth A
authors.initials: KA
authors.lastname: Egol
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D000388:Air; D002102:Cadaver; D005260:Female; D006801:Humans; D007718:Knee Injuries / Q000000981:diagnostic imaging / Q000209:etiology; D007719:Knee Joint / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011829:Radiation Dosage; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D014947:Wounds and Injuries / Q000150:complications