The Diagnostic Value Of Digital Tomosynthesis For Femoroacetabular Impingement

Part one: The diagnostic value of hip joint digital tomosynthesis infunctional view (extreme flexion abduction and extremeexternal rotation) for femoroacetabular impingementObjective: To explore the diagnostic value of digital tomosynthesis (DTS)for femoroacetabular impingement (FAI) with hip joints in flexion abductionand external rotation functional position．Methods: Forty-two patients with clinical symptoms, signs, and digitalradiography (DR) of pelvic anteroposterior image consistent with FAIunderwent DTS examination. All patients had one or more clinical impingingtest positive. The images of the DR and DTS of each hip were compared bytwo radiologists, and the FAI-related signs were recorded. The detection ratesof FAI-related signs in anteroposterior view of DR and functional view ofDTS were statistically analyzed by mean of matching four form chi-squaretest．Results: There were54symptomatic hips in forty-two patients.“Anteriorimpingement” sign was positive alone in20hips,“Posterior impingement”sign was positive alone in4hips,“Drehmann’s” sign was positive alone in17hips,“Anterior impingement” sign and “Posterior impingement” sign wereboth positive in5hips,“Anterior impingement” sign and “Drehmann’s” signwere both positive in7hips,“Posterior impingement” sign and “Drehmann’s”sign were both positive in one hip. The herniation pit of femoral neck, femoralhead–neck junction bone protrusion, ossification of labrum and acetabular rimcyst formation were observed in functional view of DTS with the detectionrate of24%、43%、22%、19%respectively, which were significantly higherthan that detected by DR anteroposterior view (13%,22%,7%,6% respectively)(binomial distribution exact test: P=0.031,0.001,0.008,0.016);The detection rate of acetabular osteophytes, coxa profunda, joint spacenarrowing, posterior wall sign showed no significant difference between thetwo kinds of modality (DTS：72%、57%、11%、13%，DR：67%、57%、11%、13%，binomial distribution exact test: P=0.25,1,1,1). Overlappinganatomy structures could be removed outside the interesting region by DTSfunctional view, the acetabular cystic chang and labrum ossification caused byimpact were more easily observed in DTS functional view than in DR view.Furthermore, DTS showed anatomic abnormalities such as coxa profunda andbony protrusion at the junction of the head and neck clearly.Conclusion: DTS of hip joints in flexion abduction and external rotationfunctional posion can improve the accuracy of X-ray diagnosis of FAI. Part two: Low-dose Studies of Pelvis Digital TomosynthesisObjective: To explore the optimizing parameters for pelvis digitaltomosynthesis and find the balance of low radiation exposure dose and highimage quality.Methods: The research objects were16human cadaver pelvises with thewhole layers of soft tissue. Two kinds of scanning parameters (kV, FOV) wereset up, so four imaging conditions were compared. the DAP values andimaging quality score were recorded. Statistical comparisons were done usingvariance analysis of factorial design, P<0.05indicated statistical significance.Then DTS examination was performed using the optimal parameters of thepelvis DR. The dose ratios of DTS for16human pelvis were set up as6,7and10, respectively. The x-ray exposure dose and image quality scores werecollected in the following groups: dose ratio-6group, dose ratio-7group, doseratio-10group. For selecting the best parameters, one-way ANOVA test were used for comparison among groups, and S-N-K method for between groups.Results: The DAP values of diffrent kV and FOV showed statisticallysignificant difference (FkV=5.475, PkV=0.023，FFOV=6.233，PFOV=0.015,P<0.05), the radiation exposure dose in95kV was less than that in80kV, andthe exposure dose using exposure field in30cm×41cm was less than that in41cm×41cm, so kV or FOV affected radiation exposure dose respctively; kVand FOV had no interaction (FkV·FOV=0.438, PkV·FOV=0.511, P>0.05). Theimage quality scores showed no statistically significant difference usingdiffrent kV and FOV (FkV=0.011, PkV=0.919，FFOV=0.038, PFOV=0.846,FkV·FOV=0.004, PkV·FOV=0.951, P>0.05). The optimal parameters of pelvisDR were95kV, FOV30cm×41cm. The exposure dose (FDAP=9.45, PDAP=0.00) and image quality scores (Fimage quality scores=139.26, Pimage quality scores=0.00) showed statistically significant difference among groups. The exposuredoses from low to high in order were: dose ratio in6,7, and10groups. Imagequality scores in dose ratio-6group were significantly lower than that in othergroups. The image quality scores were no significant difference in dose ratio-7group and dose ratio-10group but the exposure dose was significantlylower in dose ratio-7group than that in dose ratio-10group.Conclusion: The optimal parameters for pelvis DR are95kV, FOV30cm×41cm, and for DTS is dose ratio7times. The pelvis DTS x-ray exposurelow-dose examination can be achieved by optimal scan parameter, which canprotect patients from unnecessary radiation damage.