High-Definition CT Gemstone Spectral Imaging In The Application Of Osteonecrosis Of The Femeral Head In "Crescent Sign", "Fracture Sign"

Objective:To investigate the valual of Gemstone Spectral Imaging (GSI) in diagnosing Osteonecrosis of the Femeral Head (ONFH), To evaluate the correlation of bone marrow edema(BME) with comparison of "Crescent Sign", "Fracture Sign" by GSI CT and MRI.Materials and MethodsIn the prospective study, the patients were authorized by The First Affiliated Hospital of Guangdong University of Traditional Chinese Medicine and informed consent. During the period from January 2015 to February 2016, patients who hospitalized and clinically suspected ONFH were scanned with with GE Gemstone spectrum CT (Discovery CT750 HD) scanners and GE Signa HDxt 3.0T superconducting MRI machine, fifty hips were treated surgically, and the remainder’s diagnoses were confirmed by the combination with patient history, clinical signs and other information with the consensus of surgeons and radiologists. According to inclusion criteria and exclusion criteria, eighty-three hips in forty-seven patients were chose, excluded six hips who has had surgery. These patients original images with the slice thickness of 1.25 mm and spacing of 1.25 mm were sent to an AW 4.4 workstation with 140 conventional polychromatic images and keV reconstruction method. Then using spectrum imaging reconstruction and postprocessing software and a special GSI viewer for analysis.1) The keV of optimal contrast-to-noise ratio (Optimal CNR) for viewing femoral head compared to surrounding muscle and other soft tissues was selected using energy spectrum analysis software. At the same time, calculated SNR (Signal Noise Ratio) by recording the average CT value (mean) and standard CT value difference (SD, Standard Deviation). Each patients were measured for three times.2) Image-processing techniques including volume rendering (VR), multiple planner reconstruction (MPR) et al were used to observe the keV of optimal contrast-to-noise ratio imaging. Comparison of the image quality at the optimal selected monochromatic level, the conventional polychromatic images and MRI images, analysising the number of "Crescent Sign", "Fracture Sign" which displayed.3) The image quality were also analyzed at GSI CT and routine computed tomography, The emphasis of the observation was osteonecrosis’s shape, "Crescent Sign", "Fracture Sign" and cystic. Each was divided into four level:clearly,3 points; a litter fuzzily,2 points; fuzzily,1 point; could not be displayed,0 point. Using FSE T1WI, T2WI and FSE T2 fat-suppression scaning, both coronal and axid were performed in all patients. The bone marrow edema in ONFH was graded into 0-3, which correlated with the stage of ONFH was concerned.0 grade, there was no any edma; lgrade, edema limited to the femoral head; 2 grade, edema limited to the femoral head and neck area; 3 grade, edema extending to subtrochanteric femoral head.Results:1) The monochromatic images at about 67 keV (mean 67.60+1.73) provided the optimal CNR for femoral head. And there was no difference whether placed the reagion of interest (ROI) in femoral head necrosis area.2) The image quality at the optimal selected monochromatic level was superior to conventional polychromatic images (P<0.05). And there was no difference by SNR(signal-to-noise Ratio) comparison verification. GSI CT was useful in visualizing osteonecrosis’s shape, "Crescent Sign", "Fracture Sign" and cystic. There were no statistical differences between GSI and MRI with regard to "Crescent Sign", GSI was significantly more sensitive than MRI in displaying "Fracture Sign" (^=5.473, P=O.000<0.05). Wherein one type Ⅲa patients, MRI showed "crescent sign" but no edema, GSI CT had but seem the sign, the reason might be the "crescent sign" range is too small, or the patient is in a stable condition after treatment state; the other hip whereas GSI CT and hybrid energy spectrum can be observed "crescent sign", but the MRI image cannot, the reason might be the CT is more sensitive than MRI in the display of "crescent sign", or the layer thickness is too thick.3) The correlation of BME with comparison of the stage of the femoral head osteonecrosis and "Crescent Sign", "Fracture Sign" is closely related by MRI (χ2=39.243, P=0.003<0.05). And significant positive correlation were observed between the stage of ONFH and BME ((χ2=19.640, P=0.003<0.05; χ2=221.486, P=0.000 <0.05)), that is the incidence of BME is increasing with the extent of necrosis of ONFH. There is "Fissure sign" and "Crescent sign", there is suggestive of bone marrow edema.Conclusion:GSI with monochromatic images at 67 keV displays clearly the most ONFH with image quality improved, as compared with conventional polychromatic images. It may be used solely or combined with MRI in clinical work, depending on individual patient disease condition. Significant positive correlation were observed between the stage of ONFH and BME. Once BME came, there is suggestive of tiny fracture.