| Background:Scoliosis is a complex three-dimensional deformity. Idiopathic scoliosis is the mostcommon in Scoliosis, accounting for80%of all scoliosis in adolescents. The reportedincidence is up to0.75%to2.4%. Smaller in patients with scoliosis angle, can usuallybe bracing for conservative treatment. The only effective treatment for patients withsevere scoliosis is surgery. Scoliosis surgery is one of the difficulties of spine surgery.Posterior whole pedicle screw internal fixation is the most common procedure inscoliosis surgery. However,the fixation has a very high difficulty and risk. Reported inthe literature, thoracic pedicle screw misplacement rate is up to6%-54.7%.The auxiliary methods for pedicle screw safe implantation include the innovationof surgical techniques, such as the "funnel technique" and the improvement of surgicalinstruments et al. The most common used in clinic is intraoperative X-ray fluoroscopy,but the method can only show the pedicle two dimensional plane, the image of poorquality, prone to errors. Radiation exists between both doctors and patients in peration.Computer-aided navigation technology can significantly reduce the misplacement, butthere are registration errors. Incorrect navigation information leads to the failure of thecorrect screw channel. This equipment is expensive and complicated to operation. It isdifficult to be popularized. Neurophysiological monitoring can be effective in preven-ting the occurrence of neurological complications, but need the high sterile demandand assort between surgeon and anesthesiologist. With the needs of professional opera-ting and analytical judgment, clinical application is not universal.Ultrasonics has advantages of no ionizing radiation, low-cost, easy to install.Mujagic measured the penetration depth of the human vertebral cancellous bone with1MHz and3.5MHz ultrasonic transducers in the sink. The depth is1.65-1.9mm.Raphael observed the ultrasound images of sheep vertebral cancellous bone with2.5MHz transducer in the pedicle path. The increased waveform of amplitude and thedistance of1.5cm between marrow-cortex were observed. Domestic literature has noreport of such research. The study of Mujagic's and Raphael's meet the basicrequirement of the ultrasound navigation.The study discusses the feasibility of pedicle screw implantation ultrasoundnavigation and data preparation. The subject is subsidizedby the National Natural Science FundObjective:1. Clear ultrasound parameters of human vertebral cancellous bone with ultrasonictransmitted method.2. Clear the penetration depth of the human vertebral cancellous bone of ultrasoundsignal with ultrasonic backscatter method3. Investigate the ultrasonic waveform characteristics and distance for anticipatingmarrow-cortex interface refering to ultrasonic finite difference time domain(FDTD)simulation.4. Explore the advantaged ultrasound transducer for predicting marrow-cortexinterface.Methods:All experiments were performed in sink of connstant temperarure lining the innerwall of sound-absorbing material being filled with distilled water and the amount ofsurfactant. The water's temperature was controlled at about20℃. Stimulattingtransducer transmits ultrasound signals. Received signals were amplificated byultrasound analyzer, displayed on the oscilloscope. Signals inputted PC, usedMATLAB software analyzing data.The ultrasound waveform was reconstructed.1. Ultrasound transmitted experiment: the ultrasonic signal were launched from0.5MHz,1MHz,1.5MHz,2.25MHz,3.5MHz center frequency transducer, transmittedthrough seven lumbar cancellous bone samples with the thickness of0.9cm. The trans-mitted signal was received by the receiving transducer. Graphical features were analy-zed. Center frequency attenuation, broadband frequency attenuation and speed ofsound of different frequencies were measured.2. Vertebral penetration depth experiment: the ultrasonic signal were launched from0.5MHz,1MHz,1.5MHz,2.25MHz,3.5MHz center frequency transducer, transmittedthrough seven lumbar cancellous bone samples with different thickness, reflectedthrough the steel plate, transmitted through bone samples again, received by the sametransducer. Graphical features were analyzed. Penetration depth of ultrasound backs-catter was measured.3.Spinal ultrasound navigation basic research experiment: the ultrasonic signal werelaunched from1MHz,1.5MHz,2.25MHz center frequency transducer, transmittedthrough seven lumbar vertebral bone samples with different thickness, reflected throu- gh the vertebral cortex, transmitted through cancellous bone again, received by thesame transducer. Graphical features were analyzed. Penetration depth of ultrasoundbackscatter was measured. Effective ultrasound waveform and the distance to vertebralcortex were obtained.Ultrasonic finite difference time domain(FDTD) simulation: A lumbar vertebralbone sample were scanned by the Micro-CT. The two-dimensional image was interce-pted for the establishment of the FDTD simulation model. The initial conditions,boundary conditions and excitation conditions were setted to complete the FDTDsimulation. The ultrasonic backscatter simulation signal was getted.Results:1. Ultrasound transmitted experiment: Seven of the L3vertebral cancellous bonesamples were transmitted by0.5MHz,1MHz,1.5MHz,2.25MHz,3.5MHz centerfrequency transducer. Each sample were selected five regions of interests(ROIs).Acoustic data were measured. Center frequency attenuation was7.68±4.06dB/cm(0.5MHz),18.86±7.49dB/cm(1MHz),29.96±11.23dB/cm(1.5MHz),41.40±21.07dB/cm(2.25MHz),52.96±15.33dB/cm(3.5MHz);Normalized broadband ultrasound attenua-tion was28.70±6.37dB/(cm MHz,)(0.5MHz),17.31±10.39dB/(cm MHz,)(1MHz),20.70±6.94dB/(cm MHz)(1.5MHz),16.52±5.35dB/(cm MHz)(2.25MHz),12.46±5.16dB/(cm MHz)(3.5MHz); Speed of sound was1514.41±16.81m/s(1501.67-1506.30m/s),(0.5MHz);1508.61±4.97m/s,(1502.03-1518.23m/s),(1MHz);1502.56±2.19m/s,(1500.20-1507.02m/s),(1.5MHz);1500.60±0.59m/s,(1500.04-1502.44m/s),(2.25MHz);1500.15±0.15m/s,(1500.00-1500.61m/s),(3.5MHz). Statistical analysis:center frequency attenuation between the two groups was significant differencesamong all groups. nBUA: For the three groups (1,1.5,2.25MHz),there was no signifi-cant difference, was significant differences between the other groups. SOS: Therewere significant differences between groups2. Ultrasonic backscatter penetration distance experiment with reflection of Steelplate: Seven L4vertebral cancellous bone samples were backscatterred by0.5MHz,1MHz,1.5MHz,2.25MHz,3.5MHz center frequency transducer. The ultrasonic signalpenetration distance in the cancellous bone was2.19±0.0.34cm(0.5MHz),1.17±0.38cm(1MHz)0.93±0.44cm(1.5MHz),0.69±0.20cm (2.25MHz),0.69±0.20cm (3.5MHz). The statistical analysis has no significant difference among all groups.3. Ultrasound simulation and vertebral ultrasound backscatter experiment: In FDTDsimulation, two ultrasonic simulation signals with several times high amplitude thanneighboring waveform amplitude were emerged, which distance to the vertebralcortex is0.2cm. The waveform amplitudes before the distance of0.2cm fluctuated.Seven L5vertebra samples were studied in ultrasound backscatter experiment.Ultrasonic signal located in0.6cm to the diatance to vertebral cortex showed theoverall increased trend significantly, performed high amplitude, which one timehigher than the lowest neighboring waveform amplitude in1MHz and1.5MHzwaveform, but less than one time in2.25MHz waveform. The waveform amplitudesbefore the distance of0.6cm fluctuated. Experimental study was consistent withFDTD simulation. Of three types of different frequency, normalized amplitude dataof the distance in1.2cm,0.9cm and0.6cm to vertebral cortex were analysed.Normalized amplitudes in the distance of1.2cm and0.9cm showed a significantdifference with which in the distance of0.6cm separately. The two groups' norma-lized amplitude in the distance of1.2cm and0.9cm to vertebral cortex showed nosignificant difference.Conclusions:1. Ultrasonic parameters were acquired in vertebral cancellous bone with differentfrequencies. Ultrasonic attenuation and frequency in1MHz,1.5MHz,2.25MHz,approximately show linear relationship. The ultrasonic attenuation is closely relatedwith BMD. SOS in the vertebral cancellous bone was negative dispersion phenomena.Ultrasound transmitted experiments showed the superiority of the choice of the1MHz,1.5MHz,2.25MHz transducers in the pedicle ultrasound navigation.2. Ultrasonic backscatter penetration depth data in vertebral cancellous bone wasobtained. The depth data with steel plate reflection may be higher than the actualpenetration distance. Penetration depth with the ultrasonic frequency is closely relatedto BMD and bone microarchitecture. Ultrasound backscatter experiments showed thesuperiority of the choice of the1MHz,1.5MHz,2.25MHz transducers in the pedicleultrasound navigation.3. Ultrasound FDTD simulation can effectively simulate the ultrasonic signal in thetrend of cancellous bone to cortical bone conduction. But two-dimensional modelmissed a part of the actual three-dimensional information, leading to the deviation of the specific data.4. Normalized amplitudes in1MHz and1.5MHz center frequency transducers showmore than one time of adjacent minimum signals' amplitude in which of0.6cmdistance to vertebral cortex.1MHz,1.5MHz center frequency transducers in thecancellous bone penetration depth and anticipated distance to marrow-cortex interfaceshow advan-tage, apply to pedicle screw implantation ultrasound navigation.
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