please refer to fig1 and 2 , which are the exploded and combination views of the present invention . the ultrasonic positioning device of the present invention for the epidural space 1 at least includes an epidural needle 11 , a connecting cylinder 12 and a loss - of - resistance checking syringe 13 . the epidural needle 11 has a hollow interior . the epidural needle 11 at least includes a needle tube 111 and a connecting cylinder 112 . the needle tube 111 has a hollow interior , and the needle tube 111 has a top for connecting to the bottom of the connecting cylinder 112 . a syringe receptacle 1121 is disposed at the side thereof for connecting the loss - of - resistance checking syringe . a probe receptacle 1122 is disposed on the top of the connecting cylinder 112 and a tenon trough 11221 is disposed on the side of the probe receptacle 1122 . the ultrasound needle transducer 12 is disposed on the hollow interior of the epidural needle 1 . the ultrasound needle transducer 12 at least includes a probe junction 121 and a probe tube 122 . the probe junction 121 is electrically connected to an external ultrasonic driving device ( not shown ). there is a tenon 1211 disposed on the middle of the side of the probe junction 121 for engaging with the tenon trough 11221 of the probe receptacle 1122 . thus , a probe fastening ( tenoning ) mechanism between the tenon trough 11221 and the tenon 1211 . the bottom of the probe junction 121 would be connected to the top of the probe tube 122 . there is a probe sensing end 1221 at the bottom of the probe tube 122 , and there is an ultrasonic sensor ( not shown ) in the probe sensing end 1221 . the ultrasonic sensor is used for measuring the distance between a needle head 1111 and the epidural space and transferring the measured echo signal to the external ultrasonic device . the ultrasound needle transducer can be designed to have two types of front facet . one design is with the flat facet ; the other design is with a 45 degree oblique facet . the design of the flat facet is most easy approach . the oblique facet design will need to have a good match to the aperture of the tuohy needle tip . since the epidural needle is obliquely inserted into the back of the patient , therefore , the design of the oblique facet will have the emitted ultrasound waves close to perpendicularly hit the tissue layer of ligamentum flavum and dura mater . therefore , there will be a stronger reflected ultrasound signal reflected from the ligamentum flavum and dura mater . the loss - of - resistance checking syringe 13 is connected to the epidural needle 11 for determining whether the epidural needle 11 is inserted into the epidural space . the loss - of - resistance checking syringe 13 includes a sleeve 131 and a push rod 132 . the back end of the push rod 132 is fitted in the sleeve 131 , whereby the push rod 132 is moved forward and backward in the sleeve 131 . there is a syringe junction 1311 on the front - end of the sleeve 131 and the syringe junction 1311 is inserted into the syringe receptacle 1121 . referring to fig3 , which is a flow chart of the ultrasonic positioning method for the epidural space according to the present invention . the reference numeral “ 610 ” is a puncturing step , the reference numeral “ 620 ” is an advancing step , and the reference numeral “ 630 ” is a positioning step , as disclosed above . the reference numeral “ 632 ” is an actual implementation for the step 630 . if the positioning step 630 is confirmed to not be in place ( the tip of the epidural needle has not been inserted into the epidural space ), the advancing step 620 and the positioning step 630 will be repeatedly implemented . if the positioning step 630 is confirmed to be in place ( the tip of the epidural needle has been inserted into the epidural space ), a confirmation step 640 is performed ( referring to the above ). after the confirmation step 640 , a replacement step 650 is performed ( referring to the above ) and then an injection step 660 is implemented ( referring to the above ). fig4 shows the schematic view of implementing the present invention . the ultrasound needle transducer 12 is disposed in the epidural needle 11 and the epidural needle 11 is obliquely pierced into the joint between two vertebras . then , the epidural needle 11 is advanced toward the epidural space , the distance between the tip 1111 of the epidural needle 11 and the epidural space is measured based on the ultrasonic echo signal reflected from the ligamentum flavum and dura mater . when the ultrasonic echo signal indicates the tip of the epidural needle is inserted into the epidural space , the loss - of - resistance checking syringe 13 is pushed for determining whether the push rod 132 of the loss - of - resistance checking syringe 13 can be easily pushed . when an operator pushes the push rod 132 , air or saline in the sleeve 131 is injected from the syringe junction 1311 to the syringe receptacle 1121 . then , air or saline is flowed from the receptacle 1121 to the epidural needle 11 through the connecting cylinder 112 , and finally flowed to the epidural space . if the needle is in the ligamentum flavum ( lf ), which is a dense tissue , the injection pressure is increased . then , the operator would feel it is very difficult to push the push rod 132 forward . if the tip of epidural needle 11 passes through the lf and then enters into the epidural space , which is a space of negative or neutral pressure , the operator can easily pushed the push rod 132 forward and inject saline or air into the epidural space . thus , the operator could confirm whether the tip of the epidural needle is inserted into the epidural space by this method , thereby enhancing the positioning success probability for the epidural needle . fig5 is an ultrasonic a - mode graph for the probe gradually advanced toward the epidural space according the present invention . in the graph , the solid line is the location of the probe tip , the peak signal indicated by the arrow of the solid line is dura mater , and the peak signal indicated by the arrow of the dotted line is ligamentum flavum , so that epidural space is located between the dura mater and the ligamentum flavum . from top to bottom in the graph shows the probe is gradually advanced toward the epidural space , and thus the signal for the dura mater signal and the signal for the ligamentum flavum are gradually shifted towards the location of the probe tip . the bottom of the a - mode graph shows the probe tip has been inserted into the epidural space . while the invention has been described in terms of what are presently considered to be the most practical and preferred embodiments , it is to be understood that the invention need not to be limited to the disclosed embodiment . on the contrary , it is intended to cover various modifications and similar arrangements included within the spirit and scope of the appended claims which are to be accorded with the broadest interpretation so as to encompass all such modifications and similar structures .
an ultrasonic positioning method for real time measuring the distance between the epidural needle and the epidural space is provided . the ultrasonic positioning method at least includes a puncturing step ; an advancing step ; a positioning step for simultaneous detecting reflected ultrasonic signals from the ligamentum flavum and dura mater ; a replacement step for removing the ultrasound needle transducer and putting an injecting catheter ; and an injection step for injecting an anesthetic into the epidural space via the injecting catheter .