Initial Experience For Visualizing Hand And Foot Tendons And Clinical Evaluation Of Bone Removal In CT Angiography Of The Head And Neck By Dual Energy CT

Objective:The aim of this study was to assess the feasibility of visualizing hand and foot tendons and evaluating the effect of bone removal in CT angiography by using dual energy CT(DECT).Material and Methods:This study included two parts:(1) An initial study of dual energy CT in hand and foot tendons;(2) Clinical evaluation of dual energy bone removal in CT angiography of the head and neck:comparison with conventional bone-subtraction CT angiography.The details were as follows:(1) Forty patients who were clinically suspected to suffer from hands or feet were scanned on a SOMATOM Definition Dual Source CT system in dual energy mode at tube voltages of 140 and 80 kV and a ratio of 1:4 between tube currents.The effective mAs were 40mAs and 170mAs in hands for tube A and tube B,while 56mAs and 234mAs in feet;collimation of 0.6mm,pitch of 0.7,rotation time of 1.0s/rot,slice thickness of scan 2mm and reconstruction thickness 0.75mm.The extent of scan included carpal joint in hands and ankle joint in feet to the fingertip,necessarily contained forearm and leg.All of the patients were scanned bilateral except one only scanning the weak side for trauma of forearm.The reconstructed images were post-processing by VR,MPR,and CPR with Inspace software respectively.Two experienced radiologists differentiated and analyzed the tendons.The emphasis of observation was the insertion,edge,profile,density and continuity of tendons as well as the soft tissues and skeletal structure.(2) The study involved 52 patients who were divided into two groups at random, and scanned on dual source CT for head and neck CTA.This study was approved by Ethics Committee.Informed consent was obtained from all patients or their legal representatives after the nature of the procedure had been fully explained.Patients were positioned with an adjustable head-holder device.The scan range included the inferior end-plate of the atlas up to the vertex for patients with suspected aneurysms or sinus thrombosis,and the aortic arch to the vertex for patients with stroke. Non-ionic iodinated contrast medium(Omnipaque 350) was injected with a power injector,and the scan delay was individually adapted by using a bolus-tracking technique.Dual energy bone removal CTA and conventional bone subtraction CTA were applied to each of the two groups,respectively.Dual energy bone removal CTA was set by dual energy technique,while conventional bone subtraction CTA was made by Neuro-DSA software.The bone-subtraction was performed automatically in the different methods.Vascular structures as well as brain tissue remained visible.Then the subtracted images were further processed with maximum-intensity-projection (MIP),volume rendering technique(VRT) and multiple planner reconstruction(MPR) for image evaluation.Two experienced radiologists reviewed the resulting subtracted and non-subtracted volume data with respect to the delineation and detection of image quality and vascular pathology.Results:(1) Twelve patients(total 24 hands and feet) were found to be normal and the others abnormal.Dual energy techniques are very useful for visualizing most hand and foot tendons,such as Flexor pollicis longus tendon,Flexor digitorum superficialis/profundus tendon,Achilles tendon,Extensor hallucis longus tendon and Extensor digitorum longus tendon et al.Normal tendons were always showed smooth, continues,steady density and clear edge.DECT can depict the whole shape of the tendons and their fixation points clearly.But not all tendons were displayed the same clearly.Peroneus longus tendon can only be seen indistinctly in the sole of foot while the distal end of articulatio metacarpophalangea in extensor digitoium tendon and extensor pollicis longus tendon were poorly shown.Twenty-eight patients were considered to be abnormal by DECT.The lesions of tendon circuity,thickening, adherence,tear and loss were all displayed clearly with the accuracy of 92.7%. Besides the tendon lesions above,much more informations,such as bone and soft tissues were offered by DECT at the same time.(2) The means of Weighted CT Dose Index(CTDIvol) for bone removal dual energy CTA and conventional bone subtraction CTA were 20.5635±0.00977mGy and 25.5746±0.55827mGy,respectively.There was significant difference between them. The percentage of carotid and vertebral arteries and all other vessels that could be successfully assessed with these two methods were 87.8%,68.0%,83.0%,and 93.5%, 91.8%,92.6%,respectively.There were no significant differences among the carotid arteries,however there were significant differences among the vertebral arteries.In addition,15 diseases were detected by dual energy CTA,including 5 aneurysms,9 stenoses and 1 cerebral arterio-venous malformation(AVM),with the accuracy of 100%.Conclusions:DECT,as a novel technology for imaging examination,has important application value:(1) It could clearly display both anatomy and pathologic changes of most hand and foot tendons except peroneus longus tendon in the sole of foot and the distal end of articulatio metacarpophalangea in extensor digitoium tendon and extensor pollicis longus tendon,offer a new method to visualize tendons and increase the quality of diagnosis and is very useful in surgical planning.(2) Compared with conventional bone subtraction CTA,dual energy bone removal CTA had a lower radiation dose.It provided a new method for detecting vascular diseases in routine clinical work and could eliminate most bones in the head and neck successfully,while the bone subtraction effect around the vertebral artery was unsatisfactory.