Virtual Non-contrast from Dual Energy CT: an Application of Obstructive Jaundice
|School||Taishan Medical College|
|Course||Medical Imaging and Nuclear Medicine|
|Keywords||Tomography X-ray computed Dual-energy Obstructive jaundice Comparative study|
ObjectiveTo assess the value of virtual unenhanced (VU) images in finding the uses ofobstructive jaundice who underwent hepatic dual energy computed tomography (DECT).MethodsBetween April2012and October2012, thirty consecutive patients, who werediagnosed of obstructive jaundice were studied. The thirty patients is consisted of sixteenmales and fourteen females with a mean age of57.9years (range,34-75years). First, theconventional non-contrat imaging(CNC) covering whole upper abdomen was acquiredwithout oral contrast medium, then, using oral contrast medium500ml, all patientsunderwent enhancement scanning including arterial, portovenous and delayed phase bydual energy computed tomography. The dedicated software of Live VNC was used toreformat virtual non-enhanced CT at the arterial phase. We consider that conventionalunenhanced(CU) images as the gold standard. Mean CU and VU image were compared bytwo blinded radiologists in detecting the lesions. Besides, we compared the image SNR ofCU and VU using T test. At the same time, the effective radiation dose of a triple-phaseprotocol (CU, arterial and DE portal phases) was compared with that of a dual-phaseprotocol (arterial and DE portal phases).ResultsCombination of the enhancement image, VNC can show all lesions, includingcholecystolithiasis (6cases), choledocholithiasis (5cases), biliary tumor (11cases),ampulla’s carcinoma (3cases), pancreatic neoplasm (5cases). Compared with theconventional unenhanced (CU), the image quality of virtual unenhanced (VU) was poorer,which can meet the requirements of diagnosis of disease and stone, no significantdifference in detection of lesions was observed between VU and CU images. The averageCT value and the SNR had no statistical difference among conventional non-enhanced CTand virtual non-enhanced CT, but a significant difference in radiation dose was observed between VU and CU, dose was reduction achieved by omitting the unenhanced acquisitionin VU images.ConclusionsVU images can be obtained with similar image quality as CU. This approach favors areduction in patient’s radiation exposure. Therefore, the VNC of dual energy computedtomography (DECT) makes it possible to replace the conventional unenhanced images.SignificanceObstructive jaundice is a common sign in clinic, although benign disease is in themajority, including cholelithiasis, inflammation of bile duct, congenital bile ductabnormalities, the malignant obstructive jaundice has the features of misprision ofincidence, poor prognosis. Therefore, the early diagnosis is of great significance forclinical treatment plan. In current clinical work, the diagnosis of obstructive jaundice ismainly dependent on ultrasound, CT, MRCP, ERCP, etc. But they have some disadvantages,the accuracy in diagnosis of malignant obstructive jaundice by ultrasound is low, MRCPcan’t evaluate the lesions of peripheral vascular, ERCP is an invasive procedure and haspossible complication. MSCT has fast scanning speed, and you can get any direction of thereconstructed image, which can display of the small bile duct lesions, therefore, MSCT isextremely favorable in the diagnosis of biliary diseases.However, the radiation doses ofthe conventional enhanced imaging including the conventional non-contrast imaging(CNC)is high, our study points out the VNC can replace the conventional unenhanced images.Therefore, the virtual unenhanced technology can not only save scanning time, reduce theradiation doses, but also provide sufficient diagnostic information for clinician, which isimportant for the purpose of treatment.