| Objectives1. To explore the parameters optimization of NCE-MRA for imaging renal artery.2. To analyse the imaging quality of renal artery performed by NCE-MRA.3. To assess the accuracy of NCE-MRA for the detection of renal artery stenosis (RAS), in comparison with CE-MRA as the reference standard.Materials and MethodsCollected30patients that was suspected with renovascular hypertension in our hospital(excluding people with contraindication of undergoing MRI) who underwent renal artery MRI to investigate the presence of RAS from July2012to April2014,including18male patients and12female patients, average age of40years(14-81years). All of them was underwent NCE-MRA and CE-MRA exams successively on the same MR device on the same date.All MR exams including NCE-MRA and CE-MRA were performed with a GE1.5T superconductive MR scanner using an8-channel body coil.The patient underwent MRI feet first with the arms above the head where possible.The Unenhanced-MRA sequence was performed first using a3D respiratory-triggered SSFP proprietary sequence Inversion Recovery pulse sequence.The acquisition was performed in a transversal imaging plane,with an imaging range covering both kidneys.Acquisition time of NCE-MRA was about3-4.5min.Then a breath-hold3D fast spoiled gradient echo CE-MRA sequence was performed in a coronal plane with an anatomical range covering both kidneys and the aorta. After the contrast agent was injected14-20s,Data acquisition of three phase of renal vessel was started and acquisition time was about36s.All the original data was sent to Signa AW4.4image processing software to reconstruct and analyze the renal arteries.To analyze:①Statistically significant correlation between NCE-MRA and CE-MRA on the number and type of renal arteries that clearly visualized.②Statistically significant correlation in visualized branch grade of renal arteries.③The imaging quality(a diagnostic quality or not) of renal artery NCE-MRA.④Makes a correlation analysis between NCE-MRA and CE-MRA in the detection of renal artery stenosis.sensitivity, specificity,positive predictive value,negative predictive value, accuracy rate,misdiagnosis rate and missed diagnose rate of NCE-MRA was calculated,using CE-MRA as the reference standard.Results1.The number and type of renal artery showed by NCE-MRA and CE-MRAThere are61renal arteries of30patients in our research.NCE-MRA can clearly display60renal arteries, including59primary renal arteries and1accessory artery (The definition of accessory arteries is single artery that go into the renal parenchyma but not through the renal hilum),CE-MRA can clearly display59renal arteries,58primary renal arteries and1adrenal artery. Statistical analysis showed there was no statistical difference between the two methods on clearly displaying the number and the type of renal artery.2.Capacity of NCE-MRA and CE-MRA in identifying renal artery branchesIn61renal arteries of30cases,4(6.56%)only showed renal artery trunks,9(14.75%) level1branch can be identified,12(19.67%) level2branch can be identified,36(59.02%) level3branch can be displayed on NCE-MRA.And as CE-MRA, these data is4(6.56%),9(14.75%),14(22.95%) and34(55.74%) respectively. Spearman rank correlation analysis present that NCE-MRA and CE-MRA has a significant correlation on identifying renal artery branches (r=0.547, P<0.01).3. Assessment of renal artery imaging quality (a diagnostic quality or not) yielded by NCE-MRA and CE-MRAThe overall quality of the imaging was graded on a5-point scale from0(renal artery can not be identified) to4(excellent image quality allowing optimal evaluation with high diagnostic confidence).The result of NCE-MRA (point0-4) was0,0,3(4.92%),20(32.79%),38(62.29%) respectively,and as to CE-MRA,it was0,2(3.28%),2(3.28%),21(34.42%),36(59.02%) respectively.The NCE-MRA sequence was able to yield consistent diagnostic quality renal artery images,while2renal arteries’ images were not diagnostic quality (Point1) in CE-MRA.The Spearman rank correlation analysis showed an significant correlation between NCE-MRA and CE-MRA on renal artery imaging quality(r=0.868, p<0.01). 4. Comparison the number of renal artery that has stenosis detected by NCE-MRA and CE-MRA9cases (30%)11renal arteries were demonstrated has one stenosis or2by CE-MRA In30cases, while to NCE-MRA this data was10cases (33.33%)12renal arteries. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of NCE-MRA for detecting RAS are:91%,96%,83.33%,97.96%,95.08%respectively, the missed diagnosis and misdiagnosis rate is:9.09%and4%respectively,using CE-MRA as the reference standard. Statistical analysis showed a significant correlation between the two methods in the detection of RAS (P<0.05,r=0.841),and there was no statistically significant difference between the two methods on the detection rate of RAS.5. Assessment of NCE-MRA and CE-MRA for evaluating the degree of RASEach renal artery was graded for stenosis as:normal renal artery, mild luminal narrowing, moderate luminal narrowing, severe luminal narrowing.CE-MRA demonstrated total12stenosis,5mild stenosis,5moderate stenosis and2severe stenosis.8of the12stenosis that detected by NCE-MRA were Consistent with CE-MRA.The accuracy of NCE-MRA for evaluating the degree of RAS was66.67%. And another4place, including2misdiagnosed and2missed diagnosis were not Consistent with CE-MRA.2mild stenosis on CE-MRA were misjudged as normal artery on NCE-MRA,and2moderate stenosis on CE-MRA were misjudged as severe stenosis on NCE-MRA. Sensitivity of NCE-MRA for evaluating mild, moderate and severe RAS was60%,60%and100%respectively, positive predictive values of NCE-MRA for detecting mild, moderate, and severe renal artery stenosis was60%,100%and50%respectively. Spearman rank correlation analysis showed a significant correlation between the2methods on evaluation of renal artery stenosis degree (r=0.840, P<0.01).Conclusions1. NCE-MRA can well describe the morphology of renal artery, the capability of NCE-MRA to identify intraparenchymal arterial branches is superior to CE-MRA, NCE-MRA is an available method for detecting renal artery disease.2. NCE-MRA is sequences based on breathing trigger technique, patients are more likely to cooperate without a breath-hold, so the success rate and image quality is satisfactory.3. NCE-MRA showed a high accuracy and low missed diagnosis for evaluating RAS,due to its lack of ionizing radiation,non-invasiveness and reasonable scan time,NCE-MRA can be a viable alternative to CE-MRA for the evaluation of renal arteries,especially for patients with renal insufficiency. |
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