| Part1 Utilizing of multiple-modality MRI techniques for the study of lower extremity deep venous thrombusPurpose:To evaluate the diagnostic performance of MRI utilizing Sampling Perfection Application with contrast optimized using variable flip Angle Evolutions(SPACE)in detecting lower extremity deep venous thrombosis(DVT)and evaluating clot burden.To evaluate the suitability of DWI,T1 mapping,T2mapping,T2*mapping in thrombus aging.Method:This prospective study was approved by the institutional review board.94 consecutive patients(male 42,female 52,age range 14-87 years,average age 52.7 years)suspected of lower extremity DVT underwent ultrasound(US)and SPACE MRI.The venous visualization score with SPACE MR was determined by two experienced radiologists according to a 4-point scale(1-4,poor-excellent).The sensitivity and specificity of SPACE MR in detecting DVT was calculated per segment,limb,and patient with ultrasound serving as the reference standard.Clot burden for each segment was evaluated(0-3,patent to entire segment occlusion)with SPACE MR and US separately.The clot burden score obtained with SPACE MR was compared to US using a Wilcoxon test per region,limb,and patient.Interobserver agreement in assessing thrombosis(absent,non-occlusive,or occlusive)with SPACE MR was determined by calculating Cohen's kappa coefficients.The patients with DVT underwent single-b-value DWI,multiple-b-value DWI,Tlmapping,T2mapping and T2*mapping.The ADC,MK,MD,D,f,D*,T1,T2,T2*relaxation time were measured for each thrombus.All the thrombus were devided into 5 age groups:1 = 1-7 days;2=8-14 days;3=15?21 days;4=22?28 days;5=29 days and older.The mean of ADC,MK,MD,D,f,D*,T1,T2,T2*of each age group were calculated and compared.All the thrombus were then devided into two groups:acute thrombus group(?14 days)and chronic group(?15 days).The mean of ADC,MK,MD,D,f,D*,T1,T2,T2*for each group were calculated.The students' t-test was used to determine the difference of each parameter between actue thrombus and chronic thrombus.ROC curve was used to determine the performance of each parameter in differentiating thrombus.Results:The mean venous visualization score with SPACE MR was 3.82±0.50 for Reader 1 and 3.81±0.50 for Reader 2.For Reader 1,sensitivity/specificity of SPACE MR in detecting DVT were respectively 97.89%/99.90%per segment,98.77%/99.07%per limb,and 98.59%/95.65%per patient.For Reader 2,respective values were 98.58%/99.90%,100%/99.07%,and 100%/95.83%.The burden of clot assessed with SPACE MR was not statistically significantly different from that assessed with US on a per region,limb,or patient basis(P>0.05).Interobserver agreement with SPACE MR was excellent(kappa=0.894±0.014)in assessing thrombosis.52 thrombus were hyper-intensitiy on DWI image,with ADC value 662.97 ± 166.61.40 thrombus were hypo-intensity on DWI image,with ADC value 142.66 ±69.09.ADC of hyper-intensitiy thrombus was significantly higher than hypo-intensity thrombus(P<0.001).The mean of ADC for all the 92 thrombus was 435.43 ±290.75,significantly lower than that of background muscle(1661.04 ± 116.63,P<0.001).ADC for 1,2,3,4,5 age group were 810.43 ± 126.91.534.10±45.24,362.13 ±34.64.129.42± 14.67,55.55 ±32.87 respectively.ADC for acute thrombus was higher than chronic thrombus(680.73 ± 169.54 vs 224.17±142.11,P<0.001).AUC of ADC was 0.996.Sensitivity and specificity of ADC were 95.9%and 95.3%respectively,with a cutoff of 413.89.MK,MD,D,f,D*were significantly different between thrombus and background muscle.Actue thrombus and chronic thrombus had different MK and MD.Mean T2 value was 57.13 ±20.41,33.27±5.86,23.93±3.49,18.09± 1.49 and 14.99±2.03 for 1,2,3,4,5 age group.Acute thrombus had significantly higher T2 and T2*than chronic throumbus(P<0.05).AUC was 0.978,0.955 and 0.974 for T2,T2*and T1 in differentiating thrombus.Sensitivity were 95.1%,94.3%,and 91.7%for T2,T2*and T1.Specificity were 94.6%,96.6%and 94.1%for T2,T2*and T1.Conclusion:SPACE MR is highly accurate in detecting lower extremity DVT and reliable in the evaluation of clot burden.SPACE MR could serve as an important alternative for patients in whom US cannot be performed.Single-b DWI,multiple-b DWI,T2,T2*and T1 mapping were all useful in aging lower extremity thrombus.Part 2 The diagnostic value of non-contrast enhanced quiescent interval single shot(QISS)magnetic resonance angiography at 3T for lower extremity peripheral arterial disease,in comparison to CT angiography.Purpose:The purpose of the current study is to compare image quality and diagnostic performance of non-contrast enhanced Quiescent Interval Single Shot(QISS)magnetic resonance angiography at 3 T versus CT angiography for evaluation of lower extremity Peripheral Arterial Disease(PAD).Methods:32 consecutive patients(23 male,9 female,age range 40-81 years,average age 61.97 years)with clinically suspected lower extremity PAD underwent QISS MRA and CTA.19 of 32 patients underwent Digital Subtraction Angiography(DSA).Image quality of MRA was compared with CTA by two radiologists with 10 and 8 years' experience according to a 4-point scale.The Kappa test was used to determine the intermodality agreement between MRA and CTA in stenosis assessment,and interobserver agreement with each method.Sensitivity and specificity of CTA and MRA in detecting hemodynamically significant stenosis(>50%)were compared,with DSA serving as reference standard when available.Results:Image quality of QISS MRA was rated 3.70 ± 0.49 by reader 1,and 3.72 ± 0.47 by reader 2,significantly lower than that of CTA(3.80± 0.44 and 3.82 ± 0.42.P<0.001 for both readers).Intermodality agreement between MRA and CTA was excellent for assessment of stenosis(Kappa = 0.923 ±0.013 for reader 1,0.930 ± 0.012 for reader 2).Interobserver agreement was 0.936± 0.012 for CTA and 0.935 ± 0.011 for MRA.For readers 1 and 2 respectively,the sensitivity of QISS was 94.25 and 93.26%(versus 90.11 and 89.13%for CTA,P>0.05),and specificity of QISS was 96.70 and 97.75%(versus 96.55 and 96.51%for CTA,P>0.05).For heavily calcified segments,sensitivity of QISS(95.83 and 95.83%)was significantly higher than that of CTA(74.19 and 76.67%,P<0.05).Conclusion:QISS is a reliable alternative to CTA for evaluation of lower extremity PAD,and may be suitable as a first-line screening examination in patients with contraindications to intravenous contrast administration.Part 3 Utilize of high spatial resolution time-resolved magnetic resonance angiography with interleaved stochastic trajectory(TWIST)in lower extremity tumorsPurpose:The aim of this study was to compare diagnostic value of high spatial resolution time-resolved magnetic resonance angiography with interleaved stochastic trajectory(TWIST)using Gadobutrol to Computed tomography angiography(CTA)for preoperative evaluation of lower extremity tumors.To investigate the value of TWIST in differentiating benign and malignant tumors in lower extremity.Methods:This prospective study was approved by the institutional review board.Fifty consecutive patients(31 men,19 women,age range 18-80 years,average age 42.7 years)with lower extremity tumors underwent TWIST magnetic resonance angiography(MRA)and CTA.Digital subtraction angiography was available for 8 patients.Image quality of MRA was compared with CTA by 2 radiologists according to a 4-point Likert scale.Arterial involvement by tumor was compared using kappa test between MRA and CTA.The ability to identify feeding arteries and arterio-venous fistulae(AVF)was compared using Wilcoxon signed rank test and McNemar test,respectively.63 consecutive patients suspected of lower extremity tumors refer to contrast enhanced MRI examination underwent TWIST for tumor vascular evaluation.A definitive operation or open biopsy was performed within 48 hours following TWIST.The patients were divided into benign group and malignant group according to the pathology results.The maximum diameter of enhancement(MDE)was measured on the delayed phase of TWIST.Feeding arteries were detected on the arterial phase images.The number of feeding arteries(NFA)was recorded.The presence or absence of Arteriovenous Fistula(AVF)was determined by two radiologists in consensus.MDE and NFA were compared between benign and malignant tumors using Mann Whitney test.The prevalence of AVF was compared between the two groups using chi-square test.Receiver operating characteristic(ROC)curve was used for studying performance of MDE and NFA in diagnosing malignancy.Results:Image quality of MRA and CTA was rated without a statistically significant difference(3.88±0.37 vs.3.97±0.16,P=0.135).Intramodality agreement was high for the identification of arterial invasion(kappa=0.806±0.073 for Reader 1,kappa=0.805±0.073 for Reader 2).Readers found AVF in 27 of 50 MRA cases and 14 of 50 CTA cases(P<0.001).Mean feeding arteries identified with MRA were significantly more than that with CTA(2.08±1.72 vs.1.62±1.52,P?.02).MDE of malignant tumors was significantly greater than benign tumors(99.89mm vs 50.54mm,P<0.001).Malignant tumors had significantly more feeding arteries than benign tumors(2.68 vs 1.12,P<0.001).AVF were identified in 30 out of 37 malignant tumors,while in 3 out of 26 benign ones.The prevalence of AVF was significantly higher in malignancy than benign tumors(81.08%vs 11.54%,P<0.001).Area under curve(AUC)for MDE and NFA was 0.78 and 0.83.Conclusion:TWIST MRA is a reliable imaging modality for the assessment of lower extremity tumors.TWIST MRA is comparable to CTA for the identification of AVF and feeding arteries.TWIST is useful in differentiating malignant tumors from benign tumors in lower extremity. |
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