***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Background Measurement of renal perfusion is a crucial part of measuring kidney function . Arterial spin labelling magnetic resonance imaging ( ASL MRI ) is a non-invasive method of measuring renal perfusion using magnetised blood as endogenous contrast . We studied the reproducibility of ASL MRI in normal volunteers . Methods ASL MRI was performed in healthy volunteers on 2 occasions using a 3.0 Tesla MRI scanner with flow-sensitive alternating inversion recovery ( FAIR ) perfusion preparation with a steady state free precession ( True-FISP ) pulse sequence . Kidney volume was measured from the scanned images . Routine serum and urine biochemistry were measured prior to MRI scanning . Results 12 volunteers were recruited yielding 24 kidneys , with a mean participant age of 44.1 ± 14.6 years , blood pressure of 136/82 mmHg and chronic kidney disease epidemiology formula estimated glomerular filtration rate ( CKD EPI eGFR ) of 98.3 ± 15.1 ml/min/1.73 m2 .  Mean kidney volumes measured using the ellipsoid formula and voxel count method were 123.5 ± 25.5 cm3 , and 156.7 ± 28.9 cm3 respectively . Mean kidney perfusion was 229 ± 41 ml/min/100 g and mean cortical perfusion was 327 ± 63 ml/min/100 g , with no significant differences between ASL MRIs . Mean absolute kidney perfusion calculated from kidney volume measured during the scan was 373 ± 71 ml/min . Bl and Altman plots were constructed of the cortical and whole kidney perfusion measurements made at ASL MRIs 1 and 2 . These showed good agreement between measurements , with a r and om distribution of means plotted against differences observed . The intra class correlation for cortical perfusion was 0.85 , whilst the within subject coefficient of variance was 9.2 % . The intra class correlation for whole kidney perfusion was 0.86 , whilst the within subject coefficient of variance was 7.1 % . Conclusions ASL MRI at 3.0 Tesla provides a repeatable method of measuring renal perfusion in healthy subjects without the need for administration of exogenous compounds . We have established normal values for renal perfusion using ASL MRI in a cohort of healthy volunteers RATIONALE AND OBJECTIVES The aim of this study was to investigate the short-term effects of furosemide on renal perfusion by using arterial spin labeling ( ASL ) magnetic resonance imaging . MATERIAL S AND METHODS Eleven healthy human subjects were enrolled in the study . The measurement of renal blood flow ( RBF ) was performed by applying an ASL technique with flow-sensitive alternating inversion recovery spin preparation and a single-shot fast spin-echo imaging strategy on a 3.0-T magnetic resonance scanner . For all subjects , the ASL magnetic resonance images were obtained before agent injection as a baseline scan . Then 20 mg of furosemide was injected intravenously . Postfurosemide ASL images were acquired following administration to evaluate the renal hemodynamic response . RESULTS Postinjection scans showed that cortical RBF decreased from 366.59 ± 41.19 mL/100 g/min at baseline to 314.33 ± 48.83 mL/100 g/min at 10 minutes after the administration of furosemide ( paired t test , P = .04 vs baseline ) , and medullary RBF decreased from 118.59 ± 24.69 mL/100 g/min at baseline to 97.38 ± 18.40 mL/100 g/min at 10 minutes after the administration of furosemide ( paired t test , P = .01 vs baseline ) . There was a negative correlation between the furosemide-induced diuretic effect and the reduction of RBF ( Spearman 's r = -0.61 ) . CONCLUSIONS The dominant hemodynamic effect of furosemide on the kidney is associated with a decrease in both cortical and medullary blood perfusion . Furthermore , the quantitative ASL technique may provide an alternative way to noninvasively monitor the change in renal function due to furosemide administration Abstract Magnetic resonance imaging with arterial spin labeling ( ASL ) is a noninvasive approach to measure organ perfusion . The purpose of this study was to evaluate the reproducibility of ASL kidney perfusion measurements with semiautomatic segmentation , which allows separate quantification of cortical and medullary perfusion . The right kidneys of 14 healthy volunteers were examined 6 times on 2 occasions ( 3 times at each occasion ) . There was a 10-minute pause between each examination and a 14-day interval between the 2 occasions . Cortical , medullary , and whole kidney parenchymal perfusion was determined with customized semiautomatic segmentation software .  Coefficient of variances ( CVs ) and intraclass correlations ( ICCs ) were calculated . Mean whole , cortical , and medullary kidney perfusion was 307.26 ± 25.65 , 337.10 ± 34.83 , and 279.61 ± 26.73 mL/min/100 g , respectively . On session 1 , mean perfusion for the whole kidney , cortex , and medulla was 307.08 ± 26.91 , 336.79 ± 36.54 , and 279.60 ± 27.81 mL/min/100 g , respectively , and on session 2 , 307.45 ± 24.65 , 337.41 ± 33.48 , and 279.61 ± 25.94 mL/min/100 g , respectively ( P > 0.05 ; R2 = 0.60/0.59/0.54 ) . For whole , cortical , and medullary kidney perfusion , the total ICC/CV were 0.97/3.43 ± 0.86 % , 0.97/4.19 ± 1.33 % , and 0.96/4.12 ± 1.36 % , respectively . Measurements did not differ significantly and showed a very good correlation ( P > 0.05 ; R2 = 0.75/0.76/0.65).ASL kidney measurements combined with operator-independent semiautomatic segmentation revealed high correlation and low variance of cortical , medullary , and whole kidney perfusion Abstract Objectives To investigate the reproducibility of arterial spin labelling ( ASL ) and dynamic contrast-enhanced ( DCE ) magnetic resonance imaging ( MRI ) and quantitatively compare these techniques for the measurement of renal blood flow ( RBF ) . Methods Sixteen healthy volunteers were examined on two different occasions . ASL was performed using a multi-TI FAIR labelling scheme with a segmented 3D-GRASE imaging module . DCE MRI was performed using a 3D-FLASH pulse sequence . A Bl and -Altman analysis was used to assess repeatability of each technique , and determine the degree of correspondence between the two methods . Results The overall mean cortical renal blood flow ( RBF ) of the ASL group was 263 ± 41 ml min−1 [ 100 ml tissue]−1 , and using DCE MRI was 287 ± 70 ml min−1 [ 100 ml tissue]−1 . The group coefficient of variation ( CVg ) was 18 % for ASL and 28 % for DCE-MRI . Repeatability studies showed that ASL was more reproducible than DCE with CVgs of 16 % and 25 % for ASL and DCE respectively . Bl and -Altman analysis comparing the two techniques showed a good agreement . Conclusions The repeated measures analysis shows that the ASL technique has better reproducibility than DCE-MRI . Difference analysis shows no significant difference between the RBF values of the two techniques . Key Points• Reliable non-invasive monitoring of renal blood flow is currently clinical ly unavailable . • Renal arterial spin labelling MRI is robust and repeatable . • Renal dynamic contrast-enhanced MRI is robust and repeatable . • ASL blood flow values are similar to those obtained using DCE-MRI PURPOSE To evaluate renal allografts function early after transplantation using intravoxel incoherent motion ( IVIM ) and arterial spin labeling ( ASL ) MRI . METHODS This prospect i ve study was approved by the local ethics committee , and written informed consent was obtained from all participants . A total of 82 participants with 62 renal allograft recipients ( 2 - 4weeks after kidney transplantation ) and 20 volunteers were enrolled to be scanned using IVIM and ASL MRI on a 3.0 T MR scanner . Recipients were divided into two groups with either normal or impaired function according to the estimated glomerular filtration rate ( eGFR ) with a threshold of 60ml/min/1.73m(2 ) . The apparent diffusion coefficient ( ADC ) of pure diffusion ( ADCslow ) , the ADC of pseudodiffusion ( ADCfast ) , perfusion fraction ( PF ) , and renal blood flow ( RBF ) of cortex were compared among three groups . The correlation of ADCslow , ADCfast , PF and RBF with eGFR was evaluated . The receiver operating characteristic ( ROC ) curve and binary logistic regression analyses were performed to assess the diagnostic efficiency of using IVIM and ASL parameters to discriminate allografts with impaired function from normal function . P<0.05 was considered statistically significant . RESULTS In allografts with normal function , no significant difference of mean cortical ADCslow , ADCfast , and PF was found compared with healthy controls ( P>0.05 ) . Cortical RBF in allografts with normal function was statistically lower than that of healthy controls ( P<0.001 ) . Mean cortical ADCslow , ADCfast , PF and RBF were lower for allografts with impaired function than that with normal function ( P<0.05 ) . Mean cortical ADCslow , ADCfast , PF and RBF showed a positive correlation with eGFR ( all P<0.01 ) for recipients . The combination of IVIM and ASL MRI showed a higher area under the ROC curve ( AUC ) ( 0.865 ) than that of ASL MRI alone ( P=0.02 ) . CONCLUSION Combined IVIM and ASL MRI can better evaluate the diffusion and perfusion properties for allografts early after kidney transplantation Objective : We compared the effects of intravenous infusions of 0.9 % saline ( [ Cl− ] 154 mmol/L ) and Plasma-Lyte 148 ( [ Cl− ] 98 mmol/L , Baxter Healthcare ) on renal blood flow velocity and perfusion in humans using magnetic resonance imaging ( MRI ) . Background : Animal experiments suggest that hyperchloremia result ing from 0.9 % saline infusion may affect renal hemodynamics adversely , a phenomenon not studied in humans . Methods : Twelve healthy adult male subjects received 2-L intravenous infusions over 1 hour of 0.9 % saline or Plasma-Lyte 148 in a r and omized , double-blind manner . Crossover studies were performed 7 to 10 days apart . MRI scanning proceeded for 90 minutes after commencement of infusion to measure renal artery blood flow velocity and renal cortical perfusion . Blood was sample d and weight recorded hourly for 4 hours . Results : Sustained hyperchloremia was seen with saline but not with Plasma-Lyte 148 ( P < 0.0001 ) , and fall in strong ion difference was greater with the former ( P = 0.025 ) . Blood volume changes were identical ( P = 0.867 ) , but there was greater expansion of the extravascular fluid volume after saline ( P = 0.029 ) . There was a significant reduction in mean renal artery flow velocity ( P = 0.045 ) and renal cortical tissue perfusion ( P = 0.008 ) from baseline after saline , but not after Plasma-Lyte 148 . There was no difference in concentrations of urinary neutrophil gelatinase – associated lipocalin after the 2 infusions ( P = 0.917 ) . Conclusions : This is the first human study to demonstrate that intravenous infusion of 0.9 % saline results in reductions in renal blood flow velocity and renal cortical tissue perfusion . This has implication s for intravenous fluid therapy in perioperative and critically ill patients . PURPOSE To investigate non-contrast-enhanced arterial spin labeling ( ASL ) MRI for functional assessment of transplanted kidneys at 1.5 Tesla ( T ) and 3 T . MATERIAL S AND METHODS This study was approved by the local ethics committee , and written informed consent was obtained from all participants . Ninety eight renal allograft recipients ( mean age , 51.5 ± 14.6 years ) were prospect ively included in this study . ASL MRI was performed at 1.5 T ( n = 65 ) and 3 T ( n = 33 ) using a single-slice flow-sensitive alternating inversion recovery true-fast imaging with steady-state precession ( FAIR True-FISP ) sequence in the paracoronal plane . ASL perfusion was regional analyzed for the renal cortex on parameter maps . ASL was compared between patients with good or moderate allograft function ( Group a ; estimated glomerular filtration rate [ eGFR ] > 30 mL/min/1.73 m( 
    Output:
    
Renal perfusion by ASL has been vali date d against reference methods and has good reproducibility .
Technical advancements mean that a renal ASL study can acquire a whole kidney perfusion measurement in less than 5 - 10 min .
The short acquisition time permits combination with other MRI techniques that might inform drug mechanisms and renal physiology .