Indian Journal of Radiology Indian Journal of Radiology  

   Login   | Users online: 2534

Home Bookmark this page Print this page Email this page Small font sizeDefault font size Increase font size     

 

 Table of Contents    
LETTER TO THE EDITOR  
Year : 2013  |  Volume : 23  |  Issue : 2  |  Page : 186-187
Authors' reply


Department of Radiodiagnosis, All India Institute of Medical Sciences (A.I.I.M.S.), Ansari Nagar, New Delhi, India

Click here for correspondence address and email

Date of Web Publication16-Aug-2013
 

How to cite this article:
Goyal A, Sharma R, Bhalla AS, Gamanagatti S, Seth A. Authors' reply. Indian J Radiol Imaging 2013;23:186-7

How to cite this URL:
Goyal A, Sharma R, Bhalla AS, Gamanagatti S, Seth A. Authors' reply. Indian J Radiol Imaging [serial online] 2013 [cited 2017 Dec 14];23:186-7. Available from: http://www.ijri.org/text.asp?2013/23/2/186/116577
Dear Sir,

We appreciate the interest shown by Sivrioglu et al. in our article. Some of the concerns raised by the authors have already been discussed in our article. [1] Nevertheless, we take this opportunity to further clarify the contentious issues.

We have been doing diffusion-weighted MRI (DW-MRI) as part of the protocol for renal lesion evaluation since 2008, employing b-values of 0 and 500 s/mm 2 , and have published data from the same. [2],[3] The present article was based on a retrospective review of patients who underwent DW-MRI for characterization of focal renal lesions and not primarily for evaluation of renal function. Through this study, we wanted to highlight an additional benefit of renal DW-MRI which we encountered, that apparent diffusion coefficient (ADC) values may serve as an additional paradigm to identify and estimate the degree of renal dysfunction.

The ADC values in the renal cortex and medulla were not measured separately because as pointed out by previous studies, it is usually difficult to position the region of interest (ROI) cursor accurately in these areas. [4],[5],[6],[7] In addition, there is loss of cortico-medullary differentiation in renal parenchymal disease, which makes the precise placement of ROIs separately on cortex and medulla impractical. [6],[7],[8]

Low ADC values in renal parenchymal disease can be explained both by reduced perfusion as well as by reduced water diffusion, and ADC values calculated from b-values of 0 and 500 s/mm 2 represent the combined effects of both. Such a monoexponential model using two b-values has been used by majority of previous investigators [4],[5],[6],[7],[9],[10] because it is easy and straightforward to use. To separately evaluate diffusion and perfusion contributions, biexponential fitting model needs to be employed using a large range of b-values. [11] Increased acquisition time and complicated calculation software may, however, pose hindrance for its routine clinical use and such protocols are still in investigational stage. [11],[12] Prospective studies based on biexponential model may provide insights into the relative contribution of diffusion and perfusion and whether these two factors separately correlate with the degree of renal dysfunction/parenchymal fibrosis. Our study was not planned with this objective, and as alluded to earlier, DW-MRI was done to evaluate renal mass lesions.

Majority of the studies on DW-MRI in kidney [4],[6],[7],[9],[10] have employed two b-values with lower b-value 0 s/mm 2 and higher b-value ranging from 500 to 800 s/mm 2 . The maximum b-value of 500 is an optimal compromise between adequate diffusion weighting and image quality on 1.5 T, since higher b-values are associated with decrease in signal-to-noise ratio. Use of more than two b-values in the monoexponential model may not have any beneficial effect; rather, it may decrease the image quality. [10],[12]

 
   References Top

1.Goyal A, Sharma R, Bhalla AS, Gamanagatti S, Seth A. Diffusion-weighted MRI in assessment of renal dysfunction. Indian J Radiol Imaging 2012;22:155-9.  Back to cited text no. 1
  Medknow Journal  
2.Goyal A, Sharma R, Bhalla AS, Gamanagatti S, Seth A, Iyer VK, et al. Diffusion-weighted MRI in renal cell carcinoma: A surrogate marker for predicting nuclear grade and histological subtype. Acta Radiol 2012;53:349-58.  Back to cited text no. 2
[PUBMED]    
3.Goyal A, Sharma R, Bhalla AS, Gamanagatti S, Seth A. Diffusion-weighted MRI in inflammatory renal lesions: All that glitters is not RCC! Eur Radiol 2013;23:272-9.  Back to cited text no. 3
    
4.Cova M, Squillaci E, Stacul F, Manenti G, Gava S, Simonetti G, et al. Diffusion-weighted MRI in the evaluation of renal lesions: Preliminary results. Br J Radiol 2004;77:851-7.  Back to cited text no. 4
[PUBMED]    
5.Toya R, Naganawa S, Kawai H, Ikeda M. Correlation between estimated glomerular filtration rate (eGFR) and apparent diffusion coefficient (ADC) values of the kidneys. Magn Reson Med Sci 2010;9:59-64.  Back to cited text no. 5
[PUBMED]    
6.Xu Y, Wang X, Jiang X. Relationship between the renal apparent diffusion coefficient and glomerular filtration rate: Preliminary experience. J Magn Reson Imaging 2007;26:678-81.  Back to cited text no. 6
[PUBMED]    
7.Xu X, Fang W, Ling H, Chai W, Chen K. Diffusion-weighted MR imaging of kidneys in patients with chronic kidney disease: Initial study. Eur Radiol 2010;20:978-83.  Back to cited text no. 7
[PUBMED]    
8.Lee VS, Kaur M, Bokacheva L, Chen Q, Rusinek H, Thakur R, et al. What causes diminished corticomedullary differentiation in renal insufficiency? J Magn Reson Imaging 2007;25:790-5.  Back to cited text no. 8
[PUBMED]    
9.Yoshikawa T, Kawamitsu H, Mitchell DG, Ohno Y, Ku Y, Seo Y, et al. ADC measurement of abdominal organs and lesions using parallel imaging technique. AJR Am J Roentgenol 2006;187:1521-30.  Back to cited text no. 9
[PUBMED]    
10.Taouli B, Thakur RK, Mannelli L, Babb JS, Kim S, Hecht EM, et al. Renal lesions: Characterization with diffusion-weighted imaging versus contrast-enhanced MR imaging. Radiology 2009;251:398-407.  Back to cited text no. 10
[PUBMED]    
11.Thoeny HC, De Keyzer F. Diffusion-weighted MR imaging of native and transplanted kidneys. Radiology 2011;259:25-38.  Back to cited text no. 11
[PUBMED]    
12.Park MY, Byun JY. Understanding the Mathematics Involved in Calculating Apparent Diffusion Coefficient Maps. AJR Am J Roentgenol 2012;199:W784. Available from: http://www.ajronline.org/doi/full/10.2214/AJR.12.9231 [Last cited on 2013 Jun 16].  Back to cited text no. 12
    

Top
Correspondence Address:
Raju Sharma
Department of Radiodiagnosis, All India Institute of Medical Sciences (A.I.I.M.S.), Ansari Nagar, New Delhi
India
Login to access the Email id

Source of Support: None, Conflict of Interest: None


Rights and PermissionsRights and Permissions




 

Top
 
 
  Search
 
   Similar in PUBMED
   Search Pubmed for
   Search in Google Scholar for
    Email Alert *
    Add to My List *
* Registration required (free)  


    References

 Article Access Statistics
    Viewed1355    
    Printed21    
    Emailed0    
    PDF Downloaded83    
    Comments [Add]    

Recommend this journal