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LETTER TO EDITOR Table of Contents   
Year : 2003  |  Volume : 13  |  Issue : 1  |  Page : 119-120
Value of maximum intensity projections (MIP) for evaluation of craniosynostosis


Diwan Chand Satya Pal Agarwal Imaging Research Centre, New Delhi-110001, India

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How to cite this article:
Munshi M S. Value of maximum intensity projections (MIP) for evaluation of craniosynostosis. Indian J Radiol Imaging 2003;13:119-20

How to cite this URL:
Munshi M S. Value of maximum intensity projections (MIP) for evaluation of craniosynostosis. Indian J Radiol Imaging [serial online] 2003 [cited 2019 Oct 21];13:119-20. Available from: http://www.ijri.org/text.asp?2003/13/1/119/28643
Sir,

Three-dimensional CT (3D CT) shaded surface display (SSD) has been a routine investigation in the evaluation of craniosynostosis and related calvarial deformities. There has been recent interest in the use of 3D Maximum Intensity Projections (MIP) for the evaluation of craniosynostosis and calvarial fractures in children [1]. This letter is to reiterate and emphasize the value of 3D MIP for the evaluation of craniosynostosis.

Imaging plays an important role in the diagnosis of craniosynostosis and skull fractures in children. Review of literature has suggested 3D MIP to have greater diagnostic accuracy than 3D SSD. In our experience, the more commonly used 3D SSD has a few drawbacks. Since it is a threshold technique, it may give false-positive results as the open sutures may blend with the adjacent bone due to improper setting of the threshold value. Also, perisutural sclerosis, which is an early sign of premature fusion, will not be displayed. The axial images may not depict suture patency, if the plane of the section runs parallel to the suture.

MIP has been a commonly used reconstruction in the evaluation of CT angiograms [2]. MIP assigns a maximum intensity to each pixel on screen irrespective of its hounsfield value, i.e bone in this case, so as to enable separation from the soft tissue containing suture spaces. MIP images have proved to be accurate in depicting suture patency, extent of synostosis (complete or incomplete bony bridging) and conspicuity. The level of confidence for the degree of patency also increases due to better visualization of the suture lines. On comparison of the two techniques, i.e. SSD [Figure - 1] and MIP [Figure - 2] in a normal individual, the patency of the sutures is better seen on the MIP images. The frontal metopic suture appears closed on the SSD, whereas the MIP reconstructions clearly depict its patency.

In our routine protocol for evaluation of craniosynostosis, MIP images are reconstructed such that half the calvarium is cut and the other half faces the reader. This avoids overlapping of the bones and sutures on the two sides. For optimal assessment six basic views are displayed namely, frontal, posterior, base, vertex, left and right lateral along with additional oblique views, as necessary. No additional scanning time or radiation exposure is required. Reconstruction time is between 5-10 minutes.

 
   References Top

1.Medina L S. Three-dimensional CT Maximum Intensity Projections of the calvaria: A New Approach for the Diagnosis of Craniosynostosis and Fractures. Am J Neuroradiology 21:1951-1954. November/December-2000.  Back to cited text no. 1    
2.Brink J A. Technical aspects of helical "spiral CT". Radiologic Clinics of North America. 1995;33:825-841.   Back to cited text no. 2    

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Correspondence Address:
M S Munshi
Diwan Chand Satya Pal Agarwal Imaging Research Centre, New Delhi-110001
India
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Source of Support: None, Conflict of Interest: None


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[Figure - 1], [Figure - 2]



 

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