dose reduction in HRCT

 

Q.Techniques for dose reduction in HRCT are all

 except 

a.reduction in mA and kVp

b.interspaced imaging

c.use of Iterative reconstruction

d.use of bismuth shield          

e.use of Filtered back projection reconstruction

ANS ---e

Radiation

 Procedure -------------effective radiation dose (mSv )

1.background radiation dose --2.5mSV

2.PA CHEST radiograph ---.05mSv

3.MD-HRCT standard technique--- 4 to 7 mSv 

MCQ HRCT

Q. All are true regarding HCRT of lung except

a.the term first used by Todo et al.

b.MDCT allow faster acquisition and higher image quality of HRCT

c.slice thickness (1 to 1.25mm)

d.use of high spatial frequency algorithm

e.use of overenhancing algorithm

ANS----. e

High resolution CT include(  I) the use of thin collimation axial scan or thin section reconstruction of volumetric data obtained using MDCT and narrow detector width (less than or equal to 1.5mm) (II) image reconstruction with high spatial frequency ( sharp or high –resolution ) alogrithm .

Use of thin section ( less than or equal to 1.5mm ) is essential if spatial resolution and lung details are to be optimized .The image with thinner section shows clearer definition of the fissure ,vessel walls and walls of the cyst .The use of 2.5 to 5mm slice thickness should not be considered adequate for HRCT .

Boedeker et al .classified different reconstruction algorithm from different vendors into three main categories : standard ,sharp,and overenhancing

Reconstruction of images using sharp,high spatial frequency or high resolution algorithm ( bone algorithm ) reduces image smoothening and increases spatial resolution ,making structures appear sharper .Using  a high –resolution algorithm is a critical element in performing HRCT .

Overenhancing algorithm interefere with the ability to distinguish certain findings like reticulation and honeycombing .