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MAPD—an objective way to select mAs for paediatric brain CT

¹ Department of Diagnostic Radiology ² Medical Physics Division, Tuen Mun Hospital, Hong Kong

View larger version (153K): [in a new window]   Figure 1. Pilot view and the measured maximum anteroposterior diameter (MAPD).

View larger version (111K): [in a new window]   Figure 2. Axial image at maximum anteroposterior diameter, where total skull bone thickness xb=distance 1 + distance 2 was measured.

View larger version (117K): [in a new window]   Figure 3. Axial image showing where CT number and standard deviation were measured for four defined regions of interest: A, basal ganglion; B, thalamus; C,white matter; D grey matter.

View larger version (16K): [in a new window]   Figure 4. Variations of image noise with maximum anteroposterior diameter (MAPD) for (a) infant protocol (100 kVp) and (b) child protocol (120 kVp).

View larger version (19K): [in a new window]   Figure 5. (a) Distribution of the difference between calculated mAs and applied mAs. (b) Distribution of the percentage difference between calculated mAs and applied mAs. , infant protocol; , child protocol.

View larger version (20K): [in a new window]   Figure 6. The variation of image noise level with the percentage difference between calculated mAs and applied mAs for (a) infant studies and (b) child studies, where regions of interest were drawn in the basal ganglion (), the thalamus (), white matter () and grey matter (*).