The relative noise values for the same range of modulation strengths (b = 0.3, 0.5, 0.7, and
1.0) were compared with that of our clinical technique chart (b = 0.36; Table 2). A lateral
width of 36 cm was again used as the reference patient size. The relative noise for patient
sizes from 12 to 50 cm was calculated using Eq. (10). The values produced from a constant
noise requirement greatly differed from values in our current clinical practice. Image noise
for b = 1 relative to that at b = 0.36 increased with smaller patient sizes and decreased with
larger patient sizes. For the 12-cm patient and b = 1, image noise was 430% of our typical
clinical value. For the 50-cm patient and b = 1, image noise was 43% of our usual clinical
value. Thus, using the constant noise paradigm, image noise would be unacceptably high for
small patients compared with the clinical requirements reflected by our existing technique
charts. In addition, the requirement of constant noise would overexpose large patients
compared with what we currently use, delivering increased dose to achieve lower noise
values than what we have found to be clinically necessary.
The relative noise values for the same range of modulation strengths (b = 0.3, 0.5, 0.7, and 1.0) were compared with that of our clinical technique chart (b = 0.36; Table 2). A lateral width of 36 cm was again used as the reference patient size. The relative noise for patient sizes from 12 to 50 cm was calculated using Eq. (10). The values produced from a constant noise requirement greatly differed from values in our current clinical practice. Image noise for b = 1 relative to that at b = 0.36 increased with smaller patient sizes and decreased with larger patient sizes. For the 12-cm patient and b = 1, image noise was 430% of our typical clinical value. For the 50-cm patient and b = 1, image noise was 43% of our usual clinical value. Thus, using the constant noise paradigm, image noise would be unacceptably high for small patients compared with the clinical requirements reflected by our existing technique charts. In addition, the requirement of constant noise would overexpose large patients compared with what we currently use, delivering increased dose to achieve lower noise values than what we have found to be clinically necessary.
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