SSDE — Size-Specific Dose Estimate

Adjust CTDIvol for actual patient size per AAPM Reports 204 and 220

Parameters

CTDIvol (mGy)

Reference phantom

Size input mode

AP diameter (cm)

LAT diameter (cm)

—

mGy

\( \text{SSDE} = \text{CTDI}_{vol} \times f_{size} \)

\( D_{eff} = \sqrt{AP \times LAT} \) — effective diameter from AP and LAT measurements

\( f_{size} = a \cdot e^{-b \cdot D_{eff}} \) — AAPM 204 conversion factor (a, b depend on phantom)

AAPM Report 204 (2011) — Size-Specific Dose Estimates (SSDE) in Pediatric and Adult Body CT. aapm.org/pubs/reports/RPT_204.pdf
AAPM Report 220 (2014) — Use of Water Equivalent Diameter for Calculating Patient Size and SSDE. aapm.org/pubs/reports/RPT_220.pdf
Pediatric weight/age fallback uses AAPM 204 Table 1B (mean effective diameter by age).

SSDE represents absorbed dose to a reference patient of the measured size, not effective dose. For effective dose use the dedicated calculator.