Biomedical Engineering Reference
In-Depth Information
Fig. 8.67 EDA plot with linear criteria between LPM / SPM and MMAD
deposited on S4-MOC. Both linear and quadratic models (Figs. 8.67 and 8.68 ,
respectively) were fit to the data, regressing LPM / SPM by MMAD . There was little
difference between the two model fits, and therefore, the linear model was used for
simplicity. A 99% prediction interval was applied [ 3 ]. This interval would be
expected to contain 99% of the individual, clinically relevant APSD profiles. In this
way, the prediction interval was serving the same general purpose as the Hotelling
T 2 ellipse from the PCA model.
The acceptable range for the variation in LPM / SPM ratio was found to lie from
0.417 to 0.893, based on the linear modeling of the data (Fig. 8.67 ) that was
comparable with quadratic modeling (Fig. 8.68 ). The data set generated 1,258 mea-
surements that “passed” and 480 measurements that “failed” in the EDA approach,
applying this acceptance criterion to the 1,738 points that remained outside of the
clinically relevant data (i.e., the prediction set). This outcome means that 1,258 of
the 1,738 APSD profiles were deemed similar, but the remaining 480 profiles were
deemed dissimilar to the 252 clinically relevant profiles.
An additional criterion for ISM , which is the sum of deposition on S1 through to
the MOC for the NGI, was included to remove data in which the MMAD is
unchanged, but the overall impactor mass ( IM ) has increased beyond that of the
clinical batch data. Thus, a range of ISM of 21.67-32.17% of LC was derived,
which, in combination with the LPM / SPM ratio, reduced the number of “passed”
batches to 872 and accordingly increased the number of “failed” batches to 866—
again, “passing,” meaning more similar to the 252 clinically relevant APSD profiles,
and “failing,” indicating less similar. This criterion was not necessary for the PCA
model, as large changes in the ISM values would be reflected in changes in deposi-
tion on individual stages, and the data would then have appeared outside the
Hotelling T 2 ellipse.
Search WWH ::




Custom Search