The p Control Chart (fig.1) illustrates the percentage of noncompliant head CT studies and the following values were obtained for the central limit (CL),
upper limit control (ULC) and lower limit control (LLC): 60.83%,
87 57% and 34.09%.
It was found that there were no statistical control samples out of the control limits,
so it were estimated the warning limits,
according to standard ISO 8258:1991,
to study the tendency of the distribution of samples: 1 δ (69,74%),
2 δ (78,65%),
-1 δ (51,92%) e -2 δ (43,01%).
The values of the control limits gathered for the np Chart (fig.2),
responsible for assessing the number of noncompliant head CT studies are: CL (18.25),
UCL (26.27) and LLC (10,23).
There were not found sample outside the control limits,
so the warning limits were calculated: 1 δ (20,92),
2 δ (23,6),
-1 δ (15,58) e -2 δ (12,9).
The c Control Chart (fig 3) studies the number of nonconformities that arise in each sample,
and the values of the control limits are: CL (24.92),
UCL (39,
89) and LLL (9,94).
Therefore,
it were verified that there are no sample out the control limits,
so the warning limits were calculated: 1 δ (29,91),
2 δ (39,9),
-1 δ (19,93) e -2 δ (14,93).
Considering all exams,
299 were classified as non-conform (83,06%) and 61 were classified as conform (16,94%).
Considering the non-conform exams group (table 2),
the quality criteria “incorrect patient positioning” presented the highest number of non-conformities (42,81%),
followed by “absence of the Radiologist name” (27,09%) and “motion artifacts” (18,06%).