Estimation or quantification of tumour volume? CT study on irregular phantoms.
OBJECTIVE
To compare radiologists' subjective size estimation to computerised volume quantification of tumour-like phantoms in spiral CT.


METHODS
Eight tubular phantoms with the inside irregularly covered with silicone (8.7-31.6 ml) were imaged. The phantoms were pairwise compared to analyse the differences in silicone volumes. The observers, 2 radiologists and 2 residents, used both subjective image analysis (2 sessions) and computerised volume quantification (1 session). Accuracy and observer agreement of both methods were calculated.


RESULTS
Subjective size estimation was correct in 51% (mean weighted kappa, Kqw=0.73). Using four observers' mean value (Kqw=0.81) or median value (Kqw=0.77) slightly improved the results. Average intra-observer agreement was better than average interobserver agreement. In computerised volume quantification 70% of all classifications were correct (mean Kqw=0.85). The results were moderate even when every second or fourth slice were measured.


CONCLUSIONS
Subjective size estimation of irregular tumours should be repeatedly performed by the same observer, or by using the mean or median estimate of several observers. Computer-based methods are even more reliable and their use is especially recommended for film readers with limited radiological experience. Only every fourth slice may be measured without a major loss of measurement accuracy.
Tiitola
M
M
Department of Radiology, Helsinki University Central Hospital, Finland.
Kivisaari
L
L
Tervahartiala
P
P
Palomäki
M
M
Kivisaari
R P
RP
Mankinen
P
P
Vehmas
T
T
D006801:Humans; D009369:Neoplasms / Q000000981:diagnostic imaging*; D015588:Observer Variation; D019047:Phantoms, Imaging; D015203:Reproducibility of Results; D012828:Silicones; D014057:Tomography, X-Ray Computed / Q000379:methods*
D012828:Silicones