Staging lymphoma with CT: Comparison of contiguous and alternate 10 mm slice techniques

Purpose: To compare two computed tomography (CT) techniques, contiguous 10 mm and alternate 10 mm slices of the chest, abdomen and pelvis, for initial staging of lymphoma. Subjects and methods: Fifty-two consecutive patients referred at initial diagnosis for lymphoma staging by CT were examined with contiguous 10 mm slices of the chest, abdomen and pelvis. Oral contrast was administered, but no intravenous contrast. Two sets of films for each examination were printed, one with 10 mm contiguous slices and one with 10 mm alternate slices. The two sets of films for each patient were reviewed separately in a randomized order and blinded fashion by two independent observers. Discrepancies were reviewed by a third observer and subsequently resolved by consensus. Results: Staging assessments by both techniques were concordant in 51 of 52 cases: one patient was recorded as stage II on the alternate slice technique, but stage III with contiguous slices but this difference did not affect management. Inter-technique agreement was very good ( κ=0.97). The staging assessments showed discrepancies between the two observers in 12 of the 52 cases which were independent of technique ( κ=0.71; good agreement). Consensus review showed them to result from differences in perception in seven cases and differences in interpretation of abnormalities in five cases. Conclusion: Our findings support the use of an alternate 10 mm slice technique in the staging of lymphoma at initial diagnosis. Observer variation was greater than the difference between techniques.