Table 2.

Mean central processing unit (CPU) time, memory requirements and output size for calculating a dose cube, for downsampling factors from 4 to 1

Downsampling factor	CPU time (s)	Memory (MB)	Output size (kB)
4	1892 ± 262	449 ± 11	424 ± 32
2	8388 ± 1406	659 ± 28	1684 ± 128
1	33,001 ± 4208	1377 ± 71	6724 ± 511

In each case, results are from processing data for a single fraction for each of the 33 patients. Processing was performed on machines that have 24-core Intel^® Xeon X5650 CPUs (Intel, Santa Clara, WI), with a clock speed of 2.67 GHz. A downsampling factor of 2 gives an in-plane spatial resolution of approximately 1.5 mm.