Measuring the apparent diffusion coefficient in primary rectal tumors: is there a benefit in performing histogram analyses?
The apparent diffusion coefficient (ADC) is a potential prognostic imaging marker in rectal cancer. Typically, mean ADC values are used, derived from precise manual whole-volume tumor delineations by experts. The aim was first to explore whether non-precise circular delineation combined with histogram analysis can be a less cumbersome alternative to acquire similar ADC measurements and second to explore whether histogram analyses provide additional prognostic information.



Thirty-seven patients who underwent a primary staging MRI including diffusion-weighted imaging (DWI; b0, 25, 50, 100, 500, 1000; 1.5 T) were included. Volumes-of-interest (VOIs) were drawn on b1000-DWI: (a) precise delineation, manually tracing tumor boundaries (2 expert readers), and (b) non-precise delineation, drawing circular VOIs with a wide margin around the tumor (2 non-experts). Mean ADC and histogram metrics (mean, min, max, median, SD, skewness, kurtosis, 5th-95th percentiles) were derived from the VOIs and delineation time was recorded. Measurements were compared between the two methods and correlated with prognostic outcome parameters.



Median delineation time reduced from 47-165 s (precise) to 21-43 s (non-precise). The 45th percentile of the non-precise delineation showed the best correlation with the mean ADC from the precise delineation as the reference standard (ICC 0.71-0.75). None of the mean ADC or histogram parameters showed significant prognostic value; only the total tumor volume (VOI) was significantly larger in patients with positive clinical N stage and mesorectal fascia involvement.



When performing non-precise tumor delineation, histogram analysis (in specific 45th ADC percentile) may be used as an alternative to obtain similar ADC values as with precise whole tumor delineation. Histogram analyses are not beneficial to obtain additional prognostic information.
Department of Radiology, The Netherlands Cancer Institute, P.O. Box 90203, 1006 BE, Amsterdam, The Netherlands.|GROW School for Oncology and Developmental Biology- Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands.|Department of Radiology, Maastricht University Medical Centre, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands.
Miriam M
MM
van Heeswijk
Department of Radiology, The Netherlands Cancer Institute, P.O. Box 90203, 1006 BE, Amsterdam, The Netherlands. d.lambregts@nki.nl.
Doenja M J
DMJ
Lambregts
Department of Radiology, The Netherlands Cancer Institute, P.O. Box 90203, 1006 BE, Amsterdam, The Netherlands.|Department of Radiology, Maastricht University Medical Centre, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands.
Monique
M
Maas
Department of Radiology, The Netherlands Cancer Institute, P.O. Box 90203, 1006 BE, Amsterdam, The Netherlands.
Max J
MJ
Lahaye
Department of Radiology, Maastricht University Medical Centre, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands.
Z
Z
Ayas
Department of Radiology, Maastricht University Medical Centre, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands.
Jos M G M
JMGM
Slenter
GROW School for Oncology and Developmental Biology- Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands.|Department of Surgery, The Netherlands Cancer Institute, P.O. Box 90203, 1006 BE, Amsterdam, The Netherlands.
Geerard L
GL
Beets
Department of Radiology, Maastricht University Medical Centre, P.O. Box 5800, 6202 AZ, Maastricht, The Netherlands.
Frans C H
FCH
Bakers
Department of Radiology, The Netherlands Cancer Institute, P.O. Box 90203, 1006 BE, Amsterdam, The Netherlands.|GROW School for Oncology and Developmental Biology- Maastricht University, Universiteitssingel 40, 6229 ER, Maastricht, The Netherlands.
Regina G H
RGH
Beets-Tan
D000230:Adenocarcinoma / Q000000981:diagnostic imaging* / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D012004:Rectal Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology*; D012189:Retrospective Studies; D047368:Tumor Burden
Apparent diffusion coefficient; Histogram analysis; Prognostic marker; Rectal cancer