Conformal therapy for pancreatic cancer: variation of organ position due to gastrointestinal distention--implications for treatment planning.
OBJECTIVE
To quantify nonrespiratory organ motion in the pancreatic region and its effect on clinical target volume.


METHODS
Three-dimensional translations of the geometric centers of the volumes of interest--pancreatic head, body, and tail; left and right kidney; and the superior mesenteric artery--were measured in 20 patients by analyzing three spiral computed tomographic (CT) protocols performed at static exhalation and representing differential gastrointestinal distention. Wilcoxon test for paired differences was applied to determine statistical significance (P <.05). Spearman rank correlation coefficients were calculated between combinations of statistically significant translations. With the assumption that the organ positions were represented by a three-dimensional Gaussian distribution that occurs during treatment, clinical target volume expansions were calculated to account for organ motion and a typical setup error.


RESULTS
Significant translations of the volume of interest were observed. The most mobile parts of the target organs were the pancreatic tail (P =.001) and the superior mesenteric artery (P =.01). Larger variations from the mean in the planning CT protocol in which negative contrast material was used usually resulted in a slightly larger clinical target volume expansion.


CONCLUSIONS
Our data may provide a basis for further studies of organ motion and ways of modifying treatment margins.
Horst
Eckehard
E
Department of Radiation Oncology, University of Münster, Albert-Schweitzer-Strasse 33, 48129 Münster, Germany. horste@uni-muenster.de
Micke
Oliver
O
Moustakis
Christos
C
Schuck
Andreas
A
Schäfer
Ulrich
U
Willich
Normann A
NA
D000328:Adult; D000368:Aged; D003287:Contrast Media; D004064:Digestive System / Q000000981:diagnostic imaging; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000000981:diagnostic imaging; D008297:Male; D017538:Mesenteric Artery, Superior / Q000000981:diagnostic imaging; D008875:Middle Aged; D010179:Pancreas / Q000000981:diagnostic imaging* / Q000528:radiation effects; D010190:Pancreatic Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal; D014057:Tomography, X-Ray Computed
D003287:Contrast Media