Development and validation of a heart atlas to study cardiac exposure to radiation following treatment for breast cancer.
OBJECTIVE
Cardiac toxicity is an important sequela of breast radiotherapy. However, the relationship between dose to cardiac structures and subsequent toxicity has not been well defined, partially due to variations in substructure delineation, which can lead to inconsistent dose reporting and the failure to detect potential correlations. Here we have developed a heart atlas and evaluated its effect on contour accuracy and concordance.


METHODS
A detailed cardiac computed tomography scan atlas was developed jointly by cardiology, cardiac radiology, and radiation oncology. Seven radiation oncologists were recruited to delineate the whole heart, left main and left anterior descending interventricular branches, and right coronary arteries on four cases before and after studying the atlas. Contour accuracy was assessed by percent overlap with gold standard atlas volumes. The concordance index was also calculated. Standard radiation fields were applied. Doses to observer-contoured cardiac structures were calculated and compared with gold standard contour doses. Pre- and post-atlas values were analyzed using a paired t test.


RESULTS
The cardiac atlas significantly improved contour accuracy and concordance. Percent overlap and concordance index of observer-contoured cardiac and gold standard volumes were 2.3-fold improved for all structures (p < 0.002). After application of the atlas, reported mean doses to the whole heart, left main artery, left anterior descending interventricular branch, and right coronary artery were within 0.1, 0.9, 2.6, and 0.6 Gy, respectively, of gold standard doses.


CONCLUSIONS
This validated University of Michigan cardiac atlas may serve as a useful tool in future studies assessing cardiac toxicity and in clinical trials which include dose volume constraints to the heart.
Feng
Mary
M
Department of Radiation Oncology, University of Michigan Medical Center, Ann Arbor, Michigan 48109, USA. maryfeng@umich.edu
Moran
Jean M
JM
Koelling
Todd
T
Chughtai
Aamer
A
Chan
June L
JL
Freedman
Laura
L
Hayman
James A
JA
Jagsi
Reshma
R
Jolly
Shruti
S
Larouere
Janice
J
Soriano
Julie
J
Marsh
Robin
R
Pierce
Lori J
LJ
D001943:Breast Neoplasms / Q000532:radiotherapy*; D003287:Contrast Media; D017023:Coronary Angiography / Q000379:methods; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging* / Q000528:radiation effects; D006801:Humans; D008488:Medical Illustration; D015588:Observer Variation; D011832:Radiation Injuries / Q000517:prevention & control; D014057:Tomography, X-Ray Computed
D003287:Contrast Media