Contrast-enhanced US of microcirculation of superficially implanted tumors in rats.
OBJECTIVE
To determine the ability of contrast material-enhanced ultrasonography (US) to assess replenishment time in a rat kidney and adenocarcinoma tumor model.


METHODS
Mammary adenocarcinoma cells were implanted into the subcutaneous tissues of the flank of 11 rats. Resultant tumors were imaged serially with contrast-enhanced US and compared with images of the rat kidney, a highly perfused normal organ. The US acquisition and processing methods yield images of perfused tumor regions and the times required to achieve 80% replenishment. Findings at contrast-enhanced computed tomography (CT) and light microscopy of hematoxylin-eosin-stained tumor tissue were compared. Paired Student t test was performed to compare the accuracy of US with that of histologic examination and CT in the detection of viable tumor regions.


RESULTS
Replenishment of the kidney cortex microvasculature requires 1-5 seconds compared with a replenishment time of 6-14 seconds in tumors. Over the time course of tumor growth, the mean perfusion time becomes progressively longer, and a wider range of perfusion times is detected. Comparison of findings at US, CT, and histologic examination suggested that all three methods yield correlated estimates of the percentage of viable perfused tumor cells. Results of the t test suggested that the viable tumor percentages observed at US are not significantly different from those observed at CT and histologic examination (US vs CT, P =.92; US vs histologic examination, P =.94).


CONCLUSIONS
Repeated measurements of microvascular flow rate can be accomplished in a rat animal model with a minimally invasive technique.
Chomas
James E
JE
Department of Biomedical Engineering, University of California-Davis, 1021 Academic Surge, Davis, CA 95616, USA.
Pollard
Rachel E
RE
Sadlowski
Amy R
AR
Griffey
Stephen M
SM
Wisner
Erik R
ER
Ferrara
Katherine W
KW
D000230:Adenocarcinoma / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D000818:Animals; D045744:Cell Line, Tumor; D003287:Contrast Media; D007483:Iothalamic Acid; D007672:Kidney Cortex / Q000098:blood supply / Q000000981:diagnostic imaging; D007680:Kidney Neoplasms / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D015674:Mammary Neoplasms, Animal / Q000098:blood supply* / Q000000981:diagnostic imaging* / Q000473:pathology; D045423:Microbubbles; D008833:Microcirculation; D009368:Neoplasm Transplantation; D051381:Rats; D011916:Rats, Inbred F344; D014057:Tomography, X-Ray Computed; D014463:Ultrasonography
D003287:Contrast Media; D007483:Iothalamic Acid