Hypovascular tumor

For example, in a patient with a hypervascular carcinoma of the uterine cervix as defined by angiography through catheters placed in the main trunk of the internal iliac arteries, the radionuclide flow study can be utilized to demonstrate the flow distribution almost exclusively to the true pelvis. Therefore, the position of the catheters would be adequate and more selective catheterization would not be necessary. On the other hand, in a patient with a hypovascular tumor (most squamous cell carcinomas of the cervix are relatively hypovascular), catheter placement into the internal iliac artery may not only infuse the true pelvis, but may also infuse the buttocks. Embolization of the superior and inferior gluteal arteries with coils or segments of Gelfoam or both can be used to prevent the infusion of the buttocks and redistribute the chemotherapy to the true pelvis. This may result in increased pudendal flow and potentially increase local toxicity. 

Yonezawa S, Asai T, Oku N (2007) Effective tumor regression by anti-neovascular therapy in hypovascular orthotopic pancreatic tumor model. J Control Release 118 303-309... 

MDCT of the pancreas is performed using triphasic acquisition obtained prior to, and biphasic acquisition after, intravenous contrast material injection (Freeny 2005). It has been shown that an arterial-phase scan (similar in timing to the typical arterial-phase scan of the hver) is not of value for detection of pancreatic adenocarcinoma (Fletcher et al. 2003 Graf et al. 1997). Pancreatic adenocarcinoma, which is by far the most common pancreatic tumor, is hypovascular and shows only little to no contrast to the minimally enhancing pancreatic parenchyma in the early arterial phase. Lu et al. (1996) implemented a two-phase CT protocol evalu-... 

Higher contrast material flow rates have been shown to be advantageous. Tublin et al. (1999) showed that a flow rate of 5 ml s is superior to 2.5 ml s regarding enhancement of the pancreas and the fiver parenchyma. Many authors recommend using a flow rate of 4-5 ml s to optimize pancreatic enhancement and tumor-to-pancreas contrast Schueller at eh (2006) demonstrated that an even higher flow rate of 8 ml s (compared with the standard flow rate of 4 ml s ) has its merits. They demonstrated that a flow rate of 8 ml s results in better enhancement of the pancreas, but not of the typically hypovascular adenocarcinomas, which resulted in a higher tumor-to-pancreas contrast. 

A transient hyperechoic zone is seen at US within and surrounding a tumor during and immediately after ablation. However, this finding can be used only as a rough guide to the extent of tumor destruction. Contrast-enhanced US performed after the end of the procedure may allow an initial evaluation of treatment effect. Residual viable tumor can be easily identified in hypervascular lesions, such as hepatocellular carcinoma (HCC), as it stands out in the arterial phase against the unenhanced ablated area. However, interpretation of contrast-enhanced US findings is more difficult in hypovascular lesions. 

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