It is extremely important for cancer patients to have a reliable vascular access which may be used for administering irritant infusions, such as chemotherapeutic agents and intravenous nutrition supplement, and for drawing blood for routine examinations in the long term. To address patients' needs, Aubaniac introduced the central vein puncture technique for vascular infusion in 1952AD. With this technique, patients were allowed to take intravenous infusion safely but had to experience repeated punctures every 5-7 days for preventing tunnel tract infection. Later, with the improvement of medical material, the first indwelling intravenous catheter was designed by BrovIac which could be implanted for a period of time. In 1979, based on this prototype, Hickmen added a subcutaneous cuff in order to separate the proximal part of catheter from environment and minimize the risk of tunnel tract infusion, leading to cosmetic concerns and compromising patients' daily activities . It's till 1982 that Dr. Niederhuber developed the totally implantable venous device, which made vascular access set up simpler for patients. However, low injection pressure setting constrained some applications, such as power injection of contrast media for CT scan. Therefore, peripheral venous puncture was still inevitable sometimes for the patients with intravenous access devices placed.

Patients with cancer need to regularly receive imaging surveillance to evaluate treatment efficacy. Besides, the surveillance imaging provides benchmark reference for adjustment of treatment plan. To provide the enhanced quality of image, contrast media is expected to be administered at certain injection rates. Such requested injection rates would generate high pressures due to the sticky nature of the contrast media. Most of the time, the pressures incurred are far beyond the pressure setting of the conventional ports which mostly in the range of 10 \~ 12 atmospheric pressures (approximately 145 \~ 175 psi) and may cause device rupture or burst. Venipuncture is still unavoidable for oncologic patients with intravenous port implanted for administering contrast media so that patients' vessels cannot be completely protected from repeated venipunctures. Besides, patients' native vessel has its own infusion pressure limitation. Extravasation of contrast media to peripheral soft tissues would happen to the patients with poor vessels or to those in need for power injection of contrast media. Extravasation of contrast media may lead to cutaneous necrosis at different degrees. Such a consequence not only causes pain to patients, but also postpones the subsequent treatment that cannot be continued until the wound is healed up. The delay of treatment might impact on patients' survival. To avoid such a complication, radiologists are forced to lower the infusion velocity of contrast media and compromise the quality of the image requested by the diagnosis.

Tumor would induce neovascularization process which may trigger abnormal new vessels to form and surround the lesion for providing the requested nutritional support for its growth. Given by this characteristic, the contrast-enhanced image plays an important role in evaluating the degree of tumor invasion. In addition, information regarding relative anatomic relationship between tumor and surrounding vital structure is also crucial for formulation of a treatment plan. However, as medical image is not color but black and white images, images with sharp contrast can present subtle changes of tumor more clearly as reference for evaluation of physicians. If the resectability and the metastatic lesions could be identified from medical images as early as possible, personalized treatment could be planned to achieve better survival rates. Therefore, it is extremely important to acquire a clear medical image. With respect to conventional CT, it can indicate the relative anatomical relationship between tumor and surrounding vital structures, which is a key basis for formulation of treatment plan. Current initial imaging data shows CT images taken after infusion with an implanted port that can endure a high infusion pressure are actually different from those taken after infusion through peripheral vein Theoretically, contrast media administrated via central vein could increase concentration of contrast media within a short time, improving the imaging quality of tissues close to the tumor greatly and reducing the necessity of peripheral venipuncture and the risk of contrast extravasation. Therefore, an implantable port that can endure a high infusion pressure is the only solution to meet the demand both from treatment and from surveillance. Furthermore, venous thrombus is more likely to occur in patients with malignant tumor, which must be prevented as it may cause a higher in-hospital mortality rate. If loosen thrombus delivered by venous return may lead most serious complications, such as pulmonary embolism. Pulmonary artery angiography was used to be the only way for diagnosis. However, with the improvement of imaging technology, computed tomography now could be utilized in diagnosis too. High quality of image may be achieved as long as contrast media is injected at a high velocity but patients might risk getting hurt by extravasation of contrast media. After intravenous port that could endure high injection pressure was available, the characteristic of high volume profile could provide secure vascular route with minimal risk of extravasation. However, there was no agreeable conclusion on how such a device may benefit the survival of the patients. Although the port that can endure a high pressure of infusion can provide a reliable intravenous route and better medical images, the benefits of prognosis which may be brought by such port are still unknown. Besides, the national insurance hasn't reimbursed such new type of infusion port due to limited insurance budget. Therefore, investigators intend to identify the patients suitable for implantation of such port in view of features of imaging and tumor so as to improve prognosis of cancer patients.