Three years and four months after I received an implanted access port - a PowerPort® made by Bard Access Systems (Salt Lake City, UT) - it was removed at MGH today. The access port, also called a port-a-cath, consists of a two basic units: a "portal" (a small reservoir with a silcone rubber membrane for needle access) and an attached "catheter" , a plastic tube , which inserts into a large vein such as the subclavian veins or jugular. The portal is implanted under the skin near the clavicle (collar bone).
Bard Access Port
showing portal and catheter
The port is accessed using a needle which punctures the skin and the rubber membrane of the port. The membrane naturally seals around the needle and seals when the needle is removed. The device is designed to be accessed thousands of times. In the implantation procedure, the catheter is introduced into the vein using a placement tool which punctures the vein and allows the catheter to be inserted several centimeters into the vein as needed. The placement tool is extracted leaving the catheter in place.
Circulating tumor cells (CTCs) occur in the blood at very low levels - just a few cells per milliliter. Since each ml of blood contains about 5 billion erythrocytes and 10 million leukocytes, detection requires a high level of parallel processing and excellent detection statistics. Advances in the fabrication of micro-mechanics, micro-electronics (MEMS) and micro-fluidics make possible a form of flow cytometry coupled with microarray cell selection and analysis.
The BioMicroElectroMechanical Systems (BioMEMS) Resource Center of Harvard, MIT and Massachusetts General Hospital is researching ways to sort, select, and detect cells in very small quantities.