New Web Site Calculates Embolization Coil Packing Density

Article by Barbara Kram, Editor helps clinicians optimize deployed coil volume to aid patient outcomes in cerebral aneurysm procedure.

A new web site, authored by South Carolina radiologist Mike Hanley, M.D., provides a convenient online calculator for neurointerventionalists performing coil embolization. The procedure, growing rapidly in use, is a less invasive alternative to craniotomy to treat cerebral aneurysms.

In a coil embolization, a coil is deployed through a catheter that is snaked to the site of the aneurysm in the brain. The coil–usually metal–is deployed through the catheter to fill the aneurysm, rendering it harmless by reducing its pressure.

“Research on coil embolization shows that if you pack the aneurysm with a density of greater than 25% — the ratio of the volume of the coil divided by the volume of the aneurysm — patients have better outcomes,” explained Dr. Hanley, a third-year radiology resident at the Medical University of South Carolina. Calculating this ratio is commonly performed retrospectively during research studies, but was not easily done as part of routine clinical practice.

“The calculations are made mostly by hand so I contacted all the manufacturers and got specifications. Now people can go to the web site to make the calculation.” Manufacturers provided the outer diameters of their coil products, a key variable in calculating percent packing volume that unfortunately is not available on the packaging or product insert.

The web site is used by researchers and practicing clinicians alike. “In addition to neurointerventionalists, I also want to make the site useful for clinical research coordinators and principal investigators,” he said.

How the Site Works

First, the neurointerventionalist or neurosurgeon visits, then selects the aneurysm shape from a number of options. Next, the diameter or two-dimensional measure of the aneurysm is entered so that the site can calculate its approximate volume. The clinician then chooses the type of coil being used, and how much length of coil has been (or is to be) deployed. The site displays the coil-to-aneurysm ratio.

Knowing the ratio helps deploy the optimal length of coil. “Generally the neurointerventionalists try to put in as much coil as they can. They get to a point where if they push too hard there is a risk of rupture or complications,” Dr. Hanley said. He noted that can help the practitioner to gauge where they are with respect to packing the aneurysm. “Some people are calculating the percent volume while doing the procedures, and if they know the packing density they may not have to be as aggressive once they reach 25 percent.”

The new coil embolism web site is a great application of the internet to make a clinical calculation tool widely available for free. (Several coil makers sponsor The site also features an Image Library, Sample Case, Coil Comparison and Background Information on coil embolization of cerebral aneurysms. Spectacular medical illustrations round out the online experience.

“I hope it is useful for those learning about coil embolization, in clinical research, as well as daily practice,” Dr. Hanley said.

Hanley is also the radiologist behind, a radiation dose calculator that reflects the lifetime increased risk of cancer based on exposure to medical imaging procedures.