Brachytherapy is used by doctors to treat cancers at various points in the body.

Every year, some 500,000 cancer patients worldwide undergo brachytherapy, a form of radiotherapy where needles or implants are temporarily inserted into the body to guide small radioactive sources directly to the source of the problem. Brachytherapy is a widely used treatment of cancers of the prostate, pelvic sidewall, breast, liver, brain, nasal cavity, throat and tongue.

One of the challenges involved in using the method is accurately placing those sources in areas sufficient to irradiate the tumors, while simultaneously limiting radiation damage to surrounding healthy organs and tissues.

As it's done now, standardized applicators which feature internal channels to route the radiation are inserted into body cavities to guide the sources. A one-size-fits-all approach, the guides are liable to shift while inside the body and are prone to inaccuracy. Those shifts mean the dosages of radiation directly to the tumor are less than optimal.

But now a team of doctors at UC Berkeley's Berkeley Lab for Automation Science and Engineering led by Professor Ken Goldberg and Professor Pieter Abbeel has come up with a method that both improves and customizes brachytherapy for each patient.

This new approach leverages the power of 3D printing by using "steerable needle motion" and customized implants which use curved internal channels to minimize air gaps and precisely guide radioactive sources through those printed channels to the affected areas.

Using an algorithm for computing these "curvature-constrained channels," the team say customized implants with curved channels suggest that customized implants offer significant improvements over the previous methods of treatment.

Radioactive treatment sources are pushed through the needle or implant channel using an attached wire and then slowly removed by an automated "afterloader" which allows the source to remain in a specified location for precise periods of time to deliver the proper dosage.

To work correctly, the treatments require that the prescribed dose be delivered in 2-4 iterations and over the course of 5-6 hours.

As it stands, patients are now required to remain immobile over the course of treatment to maintain the geometric positions between the sources and the treatment locations, and the quality of the outcome depends on precisely positioning the sources to sufficiently irradiate tumors.

The doctors say that such customized implants can also provide a much better fit and increase patient comfort, reduce shifting due to movement and changes in bladder and bowel geometry, and permit patient mobility between treatment sessions.

The case study used anonymized data from an actual patient CT-scan taken at the UCSF Mt. Zion Center.