# Development of a portable and compact robotic system for frameless and maskless stereotactic radiosurgery

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2021 · $307,697

## Abstract

ABSTRACT
Stereotactic radiosurgery (SRS) is a non-surgical technique used to treat functional abnormalities and small
tumors of the brain. It delivers precisely targeted radiation in fewer high dose treatments than traditional
therapy and allows access to sites that would otherwise be difficult or inadvisable to treat due to potential
surgical complications to nearby nerves, arteries, and other vital structures. To achieve the 1-2mm precision
for intracranial SRS, a metal head ring is rigidly fixated to the patient’s skull using screws under local
anesthesia, and then bolted to the treatment couch. The discomfort, inconvenience, and invasive nature
associated with the frame preparation have been identified as a serious cause of poor patient compliance and
poor clinical efficiencies when SRS is medically indicated. For certain patients, with extreme cranial anatomy or
prior surgical bone flaps, ring placement is not possible. In addition, the frame prohibits cases when a hypo-
fractionated scheduled is desired leading to the use of techniques with far less accuracy. For clinics, with tight
patient linear accelerator (LINAC) scheduling, or high patient to LINAC volumes, frame based SRS scheduling
can prove to be problematic due to the necessity of performing the CT simulation, treatment planning, LINAC
SRS QA, patient setup, and treatment on the same day. Research aimed at eliminating the frame through the
use of thermoplastic face masks have resulted in SRS with less accuracy as mask flex can lead to systematic
drift of up to 2-3mm away from the intended target due to rotation about the fulcrum at the back of the skull.
Additionally, mask based immobilization accuracy is highly dependent on mask manufacturing quality, skill of
the person applying the mask, shrinkage of the mask during treatment, and physical changes of the patient’s
head due to swelling or weight loss. In certain cases this has led to uncertainties as large as 6 mm and 2.5
degrees. Such accuracies are not suitable for deep tumors located near critical structures such as the brain
stem or for newer treatment modalities such as single iso-center multiple target SRS which are highly sensitive
to rotational errors.
We propose to solve these problems by developing a novel robotic SRS system that does not require a frame
or mask. The hypothesis is that the use of real-time 6 degree of freedom (6DOF) patient head motion tracking
and active robotic control systems can assist patients in maintaining a stable sub-millimeter sub-degree head
position for long periods of time. Specific aims include: (1) To develop an advanced real-time 6DOF trajectory
control law. (2) Design and construction of a clinical robotic SRS system using real-time 3D surface image
tracking. (3) Anthropomorphic phantom, healthy volunteer and patient clinical trials.

## Key facts

- **NIH application ID:** 10074545
- **Project number:** 5R01CA227124-03
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Rodney Wiersma
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $307,697
- **Award type:** 5
- **Project period:** 2018-12-04 → 2023-11-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10074545

## Citation

> US National Institutes of Health, RePORTER application 10074545, Development of a portable and compact robotic system for frameless and maskless stereotactic radiosurgery (5R01CA227124-03). Retrieved via AI Analytics 2026-05-21 from https://api.ai-analytics.org/grant/nih/10074545. Licensed CC0.

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