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The Brachytherapy Pelvic Girdle
Spring 2018 MAE 156B Sponsored Project
University of California: San Diego
What is Brachytherapy?
Cervical cancer is a potentially lethal disease with good to excellent cure rates when treated in early stages of the disease. A majority of patients with more advanced disease are treated with radiation and chemotherapy, which is delivered by external beam radiotherapy and brachytherapy (internal radiation). Brachytherapy involves using an applicator and/or needles to administer very high local doses of radiation via a highly radioactive source. Studies have indicated that internal brachytherapy component of cervical radiotherapy is a critical component of treatment, improving survival of the patient by 10 -15% when used concurrently with external radiation treatment.
What is the Problem?
Utilization of brachytherapy in cervical cancer treatment has declined from 90% to less than 50% since the 1980's. A significant issue of the treatment is the complexity of accurate localization of the brachytherapy applicator. Potential risks of inaccurate localization of the applicator include over-treatment of normal tissues and under treatment of the cancer. Most radiation treatment centers, including UC San Diego Radiation Oncology, utilize a C-arm device connected to a heavy board in order fix the brachytherapy applicator in place. However, the current design of C-arm has no absolute fixation relative to the patient; as a result, the applicator has the tendency to move inside the patient and the potential risks of brachytherapy become a significant concern.
Cartoon depiction of commonly used
Cervical Brachytherapy Device
Current C-arm used by
UCSD Radiation Oncology
The Objective
Designing a pelvic girdle would allow a C-arm to be mounted and constrained to the patient’s pelvis throughout the brachytherapy treatment, improving the security of the brachytherapy applicator and mitigating the risk of harm to the patient. Stabilization of the brachytherapy applicator inside of the patient is a crucial; functional requirement that can be achieved with the pelvic girdle. In addition, the design must conform to the following constraints:
MRI and CT Scanner Compatibility
Lightweight C-Arm Redesign
Conformity to Individual Patient Anatomy
Designed to be Sanitized or Disposable
Work with Various Applicators
Even a modest improvement of device localization, patient comfort and/or ease of use for providers could invoke a far reaching impact, improving the outcome of brachytherapy and increasing treatment utilization at an international level.
Current Design
THE FABRIC GIRDLE
(Prototype #2: Fabrication by Druann Greer-Cisneros)
The third and final iteration of the Fabric Girdle is designed be constrained to the pelvis and serves as the foundation for the supplemental girdle components. It is composed of inexpensive canvas and velcro, allowing the girdle to be disposed of after a single use while avoiding the need to perform rigorous sterilization procedures. In order to conform to various body types, the girdle can be manufactured in small, medium and large sizes with (3) adjustable straps to ensure a secure fit. Thin HDPE plastic stays are inserted into channels on the back of the girdle to increase rigidity and stability of the girdle by maintaining uniform tension throughout the fabric. The innovative cross strap design allows the girdle to conform to the patient’s anatomy while increasing stability of the girdle. Additional velcro leg straps are included to prevent the girdle from slipping off of the patient.
THE GIRDLE INTERFACE
The Girdle Interface is a rigid PMMA plate designed to mount the articulating arm onto the girdle. The interface is both lightweight and compatible with CT/MRI Scanners. A threaded hole at the center of the plate allows the articulating arm to be screwed in, ensuring a secure attachment between the two components. The plate is sized and dimensioned to endure the stresses induced by the articulating arm while maximizing force from the strap required for proper stability. The corners of the plate are filleted in order to avoid any sharp contact points on the patient causing discomfort. The Girdle Interface is inserted into a fabric pocket lined with velcro, providing a simple and secure method of attaching the plate to the Fabric Girdle.
THE ARTICULATING ARM
The Articulating Arm was manufactured by Noga Holding Systems and it a has various features that make it optimal for brachytherapy treatment. It consists of two ball-socket joints and one elbow-joint, allowing it to extend to a maximum of 20” and rotate into the desired position. The arm weighs 0.75lbs and is lightweight enough to be place on the patient's abdomen without causing discomfort. It’s aluminum construction also makes the arm compatible with a CT scanner. The arm locks into position with a large amount of friction produced by an internal locking mechanism. The end of the arm has a ball-and-socket joint with a threaded connector, allowing the arm to be screwed in to the Girdle Interface.
THE TANDEM CLAMP
The Tandem Clamp is also manufactured by Noga Holding Systems. It can grip (3) different tandem diameters including ⅜”, 6mm and 8mm. The clamp has two different knobs. Turning knob (1) allows for small adjustments of tandem positioning while turning knob (2) allows the clamp to lock into to the tandem. The tandem clamp has a threaded bolt that screws into the ball-and-socket end of Articulating Arm, ensuring a secure attachment.
Final Design
Second Live Trial
Technician Feedback:
The old clamp/system was “very unwieldy … a pain in the ass” compared to the new girdle.
Patient Feedback:
Eliminated need to reposition equipment during procedure which was a large source of discomfort
Eliminated feeling of equipment moving separately while being transferred between gurneys
Did not have to be woken up during procedure to put the old clamp board underneath them
This is huge, they used to have to bring them back to consciousness to move them so they were exposed to very large amounts of pain.
“Procedure was much more comfortable than before”
A soft goods pelvic girdle combined with a new, smaller clamp was the final design pursued since it met the requirements best. The soft goods pelvic girdle allows for the clamp to be constrained to a variety of individual body types which greatly improves the stability of the applicator in relation to the patient. Additionally, due to the manufacturing and materials used, the soft goods girdle is entirely disposable which best satisfies the sanitation requirements. A redesigned clamp was produced to reduce the weight on the patient and to improve the usability of the locking mechanism. This clamp was designed to be easily sanitized to meet medical standards. All design decisions were made with MRI and CT Scanner compatibility in mind.
Prototype Demonstration and Feedback
First Live Trial
The first trial utilized the following features of the Pelvic Girdle prototype:
Utilized medium size girdle
Did not use leg straps
Patient was larger than expected
Girdle was placed on top of the hospital gown
Easier prep setup and maintained patient modesty for a longer period on time
Pelvic Girdle was used for the entire procedure
First brachytherapy procedure
Was not sedated due to drinking before the procedure but reported no uncomfortable feeling with the girdle
Mostly felt the applicator for the procedure instead of the girdle or clamp (success).
A prior patient who had this procedure reported huge pain caused by the board that was placed underneath her lower back. She was traumatized to such an extent that she did not want to do the procedure anymore. Offering this girdle allowed her an improved option to continue with the procedure.
“I just feel something wrapped around me, nothing uncomfortable”
Technician Feedback:
“The clamp could affect the images in CT scan, but it is fine”
Overall impressions of the Pelvic Girdle were consistent with resounding success.
Small changes could be made but a huge improvement over previous methods
The second trial utilized the following features of the Pelvic Girdle prototype:
Patient was not sedated and did not feel any discomfort from the girdle
Increased arm length from 14" to 20"
Utilized extra large size girdle
Repeated successful results
The rigid insert on the back was not used for this trial
Patient Feedback:
