I– Brachytherapy and its challenges

Prostate cancer is the most common non-cutaneous cancer in American men.  In 2009, the American Cancer Society (ACS) has estimated 192,280 new prostate cancer cases and prostate cancer is one of the leading causes of cancer death [1]. The existing prostate cancer treatment includes several procedures such as radical prostatectomy, brachytherapy, external beam radiation therapy (EBRT), hormonal therapy, cryotherapy, and ‘watchful-waiting’. Among these, brachytherapy with permanent radioactive seed implant is a popular treatment choice for patients with prostate cancer [2]. Such interstitial therapy is attractive to patients due to many reasons.  It is an outpatient procedure and in many cases has been contributed to lower long-term risks of urinary incontinence and impotence when compared to radical prostatectomy or cryotherapy and the procedure is better tolerated by patients with serious comorbidities [3]. It is a non-surgical procedure that, unlike EBRT, does not require multiple treatments. The implantation of seeds is also less technically challenging for the surgeon as compared to radical prostatectomy [4].

In brachytherapy, radioactive seeds are permanently implanted in the prostate for delivering a tumorocidal dose to the prostate tissues. A typical seed is a titanium capsule, 0.8mm in diameter and 4.5 mm in length (Fig. 1a), that contains a radioactive isotope (most commonly iodine-125 or palladium-103 for prostate therapy) and a marker of radio-opaque material (e.g. silver) for identification in computed tomography (CT) and X-ray images. The seeds provide a significant radiation dose to a relatively small volume, requiring that the seeds be placed accurately to ensure complete treatment. Sensitivity of the urethra and rectal mucosa to radiation are other factors that heighten the need for careful placement of seeds. Transrectal ultrasound (TRUS) is commonly used to guide the percutaneous placement of the seeds for this reason [5]. However, the orientation of the seed is also important for detection with TRUS, CT, and magnetic resonance imaging (MRI).

Figure 1: (a) Radioactive seeds and (b) Brachytherapy procedure

Brachytherapy is performed percutaneously.  The challenge in this procedures is guiding the needle to a precise location inside soft tissue. Moreover, quantitative real-time sensory feedback is seldom available, and the needle is usually rigid.Once the target is reached, the subsequent steps are relatively simple and usually consist of using the needle’s lumen to deliver agents ( e.g, drugs or radioactive seeds, or gene) or to capture materials ( e.g, biopsy samples) or to place analytical probes.

II– Smart neddle projects.

In recent years, much developmental effort has been directed to improving medical imaging and interventional delivery systems, but needles have been left out from this evolution. The design of most needles used clinically is several decades old [8]. Many medical procedures could benefit from closing the control loop through quantitative sensory feedback and the ability to adjust the needle trajectory in real-time. Therefore, the topic of steering flexible needles through soft tissue has attracted considerable attention in the recent years.

Therefore, we propose to develop a new type of needle, a self-actuating (“smart needle”, i.e., needle having distributed actuators and sensors along the needle’s body/shaft) needle, for percutaneous intervention in soft tissue with greater flexibility and maneuverability for accurate and easy access to the target by avoiding obstacles and with full conformity of the anatomical structure (Fig. 3).  The smart needle will be developed using the concept of smart structures and actuators. It will have sensors to track the needle tip and to monitor the needle configuration, as well as distributed actuators along the needle shaft/body to respond to an undesirable structural response (e.g., needle deflection). A closed-loop control system will be designed accordingly to process the transfer of information and real-time controlling of the needle.

Fig. 2. Accessing various part of the prostate – (a) conventional rectilinear approach of prostate brachytherapy needle insertion pattern with straight needles requiring 6 needles(note that the patient must be set up in the OR in the lithotomy position), and (b) proposed curvilinear conformal smart needle insertion requiring 4 needles (in any convenient needle entry orientation).

Composites Lab at Temple University has teamed up with Dr. Podder at Thomas Jefferson University to design this exciting new device. Composite Lab will be responsible to design the Nitinol actuator , which is a very challenging area due to its non-linear hysteresis couple with its super-elasticity and shape memory behavior. Moreover, we will also be responsible for studying the mechanical behavior of prostate, to analyze the interactions between the needle system and prostates’ tissues.

Figure 3: Needle system development and integration plan

Current student(s)/researcher(s) on the project: Tuan M. Nguyen ( Nitinol), Mohammad Honarvar (Nitinol), Joe Koo (Prostate) ,Dr. Naresh V. Dalta

III- Reference