Purpose: 
           
            We hope to develop a reliable, miniature, wireless radiation detector, that can be implanted directly into the target volumes to be treated with Radiation Therapy. We will then determine exactly what dose is actually delivered to these regions and assess means by which to improve individual treatments and hopefully treatment outcome. The design and fabrication of a reliable, miniature, wireless detector is the first and absolutely essential step in being able to carry out this assessment. The proposed detector system will be comprised of two units, a miniature bio-compatible radiation sensor, and a reusable external electronics package containing the data collection and output display. The miniature sensor nucleus can be placed or implanted at a clinically relevant position within the treatment region and transmits real-time dose rate data without wires or a battery. The reusable external package includes both a transceiver to collect the data and appropriate electronics to interpret and display dose rate information. This system would provide a direct measurement of radiation dose at relevant prescription locations, enabling more effective therapy and improved patient outcome. 

Significance: 
           
            In Radiation Therapy, verification that the prescribed dose has actually been delivered is essential for successful treatments since optimal radiation therapy depends upon delivering a tumoricidal dose to a specific, anatomical target while sparing as much normal tissue as possible. With progress being made in image based radiation therapy and new techniques such as intensity modulated radiation therapy, gated radiation therapy, and 3-D Conformal radiation therapy, the challenge of delivering the proper dose to the selected target region is even more daunting. In addition, prostate seed implant therapy is becoming more popular and dose verification is essential in implant therapy as well. The common theme in all of these new advances in radiation therapy is that the target to be treated is based on initial imaging of the region to be treated. Changes in the size of the target (tumor) during the course of therapy are seldom taken into account, and movement of the target region during each individual treatment are never quantified. Consequently, the sophisticated planning and treatment delivery schemes that are designed on the basis of initial imaging are not actually delivered during the course of treatment. This situation exists in external beam therapy and interstitial implant therapy such as prostate seed implantation where swelling is initially evident with volume changes over time. The reason that these changes in position, volume, and ultimately the final delivered dose, could not be quantified is due to a lack of a miniature, real-time, radiation detector that could easily be implanted directly into the region to be treated. A detector of this nature with the proper design characteristics could indicate both the dose being delivered and the position of the dosimeters within the body. Thus changes in position of the treatment volume during individual treatments, and changes in the total treatment volume over the entire treatment course could be monitored, documented, and optimized on the basis of this additional information.

            The design criteria of this new detector system are that the detector is extremely small (1x 1 x 2 mm3 max.), wireless, has a uniform response to radiation of different energy, and is independent of beam direction. The small size and wireless capability would allow this detector to be used in both external beam radiation treatments, and also in implant radiation treatments. For external beam treatments, the detectors could be placed at the beginning of treatment and left in place for the entire treatment course, between 20 - 35 treatment sessions. Since no time would be required in the treatment room for application of the detectors, there would be no interruption of the regular treatment routine or inconvenience for the patient. With the advent of more sophisticated treatments such as Intensity Modulated Radiation Therapy (IMRT) where the beam intensity is changing constantly, the need for real-time verification and dosimetry is even more important.      
            Real-time dosimetry for brachytherapy has been attempted several times but has always failed to provide usable data. Detector placement has been difficult to verify or the dose measurement points have been clinically irrelevant. The small, wireless detectors that we are proposing, can be made part of the actual implant apparatus for intracavitary application and thus yield accurately known and clinically relevant dose verification points. For High Dose Rate brachytherapy (HDR) where 500 cGy can be delivered in as little as 5 minutes, real-time dose verification at clinically relevant points is extremely important to verify the dose and guard against patient mistreatment. Small, wireless detectors can also be used to verify the dose during interstitial seed implants since they can be inserted directly into the implanted region in the same manner as the radioactive seeds.          

Methods and Goals: 

            Our ultimate goal is to determine exactly what dose is actually delivered to tumorous target regions and assess means by which to improve individual treatments and patient treatment outcome. As a first step in reaching this goal, the production of a reliable, miniature, wireless radiation detector is absolutely essential. Initial testing will be done to verify the operation of the basic prototype - that the diode can operate usefully as a radiation detector and that this information can be conveyed to a display device without the use of wires. After construction of the basic device, the radiation detector will be tested to ensure that its response to radiation can produce an accurate description of the dose delivered to patients. Finally, the response of the detector as a function of overlying tissue will be tested. For this step, we will test the detectors ability to communicate accurately with the display device versus different amounts of overlying tissue. We will also test the maximum distance from the detector to the display device that can still produce accurate and reliable dose delivered to patients. It is hoped that the data acquired from these investigations will lead to a viable detector that is clinically useful for remote, real-time patient dosimetry.
                      

1. What is the device and what does/would it do?

The proposal is to develop a miniature, wireless, radiation detector that would give a real-time indication of delivered dose in radiation therapy along with the position in the patient to which the dose was delivered. The basic idea is that a miniature radiation detector would be implanted, detect the dose, and transmit that dose to an external display. That would be the first goal. The second goal would be to use the transmitted signal to determine the location of the implanted detector. The signal would be sensed by two external devices to triangulate the position of the implanted detector in 3-D space thus giving both an indication of the dose in real-time and the location of the delivered dose in the patient.

2. Describe the clinical problem associated with the device.
The problem in radiation therapy is to deliver a therapeutic dose to a well specified region of the body and to be able to prove that the correct dose was delivered.

3. Has this idea ever been tried? If so, what didn’t work?
The particular approach has not been tried but they are many currently existing approaches to measure dose in radiation therapy.

4. Is there a current device that attempts to perform the same function?
There are many dose verification devices used currently in radiation therapy. However, none are small enough to be implanted and if they were implanted, easily give and indication of the delivered dose.
                         
5. Describe the potential magnitude of use.

Even though this is presented as a radiation dose detector for radiation therapy, this is basically any miniature detector, biological, medical, or industrial, mated to a meter via a wireless connection. There are extensive applications in radiation therapy for real-time dose determination from external beam dosimetry to real-time verification of implant dosimetry. I could easily envision many other detectors that could be employed that could benefit from having a small detector that could communicate wirelessly to an external meter.