Prototype configuration for a USB Powered Low cost; real time continuous radiation monitoring system for Hospital Surgical Pathology, Hematology, Biological waste management and Research facilities

Running Title: USB Powered Continuous Radiation Monitoring for Field Research

R. Siderits M.D. 1

C. Rimmer M.D.1

D. Sung PGYIV
A. Weiss 2

B. Hoffman 4

H. Rahimi 3

O. Ouattara 1

W. Lecorchick 1

M. Maksymow 1

1. RWJ University Hospital Hamilton -Experimental-Path Dept.

2. Engineer SparkFun Corporation

3. PGYIV RWJ Medical School

4. Engineer National Instruments

 

Abstract:

The increasing use of radioactive materials in imaging and treatment modalities in combination with the evolving complexity (and integration) of medical, laboratory research environments and the need to monitor E-Waste sites for contamination has prompted us to consider the value of configuring a real time, USB powered radiation monitoring device that is inexpensive, robust and flexible.  Radioactive isotopes may be used during imaging studies,  during surgical procedures or may be given to patients for cancer treatment.  Radioactive contamination may occur in several areas in the hospital including surgical pathology, radiation physics “hot bench”, hematology, biological waste and E-Waste sites.  Monitoring for contamination, in real time, is needed to maintain a safe workplace and for efficiently managing hospital material for transportation.  These concerns prompted us to describe the configuration of a low cost USB powered, real time, radiation monitoring system which can provide audible and visual alerts, time stamping of events, email notification, maintenance, form based data logging and traffic-control lighting for “Stop and Scan” modes.  We discuss several different implementation strategies.

KeyWords: radiation, USB, continuous, monitoring, labview

Introduction:

Radioactive materials are increasingly used in medicine for treatment and diagnosis.  Hospital and laboratory facilities are complex and increasingly inter-related.  This complexity mandates a high priority be given to  monitor various safety parameters in real time throughout a multi-site system.  The cost of implementing and supporting real time monitoring of safety parameters, such as radiation emission can be prohibitive.  State and federal mandates have compelled many organizations to develop more cost effective solutions to meet these requirements.  We describe the configuration of a low cost USB powered real time radiation monitoring system that is flexible, robust and easily distributed over a networked multi-site system.  We first evaluated the types of isotopes and their medicinal usages that we would need to monitor.    

The different types of radiation used in clinical medicine include alpha, beta and gamma emitters.  Alpha radiation is short range and does not penetrate skin or clothing but may be dangerous if inhaled, swallowed or absorbed into a wound.  Examples include radium, radon, uranium, thorium.  Beta radiation may travel several feet in air and is moderately penetrating which means it can penetrate human skin to the "germinal layer" and may cause skin injury.  Clothing provides some protection.   Examples of some pure beta emitters include strontium-90, carbon-14, tritium, and sulfur-35. Gamma radiation and x-rays are considered penetrating, thus they are able to travel many feet in air and several inches into human tissue.  Examples of gamma emitters often used in medical and research applications include iodine-131, cesium-137, cobalt-60, radium-226, and technetium-99m.

Decay profiles for radio-nucleotides used in imaging human organs (gamma scans) like technetium-99M have a half life of approximately 6 hours while iodine-131 has a half life of 8 days.

Several isotopes have complex emission profiles.  For example, primary emissions of iodine-131 decay are 364 keV gamma rays (81% abundance) and beta particles with a maximal energy of 606 keV (89% abundance).  These profiles may be configured as in therapeutic “seed” implants which may have a titanium shell that filters beta radiation to allow low energy gamma emissions to reach surrounding tissue.  Common biomedical uses and types of radioactive materials include the following: thyroid malignancy treatment using iodine-131; introperative identification of sentinel lymph nodes using technetium-99 and gamma organ scanning; prostate “seeding” using iodine-125 beta or palladium -103 gamma.

Materials and Methods:

The prototype system includes a USB powered Geiger-Meuller tube, a warning lamp, a light tower, USB controlled DC voltage relays and a low voltage solenoid.  The configuration of the prototype was accomplished in the following manner.  The USB Geiger tube and the USB “Phidget” relay board were attached to the controlling computer.(7)  The solenoid, the warning lamp and the light tower were wired to the relay board.  The graphical program LabView was then used to identify the USB Geiger  tube and the Relay board as “virtual” instruments.  This permitted us to rapidly develop a program and user interface that registered the counts from the Geiger tube, tracked counts/unit time and assigned thresholds for triggering the warning lamp.  The light tower permitted a traffic control lighting for Stop-and-Scan mode and the solenoid allowed for a swing gate control latch based on the light tower signal.

 

Figure 1. Components of the prototype radiation monitoring system (clockwise from top left) warning lamp (for radiation threshold alert), phidget USB 4-relay board, traffic control lighting (green-red light tower), USB powered Geiger tube and a fourth relay used for a tubular pull type solenoid (spring gate release mechanism).

Materials:

Parts list (part cost in US dollars):

    9.99    Flashing rotating warning lamp

  23.00    Light tower 23.00

  60.00    Phidget USB relay

149.00    SparkFun USB Geiger counter

  18.00    Tubular pull Solenoid (Spring gate release)

  40.00    Misc Hardware (spring gate fixture, plastic for vacuum formed enclosures,

                                          mounting brackets, DC power supply for lights)        

299.99    Total cost of prototype development for a system that will run on any available PC.

Key components: Labview graphical programming environment:

The Labview 2010 Rapid Application Development Platform was chosen for its graphical interface, program development, and the ease of User interface configuration.

The LabView program creates a Virtual Instrument (VI) that is used to interface with the Geiger tube on the USB port. The VI has a “Block diagram” for program configuration and a “Front panel” for development of the user interface.   Components corresponding to either “Controls” (switches, knobs or sliders) or “Indicators” (gauges, lighted LED representations or result fields) are placed on the front panel to form the user interface.  The block diagram then allows a “Wiring” tool to connect these components in a functional manner.  A similar approach would allow the representation of the serial port with the Geiger tube to provide information directly to an indicator on the front panel.  The processing elements provide a way to keep track of time and number of events with a rest function.

Using a similar approach we identify a phidget 4-relay board connected to a second USB port and use the events detected by the Geiger tube port to trigger relays on the second port.  These are configured to activate the warning lamp, control a traffic control lighting tower and a pull type solenoid for a swinging entrance/exit gate bar. Together this permits radiation monitoring of count thresholds, audible and visual alerts, time stamping of events, email notification, maintenance and data logging forms while being able to simultaneously control the phidget USB relay board for traffic-control lighting, warning lamps and the tubular pull type solenoid.

Figure 2: Left - Block Diagram showing program components “wired” together to form functional units. Right - “Front Panel” showing both controls and indicators identified in the block diagram. these include switches, gauges and LED type buttons/ indicators (background image is placed on Front panel for aesthetics).

Key components: Geiger Counter

A Geiger-Meuller tube is filled with a gas. When a high voltage of radiation interacts with the wall or gas in the tube it creates a pulse. The pulses are sent to a meter and can generate an audible signal. Common readout units are roentgens per hour (R/hr), milliroentgens per hour (mR/hr), rem per hour (rem/hr), millirem per hour (mrem/hr) and counts per minute (cpm).

We chose the SparkFun USB powered unit with the LND712 Geiger tube which can detect alpha, beta and gamma radiation.  The v19 Geiger Counter is comprised of a Geiger-Meuller tube, a high voltage power supply, a transistor to transitor logic (TTL) circuit and a microprocessor. The Geiger Counter is powered over a 5V mini-B USB cable. Once the unit is powered, an event within the Geiger-Meuller tube will create a small amount of current exiting the tube, which is then converted into a digital logic signal that is active low. In other words, the line remains at 5V when there is no event and goes to GND for a short time when an event occurs. The microprocessor uses a digital input pin that detects the low signal. The signals are then computed into counts per second with an overall running total of counts, every second. This data is then sent out of the microprocessor and converted to USB which is relayed to a host computer. The host computer runs FTDI drivers that take the data over USB and puts the data on a COM port to be read by software.

The maximum count rate for this device is determined by two factors:

1) The intrinsic quench rate of the Geiger-Meuller  tube. http://en.wikipedia.org/wiki/Geiger_tube#Quenching

2) The rate at which the current from an event exiting the tube can be resolved, then read by a microcontroller’s input pin. The v19 hardware uses a NPN transistor as the trans impedance amplifier and a RC circuit as a filter. The resulting maximum count rate is approximately 60 counts per second.

Results and Discussion:

 

Although commercially available radiation monitoring systems may offer many advantages for real time discrete emission band evaluation of radioactive isotopes, they are relatively expensive, may be difficult and costly to maintain over time and often are designed to monitor only one specific area.  We define a low cost (under 300 dollars) yet robust USB powered real time radiation monitoring/alert system that is capable of sensing alpha, beta, and gamma radiation in a non-discrete manner.

Advantages of our alert system include the following: 1) low cost which enables multiple side-by-side tubes to be implemented simultaneously for filtered Alpha, Beta and Gamma differentiation, 2) network implementation for remote monitoring of multiple sites using serial-Ethernet conversion modules, 3) online form based maintenance logs; 4) email notification of “event alerts; 5) USB powered for ease of maintenance and for field applications; 6) traffic control lamps for Stop-and-Scan modes and 6) a latching mechanism for a USB powered relay controlled pull type solenoid spring gate release mechanism.

Limitations include relatively rapid quenching of the LND 712 end window-alpha-beta-gamma detector tube in high radiation environment and a lower sensitivity to low energy isotopes when compared to more expensive and delicate scintillation counter based type systems.

The baseline limit of approximately 60 Counts/Sec is adequate for most generic radiation monitoring purposes where the ambient radiation levels do not exceed 10-15 counts per minute.  Although it would be possible to use separate Geiger tubes to discriminate types of radiation by masking the window of the tube with aluminum shielding (allowing Gamma radiation to pass),  the simple presence of a radioactive substance is sufficient for monitoring workplace contamination.  This would be particularly useful for monitoring linen soiled by biological materials containing an isotope and may be sufficient for most implementations rather than specific isotope emission profiles.        

Using this approach it would be a straightforward procedure to connect other more sensitive Geiger tubes to the interface.  We have chosen the USB powered version due to its rapid  implementation, low cost and ease of maintenance over time.

An alternative to using the Labview programming environment would be to connect the USB powered Geiger tube directly to a computer and monitoring the USB-Serial Port and a terminal emulator. An example would be “Terra Term” to monitor the Geiger tube in real time.(6)  A terminal emulator would allow access to the local computer or,if remote monitoring were required, a microcontroller.

Another interesting approach would be to use the “ModKit” graphical web-based microcontroller programming language based largely on the Scratch Graphical programming language.  This approach would use an Arduino based microcontroller rather than the LabView virtual instrument programming interface.

 

In summary, we have configured a low cost USB powered, flexible, robust real time radiation monitoring system for use in health care environments, “hot” benches, field research and in monitoring contamination threshold levels in contaminated waste products.  The total development time for our prototype was approximately 5 hours and the total cost of implementation was less than 300 dollars.

Acknowledgements:

We would like to acknowledge the encouragement of the RWJ University Department of Pathology and the RWJ University Hospital-Hamilton.

 

References:

1) Glass EC, et al. Editorial: radiation safety considerations for sentinel node techniques. Ann Surg Oncol. 1999:6:10

2) Miner TJ, et al. Guideline for the safe use of radioactive materials during localization and resection of sentinel lymph nodes. Ann Surg

Oncol. 1999;6:75-82

3) Cibull ML. Handling sentinel lymph node biopsy specimens. A work in progress. Arch Pathol Lab Med. 1999;123:620-621

4) Pfeifer JD. Sentinel lymph node biopsy. Am J Clin Pathol. 1999;112:599-602

5) Barnes CA. False-negative frozen section results. Am J Clin Pathol. 2000;113:900; 6) Fitzgibbons PL, et al. Recommendations for handling radioactive specimens obtained by sentinel lymphadenectomy. Am J Surg Pathol. 2000;24:1549-1551

6) TerraTerm Terminal Emulator software Website: http://hp.vector.co.jp/authors/VA002416/teraterm.html

7) Phidget USB relay board, Website: http://www.phidgets.com/products.php?category=9&product_id=1014

8) SparkFun USB powered Geiger tube. Website:

http://www.sparkfun.com/products/9848