Systems for In Vivo Activity Measurement

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INTRODUCTION

Assessment of dose has legal, physical, and psychological ramifications. Systems which can accurately perform In Vivo activity measurements are critical health and safety tools for nuclear facilities. CANBERRA has provided the hardware and software needed for In Vivo counting for over three decades. Today CANBERRA has over three hundred systems installed in nuclear power plants, fuel and weapons production facilities, and medical and research institutes throughout the world.

CANBERRA has developed and offers a wide range of standard field-proven products for radiation detection, identification and quantification on the nuclear worker. From this extensive experience and by working closely with our customers and the regulatory agencies, our capabilities range from high throughput systems capable of counting 500 people per day to high resolution scanning systems that can precisely locate the source of the radiation. All are available for permanent installation or in mobile laboratory facilities, and some are available as temporary, short term rentals.

Additionally CANBERRA has a staff of experienced Engineers and Certified Health Physicists to assist you in the planning and implementation of your dosimetry procedures.

Walk-in Counter - FASTSCAN

The FASTSCAN walk-in counter is an ideal quantitative assay system for use when a large number of subjects must be counted quickly. With its large NaI(Tl) detector array, one minute is all that is required for a typical fully quantitative whole body count.

An automated FASTSCAN option is available. This feature allows subjects to count themselves with or without a technician present. The AutoScan uses a bar code reader and a user defined preset count sequence to make operations as easy as using an ATM.

Scanning Counters - ACCUSCAN and ACCUSCAN II

ACCUSCAN Scanning Whole Body Counters are available in both Bed and Standing configurations, allowing you to choose the type best suited for the length of count you will normally be using. The ACCUSCAN II uses high resolution Ge detectors, making it ideal for positive nuclide identification when complex mixtures are involved. The original ACCUSCAN bed counter, now available with either NaI(Tl) or Ge detectors, is the best choice for subject comfort when long count times are required.

Both of the ACCUSCAN systems provide position as well as activity data, and both can be used for specific body region analysis, for they allow counting to be done with the detectors at a fixed position relative to the body.

Actinide Lung Counters - U/Pu and Dual Purpose

Special high resolution low background Broad Energy Ge detectors are the heart of our Actinide Lung Counters. With their multiple detector arrays, flexible subject:detector positioning mechanism, and totally shielded counting rooms, these systems are ideal for detecting extremely low levels of uranium or plutonium in the lungs.

The standard WBC products have shadow shields for economy. However, at energies less than 300 keV, their increased background raises the minimum detectable activity. For many low energy gamma emitters (especially alpha emitters) this is unacceptable. These low energy systems combine multiple semi-planar (BEGe) detectors, with a flexible subject-detector positioning mechanism, and are operated inside a large totally enclosed shielded steel room. The typical purpose is for uranium or plutonium lung counting at extremely low levels. However, other organs (liver, skull, even Total Body) and other energy levels can also be measured. Some facilities have the need to measure workers for both lung and total body radioactivity. CANBERRA combines both in an economical Dual Purpose counter. Simultaneous counts are made on both the lung (with four BEGe detectors) and the total body (with a large scanning NaI(Tl)) detector.

And More

CANBERRA also offers In Vivo measurement systems suitable for both large and small animals, as well as In Vitro systems for urine bioassay. A range of software tools like the CINDY software system for internal dosimetry and the HIS-20 health physics database information system are also available, as are WBC calibration phantoms, mobile WBC services, and on-site WBC system calibration.

Details on our various standard system configurations and our WBC and internal dosimetry software packages are included in the pages which follow.

Selecting the proper In Vivo Whole Body Counter for a given installation should begin with a careful look at the needs of your WBC program. Among the items you should consider are:

What nuclides are important to measure and what other nuclides are present even if not important?
Where do you expect each nuclide to be located in the body?
What is the desired detection limit?
What counting time and throughput (people per hour) is acceptable?
What is the environment in the counter location (background levels, temperature level and range, humidity)?
What is the floor space available and the maximum weight the area can support and the maximum size and weight that can be easily moved to the WBC area?
What is the skill level of the routine operator, and what technical support staff is available for analyses of unusual data?
Are the subjects capable of standing up during the count?
What is the major use of the counter?
Do you intend to operate this system over a network?

Taking the answers to the above into consideration, the following charts will help you in selecting the best type of system for your specific needs. Of course, our Applications Specialists are also available to assist you in selecting the appropriate standard product, or to work with you on a minor modification or new design should your application require it.

The similarities between CANBERRA's In Vivo counting systems are even more important than the differences between them. All CANBERRA In Vivo Counting Systems share the following.

Linear Geometry

The linear geometry (where the axis of the subject and the axis of the effective detector array are parallel) has been selected as the optimum geometry for the CANBERRA In Vivo systems. The linear geometry is achieved by multiple detectors (FASTSCAN), or by moving the detectors (ACCUSCAN II), or by moving the subject (ACCUSCAN).

The linear geometry has a significant advantage in the accuracy of the determination of internal deposition results for individuals of varying anthropometric measurements, such as height, weight, and cross-sectional thickness. Compensating factors serve to minimize the change in calibration factors if the distance from the subject's back to the detector is fixed. For subjects larger than normal, their increase in size increases self-absorption and therefore decreases the apparent activity, but because the body is closer to the detector, the geometric efficiency is increased. These two factors compensate for each other. If the individual is counted a second time (both posterior and anterior) and the results geometrically averaged, the uncertainty from source variation is reduced even further.

There are a few situations where the absolute best in detection sensitivity is important (measurement of alpha emitters in lung). For these cases, the contact geometry is used, but the additional inaccuracy must be accepted.

Contamination-Free Shielding

Each of our counters is constructed from guaranteed low background steel. Lead is avoided where possible because of ²²⁶Ra and ²¹⁰Pb contamination. Normal steel has ⁶⁰Co contamination. Unfortunately, this is one of the most important nuclides to measure in the sample. Our steel is from a unique source that has zero ⁶⁰Co or other measurable contamination.

Analysis Software

The analysis software is our ABACOS family, consisting of Abacos-PLUS for the DEC Alpha and Abacos-2000 for the PC. Both programs have the same data organization and low level background erosion and library driven peak search features and allow choices of peak search and calibration techniques. These unique features allow the truly lowest detection levels statistically possible. The human interface has been successfully designed to make ABACOS both easy to use for the novice operator and flexible for unusual situations. The same software operates the entire CANBERRA family of WBC systems, including NaI and Ge detectors.

Complete Systems and Solutions

All CANBERRA Whole Body Counters are supplied as complete turnkey systems. They are fully assembled at the factory and thoroughly tested. All software parameters for normal WBC operation are preset and a complete set of calibrations are performed.

All items necessary for operation are supplied, including a calibration document, a US-NIST traceable calibration source, and a QA check source. Optionally, a calibration phantom and a desk or cabinet may be added to the system.

On the following pages you will find brief descriptions of all of our In Vivo Counting Systems and Software. More detailed literature and specifications are available. Simply contact your CANBERRA representative or call CANBERRA directly at (203) 238-2351.

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