Dosimeter Stock Receiving Inspection - Procedure

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1 - Purpose

This document describes GEX recommended practices for the receipt and inspection of GEX B3 Dosimeter shipments. The customer must determine a dosimeter stock and receiving inspection procedure, and this document can serve as guidance.

 2 - Application(s)

Incoming receiving inspection should be performed on all shipments of B3 dosimeter products (referred to as Dosimeter Stock or Stock) including initial stock shipment of a new batch and all subsequent stock shipments of an existing batch.

There are three activities associated with incoming inspection:

• Verification of the initial absorbance of dosimeter samples to detect possible exposure to a source of ionizing radiation which could increase the un-irradiated background absorbance of the B3 film.

• Verification that the dosimeters were not exposed to an extreme maximum temperature during shipment which could have adversely impacted the dosimeters. Dosimeter shipments from GEX are temperature monitored by using either an irreversible temperature indicator or temperature data logger.

• Incoming response comparison testing is performed to verify that the new stock will respond the same as the dosimeter stock used in the batch calibration, within acceptable limits.

3 - General Information

A batch of B3 dosimeters may involve multiple dosimeter stock shipments over a two (2) to three (3) year period, which is the typical lifespan of a B3 dosimeter batch.

NOTE: The response of a batch of dosimeters is established through a formal process that relates the dosimeter response (absorbance/thickness) to doses traceable to a national standard, known as a dosimeter calibration. For more information on dosimeter calibration process, see Performing a Dosimeter Batch Calibration. GEX characterizes the response of all B3 film rolls used to produce GEX B3 dosimeters to verify that each roll exhibits a response per unit dose that is not more than 1.0% different from the batch baseline established during GEX’s batch characterization testing.

3.1     Materials

• Dosimeter Stock Receiving Inspection Form (GEX Doc# 100-257) - Download from the GEX Document Library https://library.gexcorp.com

• Sample dosimeters (QA retains)

3.2     Frequency

Testing is recommended to be performed on every incoming shipment of stock dosimeters to verify that the dosimeters perform within specified limits.

3.3 References

• ISO/ASTM 51261: Practice for calibration of routine dosimetry systems for radiation processing

• NPL CIRM 29 Guidelines for the Calibration of Dosimeters for use in Radiation Processing, Peter Sharpe and Arne Miller, 1999; National Physical Laboratory, Teddington, UK

4 - Procedure

4.1     Dosimeter Sampling:

A proper sampling technique and obtaining the proper number of samples from all stock shipments of a batch must be sufficient to support statistical evaluation of the characteristics of the stock being tested.

When sampling the initial stock shipment from a new batch of dosimeters, a sufficient quantity of representative samples should be secured and retained in order to have a supply of samples to meet: the needs of performing the initial batch calibration, anticipated verification audits, samples required for future testing and investigations, as well as samples necessary to support future receiving inspection testing of other stock shipments of the same batch. GEX recommends retaining a minimum of 400 samples from the initial stock shipment of a dosimeter batch to perform these activities.

4.2     Receiving and Management of Stock

Verify the product identification, product quantity, dosimeter batch number, and dosimeter average thickness on all incoming shipments.

• The expiration date is stated on the Certificate of Compliance (CoC) and labeled on the front of each GEX dosimeter box. The expiration date may differ from box to box. The Job number is found on the bottom of each box. Boxes with the oldest expiration date (and lowest Job Number) should be utilized first, and always in accordance with the expiration date stated on the Certificate of Compliance accompanying each shipment. Assign an incoming dosimeter stock shipment identification or receiving date ID to the boxes, and number the boxes (e.g. 1 of 20, 2 of 20, etc.). Number the boxes in sequence from oldest to newest to encourage proper stock utilization (FIFO).

• Upon receipt, store the dosimeters between 15°C - 30°C (59°F – 86°F) in darkness (inside their GEX boxes or equivalent). Exposure of B3 film to temperatures above 45°C during shipment is detectable by observing the maximum temperature triggered on the Irreversible Temperature Indicators (GEX Product Number P8003), which are included by GEX in all dosimeter shipments. Report any deviations observed to GEX Customer Service to discuss appropriate actions.

• Do not intermix the new dosimeter stock with any other dosimeter stock until acceptance testing is complete.

4.3     Verification of Initial Absorbance (A)

Characterization of the initial absorbance (A) of all stock shipments of dosimeters should be performed to confirm that the dosimeters were not exposed to a source of radiation prior to receipt.

• Verify the calibration of the spectrophotometer(s) prior to beginning the initial absorbance verification.

• Complete the header information on GEX Doc# 100-257, Dosimeter Stock Receiving Inspection Form ‘Analysis’ tab.

• Draw 32 representative samples (e.g. 16 pouches of B3002DS) from the Dosimeter QA Retains for the stock being verified.

• Measure the initial absorbance of the dosimeters at the wavelength used in the dosimeter calibration (historically 552 nm for B3). There is no specific left-right, top-bottom, or front-back orientation of the dosimeter in the dosimeter holder. Record dosimeter ID’s and their absorbance values on GEX Doc# 100-257, Dosimeter Stock Receiving Inspection Form ‘Raw Data’ tab. The average absorbance, standard deviation (stdev), and coefficient of variance are automatically calculated on the ‘Analysis’ tab.

• Typically, the measured average absorbance will be found between 0.038 – 0.048 absorbance units (A). This initial absorbance average can be expected to vary slightly depending on the average thickness of the dosimeters and the type of measurement equipment used.

• Using an average initial absorbance established from the initial stock shipment of a dosimeter batch (entered into the “Baseline Ave. Value” on the ‘Analysis’ tab), as well as the standard deviation value established from the initial stock shipment (entered into the “Baseline St. Dev.” on the ‘Analysis’ tab), compare results from future stock shipments of the same batch against the established baseline. The results should not vary by more than ±2 standard deviations from the baseline.

  • If the initial absorbance fails two standard deviations but passes three standard deviations, response testing results may be used to determine if the dosimeter stock is statistically equivalent.

  • The test dosimeters may be discarded after verification testing is complete.

4.4    Verification of Dosimeter Response

Incoming response comparison testing is performed to verify that the new stock response is within statistically acceptable limits when compared against the average response of the current dosimeter stock or dosimeters used in the batch calibration.

Appropriately selected samples from the incoming stock and the existing stock should be co-located and irradiated so that all samples receive the same doses (low, medium, and high) within the calibrated range of the batch. Use of a test fixture and process conditions that provide a uniform dose to all samples is required to successfully execute the test (see the NOTE below for detail).

• Draw representative samples from the incoming stock to be tested, and label accordingly.

• Draw representative samples from the retained samples for the initial or current stock shipment, and label accordingly.

• Irradiate the samples to the target doses.

• Perform appropriate post-irradiation heat-treatment of the dosimeters in accordance with company procedure, if applicable.

• Verify the calibration of the spectrophotometer(s) prior to beginning the dosimeter measurements.

• Measure the absorbance values of both sets of samples for each dose point. Record the absorbance values into GEX Doc# 100-257, Dosimeter Stock Receiving Inspection Form ’Raw Data’ tab.

• The mean average, standard deviation, and CV will automatically calculate on the ‘Analysis’ tab for each set of responses. Compare the mean averages of the two sample sets to verify equivalency. GEX recommends that the incoming stock average response should lie within ± 2 standard deviations of the average response of the current or initial stock. If the incoming stock average response if found outside 3 standard deviations, it is considered to have failed. If the results lie between two and three standard deviations, results should be investigated for possible outliers. Dosimeters may be re-measured and/or a repeat of the test considered.

• In the event that the incoming dosimeter stock shipment fails, contact GEX to discuss appropriate actions to be taken.

• All test dosimeters should be retained until the test results pass the acceptance criteria or investigations are completed.

Disclaimer - The information contained in this document is provided “as is” and is not a substitute for the user’s professional judgement.  It is provided as a convenience to those using products provided by GEX Corporation who have sufficient technical skills to evaluate and properly apply the information in this document.  It is the responsibility of the user of this document to ensure that the information in this document, and the use of such information, is accurate, complete, applicable to the product, suitable for the user’s purposes, and in compliance with all laws and regulations.  GEX Corporation believes the information provided in this document is accurate and reliable as of the time of writing, but it undertakes no obligation to update or correct this document.  GEX Corporation may, but is not required to, make changes to this document at any time without notice.  By using the information in this document, the user represents and warrants that he or she has the skills necessary to properly understand and apply this information and that he or she will comply with all applicable laws and regulations including, without limitation, those relating to medical devices, pharmaceutical products, or other applicable industries.  The user assumes all risks associated with using this information and any results or output resulting from the application of this information to GEX Corporation’s products.  The user agrees not to hold GEX Corporation liable for any errors or omissions contained within.