Solid-State Dose Calibrator with Nested Shielding

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Solution Overview

Problem

Existing dose calibrators for radioactive materials are bulky, provide slow and imprecise readings, and require the sample to be removed from its primary shield for measurement, leading to potential exposure risks and inaccuracies due to placement variations.

Innovation Solution

A compact dose calibrator using dual solid-state radiation detectors with trans-resistance amplifiers and a dual-channel data acquisition system, allowing for precise measurement within a prescribed volume envelope without removing the sample from its shield, and verifying sample placement for accurate readings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a traditional ion chamber is used for dose calibration, then the measurement can be performed, but the device becomes bulky and requires extensive shielding

Engineering Contradiction:

Improveradioactivity measurementVSAvoiddevice mass

Core Design Contradiction:

Measurement precisionVSWeight of stationary object

Solution Approach 1:

The patent changes the fundamental detection parameter from ionization current measurement in air to solid-state radiation detector signals. This parameter change enables compact device design while maintaining measurement capability, directly resolving the contradiction between measurement precision and device mass.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If a traditional ion chamber is used, then measurement is possible, but the reading speed and precision are slow and imprecise

Engineering Contradiction:

Improvereading accuracyVSAvoidreading speed

Core Design Contradiction:

Measurement precisionVSProductivity

Solution Approach 1:

The patent replaces the mechanical/electrical ionization measurement system with an electronic solid-state detection system. This substitution enables faster signal acquisition and processing, simultaneously improving both reading speed and precision without the trade-off present in traditional systems.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Measurement precision

If the sample is removed from its primary shield for measurement, then the ion chamber can measure, but personnel are exposed to radiation

Engineering Contradiction:

Improveradioactivity measurementVSAvoidradiation exposure

Core Design Contradiction:

Measurement precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements a nested configuration where the ionization chamber is positioned inside the primary shield container. This allows the sample to remain shielded during measurement, with the ionization chamber detecting radiation through the shield wall, thereby eliminating personnel exposure while maintaining measurement capability.

Inventive Principle:

Principle #7Nested doll (Nesting)

4Stability of the object's composition

If the ion chamber dimensions are large, then uniform response is achieved, but the device becomes bulky and harder to shield

Engineering Contradiction:

Improveresponse uniformityVSAvoiddevice mass

Core Design Contradiction:

Stability of the object's compositionVSWeight of stationary object

Solution Approach 1:

The patent changes the detection parameter to solid-state detector signals, which have inherently different spatial response characteristics. This enables achieving response uniformity through electronic signal processing and geometric arrangement rather than requiring large physical dimensions, thus reducing device mass.

Inventive Principle:

Principle #35Parameter changes

5Object-affected harmful factors

If thick shielding is used, then personnel protection is improved, but the device becomes bulkier

Engineering Contradiction:

Improveradiation protectionVSAvoiddevice mass

Core Design Contradiction:

Object-affected harmful factorsVSWeight of stationary object

Solution Approach 1:

The patent nests the measurement chamber inside the existing primary shield, utilizing the shield's structure for both containment and radiation protection. This eliminates the need for additional external shielding, maintaining personnel protection while avoiding increased device mass.

Inventive Principle:

Principle #7Nested doll (Nesting)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This solution provides rapid, precise, and shielded measurements that are independent of sample placement, reducing personnel exposure and ensuring accurate dosing without the need to remove the sample from its primary shield, thus enhancing safety and efficiency in nuclear pharmacies.

Implementation Method 1

A first solid-state radiation detector 10 and a second solid-state radiation detector 12 are positioned a predetermined distance apart on a common axis A-A'

Methodology Applied

Scientific EffectIonizing radiation detection: Ionisation

Implementation Method 2

Each detector 10, 12 is coupled to a trans-resistance amplifier 16, 17, respectively

Methodology Applied

Scientific EffectTrans-resistance amplification:

Data Source

PatentUS7608831B2Radioactivity dose calibrator

Publication Date: 2009.10.27 LAMB JAMES F

AI summary

A radioactivity dose calibrator system measures the quantity of radioactive material contained in a sample-vial or syringe without removing the vial or syringe from its primary radiation shield. The system comprises a first radiation detector, a second radiation detector, a transportable, shielded radioactive material sample-holder, a signal-processing circuit and a video display.