Method and apparatus for tissue equivalent solid state microdosimetry

• US 8,421,022 B2
• Filed: 12/19/2007
• Issued: 04/16/2013
• Est. Priority Date: 12/19/2006
• Status: Active Grant

• Current Assignee: University Of Wollongong
• Original Assignee: University Of Wollongong
• Inventors: Rozenfeld, Anatoly
• Primary Examiner(s): Porta, David
• Assistant Examiner(s): Malevic, Djura
• Application Number:
  US12/520,077
• Publication Number:
  US 20100090118A1
• Time in Patent Office: 1,945 Days
• Field of Search: 250/370.07, 250/371, 250/475.2
• US Class Current: 250/370.07
• CPC Class Codes: G01T 1/026 Semiconductor dose-rate meters
• CPC Class Codes: H01L 27/1446 in a repetitive configuration

Abstract

A microdosimeter, comprising an array of three-dimensional p-n junction semiconductor detectors, each providing a sensitive volume-target and a tissue equivalent medium for generating secondary charged particles. The array is manufactured from a semiconductor on insulator wafer and the detectors are located to detect secondary charged particles generated in the tissue equivalent medium.

Claims

1. A microdosimeter, comprising:

an array of mutually spatially separated, three-dimensional p-n junction semiconductor detectors, each providing a micron- or submicron-scale sensitive volume-target; and

a tissue equivalent medium for generating secondary charged particles, respective portions of said tissue equivalent medium being located between said detectors;

wherein said array is manufactured from a semiconductor on insulator wafer, said detectors are located to detect secondary charged particles generated in said tissue equivalent medium, and each of said detectors is electrically connected to a plurality of other detectors of said detectors.

2. A microdosimeter as claimed in claim 1, wherein said semiconductor detectors are silicon detectors.

3. A microdosimeter as claimed in claim 1, wherein said detectors are cylindrical or near-cylindrical.

4. A microdosimeter as claimed in claim 1, wherein each of said detectors has a core comprising a p+electrode, and an outer n+electrode region.

5. A microdosimeter as claimed in claim 1, wherein each of said detectors has a core comprising a rod-like p+region within a Si sensitive volume.

6. A microdosimeter as claimed in claim 5, wherein said core has a small radial size.

7. A microdosimeter as claimed in claim 6, wherein said core has a diameter of from 1 μ

m to 5 μ

m.

8. A microdosimeter as claimed in claim 6, wherein amplification of deposited charge is controllable with p-n junction bias.

9. A microdosimeter as claimed in claim 1, wherein said tissue equivalent medium comprises polymethylmethacrylate.

10. A microdosimeter as claimed in claim 1, wherein said detectors are electrically connected such that each of said detectors is not connected to at least one of its immediately neighboring detectors of said detectors.

11. A microdosimeter as claimed in claim 1, comprising a multi-channel analyser for acquiring at least one spectrum of data from said detectors, and computational means for determining absorbed dose in Si from said spectrum, converting said spectrum to a lineal energy spectrum, determining from said lineal energy spectrum a differential dose d(y) deposited in tissue equivalent material by secondary events within a lineal energy range y to y+dy, converting semiconductor absorbed dose to tissue equivalent absorbed dose using respective semiconductor and tissue equivalent ionizing stopping powers for secondary particles, and determining dose equivalent in a tissue from said tissue equivalent absorbed dose, comprising convoluting said differential dose with a lineal energy dependent quality coefficient.

12. A method for processing microdosimeter data, comprising:

acquiring at least one spectrum with a microdosimeter as claimed in claim 1;

determining absorbed dose in Si from said spectrum;

converting said spectrum to a lineal energy spectrum;

determining from said lineal energy spectrum a differential dose d(y) deposited in tissue equivalent material by secondary events within a lineal energy range y to y+dy;

converting semiconductor absorbed dose to tissue equivalent absorbed dose using respective semiconductor and tissue equivalent ionizing stopping powers for secondary particles; and

determining dose equivalent in a tissue from said tissue equivalent absorbed dose, comprising convoluting said differential dose with a lineal energy dependent quality coefficient.

13. A method as claimed in claim 12, comprising converting said spectrum to a lineal energy spectrum with a tissue equivalent average chord.

14. A microdosimeter as claimed in claim 1, wherein said detectors are covered with said tissue equivalent medium.

15. A microdosimeter as claimed in claim 1, wherein said detectors are frusto-conical.

16. A method for performing microdosimetry, comprising:

exposing a tissue equivalent medium to a radiation source, thereby generating secondary charged particles in said tissue equivalent medium; and

detecting at least some of said secondary charged particles with an array of mutually spatially separated, three-dimensional p-n junction semiconductor detectors, each providing a micron- or submicron-scale sensitive volume-target, said array manufactured from a semiconductor on insulator wafer

wherein respective portions of said tissue equivalent medium are located between said detectors and each of said detectors is electrically connected to a plurality of other detectors of said detectors.

17. A method as claimed in claim 16, comprising electrically connecting said detectors such that each of said detectors is not connected to at least one of its immediately neighboring detectors of said detectors.