WO1996018914A1

WO1996018914A1 - Improved scintillation crystal module for use in scintillation cameras

Info

Publication number: WO1996018914A1
Application number: PCT/US1995/010127
Authority: WO
Inventors: Taras Hazek; Dennis E. Persyk
Original assignee: Siemens Medical Systems, Inc.
Priority date: 1994-12-13
Filing date: 1995-08-08
Publication date: 1996-06-20
Also published as: IL114928A0

Abstract

A lead shield is adhesively secured to the backcap and window of a scintillation crystal module. The scintillation crystal is located within a hermetically sealed volume to prevent hydration resulting from hygroscopic absorption of airborne water. The shield is shaped to mate with a detector housing of a scintillation camera.

Description

IMPROVED SCINTILLATION CRYSTAL MODULE FOR USE IN SCINTILLATION CAMERAS

Background of the Invention The invention relates to scintillation cameras, and more particularly relates to the scintillation crystal which is used in the detector of a scintillation camera. In its most immediate sense, the invention relates to the crystal module which is secured to the detector housing of a scintillation camera.

U.S. Patent No. 5,148,029 discloses a crystal module of this type. As is shown there, the module is mounted within a flange 30 which is secured to the camera detector. Conventionally, the flange 30 is a large piece of aluminum or steel. Because the flange 30 is massive, there is a wide margin between the exterior of the detector and the edge of the sensitive crystal surface. This makes it unnecessarily difficult to properly position the detector so that the sensitive crystal surface is properly located with respect to the patient. Additionally, to block uncollimated gamma radiation from entering the detector, lead inserts are sometimes mounted into the flange (depending on the thickness of the flange and the material of which it is made) . As a result of this structure and the material and labor necessary to make the flange itself, the flange is an expensive part. It would be advantageous to improve over such known scintillation crystal modules. One object of the invention is to provide a scintillation crystal module which would reduce the margin between the exterior of the detector and the edge of the sensitive crystal surface. Another object is to reduce the cost of existing scintillation crystal modules. Yet a further object is, in general, to improve upon known scintillation crystal modules of this general type. In accordance with the invention, a shield is made of material, e.g. lead, which is highly opaque to gamma radiation. The shield is mechanically secured to the window and backcap of the scintillation crystal module in such a manner that the crystal is enclosed within a hermetically sealed volume and is protected from hydration caused by hygroscopic absorption of airborne moisture. The shield is shaped to mate with the detector housing in which the module is installed. In accordance with the invention, the shield performs two functions simultaneously; it blocks incoming uncollimated radiation from entering the scintillator crystal and mechanically secures the scintillation crystal module to the detector. The material and labor required to fabricate a separate aluminum or steel flange and to insert lead pieces into it is eliminated, and the margin around the edge of the sensitive crystal surface is reduced. Consequently, superior performance is achieved at lower cost.

Brief Description of the Drawings The invention will be better understood with reference to the following illustrative and non-limiting drawings, in which: Fig. 1 shows a conventional scintillation crystal module structure such as is used on existing products of Siemens Medical Systems, Inc.;

Fig. 2 shows a first preferred embodiment of the invention; and Fig. 3 shows a second preferred embodiment of the invention.

Detailed Description of Preferred Embodiments In a scintillation camera module as presently delivered to Siemens Medical Systems, Inc. by its vendor in a preasse bled state, a scintillation crystal 2 (see Fig. 1) is secured to a glass window 4 which advantageously is made of glass made by PPG and marketed under the STARPHIRE trademark. An aluminum backcap 6 is adhesively secured to the window 4 by a layer of epoxy adhesive 8, thereby hermetically sealing off the crystal 2 so that it does not become hydrated by hygroscopic absorption of airborne moisture.

This module is advantageously potted into a flange 10 (which advantageously is of aluminum or steel) using epoxy adhesive 12 in accordance with the teachings of the above-referenced U.S. Patent No. 5,148,029. To block uncoilimated gamma radiation from entering the scintillation crystal an annular insert 14 of e.g. lead may be inserted into the flange 10 (and is so inserted in units manufactured by Siemens Medical Systems, Inc.) To mount the completed assembly in the detector, the flange 10 is then secured to the detector as by bolts or other means.

The flange 10 is rather wide. As a result, there is a rather large margin which extends outwardly from the edge of the scintillation crystal 2. Furthermore, the flange 10 is expensive because of the material and labor necessary to make it, and the inserts 14 add to this cost.

In accordance with a first preferred embodiment of the invention as illustrated in Fig. 2, the preassembled assembly of crystal 2, window 4, backcap 6 and adhesive 8 is adhesively secured to a lead shield 16. While lead is preferred for the shield 16, this is not necessary, and any other material which is highly opaque to gamma radiation can be used instead. Advantageously, the shield 16 and preassembled assembly are secured at two regions of support 18 and 20; region 18 extends around the top edge of the window 4 and region 20 extends around the bottom edge of the backcap 6. The top surface of the shield 16 is shaped to mate with the housing 22 of the detector in which it is installed. The shield 16 (and therefore the crystal 2, window 4 and backcap 6 which are attached to it) is secured to the housing 22 by a flange 24.

Because in accordance with the invention the shield 24 is much narrower than the flange 10, the margin between the outside of the housing 22 and the edge of the crystal 2 is much reduced over the prior art. Furthermore, the cost of the shield 16 is less than the cost of the flange 10. As a result, better performance is achieved at a reduced manufacturing cost. In accordance with the second preferred embodiment of the invention as illustrated in Fig. 3, the backcap 6¹ is flat and is not adhesively secured to the window 4. Rather, the shield 16' is adhesively secured to the window 4 at region 18* (around the edge of the window 4) and to the backcap 6' at region 20' (around the edge of the backcap 6'). Advantageously, the adhesive is in accordance with the teachings of the above-referenced •029 patent.

The first preferred embodiment of the invention may advantageously be used when preassembled assemblies are purchased from a vendor; the second preferred embodiment of the invention may be preferred if the vendor can also provide the shield.

The second preferred embodiment has cost and performance advantages over the first preferred embodiment. From the cost standpoint, it is less expensive to manufacture the backcap 6'. This is because the backcap 6 must be formed using matched dies or using a male die in a hydroform press, and must therefore be of comparatively thick material. On the other hand, the backcap 6' may be cut from thin sheet stock. Thus, the backcap 6' is not only less labor-intensive than the backcap 6, but also requires less material. Furthermore, less gamma radiation is blocked by the backcap 6'. This is because thinner material transmits more gamma radiation than does thicker material.

Although a preferred embodiment has been described above, the scope of the invention is limited only by the following claims:

Claims

1. A scintillation crystal module, comprising: a scintillation crystal; a glass window; a backcap of a material which is highly transparent to gamma radiation; and a shield which is mechanically secured to the window and the backcap in such a manner that the crystal is enclosed within a hermetically sealed volume and is protected from hydration caused by hygroscopic absorption of airborne moisture, the shield being of a material which is highly opaque to gamma radiation and being shaped to mate with a detector housing of a scintillation camera.

2. The module of claim 1, wherein the shield is hermetically sealed to said window and said backcap and said volume is defined by the shield, the window and the backcap.

3. The module of claim 2, wherein the backcap, crystal and window constitute a preassembled assembly enclosing said hermetically sealed volume, and wherein said assembly is adhesively secured within the shield.