GB2123169A - Microtome with specimen illumination system - Google Patents

Abstract

A microtome, in particular an ultramicrotome, having a specimen carrier 2 which can be moved relative to a knife. The specimen carrier includes a clamping aperture for holding a specimen 3. A light source is located inside the clamping aperture in the specimen carrier so that light is transmitted, from the rear of the clamping aperture, through a specimen block which is composed of a transparent material, and through the specimen. The light source may be a bulb or a mirror 21 with a remote source 21 optically connected by a fibre optic hurdle 23. <IMAGE>

Description

SPECIFICATION Microtomewith specimen illumination system This invention relates to microtomes, more particularly ultramicrotomes, ofthetype having a specimen carrierwhich can be moved relative to a knife, the specimen carrier possessing a clamping aperture for the purpose of holding a specimen, and with a light source for illuminating the specimen.

The majority of specimens cannot be sliced in their natural form and condition. In most cases, the preparation of such specimens (small pieces of animal or human organs, such as liver, spleen or brain, residues centrifuged from bodyfluids, parts of plants or micro-organisms, ortissue-cultures, etc.) is required. This usually involves, a stabilisation treatment by means of an aldehyde and/or a heavy metal, followed by dewatering and embedding the specimen in a plastics material which is normally transparent or translucent (e.g. an epoxide or a polyester).

The cylindrical, flat or prismatic "specimen blocks" which are obtained by means ofthis process, and which can readily be cut, are clamped in a specimen carrier and, aftertrimming to size the specimen blocks are sliced intothethin sections for examination under a microscope or an electron microscope. The slicing operation is usually carried out with a knife made of metal, glass or diamond.

The abilityto observethe specimen/knife region in an extremelyprecise manner is a prerequisiteforthe production of perfectthin sections in a microtome and especially in an ultramicrotome. In particular, the success of a slicing operation of this type depends critically on selecting the correct region of the specimen block. Forthis purpose, especially in the case of ultramicrotomes, a stereo microscope and a light source are provided, the former for observing the specimen/knife region and the latterforilluminating it.

The light source is installed above the specimen/knife region, and/or beneath it, and is frequently adjustable, in order to enable itto be aligned as precisely as possible with the cutting edge ofthe knife, and/orthe surface ofthe specimen blockto be cut.

Up to the presenttime, the means for enabling the specimen/knife region to be observed in a precise manner has not been completely satisfactory. Thus it is not always possible for an operatortoselectthe correct region ofthe specimen block, because the internal structure of the specimens,thefine surface structure, orverysmall objects, are poorlydisplayed and cannot be identified so reliably thatthe details of interest occur in the selected slice.Sometimes interesting regions ofthe specimen are unintentionally removed during the trimming operation, and have hence been lost, so that the surface of the prepared section contains regions which not only are of no interest,butwhich may interferewiththe cutting process (e.g. hard inclusions, collagen fibres which are difficult to cut, orfat cells). Neither incident-light illumination bymeansofcold-lighttubesorsimilar light sources above the specimen, as generally employed nowadays, nor dark-field illumination, which is often employed to illuminate the specimen/ knife region from below (sublevel illumination) is satisfactory to facilitate identifying the desired areas ofthe specimen.The only effective procedure involves trimming the specimen while it is fastened to the specimen carrier, during which process it is observed from the front by means of a mirror system ("structure viewer").

Furthermore, when an adjustment of the light source (incident-light illumination, and/or sublevel illumination), or a setting of the specimen in relation to alightsource, has beenfoundto give optimum illumination of the specimen, it is exceedingly irritating if the position of the specimen, relative to the knife, has to be altered in orderto obtain thin sections of optimum quality. This is because the illumination must be readjusted in order to ensurethatthe desired precision of observation is maintained. This situation arises, for example, in the case of specimen carriers which are combined, for the purpose of angular adjustment, with so-called segment-arcs, along which they can be swung horizontally, about a pivot axis which lies approximately on the cutting edge ofthe knife.

An object ofthe present invention isto avoid the above mentioned disadvantages, to provide a microtome, in particular an ultramicrotome, having an improved illuminating system which brings out the fine structures in a specimen more effectively than hitherto, and at the same time eliminates the need for readjustments wheneverthe position ofthe specimen is altered.

Afurther object is to permit the successful and easy use of a "structure viewer" in all possible positions of the specimen block, to select interesting regions of the specimenforcutting, and/or to eliminate those regions ofthe specimen which are not of interests in a systematic manner.

According to the present invention we provide a microtome having a specimen carrierwhich can be moved relative to a knife, the specimen carrier being provided with a clamping aperture for holding a specimen, and a light sourcefor illuminating the specimen, the light source being located inside the clamping aperture in the specimen carrier.

A miniaturefilament-type light bulb, for example, may be located inside the clamping aperture of the specimen carrier, as the light source, this bulb being installed in a manner such thatthe light from it passes through the specimen block when the latter is in its clamped state.

A surprising discovery with this arrangement is that the internal structure ofthe specimen is clearly displayed as a result of the transparency ortrans- lucency of the material which is used for embedding the specimen. The light source may be installed in the bottom of the clamping aperture, or at its rear end, for example in a segment-arc, in a manner such that, when the specimen block is in the clamped state, it is located behind this block, so thatthe light passes through the block in the iongitudinal direction ofthe clamping aperture. However, it is also possible to illuminate the specimen block from the inside, if the light source is instalied beside it, in the wall of the clamping aperture, and radiates into the specimen blockata defined angle.

In a further embodiment of the invention, a deflect ing mirror can be installed in the clamping aperture, as the light source, this mirrordirecting the light from a lamp outside the clamping aperture into the specimen block. This arrangement prevents the specimen from being heated above a permissible temperature, a factor which must be taken into account especially when working in the cryo-range.In yet a further embodiment, heating ofthe specimen is avoided by guiding the light intothe specimen blockvia a fibre-type light guide, orsimilar device, the end ofthe light guide which emits the light being located in the clamping aperture, or in the wall of this aperture, in a mannersuchthatconcentrated lightis directed into the specimen block. In some circumstances, a filter, serving as a heat barrier, may be installed betweenthe light source (filament-type bulb, deflecting mirror, end ofthefibre-type light guide) which is present in the clamping aperture, and the specimen block.

Within the scope of the invention, it is possible for the internal illumination ofthe specimen blockto be switched on and off, independently of any other illumination sources which may be present, this being ot^-,ted by a suitable switch. In addition, certain advantageous combinations involving the incidentlight light source and/or the sublevel light source and the internal illumination according to the invention can be rendered settable, by means of a handle and a combination switch to facilitate advantageous varieties of mixed illumination to be obtained, without having to operate a plurality of switches separately.

Sincethe light source is installed in the specimen carrier, it moveswith thespecimen carrier, and thus follows any adjusting movements ofthe specimen carrierforthe purpose of adjusting the specimen in relation to the knife. In consequence ofthis, the quality ofthe illumination remains unchanged at all times, even during pivoting adjustments of the specimen carrier, for example on a segment-arc, no matter how extensive these movements may be.

Illustrative embodiments ofthe invention are described below, with reference to the drawings, in which: Figure lisa diagrammatic side view of an ultramicrotome, partially in section; Figure 2 is a detailed representation of a specimen carrier according to the invention, in longitudinal section, this specimen carrier being intended for use in the ultramicrotome shown in Figure 1; and Figure 3 is a modified embodiment ofthe specimen carrier shown in Figure 2.

In Figure 1 an ultramicrotome is illustrated having a specimen arm 1 which can move upwards and downwards. Aspecimen carrier 2, for a specimen or preparation 3, is located atthefrontend ofthe specimen arm 1 the specimen 3 being attached to the specimen carrier 2, which is fastened to a segment-arc 4in a manner which permits itto swing horizontally, in such a way that the angular position of the preparation 3, relative to the cutting edge of a knife 5, can be altered. The segment-arc 4 enables the specimen carrier2 to be angularly adjusted about a pivot point which lies virtuaily on the cutting edge of the knife.

To permit observation, a stereo microscope 6 is provided above the region occupied by the specimen 3 and the knife 5. A deflecting mirror 6', a so-called "structure viewer" is arranged in the light path ofthe stereo microscope 6; this "viewer" enables the end face of the specimen 3 to be observed and examined forthe purpose oftrimming it in a precise manner. The ultramicrotome shown in Figure 1 is of known design and forthis reason details of its construction are not described.

In Figure 2, the specimen carrier 2 is clamped to the segment-arc 4, and can be angularly adjusted in the directions shown by the double arrows in the drawing.

Ajournal-shaped projection 7 is located on the rear surface ofthe segment-arc 4, or on the rear surface of the specimen carrier 2. The projection 7 can be pushed into a bore 8 in the specimen arm 1, in which it can be securely clamped by means of a locking screw 9.

At its front end, the specimen carrier 2 possesses a clamping aperture 1 Oforthe specimen 3, which is cast into a specimen block 3' which is composed of a transparent material, such as paraffin or a plastics material. The clamping aperture 10 is deep enough to leave a space 11, when the specimen block 3' is clamped within the clamping aperture. The space 11 extends from one end of the specimen block 3' to the bottom of the clamping aperture 10. In the space 11 a light source 12 is installed, and comprises a miniature filament-type light bulb. The light source 12 is seated in a holder 13 which is provided atthe bottom ofthe clamping aperture 10.

Power supply leads (not shown) to supply powerto the holder 13 run outside or inside the seg ment-a re 4 to contact-ends 14 at the end ofthejournal-shaped projection 7. The contact-ends 14 form electrically conducting connections with corresponding contacts 15 in the bore 8 ofthe specimen arm 1. From the contacts 15, leads 16 run to a source of electrical power (not shown).

An additional light source 17 can be arranged above the specimen carrier 2, and a sublevel light source 18 can be arranged beneath it. Optimum illumination of the specimen 3, or ofthe specimen/knife region ofthe ultramicrotome, is provided by these light sources, in conjuction with the direct illumination ofthe preparation provided by the light source 12.

In Figure 3 the specimen carrier 2 includes many components which are substantially identical to components shown in Figure 2, and like components are marked with like reference numbers. However, in the embodiments shown in Figure 3 a deflecting mirror20 is located in the space 11 within the clamping aperture 10, instead ofthe light bulb 12 used in the embodiment shown in Fig.ure 2. Afilament-type light bulb 21, having a reflector22,supplies lighttothe deflecting mirror 20 along a fibre-type light guide 23, the end of which is secured in a lateral hole 24, in the specimen carrier 2. The deflecting mirror 20 deflects the lightfrom the light bulb 21 through 90" and radiates it into the specimen block 3'. A heatabsorbing screen 25, such as a thin crystal-glass plate, is installed between the deflecting mirror 20 and the specimen block 3'. The screen 25 protects the specimen block3' from heating which occurs as a resultof thermal radiation. (Clearly a heat-absorbing screen, or a heat filter, can be similarly provided in the embodimentofthe invention shown in Figure 2, if the specimen block 3' needs to be protected from thermal radiation; this is particularly important when working at lowtemperatures).

Since thefibre-type I ig ht guide 23 conducts light with comparatively low losses, the filament-type light bulb 21 can be located on the ultramicrotome, and the length ofthefibre-type light guide 23 can be made sufficiently long to prevent itfrom impeding eitherthe movement of the specimen arm 1, orthe adjustment of the specimen carrier 2 on the segment-arc 4.

It is possible, within the scope of the invention, to devise modifications to the illustrative embodiments described above. For example, the miniature filamenttype light bulb 12, orthe deflecting mirror 20, can be located in an extension of the clamping aperture 10, and hence ofthe space 11, or in the seg ment-are 4, behind the bottom ofthe clamping-aperture. However, the light radiated by the light source must enter the specimen block 3' in such a mannerthatthe internal structure ofthe specimen 3 is rendered bright, and is thereby displayed, due to the transparency ortrans lucency of the specimen block 3'.

Claims (11)

1. A microtome having a specimen carrier which can be moved relative to a knife, the specimen carrier being provided with a clamping aperture for holding a specimen, and a light source for illuminating the specimen,the lightsource being located inside the clamping aperture in thespecimen carrier.

2. A microtome according to Claim 1, in which the light source is located at the bottom of the clamping aperture behind the specimen.

3. A microtome according to Claim 1 in which at least one additional light source is provided to illuminate the specimen/knife region of the microtome from above.

4. A microtome according to Claim 1 in which the light source is a miniaturefilament-type light bulb.

5. A microtome according to Claim 1, in which the light source comprises a deflecting mirrorto which light can be directed from a source of illumination located outside the specimen carrier.

6. A microtome according to Claim 5, in which the end of a fibre-type light guide is secured in a lateral bore in the specimen carrier, which bore is open towards the clamping aperture, the light guide serving to direct lightfrom said source of illumination to said mirror.

7. A microtome according to Claim 1, in which a heat-absorbing screen is installed between the specimen and the light source, the screen being transparent to light.

8. A microtome according to Claim 1, in which the specimen carrier is angularly adjustable about a pivot point which lies virtually on the cutting edge ofthe knife, sothatthe angularadjustment is along an arc of a circle.

9. A microtome according to Claim 3, in which the light source is provided with switching means whereby it can be switched independently of said at least one additional light source.

10. A microtome according to Claim 3, in which the light source is provided with switching means whereby it can be switched in combination with at least one additional light source.

11. A microtome substantially as herein described with reference to and as shown in the accompanying drawings.