JP2007219056A - Radiation image reader and radiation image reading method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a reliable radiation image reader and a reliable radiation image reading method free from the interruption of diagnostic operation caused by the failure of an erasing light source while suppressing drastic increase in cost, size and power consumption. <P>SOLUTION: The radiation image reader 10 has an erasing system 12 which reads image information from a radiation image converting plate 2 on which a radiation image is recorded, and erases the information remaining on the radiation image converting plate after reading by photoirradiation, and the erasing system has at least one erasing light source 12a. The erasing light source is driven to emit light at voltage of ≤80% to its rated voltage in the photoirradiation. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a radiation image reading apparatus and a radiation image reading method for reading image information from a radiation image conversion plate on which a radiation image is recorded.

  Radiation images such as X-ray images are often used in fields such as disease diagnosis. The X-ray image is obtained by irradiating the phosphor layer (phosphor screen) with X-rays that have passed through the subject, thereby generating visible light, and then using this visible light as when taking a normal photograph. Thus, a so-called radiographic method is widely used in which a silver halide photographic light-sensitive material (hereinafter also simply referred to as “photosensitive material”) is irradiated and then subjected to development processing to obtain a visible silver image.

  However, in recent years, a new method for taking out an image directly from a phosphor layer has been proposed instead of an image forming method using a photosensitive material having a silver halide salt. In this method, the radiation transmitted through the subject is absorbed by the phosphor, and then the phosphor is excited by light or thermal energy, for example, so that the radiation energy accumulated by the phosphor is absorbed as fluorescence. There is a method of emitting and detecting this fluorescence and imaging.

  Specifically, for example, a radiation image conversion method using a stimulable phosphor as described in Patent Document 1 and Patent Document 2 below is known. This method uses a radiation image conversion plate (hereinafter also simply referred to as “plate”) containing a stimulable phosphor, and the radiation transmitted through the subject is applied to the stimulable phosphor layer of this plate. The radiation energy corresponding to the radiation transmission density of each part of the subject is accumulated, and then the stimulable phosphor is raster scanned with excitation light such as laser light in the visible to near-infrared region, thereby stimulating the stimuli. Radiation energy accumulated in the phosphor is emitted as stimulated emission. The signal resulting from the intensity of this stimulating light is converted into an electrical signal by a photoelectric conversion element such as a CCD or photomultiplier tube, then sampled and converted into a digital signal, and this signal is converted into a silver halide photographic light sensitive material or the like. It is reproduced as a visible image on a display device such as a recording material or a CRT.

  According to the radiographic image recording / reproducing method described above, a radiographic image with a much smaller exposure dose and abundant information can be obtained as compared with a radiographic method using a combination of a conventional radiographic film and an intensifying screen. Has the advantage of being able to.

  As described above, a stimulable phosphor is a phosphor that exhibits stimulated emission when irradiated with radiation and then irradiated with excitation light, and practically has a wavelength corresponding to the excitation spectrum of the stimulable phosphor. Generally, phosphors exhibiting stimulated emission in the wavelength range of 300 to 500 nm by excitation light in the range of 550 to 750 nm are used.

  Plates using these photostimulable phosphors release accumulated energy by scanning excitation light after accumulating radiation image information, so that radiation images can be accumulated again after scanning and can be used repeatedly. Is possible. Usually, the accumulated information remains on the plate only by the excitation light scanning and appears as noise at the next photographing, so the accumulated information is erased by a fluorescent tube, a halogen lamp or the like (for example, see Patent Document 3 below).

In other words, the conventional radiographic method consumes a radiographic film for each imaging, whereas this radiographic image conversion method allows the plate to be used repeatedly, which is advantageous in terms of resource protection and economic efficiency. is there. This system using photostimulable phosphor plates is called computed radiography (CR), and it is widely used in the medical field today because of its economical efficiency and the convenience of handling images as digital data. It has been.
US Pat. No. 3,859,527 Japanese Patent Laid-Open No. 55-12144 Japanese Patent No. 2866264

  By the way, when a fluorescent tube is used as an erasing light source for stored information used in CR, since the amount of light is insufficient, it is necessary to irradiate five or more fluorescent tubes side by side, resulting in an increase in apparatus size ( For example, see Patent Document 3 above).

  On the other hand, when a halogen lamp is used, the lamp will run out due to its life after several thousand to tens of thousands of times of lighting, and the device cannot be used temporarily until it is repaired. There was a problem that.

  In view of the above-described problems of the prior art, the present invention provides highly reliable radiation without causing a significant interruption in diagnostic work due to the erasing light source running out while suppressing a significant increase in cost, an increase in size of the apparatus, and an increase in power consumption. An object of the present invention is to provide an image reading apparatus and a radiation image reading method.

  In order to achieve the above object, a radiographic image reading apparatus according to the present invention reads image information from a radiographic image conversion plate on which a radiographic image is recorded, and erases information remaining on the radiographic image conversion plate after the reading by light irradiation. A radiation image reading apparatus having an erasing system for performing erasing, wherein the erasing system has at least one erasing light source, and the erasing light source is driven at a voltage of 80% or less with respect to its rated voltage during the light irradiation. And emitting light.

  According to this radiation image reading apparatus, when erasing information remaining on the radiation image conversion plate after reading image information by light irradiation, the erasing light source is simply driven at a voltage of 80% or less with respect to the rated voltage of the erasing light source. With a simple configuration, the lifetime of the erasing light source can be extended beyond the useful life of the device, so there is no significant increase in cost, increase in size of the device, or increase in power consumption, and without interrupting diagnostic work due to the erasing light source running out. A highly reliable radiation image reading apparatus can be realized.

  In the radiation image reading apparatus, the erasing light source is preferably a halogen lamp.

  In addition, as described above, since the life of the erasing light source is extended, only one erasing light source can be provided, and thus power consumption can be reduced.

  Further, when the erasing light source is AC driven, the device can be further reduced in size, weight, and cost.

  The radiation image reading method according to the present invention reads image information from a radiation image conversion plate on which a radiation image is recorded, and erases information remaining on the radiation image conversion plate after the reading by light irradiation from an erasing system. In the method, the erasing system includes at least one halogen lamp, and the light is emitted by driving the halogen lamp at a voltage of 80% or less with respect to its rated voltage during the light irradiation.

  According to this radiological image reading method, when information remaining on the radiographic image conversion plate after reading image information is erased by light irradiation, the halogen lamp is driven at a voltage of 80% or less of the rated voltage of the halogen lamp. Since the life of the halogen lamp can be extended beyond the life of the device, the reliability of the device can be trusted without interrupting the diagnostic work due to lamp breakage while suppressing a significant increase in cost, equipment size and power consumption. Can increase the sex. In this case, the erasing light source is preferably AC driven.

  Note that the lower limit of the voltage when the erasing light source and the halogen lamp are driven is desirably 30% or more of the rated voltage, whereby the light emission stability of the erasing light source and the halogen lamp can be maintained.

  Also, the rated voltage of the erasing light source and halogen lamp is the maximum value of the DC applied voltage or AC applied voltage for safe and stable use without any element destruction or output fluctuation in terms of the light source usage performance, Usually specified by the manufacturer of the light source.

  According to the radiographic image reading apparatus and radiographic image reading method of the present invention, with a simple configuration, the diagnostic work is not interrupted due to the erasing light source running out while suppressing a significant cost increase, an increase in the size of the apparatus, and an increase in power consumption. A highly reliable radiation image reading apparatus can be realized.

  The best mode for carrying out the present invention will be described below with reference to the drawings. FIG. 1 is a side view showing a schematic configuration of a radiation image reading apparatus according to the present embodiment.

  As shown in FIG. 1, the radiographic image reading apparatus 10 is a cassette type CR, and includes a cassette that contains therein a radiographic image conversion plate 2 in which radiation transmitted through a subject is absorbed by a stimulable phosphor. 1 is inserted into the apparatus in the input direction a.

  The cassette 1 is rotated in the rotation direction b in the figure inside the radiographic image reading apparatus 10 and the plate 2 is taken out from the cassette 1. Next, while the plate 2 is sub-scanned and moved in the upward direction c by a conveyance system including a pulley 13, a balance weight 13 a, a driving source (not shown) such as a motor, etc. The laser beam m shown is scanned and irradiated.

  In this way, the stimulated emission light generated by irradiating the plate 2 with the laser beam m while scanning two-dimensionally is condensed by the reading optical system 11, and is obtained by a photoelectric conversion element such as a photomultiplier tube or a CCD. After the optical signal is converted into an electrical signal, it is further converted into a digital signal. This digital signal is displayed as a visible image on a film-like recording material such as a silver halide photographic light-sensitive material or a display device such as a CRT / liquid crystal panel. Displayed and can be stored in a storage device.

  The radiation image reading apparatus 10 includes an erasing system 12 for erasing image information remaining on the plate 2 after image reading. As shown in FIG. 1, the erasing system 12 includes a single halogen lamp 12 a disposed so as to face the plate 2, and a reflection portion 12 b that reflects light from the halogen lamp 12 a toward the plate 2. The halogen lamp 12a and the reflecting portion 12b are arranged so as to extend in the width direction of the plate 2 (the direction perpendicular to the paper surface of FIG. 1).

  After the image reading is performed as described above, the plate 2 is transported in the downward direction d of FIG. 1, and the erasing light k is irradiated from the halogen lamp 12a of the erasing system 12 to almost the entire surface of the plate 2 during the transport. Thus, the image information remaining on the plate 2 can be erased, and the plate 2 can be prepared for the next radiation imaging.

  The plate 2 that has been read and erased as described above is conveyed downward in the drawing, rotated in the direction b ′ opposite to the rotation direction b in the drawing, returned to the cassette 1, and then opposite to the direction a. It is moved in the direction a ′ and carried out of the apparatus.

  Next, erasing of the remaining plate image information by the halogen lamp 12a of the erasing system 12 will be further described.

  When the erasing light k is applied to the plate 2 from the halogen lamp 12a by the erasing system 12 to erase the remaining image information on the plate 2, the halogen lamp 12a has a driving voltage of 80% or less with respect to the rated voltage of the halogen lamp 12a. And is controlled to emit light. Further, the lower limit of the drive voltage is desirably 30% or more of the rated voltage, and if it is lower than this, there is a high possibility that the stability of lamp emission is lost.

  An effect of extending the life of the halogen lamp 12a by driving the halogen lamp 12a with a driving voltage equal to or less than 80% of the rated voltage of the halogen lamp 12a will be described.

  The lifetime L of the halogen lamp is given by the following formula (1) (refer to the technical data of Harrison Toshiba Lighting Co., Ltd.).

L = L ₀ × (V ₀ / V) ^N (1)
Here, L ₀ is the life when used at the rated voltage, V ₀ is the rated voltage, V is the drive voltage, and N is a constant.

As an example, in the above formula (1), as _{V 0 = 100 (V),} N = 12, is plotted relative lifetime L / L ₀ life was defined as 1 in the case of V = V _0, as shown in FIG. 2 Become.

  From FIG. 2, it can be seen that the lifetime of the halogen lamp increases rapidly as the drive voltage decreases. The lifetime here is the lighting time in the case of continuous lighting (light emission), and the number of lighting times in the case of intermittent lighting (light emission), but in the case of the radiographic image reading apparatus of the present embodiment, it is intermittent lighting. Therefore, the number of times of lighting (number of times of light emission) is obtained.

  Erasing in the radiation image reading apparatus 10 requires a light beam of 1,000 to 20,000 Lm (lumen). The lifetime of the halogen lamp that generates this level of luminous flux is about 10,000 times with intermittent lighting at the rated voltage drive. Here, assuming that the durable use years of the radiation image reading apparatus is 10 years, and the total number of erasures, that is, the total number of readings during this period is estimated, the average is 50 times a day, 300 days a year, and 150,000 times. In short, if the erasing light source has a life of 150,000 times or more as the number of lighting (number of times of light emission), the replacement becomes substantially unnecessary within the product life of the apparatus. From FIG. 2, it can be seen that the number of times of lighting 150,000 times corresponds to the lifetime when the driving voltage is about 80V.

  Thus, it is very important for the use of the apparatus that the halogen lamp as the erasing light source has a life exceeding the product life. That is, it is possible to avoid an unexpected situation in which the diagnosis is interrupted due to the erasing light source running out.

  As described above, by driving the halogen lamp at a driving voltage of 80% or less with respect to the rated voltage, the erasing light source can be substantially maintenance-free during the product life of the apparatus.

  The fact that the erasing light source is not substantially cut off is very advantageous for the overall configuration of the apparatus. In other words, when it is assumed that the erasing light source has run out, it is necessary to consider, for example, that two halogen lamps are provided, which increases the size, power consumption, and cost of the device. Since it is not necessary to assume that the erasing light source runs out by driving at a low voltage as in this embodiment, only one halogen lamp may be mounted, which reduces the size of the device, reduces power consumption, and reduces costs. It can contribute.

  Furthermore, if the halogen lamp is driven by alternating voltage (AC) via a transformer, it is not necessary to provide a dedicated low voltage power supply, and further miniaturization, power consumption reduction, and cost reduction can be achieved. In this case, the driving voltage is the effective voltage of the AC voltage.

  The erasing performance in the CR device is determined by the optical energy applied, that is, the light efficiency × time. The decrease in the amount of light due to the decrease in drive voltage can be compensated for by increasing the irradiation time. With normal imaging dose, the extended time of this irradiation time is about several seconds at most, and is not in a range that affects the diagnostic work.

  When a long halogen lamp with a rated voltage of 90 V and a total luminous flux of 6000 Lm was driven with an AC effective voltage of 70 V (78% of the rated voltage) and the number of lighting times until the lamp was cut off, it was about 200,000 times. On the other hand, when a halogen lamp of the same standard was driven at a rated voltage of 90 V as a comparative example, the number of lightings until the lamp burned out was about 15,000 times.

  In this example, the number of times of lighting until the lamp was burned out exceeded the product life. The time required for erasing at this time was 10 seconds with respect to the half-cut plate (length: about 430 mm) at the time of 30 mR (milli-entgen) irradiation. Currently, most CR devices used in the market have a processing speed of about 1 minute per plate, and 10 seconds is a sufficiently acceptable time.

  As described above, the best mode for carrying out the present invention has been described. However, the present invention is not limited to these, and various modifications are possible within the scope of the technical idea of the present invention. For example, in the present embodiment, the halogen lamp is driven to emit light with a driving voltage of 80% of the rated voltage. Preferably, when the voltage is 30% or more of the rated voltage, a lower driving voltage of 80% or less of the rated voltage is used. You may make it light-emit.

  Further, although the radiation image reading apparatus of the present embodiment is configured as a cassette type, it is needless to say that it may be configured as a dedicated type with a built-in plate.

It is a side view which shows schematic structure of the radiographic image reading apparatus by this Embodiment. In the equation (1), the rated voltage V ₀ = 100 (V), N = 12, and a graph showing the relationship between the relative life L / L ₀ and the drive voltage V when the life when V = V ₀ is 1. is there.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Cassette 2 Radiation image conversion plate and plate 10 Radiation image reader 11 Reading optical system 12 Erasing system 12a Halogen lamp (erasing light source)
12b Reflector k Erase light

Claims (6)

A radiographic image reading apparatus having an erasing system for reading image information from a radiographic image conversion plate on which a radiographic image is recorded, and erasing information remaining on the radiographic image conversion plate after the reading by light irradiation,
The erasing system has at least one erasing light source;
A radiation image reading apparatus, wherein, during the light irradiation, the erasing light source is driven to emit light at a voltage of 80% or less of its rated voltage.   The radiation image reading apparatus according to claim 1, wherein the erasing light source is a halogen lamp.   The radiation image reading apparatus according to claim 1, wherein the number of erasing light sources is one.   The radiation image reading apparatus according to claim 1, wherein the erasing light source is AC driven. A radiation image reading method for reading image information from a radiation image conversion plate on which a radiation image is recorded, and erasing information remaining on the radiation image conversion plate after the reading by light irradiation from an erasing system,
The radiation image reading method, wherein the erasing system has at least one halogen lamp, and the light is emitted by driving the halogen lamp at a voltage of 80% or less with respect to its rated voltage during the light irradiation. The radiation image reading method according to claim 5, wherein the halogen lamp is AC driven.

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