Abstract:
A subject of the present invention is to achieve accurate measurement of an ultraviolet dose of a test region of a subject (patient) by a single measuring cycle, to provide a measuring tool not including any members requiring manual operations, to prevent an examiner from exposure to ultraviolet radiation and to improve safety. An optimum ultraviolet dose determining tool, for ultraviolet radiotherapy, is used to determine an optimum ultraviolet dose in advance. The optimum ultraviolet dose determining tool can be placed on the skin of a patient and is provided with an attenuation filter ( 1 A,  1 B or  1 C) having a plurality of optical areas respectively having different, known ultraviolet-ray transmittances or reflectances.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The present invention relates to an optimum ultraviolet dose determining tool for ultraviolet radiotherapy to be used for determining a proper ultraviolet dose prior to ultraviolet radiotherapy.  
         [0003]     2. Description of the Related Art  
         [0004]     Ultraviolet radiotherapy is an effective medical treatment of dermatoses, such as atopic dermatitis, psoriasis and leukoderma.  
         [0005]     Doctors selectively use either of UV-B ultraviolet rays having wavelengths in the range of 285 to 320 nm and UV-A ultraviolet rays having wavelengths in the range of 320 to 400 nm for the treatment of dermatoses.  
         [0006]     Ultraviolet radiotherapy using ultraviolet radiation of various wavelengths, similarly to medication, must be performed very consciously and carefully because ultraviolet radiation of those wavelengths is hazardous.  
         [0007]     Patients have individual differences; some have tough skins resistant to light and others have weak skins sensitive to light. Therefore, it is important to grasp the quality of the patient&#39;s skin prior to ultraviolet radiotherapy.  
         [0008]     The individual patient is subjected to an examination to determine a UV-A wave dose and a UV-B wave dose to which the patient is resistant. A UV-B wave used to determine a minimum erytherma dose (MED) and a UV-A wave is used to determine a minimum phototoxic dose (MPD). A safe ultraviolet dose is determined on the basis of the measured MED and MPD.  
         [0009]     The foregoing examination uses an optimum ultraviolet dose determining tool.  
         [0010]     Referring to  FIG. 9 (A), a currently used optimum ultraviolet dose determining tool has a base plate b provided with two rows of windows of the same size arranged at fixed intervals, namely, a first row of five windows a 1  to a 5  and a second row of five windows a 6  to a 10 , first and second slide guides c respectively extending along the first row of the five windows a 1  to a 5  and the second row of the five windows a 6  to a 10  of the base plate b, and first and second shutter plates d 1  and d 2  guide for sliding by the guides c, respectively. The first shutter plate d 1  is slid periodically in the direction of the arrow by a distance corresponding to the pitch of the windows at a time to close the windows a 1  to a 6  successively. Subsequently, the second shutter plate d 2  is slid similarly to close all the windows.  
         [0011]     The windows a 1  to a 10  are square openings 10 mm sq. The shutter plates d 1  and d 2  are slid by a pitch corresponding to that of the windows after ultraviolet irradiation for 30 s.  
         [0012]     The base plate b is attached to a part of the patient&#39;s skin mostly concealed from sunlight, such as the skin of back, the thigh or the inner side of the arm, by a suitable means for the examination. Subsequently, the part of the patient&#39;s body is irradiated with ultraviolet rays of the same intensity through the windows a 1  to a 10  of the base plate b. The first slide plate d 1  is slid at equal time intervals (normally, time intervals of 30 s) to close the windows a 1  to a 5  successively. After all the windows a 1  to a 5  have been closed, the second shutter plate d 2  is slid similarly. Radiation of ultraviolet rays is stopped after all the windows a 6  to a 10  have been closed to complete the examination.  
         [0013]     Then, the base plate b s removed from the skin, the colors of positions of the skin corresponding to the windows a 1  to a 10  are examined to determine an MED and an MPD  
         [0014]     When the conventional optimum ultraviolet dose determining tool is used, the shutter plates d 1  and d 2  are slid manually to close the windows a 1  to a 10  successively while exposure is timed by the examiner. Therefore, doses respectively for the windows a 1  to a 10  are not necessarily accurate due to inaccurate timing of ultraviolet irradiation and delay in operations. Consequently, measurements are inaccurate and it is difficult to obtain precise test data.  
         [0015]     Since the shutter plates d 1  and d 2  are operated under ultraviolet radiation, the examiner is exposed to ultraviolet radiation.  
         [0016]     A procedure for ultraviolet radiotherapy irradiates the whole body of a patient standing or sitting on a chair in a treatment chamber in a cabin like a telephone booth. When the patient is examined for an acceptable ultraviolet dose in such a treatment chamber by using the foregoing conventional optimum ultraviolet dose determining tool, the examiner needs to open the door of the cabin and to enter the treatment chamber periodically to operate the shutter plates d 1  and d 2  manually. Thus the measurement of doses has been difficult.  
         [0017]     A means to protect the examiner from exposure to ultraviolet radiation, may electrically drive the shutter plates d 1  and d 2  and to operate the shutter plates d 1  and d 2  by remote control. However, such a method of operating the shutter plates d 1  and d 2  needs an expensive, large-scale, complicated mechanism.  
         [0018]     Patent Document 1: IP-A 2004-65330  
       SUMMARY OF INVENTION  
       [0019]     It is an object of the present invention to provide an optimum ultraviolet dose determining tool, for ultraviolet radiotherapy, having simple construction, capable of preventing exposing an examiner to ultraviolet radiation, not requiring the examiner to enter a treatment chamber of a cabin when doses are measured in the treatment chamber, and capable of efficiently achieving measurement in a short time.  
         [0020]     An optimum ultraviolet dose determining tool for ultraviolet radiotherapy according to the present invention for determining an optimum ultraviolet dose prior to ultraviolet radiotherapy includes an attenuation filter capable of being placed on the skin of a patient and having optical areas respectively having different, known ultraviolet-ray transmittances or reflectances.  
         [0021]     An optimum ultraviolet dose can be efficiently determined in advance through the comparative observation of the respective degrees of cauterization of parts of the skin exposed to ultraviolet radiation through the optical areas respectively having different, known ultraviolet-ray transmittances or reflectances.  
         [0022]     In the optimum ultraviolet dose determining tool according to the present invention, parts of the skin respectively corresponding to the optical areas of the base plate are exposed simultaneously to ultraviolet radiation for the same exposure time.  
         [0023]     Thus an optimum ultraviolet dose can be determined through only one measuring cycle.  
         [0024]     In the optimum ultraviolet dose determining tool according to the present invention, the attenuation filter has gradient ultraviolet-ray transmittance or reflectance continuously decreasing from one end toward the other end thereof.  
         [0025]     When the skin is exposed to ultraviolet radiation by uniformly irradiating the attenuation filter with ultraviolet radiation for a fixed time, parts of the skin are cauterized according to the ultraviolet-ray transmittances or reflectances of parts, corresponding to the parts of the skin, of the attenuation filter in different tints, respectively, because the ultraviolet-ray transmittance or reflectance of the attenuation filter varies continuously from one end toward the other end of the base plate. An optimum ultraviolet dose can be determined through the visual examination of the tints of the parts of the skin. Since the ultraviolet-ray transmittance or reflectance of the attenuation filter changes continuously from one end toward the other end of the base plate, delicate tint variation can be perceived.  
         [0026]     In the optimum ultraviolet dose determining tool according to the present invention, the attenuation filter has gradient ultraviolet-ray transmittance or reflectance decreasing stepwise from one end toward the other end thereof.  
         [0027]     Thus an optimum ultraviolet dose can be determined through the comparative observation of the tints of the parts, corresponding to the parts of the attenuation filter respectively having different ultraviolet transmittances or reflectances, of the skin.  
         [0028]     In the optimum ultraviolet dose determining tool according to the present invention, the attenuation filter is provided with a row of a plurality of windows arranged such that the respective ultraviolet-ray transmittances or reflectances of the windows decrease stepwise in order of arrangement of the windows.  
         [0029]     When parts of the skin are exposed simultaneously to ultraviolet radiation through the windows of the attenuation filter, respectively, by uniformly irradiating the attenuation filter with ultraviolet radiation, the parts of the skin are cauterized according to the ultraviolet-ray transmittances or reflectances of the windows, respectively, in different tints, respectively. Therefore, the different tints of the parts of the skin can be easily perceived.  
         [0030]     In the optimum ultraviolet dose determining tool according to the present invention, the attenuation filter is held in a case in combination with an ultraviolet lamp.  
         [0031]     Since both the attenuation filter and the ultraviolet lamp are held compactly in the case, the optimum ultraviolet dose determining tool is compact in construction and easily portable. Doses can be measured simply by placing the optimum ultraviolet dose determining tool for ultraviolet radiotherapy on the back or the like of the patient, and the optimum ultraviolet dose determining tool for ultraviolet radiotherapy can be used in a narrow hospital room.  
         [0032]     The attenuation filter may be formed of a filtering material having parts of different optical densities respectively having different ultraviolet-ray transmittances or reflectances. In the optimum ultraviolet dose determining tool according to the present invention, the attenuation filter may be formed by superposing dielectric layers on a base plate of a nonreflective material, such as quartz glass, and dielectric layers may be superposed on the base plate such that different parts of the dielectric layers have different ultraviolet-ray transmittances or reflectances, respectively.  
         [0033]     Thus an optimum ultraviolet dose can be determined in advance through only one measuring cycle by comparatively examining the respective degrees of cauterization of the parts of the skin exposed to ultraviolet radiation through the plurality of optical areas respectively having different, known ultraviolet-ray transmittances or reflectances, respectively.  
         [0034]     Since any manual operation for moving a shutter plate is not necessary at all, exposure of the skin to ultraviolet radiation at in correct doses different from intended doses due to failure in correctly timing exposure and delayed operations can be avoided. Consequently, the parts of the skin can be exposed to ultraviolet radiation at correct doses, respectively, and an optimum dose can be accurately determined.  
         [0035]     Since the optimum ultraviolet dose determining tool does not have any member requiring manual operation at all, the examiner does not never undergo experience hazardous exposure to ultraviolet radiation, the security of the examiner can be insured, the optimum ultraviolet dose determining tool can be built in very simple construction and is easy to handle.  
         [0036]     The optimum ultraviolet dose determining tool is capable of being used for measuring both MED and MPD. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0037]      FIG. 1  is a plan view of an optimum ultraviolet dose determining tool in a first embodiment according to the present invention for ultraviolet radiotherapy;  
         [0038]      FIG. 2  is a graph showing the variation of ultraviolet-ray transmittance of the optimum ultraviolet dose determining tool with distance from one end of the optimum ultraviolet dose determining tool shown in  FIG. 1 ;  
         [0039]      FIG. 3  is a typical sectional view taken on the line A-A in  FIG. 1 ;  
         [0040]      FIG. 4  is a pictorial view of assistance in explaining the operation of an ultraviolet irradiation system;  
         [0041]      FIG. 5  is a plan view of an optimum ultraviolet dose determining tool in a second embodiment according to the present invention;  
         [0042]      FIG. 6  is an enlarged, fragmentary sectional view of an attenuation filter;  
         [0043]      FIG. 7 (A) is a plan view of an optimum ultraviolet dose determining tool in a third embodiment according to the present invention;  
         [0044]      FIG. 7 (B) is a sectional view taken on the line B-B in  FIG. 7 (A);  
         [0045]      FIG. 8 (A) is a plan view of an optimum ultraviolet dose determining tool in a modification of the optimum ultraviolet dose determining tool in the third embodiment;  
         [0046]      FIG. 8 (B) is a sectional view taken on the line C-C in  FIG. 8 (A);  
         [0047]      FIG. 9 (A) is a plan view of a conventional optimum ultraviolet dose determining tool;  
         [0048]      FIG. 9 (B) is a sectional view taken on the line D-D in  FIG. 8 (A); and  
         [0049]      FIG. 10  is a sectional view of an optimum ultraviolet dose determining tool in a fourth embodiment according to the present invention for ultraviolet radiotherapy. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0050]     Referring to  FIG. 1  showing an optimum ultraviolet dose determining tool in a first embodiment according to the present invention for ultraviolet radiotherapy in a plan view, the optimum ultraviolet dose determining tool has an attenuation filter  1 A. The attenuation filter  1 A has ultraviolet-ray transmittance decreasing from one end  1   a  thereof toward the other end  1   b  thereof. The attenuation filter  1 A may be a transmission-type attenuation filter having a plurality of optical areas (transmission areas) respectively having different, known transmittances or may be a reflection-type attenuation filter having a plurality of optical areas (reflecting areas) respectively having different ultraviolet-ray reflectances. When the attenuation filter  1 A is of a reflection-type, part of light rays emitted by a light source may be reflected toward a human body.  
         [0051]     As shown in a typical sectional view in  FIG. 3 , the attenuation filter  1 A is a plastic sheet formed by forming a material prepared by mixing particles  2  of an ultraviolet-ray intercepting substance in a plastic material in a sheet such that the sheet has gradient density or by applying a material containing particles  2  of an ultraviolet-ray intercepting substance to a sheet such that the plastic sheet has gradient density.  
         [0052]     A desired scale may be graduated in one longitudinal side edge of the attenuation filter  1 A to facilitate determining doses after irradiation with ultraviolet radiation.  
         [0053]     Referring to  FIG. 4 , the attenuation filter  1 A is used by an ultraviolet irradiating apparatus  3  to determine an optimum ultraviolet dose for a patient. The attenuation filter  1 A is attached to a test region of the body of a subject (patient)  5  lying on a bed  4 . The irradiating head  6  is positioned so that the entire attenuation filter  1 A is irradiated uniformly with ultraviolet radiation, and the test region of the body of the patient  5  is exposed to ultraviolet radiation through the attenuation filter  1 A. Parts of the skin in the test region are exposed to ultraviolet radiation at ultraviolet doses corresponding to the densities of parts, corresponding to the parts of the skin in the test region, of the attenuation filter  1 A.  
         [0054]     Consequently, the parts of the skin in the test region are cauterized in tints according to the transmittances of the parts, corresponding to the parts of the skin, of the attenuation filter  1 A.  
         [0055]     After ultraviolet irradiation has been continued for a predetermined time, ultraviolet irradiation is stopped and the attenuation filter  1 A is removed from the skin of the subject  5 . Then, the tints of the exposed parts of the test region are visually examined to grasp an optimum ultraviolet dose.  
         [0056]     The subject (patient)  5  may be exposed to ultraviolet radiation while the subject  5  is in a standing position in a treatment cabin instead of in a lying position o the bed  4 . To avoid exposing parts of the skin around the attenuation filter  1 A to ultraviolet radiation, those parts may be covered with a proper mask.  
         [0057]     Referring to  FIG. 5  showing an optimum ultraviolet dose determining tool in a second embodiment according to the present invention, an attenuation filter  1 B is formed longitudinally on a sheet  7 . The attenuation filter  1 B has parts respectively having different ultraviolet-ray transmittances. The ultraviolet-ray transmittances change stepwise from one end toward the other end of the sheet  7 .  
         [0058]     As shown in  FIG. 5 , the successive parts of the attenuation filter  1 B have ultraviolet-ray transmittances  1 B 1  to  1 B 5 , respectively. The number of the parts of the attenuation filter  1 B is not limited to five and may be any optional number.  
         [0059]     The sheet  7  is attached directly to a test region of the body of a subject, and the test region of the subject&#39;s body is exposed to ultraviolet radiation through the attenuation filter  1 B. Parts of the skin in the test region are exposed to ultraviolet radiation at ultraviolet doses according to the respective ultraviolet-ray transmittances  1 B 1  to  1 B 5  of parts, corresponding to the parts of the skin in the test region, of the attenuation filter  1 B, and the same parts of the skin are cauterized in tints according to intensities of ultraviolet radiation respectively proportional to the ultraviolet-ray transmittances  1 B 1  to  1 B 5 . Then, the sheet  7  is removed from the skin of the subject. Then, the tints of the exposed parts of the test region are visually examined to grasp an optimum ultraviolet dose. The ultraviolet-ray transmittances of the parts of the attenuation filter  1 B may be determined by forming the parts in different densities as explained in connection with FIGS.  1  to  3 . An attenuation filter as shown in  FIG. 6  may be used. The attenuation filter shown in  FIG. 6  is formed by superposing dielectric layers  9  respectively having different reflectances on a base  8  of a nonreflective material, such as quartz glass so that different parts of the attenuation filter have different ultraviolet-ray transmittances.  
         [0060]      FIG. 7 (A) is a plan view of an optimum ultraviolet dose determining tool in a third embodiment according to the present invention and  FIG. 7 (B) is a sectional view taken on the line B-B in  FIG. 7 (A).  
         [0061]     The optimum ultraviolet dose determining tool in the third embodiment includes a base plate  11  provided with ten windows  10   1  to  10   10  arranged in two rows, and attenuation filters  1 C 1  to  1 C 10  placed in the windows  10   1  to  10   10 , respectively.  
         [0062]     The base plate is formed from a material having affinity to the skin of human bodies, such as a plastic sheet, a cardboard or the like. The windows  10   1  to  10   10  are, for example, square openings 10 mm sq.  
         [0063]     The number of the windows may be properly determined taking into consideration a required level of measuring accuracy.  
         [0064]     The respective ultraviolet-ray transmittances of the attenuation filters  1 C 1  to  1 C 10  decrease stepwise in order of the attenuation filters  1 C 1  to  1 C 10 . The attenuation filters  1 C 1  to  1 C 10  are bonded adhesively to the base plate  10 .  
         [0065]     The transmittances of the attenuation filters  1 C 1  to  1 C 10  may be determined by properly adjusting density as shown in  FIG. 3  or by properly adjusting reflectance as shown in  FIG. 6 .  
         [0066]     The base plate  11  is attached directly to a test region of the body of a subject, and the attenuation filters  10   1  to  10   10  are irradiated uniformly with ultraviolet radiation to expose the test region of the subject&#39;s body to ultraviolet radiation through the attenuation filters  10   1  to  10   10 . Then, the base plate  11  is removed from the subject&#39;s body and the tints of the exposed parts of the test region are visually examined to grasp an optimum ultraviolet dose.  
         [0067]     The base plate  11  does not necessarily need to be provided with the ten square windows  10   1  to  10   10  the base plate  11  may be provided, for example, with five round windows as shown in  FIG. 8 .  
         [0068]     Both MED and MPD can be measured by using the optimum ultraviolet dose determining tool in the third embodiment.  
         [0069]     Referring to  FIG. 10  showing an optimum ultraviolet dose determining tool in a fourth embodiment according to the present invention for ultraviolet radiotherapy, the optimum ultraviolet dose determining tool includes an irradiation head  6 , the attenuation filter  1 A and a case  20  holding the irradiation head  6  and the attenuation filter  1 A. The irradiation head  6  has a straight ultraviolet lamp  21  and a cylindrical lens  22  for directing ultraviolet rays emitted from the ultraviolet lamp  21  so that the ultraviolet rays may uniformly fall on the attenuation filter  1 A. The case  20  has a substantially cylindrical reflecting surface  23  formed on the inner surface of the upper wall thereof. The reflecting surface  23  reflects Ultraviolet rays emitted from the ultraviolet lamp  21  toward the reflecting surface  23  toward the attenuation filter  1 A. The ultraviolet lamp  21  is optically sealed in the case  20  such that ultraviolet rays emitted from the ultraviolet lamp  21  travel outside only through the attenuation filter  1 A. Either a UV-A lamp or a UV-B lamp is employed as the ultraviolet lamp  21 . The ultraviolet lamp  21  of the desired type is attached to sockets attached to the case  20 . The attenuation filter  1 A may be replaced with the attenuation filter  1 B or  1 C. When the ultraviolet lamp  21  is able to emit ultraviolet rays uniformly, the cylindrical lens  22  may be omitted.  
         [0070]     The optimum ultraviolet dose determining tool provided with the attenuation filter  1 A does not need any manual operation, such as a manual operation of the shutter plate, at all and does not need additional members, such as the shutter plates. The irradiation head  6  and the attenuation filter  1 A can be easily held in combination in the case  20 . Since manual operations, such as the manual operation of the shutter plate, are not necessary, the irradiating head  6  and the attenuation filter  1 A can be held in combination in the case  20 .  
         [0071]     Since the irradiation head  6  and the attenuation filter  1 A are combined in an integral unit, the optimum ultraviolet dose determining tool is easy to carry around, needs only being placed on a desired part of the patient, such as the patient&#39;s back, for use and can be used in a narrow patient&#39;s room.  
         [0072]     Since the ultraviolet lamp  21  is optically sealed in the case  20 , there is no danger of the examiner being exposed accidentally to ultraviolet radiation.  
         [0073]     As mentioned above, the reflection-type attenuation type may be employed instead of the transmission-type attenuation filter to reflect part of light rays emitted from a light source and to irradiate a human body with the rest of the light rays.