Radiographic apparatus

The disclosure provides a radiographic apparatus that allows suppression of needles radiation exposure to a subject. Specifically, the disclosure includes an X-ray tube, a collimator, and a visible light source. The spread of visible light beams through the collimator opening too largely may not possibly conform to the spread of radiation. Such a situation may occur when the apparatus is provided with the X-ray tube that emits narrow radiation. In order to avoid such a situation, the disclosure sets an upper limit of a degree of opening as an upper limit of a degree of opening of the collimator. With a construction of the disclosure, there is no need to perform further radiography. This achieves the radiographic apparatus that allows suppression of needless radiation exposure to a subject.

RELATED APPLICATIONS

This application is the U.S. National Phase under 35 U.S.C. §371, of International Application No. PCT/JP2012/007797, filed on Dec. 5, 2012, which in turn claims the benefit of Japanese Application No. 2011-286034, filed on Dec. 27, 2011, the disclosures of which Applications are incorporated by reference herein.

TECHNICAL FIELD

The present invention relates to a radiographic apparatus for performing fluoroscopy to a subject. More particularly, the present invention is directed to a radiographic apparatus having a collimator for restricting an irradiation direction of radiation.

BACKGROUND ART

Medical institutions are equipped with a radiographic apparatus configured to emit radiation to image a subject M. Such a radiographic apparatus includes a radiation source53and a cassette54as illustrated inFIG. 9. The radiation source53emits radiation, and the cassette54detects the radiation. A top board52is provided between the radiation source53and the cassette54. The top board52supports the subject M placed thereon.

The radiation source53has a collimator53aattached thereto. The collimator53arestricts an irradiation area of radiation. The radiation from the radiation source53passes through the collimator53a, whereby the spread of the radiation is restricted. Then the restricted radiation is applied to the subject M.

The radiation source53also includes an optical lamp53pfor confirming the irradiation area of the radiation. The optical lamp53pis disposed behind the collimator53a, seen from the top board52, together with a mirror65. Similarly to the radiation, light beams from the optical lamp53ppass through the collimator53ato the top board52.

When an operator issues a command to turn on the optical lamp53pprior to irradiation with radiation, the optical lamp53pis turned on such that visible light beams whose spread is restricted by the collimator53aare applied to a part of the subject M. Here, the part of the subject M irradiated by the optical lamp53pcorresponds to an area to be irradiated with radiation.

The radiation from the radiation source53is not visible light beams. Consequently, an area of the subject M irradiated with the collimated radiation is invisible. Accordingly, the operator turns on the optical lamp53pprior to the irradiation with radiation, thereby confirming the area of the subject M irradiated with the radiation. Then the operator controls a degree of opening of the collimator53awhile the optical lamp53pis turned on, achieving control of the irradiation area of the radiation. Japanese Patent Publication No. 2010-094212A describes a construction with such a collimator53a.

PATENT LITERATURE

Patent Literature 1

SUMMARY

Technical Problem

The conventional radiographic apparatus has a drawback as under. Specifically, the conventional radiographic apparatus sets the collimator53aregardless of specifications of the radiation source53. This leads to needless exposure to the subject.

The radiation source53is manufactured so as to restrict an irradiation direction of radiation without the collimator53a. That is, the radiation source53has a maximum irradiation width. This causes a ceiling that no radiation is applicable any more however the collimator53amay operate. The maximum irradiation width of radiation in the radiation source53varies depending on types of the radiation source53.

It is not determined into which radiation source53the collimator53ais incorporated upon manufacture. As a result, the collimator53ais manufactured with a sufficient degree of opening so as to operate satisfactorily when incorporated into any radiation source53.

Here, it is assumed that the radiographic apparatus is manufactured with the above collimator53abeing attached to a radiation source53having the small spread of radiation. In such an apparatus, when radiation is emitted with the collimator53afully opened, the radiation emitted from the radiation source53passes through the collimator53awithout reaching the collimator53a. That is because the radiation emitted from the radiation source53is narrower than an expanding width of the collimator53ain a full-open state.

Next, radiography with such an apparatus is to be considered. An operator confirms the spread of the radiation using an optical lamp53pattached to the collimator53aprior to radiography. The light from the optical lamp53psufficiently spreads for faithfully representing the degree of opening of the collimator53a.

Consequently, when the optical lamp53pis turned on, the collimator53ain the full-open state restricts and emits visible light beams from the optical lamp53p. In fact, however, radiation is emitted not to an irradiation area of the visible light beams but to an area narrower than the irradiation area of the visible light beams. As above, an irradiation width of the visible light from the optical lamp53pdoes not conform to that of radiation. Such a phenomenon may occur. In other words, radiation is narrower than the visible light.

However, the operator continuously performs radiography without noticing such discrepancy. That is, the operator performs radiography while believing the radiation entering into the area of the subject irradiated with the visible light beams. Accordingly, an image is not obtainable having a site of interest of the subject appearing desirably. This requires further radiography. In other words, the conventional apparatus causes needless exposure to the subject.

The present invention has been made regarding the state of the art noted above, and its primary object is to provide a radiographic apparatus that allows suppression of needles radiation exposure to a subject.

Solution to Problem

The present invention adopts the following construction for overcoming the above drawback. One embodiment of the present invention discloses a radiographic apparatus. The radiographic apparatus includes a radiation source configured to emit radiation, a detecting device configure to detect radiation passing through a subject, a collimator configured to restrict the spread of the radiation emitted from the radiation source, a collimator activating device configured to activate the collimator to change a degree of opening of the collimator, a visible light source provided on the collimator and configured to emit visible light beams, a visible light source controller configured to control the visible light source, and a collimator controller. The collimator controller is configured to control the collimator activating device so as the spread of the radiation not to exceed an upper limit of the degree of opening, the degree corresponding to a minimum degree of opening, at which the spread of the radiation does not increase any more when the degree of opening of the collimator gradually increases while the radiation is emitted.

Operation and Effect

The embodiment of the present invention includes the radiation source, the collimator, and the visible light source. The collimator is provided for restricting the spread of radiation. The visible light source is provided for representing the area to which radiation is applied instead of the radiation source by applying visible light passing through the collimator, the radiation from the radiation source being invisible. With some type of the radiation source, when the collimator opens too largely, the spread of the visible light beams through the collimator may not possibly conform to the spread of radiation. Such a situation may occur when the apparatus is provided with the radiation source that emits narrow radiation.

In order to avoid such a situation, the embodiment of the present invention sets the upper limit of the degree of opening as an upper limit of the degree of opening of the collimator. The degree of opening of the collimator gradually increases while radiation is emitted to reach the minimum degree of opening at which the spread of X-ray beams does not increase any more. The minimum degree corresponds to the upper limit of the degree of opening. In the embodiment of the present invention, the irradiation area of the visible light beams always conforms to the irradiation area by the radiation source. Accordingly, there is no need to perform further radiography. This achieves the radiographic apparatus that allows suppression in needless exposure of radiation to the subject.

Moreover, the embodiment of the radiographic apparatus further includes an input device via which an operator inputs a command, an alarm-activating device configured to activate an alarm to the operator; and an alarm-activation controller configured to issue a command to the alarm-activating device to activate the alarm. The alarm-activation controller controls the alarm-activating device to activate the alarm when the degree of opening of the collimator is controlled to exceed the upper limit of the degree of opening via the input device. Such is more desirable.

Operation and Effect

The above construction describes one example of the radiographic apparatus in the embodiment of the present invention. That is, the alarm is activated when the degree of opening of the collimator is controlled so as to exceed the upper limit of the degree of opening. This obtains the apparatus with a higher degree of safety, ensuring to suppress needless exposure.

Moreover, in the embodiment of the radiographic apparatus, the collimator controller informs the alarm-activation controller so as to activate the alarm when a required degree of opening exceeds the upper limit of the degree of opening, the required degree of opening being a degree of opening of the collimator required upon radiography to be conducted by the operator. Such is more desirable.

Operation and Effect

The above construction describes one example of the radiographic apparatus in the embodiment of the present invention. That is, the alarm is activated when the degree of opening of the collimator required upon radiography to be conducted by the operator exceeds the upper limit of the degree of opening. This obtains accurate informing to the operator.

Moreover, the radiographic apparatus of the embodiment further includes a storing device configured to store a plurality of upper limits of the degrees of opening in association with types of the radiation source, and a radiation source controller configured to control the radiation source. The radiation source controller outputs type information representing one of the types of the radiation source to the collimator controller. The collimator controller reads out one of the plurality of upper limits of the degrees of opening, corresponding to the obtained type information, from the storing device. Such is more desirable.

Operation and Effect

The above construction describes one example of the radiographic apparatus in the embodiment of the present invention. That is, the collimator controller reads out the upper limit of the degree of opening corresponding to the type of the radiation source. This achieves the apparatus with more flexibility. Specifically, any type of the radiation source provided in the apparatus ensures to control the collimator in accordance with the upper limit of the degree corresponding to the type of the radiation source.

Advantageous Effects of Invention

The embodiment of the present invention includes the radiation source, the collimator, and the visible light source. When the collimator opens too largely, the spread of the visible light beams through the collimator may not possibly conform to the spread of radiation. Such a situation may occur when the apparatus is provided with the radiation source that emits narrow radiation. In order to avoid such a situation, the embodiment of the present invention sets the upper limit of the degree of opening representing the upper limit of the degree of opening of the collimator. With the embodiment of the present invention, there is no need to perform further radiography. This achieves the radiographic apparatus that allows suppression in needless exposure of radiation to the subject.

DESCRIPTION OF EMBODIMENTS

The following describes a concrete example as an embodiment for carrying out the present invention.

One embodiment of the present invention is to be described as under. X-rays in the embodiment correspond to radiation in the present invention.

Firstly, an X-ray apparatus1according to Embodiment 1 is to be described. As illustrated inFIG. 1, an X-ray apparatus1includes a top board2configured to support a subject M placed thereon in a supine position, an X-ray tube3disposed above the top board2(at a first face side) and configured to emit X-rays, and a cassette4disposed below the top board2(at a second face side) and configured to detect X-rays. The cassette4is rectangular having four sides along either a body axis direction A or a body side direction S of the subject M. The X-ray tube3emits X-rays in a quadrangular pyramid shape to the cassette4. An entire surface of the cassette4receives X-rays. A strut5extends from below the top board2(from the second face side) to above the top board2(to the first face side). The strut5supports the X-ray tube3. The X-ray tube3corresponds to the radiation source in the present invention. The cassette4corresponds to the radiation detecting device in the present invention.

The X-ray tube3is provided with a collimator3a(seeFIG. 1). The collimator3arestricts an irradiation area of X-rays. The collimator3ahas an adjustable degree of opening. As illustrated inFIG. 2, the collimator3ahas one pair of shielding vanes3bthat moves in a mirror-image symmetrical manner relative to the center axis C, and has another pair of shielding vanes3bthat similarly moves in a mirror-image symmetrical manner relative to the center axis C. Movement of the shielding vanes3bof the collimator3aallows not only irradiation of an entire detecting surface4aof the cassette4with X-rays B in a cone shape, but also irradiation of only a center portion of the detecting surface4awith X-rays B in a fan shape. Here, the center axis C represents the center of X-rays B. One pair of the shielding vanes3bcontrols the spread of the quadrangular pyramid X-rays B in the body axis direction A. The other pair of the shielding vanes3bcontrols the spread of the X-rays B in the body side direction S. When the X-ray tube3moves, the collimator3amoves along with the movement of the X-ray tube3accordingly. A collimator activating mechanism7(seeFIG. 1) changes a degree of opening of the collimator3athrough activating the shielding vanes3b. A collimator controller8is provided for controlling the collimator activating mechanism7. The collimator activating mechanism7corresponds to the collimator activating device in the present invention. The collimator controller8corresponds to the collimator activation controller in the present invention. Here,FIG. 2illustrates the shielding vanes3b, and a visible light source9and a mirror15of the collimator3aare omitted. These elements are to be mentioned later.

An X-ray tube controller6(seeFIG. 1) is provided for controlling the X-ray tube3with a given tube current, a given tube voltage, and a given pulse width. The X-ray tube controller6controls the X-ray tube3to emit X-rays. Then, the X-rays pass through the subject M to enter into the detecting surface4aof the cassette4. The cassette4contains an X-ray sensitive film. Accordingly, when the X-rays are applied to the film, a fluoroscopic image of the subject M is printed on the film. Here, the X-ray tube controller6corresponds to the radiation source controller in the present invention.

An area setting unit11sets a detection area of the cassette4where X-rays are detected. The area setting unit11is to be described. When the operator inputs a type of the cassette4to be used for radiography to a console26, information representing the type of the cassette4is sent to the area setting unit11. The area setting unit11refers to a table stored in a storing unit28, the table being associated with the cassette4and a length of the film corresponding to the cassette4, thereby obtaining the length of a film of the cassette4to be used for radiography. The length of the film is a length of the subject M in the body axis direction, and thus corresponds to an area where the cassette4detects X-rays. The area setting unit11sets this area as a detection area where X-rays are detected. The console26is used for inputting commands from the operator. The area setting unit11corresponds to the area setting device in the present invention. The console26corresponds to the input device in the present invention. The storing unit28corresponds to the storing device in the present invention.

As illustrated inFIG. 1, the visible light source9is provided on the collimator3a. The visible light source9emits visible light beams. The visible light beams pass through a space between the shielding vanes3bof the collimator3a, whereby a part of the subject M is irradiated with the visible light beams. Similarly, X-rays from the X-ray tube3pass through the space between the shielding vanes3bof the collimator3a, whereby a part of the subject M is irradiated with the X-rays. Accordingly, the part of the subject M irradiated by the visible light source9conforms to the part of the subject M irradiated with X-ray beams from the X-ray tube3. The visible light from the visible light source9is visible by the operator. Consequently, the operator can confirm visually an area (irradiation area or an irradiation field) of the subject M to which X-rays are applied prior to X-ray radiography. A visible light source controller10is provided for controlling the visible light source9. The visible light source controller10corresponds to the visible light source controller in the present invention.

The following describes a positional relationship between the X-ray tube3and the collimator3a.FIG. 3is a schematic view illustrating a positional relationship of the elements. The X-ray tube3is provided with an emitting hole3pthrough which X-rays are emitted. The collimator3ais provided with a mirror15inclined relative to the emitting hole3p. The collimator3aincludes the visible light source9. The visible light source9is disposed at the position as a mirror image of the X-ray tube3in a focus position by the mirror15, seen from a subject M.

When the visible light source9is turned on, the visible light beams are emitted. The visible light beams are reflected on the mirror15to travel toward the collimator3a. Thereafter, the collimator3arestricts the spread of the visible light beams, whereby the visible light beams with a cone shape are generated. The cone visible light beams are outputted to the subject M.

When the visible light source9is turned off, X-rays are emitted from the X-ray tube3. The X-rays pass through the mirror15toward the collimator3a. Thereafter, the collimator3arestricts the spread of the X-rays, whereby the X-ray beams with a cone shape are generated. The cone X-ray beams are outputted to the subject M. The visible light beams and the X-ray beams travel toward the subject M while spreading in the same manner unless the shielding vanes3bof the collimator3amove.

<Unconformity of Visible Light Beam and X-Ray Beam>

According to the above description, the part of the subject M irradiated by the visible light source9conforms to that irradiated with the X-ray beams from the X-ray tube3. However, this is not always so. Specifically, the visible light beams may possibly be emitted more widely than the X-ray beams depending on types of X-ray tube3. The following describes a reason why such a drawback occurs.

FIG. 4illustrates different types of X-ray tube3. The X-ray tube3on the left ofFIG. 4has a large emitting hole3p, allowing emission of wide X-ray beams. On the other hand, the X-ray tube3on the right ofFIG. 4has a small emitting hole3p, merely allowing emission of narrow X-ray beams. As noted above, the X-ray tube3emits X-ray beams with various widths in accordance with variations in design, such as a dose of emittable X-rays and a weight.

FIG. 5illustrates X-ray beams from two types of X-ray tubes3passing through the collimator3a. Here, the collimator3ainFIG. 5is fully opened. The X-ray tube3on the left ofFIG. 5allows emission of wide X-ray beams. The X-ray beams are too wide for entirely passing through the collimator3a. Consequently, the X-ray beams emitted from the X-ray tube3pass through the fully-opened collimator3awhile the spread thereof is restricted. On the other hand, the X-ray tube3on the right ofFIG. 5merely allows emission of narrow X-ray beams. The X-ray beams are sufficiently narrow for entirely passing through the collimator3a. Consequently, the X-rays emitted from the X-ray tube3pass through the fully-opened collimator3awith no restriction to the spread. As noted above, the X-ray beams from some type of the X-ray tube3may pass through the fully-opened collimator3awithout reaching the collimator3a.

FIG. 6illustrates the visible light beams emitted from the visible light source9. In this drawing, illustration of the X-ray tube3is omitted for convenience of description.FIG. 6illustrates on the left thereof the visible light beams whose spread is restricted. The visible light beams pass through the fully-opened collimator3a. In this manner, the spread of the visible light beams is restricted although the collimator3ais fully opened. This case does not depend on types of the X-ray tube3provided in the X-ray apparatus. Consequently, when the X-ray tube3emitting narrow X-ray beams is adopted, the visible light beams passing through the fully-opened collimator3ais made wider than the X-ray beams. Such a phenomenon may occur.FIG. 6illustrates this state on the right thereof. Specifically,FIG. 6illustrates on the right thereof an irradiation condition of the visible light beams by solid lines, and an irradiation condition of X-ray beams by dotted lines.

Such a phenomenon does not necessarily occur when the collimator3ais fully opened.FIG. 7illustrates a relationship between the degree of opening of the collimator3aand the spread of the visible light beams and X-ray beams. In a graph, the spread of the visible light beams is represented by solid lines. When the degree of opening is zero, no visible light beam spreads. The degree of opening gradually increases from this condition. Accordingly, the spread of the visible light beams increases monotonously. When the degree of opening reaches 100%, the visible light beams has the maximum spread.

FIG. 7illustrates the spread of X-ray beams by dotted lines. When the degree of opening is zero, no X-ray beams spread. The degree of opening increases gradually from this condition. Accordingly, similar to the visible light beams, the spread of X-ray beams increases monotonously. On the other hand, when the degree of opening of the collimator3aincreases to a certain level, the spread of X-ray beams does not increases any more and becomes constant although the degree of opening of the collimator3aincreases. That is, the spread of X-ray beams does not change because it is impossible to increase the width of X-ray beams any more outputted from the X-ray tube3. The degree of opening of the collimator3agradually increases to reach the minimum degree of opening at which the spread of X-ray beams does not increase any more. The minimum degree of opening is referred to as a degree of saturation.

When the visible light beams do not conform to the X-ray beams, the following problem may arise. Specifically, when the visible light beams are emitted upon radiography by the operator, the spread of the visible light beams at this time does not represent the spread of X-ray beams. In other words, the operator cannot perform desired radiography. Such a phenomenon should be avoided in view of prevention of needless X-ray exposure.

<Suppression of Unconformity in Spread of Beams>

Consequently, in Embodiment 1, the collimator controller8is devised. Specifically, the collimator controller8controls the collimator activating mechanism7such that the degree of opening of the collimator3ais lower than the spread of the X-ray beams emitted from the X-ray tube3.

Specifically, the collimator controller8reads out information on the degree of opening stored in the storing unit28, the information representing the upper limit of the degree of opening of the collimator, and controls the degree of opening of the collimator3aso as not to exceed the upper limit of the degree of opening. The upper limit of the degree of opening is obtainable through geometric calculation from the spread of X-ray beams emitted from the X-ray tube3provided in the apparatus and a distance between a focus of the X-ray tube3and the shielding vanes3bof the collimator3a. The upper limit of the degree of opening conforms to the degree of opening of saturation. Specifically, the upper limit of the degree of opening is the minimum degree of opening at which the spread of X-ray beams is constant inFIG. 7. The upper limit of the degree of opening is denoted by a %. That is, the minimum degree corresponds to the upper limit of the degree of opening. The degree of opening of the collimator3agradually increases while the X-ray tube3emits X-ray beams to reach the minimum degree of opening at which the spread of X-ray beams does not increase any more. The storing unit28stores the upper limit of the degree of opening.

With Embodiment 1, the collimator controller8changes the degree of opening of the collimator3afrom zero to a % as the upper limit of the degree of opening. Consequently, in Embodiment 1, no phenomenon occurs that the visible light beams emitted from the collimator3aare wider than the X-ray beams.

The following describes actual operation of the collimator controller8. The collimator controller8receives the detection area set by the area setting unit11. The detection area represents a length of a film of the cassette4in the body axis direction A. Then the collimator controller8determines through geometric calculation a required level of the degree of opening of the collimator3ain the body axis direction A for reaching the X-rays on the entire detection area. At this time, the collimator controller8adopts a distance from the X-ray tube3to the cassette4. The distance is stored in the storing unit28. In this manner, the collimator controller8determines the level of the degree of opening of the collimator3anecessary for radiography using the cassette4designated by the operator. The determined degree of opening is referred to as a required degree of opening. For the required degree of opening, the minimum degree of opening necessary for emitting the entire detection area of the cassette4is adopted. This prevents the X-ray beams from passing beyond the end of the cassette4, leading to avoid needless exposure to the subject M. Here, the required degree of opening corresponds to the degree of opening of the collimator3anecessary for radiography to be conducted by the operator.

The collimator controller8compares the required degree of opening with the upper limit of the degree of opening. When the required degree of opening is lower than or equal to the upper limit of the degree of opening, the collimator controller8controls the collimator activating mechanism7so as to open the collimator3ato the required degree of opening. When the required degree of opening is higher than the upper limit of the degree of opening, the collimator controller8controls the collimator activating mechanism7so as to open the collimator3ato the upper limit of the degree of opening. Then the collimator controller8informs the alarm-activation controller14so as to activate an alarm. The alarm-activation controller14corresponds to the alarm-activation controller in the present invention.

The following describes an alarm function according to Embodiment 1. An alarm13is provided for notifying the operator by producing noises. This causes the operator to notice that radiography is to be conducted requiring X-rays having the maximum width or more that the X-ray tube3can output. Control of the alarm13is to be described. When the degree of opening of the collimator3ais controlled so as to exceed the upper limit of the degree of opening, the alarm-activation controller14controls the alarm13to activate an alarm. The alarm-activation controller14controls the alarm activation in accordance with information from the collimator controller8. Specifically, the collimator controller8sends to the alarm-activation controller14information that the required degree of opening exceeds the upper limit of the degree of opening. The alarm-activation controller14controls the alarm13to activate an alarm in accordance with the information. The alarm13corresponds to the alarm-activating device in the present invention.

A console26(seeFIG. 1) is provided for inputting operator's instructions such as start of emitting X-rays. Moreover, a main controller27(seeFIG. 1) is provided for performing an overall control of each controller. The main controller27has a CPU, and implements the X-ray tube controller6and each unit by executing various programs. The above units may each be divided into arithmetic units that perform their functions. The storing unit28(seeFIG. 1) stores all parameters with respect to control of the apparatus such as information on the upper limit of the degree of opening.

The following describes operation of the X-ray apparatus1. As illustrated inFIG. 8, for performing radiography to the subject M with the X-ray apparatus1, the subject M is firstly placed in the apparatus (placing step S1), and then a radiography mode is selected via the console26(selecting step S2). Thereafter, a degree of opening of the collimator3ais automatically controlled in accordance with the selected radiography mode (collimator controlling step S3). Then a light source in the X-ray tube3is turned on for applying visible light (visible light applying step S4). Finally, the X-ray tube3emits X-rays to perform radiography (X-ray emitting step S5). Each of these steps will be described in order.

Firstly, the subject M is placed in the X-ray apparatus1(seeFIG. 1). Then, the operator inputs a type of the cassette4to be used for radiography via the console26.

When the operator finished inputting via the console26, the collimator controller8controls the degree of opening of the collimator3a. Specifically, when the required degree of opening necessary for radiography using the designated cassette4is less than or equal to the upper limit of the degree of opening, the collimator controller8controls the degree of opening of the collimator3ato be the required degree of opening. When the required degree of opening exceeds the upper limit of the degree of opening, the collimator controller8controls the degree of opening of the collimator3ato be the upper limit of the degree of opening, and controls the alarm-activation controller14to activate an alarm. Operation of the collimator controller8at this time has already been described.

When the degree of opening of the collimator3ais controlled, the X-ray tube controller6turns on the visible light source9attached to the X-ray tube3. The visible light beams emitted from the visible light source are reflected on the mirror15included in the collimator3a. The visible light beams spread from the position as a mirror image of the X-ray tube3in a focus position by the mirror15as the center toward the collimator3a. Then, the collimator3arestricts the spread of the visible light, and the visible light is applied to a part of the subject M. The operator can confirm the invisible irradiation area of X-rays prior to X-ray application by visibly confirming the irradiation area of the visible light.

When the operator issues a command to start irradiation with X-rays via the console26, the X-ray tube controller6controls the visible light source in the X-ray tube3to be turned off. Simultaneously, the operator issues another command to irradiate the X-ray tube3with X-rays. At this time, the X-ray tube controller6controls the X-ray tube3under a condition of controlling the X-ray tube depending on a selected site of the subject. The X-rays from the X-ray tube3are collimated with the collimator3a, and then pass through the subject M into the cassette4. In this manner, radiography is completed.

As noted above, the embodiment of the present invention includes the X-ray tube3, the collimator3a, and the visible light source9. The collimator3ais provided for restricting the spread of X-rays. The visible light source9is provided for representing the area where X-rays are applied instead of the X-ray tube3by applying visible light passing through the collimator3a, the X-rays from the X-ray tube3being invisible. With some type of the X-ray tube3, the spread of the visible light beams through the collimator3aopening too largely may not possibly conform to the spread of X-rays. Such a situation may occur when the apparatus is provided with the X-ray tube3that emits narrow X-rays.

In order to avoid such a situation, the embodiment of the present invention sets the upper limit of the degree of opening as the upper limit of the degree of opening of the collimator3a. The degree of opening of the collimator3agradually increases while the X-rays are emitted to reach the minimum degree of opening at which the spread of X-rays does not increased any more. The minimum degree corresponds to the upper limit of the degree of opening. In the embodiment of the present invention, the irradiation area of the visible light beams always conforms to the irradiation area by the X-ray tube3. Accordingly, there is no need to perform further radiography. This achieves the X-ray apparatus that allows suppression in needless exposure of X-rays to the subject M.

As noted above, the alarm is activated when the degree of opening of the collimator3ais controlled so as to exceed the upper limit of the degree of opening. This obtains the apparatus with a higher degree of safety, ensuring to suppress needless exposure.

Moreover, the alarm is activated when the degree of opening of the collimator required upon radiography by the operator exceeds the upper limit of the degree of opening. This obtains accurate notification of the operator.

The present invention is not limited to the above, but may be modified as under.

(1) In the above embodiment, the type of the cassette4is identified, and the degree of opening of the collimator3ais controlled in accordance with the type. However, the present invention is not limited to this. Specifically, the operator may control the degree of opening of the collimator3avia the console26. At this time, the degree of opening of the collimator3adesignated by the operator is adopted as a designated degree of opening. In this modification, the collimator controller8operates using the designated degree of opening instead of the required degree of opening. That is, the collimator controller8compares the designated degree of opening with the upper limit of the degree of opening. When the designated degree of opening is lower than or equal to the upper limit of the degree of opening, the collimator controller8controls the collimator activating mechanism7to open the collimator3ato the designated degree of opening. When the designated degree of opening is higher than the degree of opening, the collimator controller8controls the collimator activating mechanism7to open the collimator3ato the upper limit of the degree of opening. Then, the collimator controller8controls the alarm-activation controller14to activate an alarm. Such a construction achieves more flexible control to provide the X-ray apparatus that allows radiography easily.

(2) In the embodiment, the storing unit28stores one type of upper limit of the degree of opening. However, the present invention is not limited to this. Specifically, the storing unit28may store a plurality of upper limit of the degrees of opening in association with types of X-ray tube3. In the construction, the X-ray tube controller6holds type information representing the types of X-ray tube3. The X-ray tube controller6outputs the type information to the collimator controller8. The collimator controller8reads the upper limit of the degree of opening, corresponding to the obtained type information, from the storing unit28. Here, the collimator controller8performs no control to the collimator3aprior to reading the upper limit of the degree of opening from the storing unit28. That is, it is sufficient to obtain the type information as above once when the X-ray apparatus1is set in an examination room. After the type information is given and received once, the collimator controller8can read out the upper limit of the degree of opening, corresponding to the type of X-ray tube3, from the storing unit28. As in this modification, the collimator controller8reads out the upper limit of the degree of opening corresponding to the types of X-ray tube3. This achieves the apparatus with more flexibility. That is, the collimator is surely controlled regardless of types of the X-ray tube3provided in the apparatus in accordance with the upper limit of the degree corresponding to the type.

(3) The embodiment mentioned above describes control of the degree of opening of the collimator3ain the body axis direction A of the cassette4. Alternatively, the collimator3amay be controlled similarly in the body side direction S. In this construction, the collimator controller8reads out the upper limit of the degree of opening in the body side direction S from the storing unit28. Then the area setting unit11determines a detection area in the body side direction S through input by the operator. Thereafter, the collimator controller8compares a required degree of opening determined from the detection area with the upper limit of the degree of opening, and operates similarly to the above.

(4) The foregoing embodiments discuss an apparatus for medical use. The present invention is applicable also to an apparatus for industrial use or for the nuclear field.

(5) X-rays described in the foregoing embodiments are an example of radiation in the present invention. Therefore, the present invention may be adapted also to radiation other than X-rays.

INDUSTRIAL APPLICABILITY

As noted above, the radiographic apparatus of the present invention is suitable for the medical field.

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