`
`
`3,906,233
`
`
`
`
`
`[451 Sept. 16, 1975
`Vogel
`
`[191
`
`
`
`[111
`
`[54] SYSTEM AND METHOD FOR
`
`
`
`
`
`ADNIINISTERING RADIATION
`
`
`lnventor: Thomas M. Vogel, Sunnyvale, Calif.
`
`
`
`
`
`[73] Assignee: Varian Associates, Palo Alto, Calif.
`
`
`
`
`
`
`Oct. 12, 1973
`Filed:
`
`
`
`
`
`[21] Appl. No.: 406,080
`
`
`
`
`
`[75]
`
`[22]
`
`
`
`
`
`[52] U.S. Cl................................ .. 250/355; 250/354
`
`
`
`
`
`[51]
`Int. Cl. ............................................ .. G0lt 1/17
`
`
`
`
`
`
`[58] Field of Search ............. .. 250/354, 355, 445 T
`
`
`
`
`
`
`
`
`[56]
`
`
`
`3,334,231
`
`3,499,152
`3,675,019
`
`
`
`
`References Cited
`
`
`UNITED STATES PATENTS
`
`
`
`8/1967
`Bernstein .......................... .. 250/355
`
`
`
`3/1970 Hetenhouser . . . . . .
`. . . . .. 250/354 X
`
`
`
`
`Hill et al. ...................... .. 250/355 X
`7/1972
`
`
`
`
`
`
`
`
`
`
`
`
`
`Primary Examiner—Archie R. Borchelt
`
`
`
`Attorney, Agent, or Firm—Stanley Z. Cole; Leon F.
`
`
`
`
`
`Herbert; Edward J. Radlo
`
`
`
`
`[57]
`
`ABSTRACT
`
`
`
`A system and method for metering the quantity of ra-
`
`
`
`
`
`
`
`
`diation administered a subject by a source of radiation
`
`
`
`
`
`movable along a path relative to the subject. The sys-
`
`
`
`
`
`
`
`
`tem cumulatively counts the amount of radiation di-
`
`
`
`
`
`
`
`rected toward the subject during each of a succession
`
`
`
`
`
`
`
`of increments of motion of the source. When a prede-
`
`
`
`
`
`
`
`termined amount of radiation is delivered during an
`
`
`
`
`
`
`increment,
`the source is disabled until
`the source
`
`
`
`
`
`
`
`passes into the next increment of displacement. The
`
`
`
`
`
`
`
`count of radiation is restarted at the instant the source
`
`
`
`
`
`
`
`is disabled, to accumulate accurately any added spuri-
`
`
`
`
`
`
`
`ous radiation dosage which may occur and to include
`
`
`
`
`
`
`
`
`that dosage in the count of the permitted amount for
`
`
`
`
`
`
`
`
`the next succeeding increment of motion. Several in-
`
`
`
`
`
`
`terlocks for disabling the system in response to various
`
`
`
`
`
`
`
`malfunctions are included. Means for controlling the
`
`
`
`
`
`
`
`speed of movement of the source and/or the dose rate
`
`
`
`
`
`
`
`
`of the source are also included.
`
`
`
`
`
`
`
`33 Claims, 4 Drawing Figures
`
`
`
`
`
`
`60
`
`
`40
`
`
`COUNTER -COMPARATOR
`
`
`
`
`
`Z0
`
`
`
`
`
`30
`
`
`I
`
`
`I
`
`
`
`
`
`
`To
`
`DISPLAY
`
`
`
`
`OFF STATECOUNT
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`.
`
`70
`
`II
`T0
`
`VTRAD.
`
`SOURCES
`
`
`
`
`
`
`SWITCH
`PRESET
`
`
` 90
`
`
`
`
`
`DECODER
`
`50
`
`
`
`
`
`PROGRAMABLE
`AMPLIFIER
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
` CD
`‘IIIIIII
`
`
`
`
`
`
`
`
`
`ONI
`'
`OFF
`SWITCH
`
`I on
`
`
`SENSE
`
`TRAVERSAL
`
`
`
`I10
`
`
`
`« COUNTER
`1
`
`
`
`
`705‘?
`
`POWER
`
`‘
`
`I30
`
`
`
`
`‘ME
`
`TIMER
`
`
`
`
`
`
`POSITION
`PRES“
`
`00
`
`
`2
`
`
`
`
`
`COMPARATOR
`
`210
`
`
`
`
`
`SENSE
`
`POSHWN
`
`80
`
`
`
`214
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Page 1 of 14
`
`Elekta Exhibit 1034
`
`Page 1 of 14
`
`Elekta Exhibit 1034
`
`
`
`a"AIEN1tUSEP!639?5
`
`3,905,233
`
`
`
`SHEET 1
`
`
`
`£3
`
`
`
`
`
`
`
`
`
`
`
`SWITCH
`PRESET
`
`COUNTER ICOMPARATOR
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`N
`
`
`
`
`
`
`
`T
`D
`
`
`
`Y
`
`
`
`
`
`
`
`
`
`IIO
`
`
`
`
`
`orrsmecouwr
`
`
`
`COUNTER
`
`
`
`I
`
`H o~
`
`
`
`
`
`70
`
`I
`,o—-(T0
`
`
`
`
`
`
`
`
`
`so
`
`‘am
`
`90
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`PROGRAMABLE
`
`
`AMPLIFIER
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`on
`swncn
`
`
`
`
`
`
`
`
`
`
`fofi
`
`
`
`
`I50
`
`TIMER
`
`
`
`
`T'“E
`
`
`
`
`
`
`SENSE
`TRAVERSAL
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`FlG.l
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Page 2 of 14
`
`Page 2 of 14
`
`
`
`;3ATENTE[] SEP 1 61975
`
`2|
`<-4+
`
`30
`
`1
`SN7420
`
`22
`
`so
`
`FIG. 2
`
`. Page 3 of 14
`
`VARIABLE
`SPEED
`MOTOR
`
`Page 3 of 14
`
`
`
`
`PATENTEDSEPISIQYS
`
`
`
`
`
`sum 3 or 4
`
`
`
`
`90
`
`2”)
`
`A
`
`a
`
`95W,
`Q~
`2
`
`=1
`
`
`‘‘5V mum
`Iiiiiifii
`
`|||||||
`84
`8’
`:55 aaaaa
`
`
`
`
`
`
`
`as
`
`3°
`
`
`
`
`
`
`5 =35
`
`*3
`K
`'
`'
`L Z‘
`§?:_}__
`S>>—;‘l_“—+5V
`
`l =g==-..-.-:
`
`82/
`U3 ‘I
`tuj :2 I “:“"<,
`31
`Hgfi
`85”
`2”
`+5‘, llll
`
`
`
`FlG.3
`
`
`
`Page 4 of 14
`
`Page 4 of 14
`
`
`
`
`PATENTEDSEP : 5 1975
`
`
`
`3, gQ5,233
`
`
`
`wmuM4..,.- "
`
`
`
`
`15
`
`RADIA no
`T N
`
`
`
`SENSOR
`
`
`470
`
`DOSE RATE
`
`CONTROL
`
`
`
`
`
`450
`DECODER
`
`
`
`
`
`540
`
`
`COUNTER
`
`
`
`
`
`3,50
`
`
`COMPARATOR
`
`
`
`||l'l‘I“!luN‘||
`
`COMPARATOR
`
`
`
`
`
`
`
`
`PRESET
`
`
`
`SWITCH
`
`
`
`
`
`
`
`
`
`
`
`COUNTER
`
`
`
`
`
`320
`
`
`
`
`330
`
`
`DIVIDER
`
`20
`
`
`' DIVIDER
`
`
`
`’
`
`
`
`
`
`
`
`
`
`
`
`
`lo-«Io
`
`TRADI
`sou
`
`swncn
`
`
`
`ON
`
`
`
`OFF
`
`
`
`
`IIO
`
`« COUNTER I
`
`
`
`
`
`
`
`_
`
`.
`
`TV]
`
`
`
`T0
`POWER
`
`
`
`’
`
`_
`
`30
`
`I
`
`
`
`“ME O
`
`
`
`
`
`
`
`
`SENSE »
`
`TRAVERSAL
`
`90
`
`
`
`.
`
`
`
`
`
`DECODER
`
`
`.50
`
`
`COMPARATOR
`
`
`
`A
`
`
`
`
`SENSE
`POSITION
`
`
`so A
`
`
`
`2l4
`
`
`
`210
`
`I
`E.
`
`
`200
`
`
`POSITION
`
`RESET
`
`
`To
`POWER
`
`
`
`, Page 5 of 14
`
`F|G.4
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`Page 5 of 14
`
`
`
`1
`
`SYSTEM AND METHOD FOR ADMINISTERING
`
`
`
`
`
`RADIATION
`
`
`3,906,233
`
`
`
`2
`
`l0
`
`20
`
`
`
`25
`
`
`
`30
`
`35
`
`
`
`
`
`
`BACKGROUND OF THE INVENTION"
`.
`,
`1. Field of the Invention
`
`
`
`
`
`
`This invention relates to the field of apparatus and
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`method for controlledly irradiating a subject. More
`
`
`
`
`
`particularly, the invention pertains to administering a
`
`
`
`
`
`
`predetermined maximum dose of radiation during each
`of several increments of relative motion of the radia-
`
`
`
`
`
`
`
`tion source relative to the subject.
`
`
`
`
`
`,
`.
`2. Description of Prior Art
`
`
`
`
`
`
`It is known to irradiate a subject by relatively moving
`
`
`
`
`
`
`a source of radiation about the subject along a path. A
`
`
`
`
`
`
`
`
`15
`
`
`
`
`
`
`
`benefit of this method of delivering radiation is that the
`radiation may be focused upon a “target” area which
`
`
`
`
`
`
`
`will be constantly irradiated during the movement of
`
`
`
`
`
`
`
`the source. The surroundingareas, however, receive
`
`
`
`
`
`
`only a portion of the radiation dosage which is deliv-
`
`
`
`
`
`
`
`
`ered to the target. This technique has utility in thera-
`
`
`
`
`
`
`
`
`
`peutic applications where it is generally desirable to
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`apply a high dosage of radiation to a target organ or
`part of the body, and where it is desirable as well to re-
`
`
`
`
`
`
`
`
`strict as much as possible the radiation delivered to sur-
`
`
`
`
`
`
`
`rounding tissues.
`-
`
`
`
`The normal way ofadministering radiation according
`
`
`
`
`
`
`to the above limitations is to position the patient or sub-
`
`
`
`
`
`
`
`
`ject on a stationary object, while moving the radiation
`
`
`
`
`
`
`
`source along a circular path surrounding the target re-
`
`
`
`
`
`
`
`gion. The source of radiation is preset to emit the radia-
`
`
`
`
`
`
`
`
`tion at a known rate. The length of the path or are tra-
`
`
`
`
`
`
`
`
`
`versed by the source is predetermined, as is the velocity
`
`
`
`
`
`
`with which the source moves. These variables together
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`determine the dosage ultimately administered to the
`target area.
`
`
`Several difficulties, however, are commonly experi-
`
`
`
`
`
`
`enced in the execution of this technique. First, it is
`
`
`
`
`
`
`
`
`
`often difficult to govern with the desired accuracy‘ the
`
`
`
`
`
`
`
`
`velocity of the source. Radiation sources are commonly
`
`
`
`
`
`
`
`40
`very massive components, and apparatus to govern
`
`
`
`
`
`
`
`their motion generally involves the use of counter-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`weights, which counterweights may not be perfectly
`balanced, thus imparting variations in speed of the en-
`
`
`
`
`
`
`
`tire combination. Other factors, such as bearing mal-
`
`
`
`
`
`
`
`function may also exert anundesirable influence.
`
`
`
`
`
`
`Moreover, it is not always possible to regulate the
`
`
`
`
`
`
`
`
`rate at which the source emits radiation with the de- .
`
`
`
`
`
`
`
`
`
`
`sired precision. Such factors as line voltage variations,
`
`
`
`
`
`
`
`which are difficult to detect and eliminate, can substan-
`
`
`
`
`
`
`
`
`tially affect the output of the source.
`
`
`
`
`
`
`It sometimes occurs in the operation of such radia- ~
`
`
`
`
`
`
`
`tion systems that spurious radiation may be emitted by
`
`
`
`
`
`
`
`the source. The dangers and complications of such
`
`
`
`
`
`
`
`
`emissions are clear.
`
`
`
`Furthermore, certain other basic malfunctions of the
`
`
`
`
`
`
`system may arise which render its operation ineffective
`
`
`
`
`
`
`
`or deleterious. For example, the velocity of the source
`
`
`
`
`
`
`
`
`may be so low as to severely overexpose a portion of
`
`
`
`
`
`
`60
`the target area to radiation. Also,‘ the output of -the
`
`
`
`
`
`
`
`
`
`source may for any of a -number of reasonsdrop -below‘ .
`
`
`
`
`
`
`an effective value, notwithstanding that the sourcemay;
`
`
`
`
`
`
`
`remain operable to some degree.
`
`
`
`
`Consequently, it is a major object of this invention to
`
`
`
`
`
`
`provide a method and system< for controlling -‘the
`
`
`
`
`
`
`
`amount of radiation incident onto a target, while com-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`pensating for the unwanted ‘variations and irregularities
`noted above.
`
`
`
`
`
`
`
`
`
`It
`is another object of the invention to provide a
`
`
`
`
`
`
`
`
`
`method and system having sufficient flexibility to com-
`
`
`
`
`
`
`
`pensate for variations in radiation which tend to result
`
`
`
`
`
`
`
`from imprecise control of source velocity and of inten-
`
`
`
`
`
`
`
`sity of radiation from the source.
`
`
`
`
`
`
`It is a further object to provide a system and method
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`in which the path of motion of the source is divided into
`a plurality of increments, and the radiation emanating
`
`
`
`
`
`
`
`from the source is regulated to a predetermined maxi-
`
`
`
`
`
`
`mum value during the traversal by the source of each
`
`
`
`
`
`
`
`
`of the increments of motion.
`
`
`
`
`It is a further object of this invention to provide a sys-
`
`
`
`
`
`
`
`tem and method according to the above description in
`
`
`
`
`
`
`
`which the existence of any spurious radiation from the
`
`
`
`
`
`
`
`
`source is taken into account in establishing the afore-
`
`
`
`
`
`
`
`mentioned maximum dosage for each increment of mo-
`
`
`
`
`
`
`tion.
`
`It is an additional object of this invention to provide
`
`
`
`
`
`
`
`
`a method and system whereby, notwithstanding the po-
`
`
`
`
`
`
`
`tential irregularity of radiation resulting from the nonu-
`
`
`
`
`
`
`
`niformity of source velocity and radiation output, the
`
`
`
`
`
`
`
`radiation is administered to the subject in a substan-
`
`
`
`
`
`tially uniform fashion throughout the movement of the
`
`
`
`
`
`
`
`‘source along its predetermined path.
`
`
`
`
`
`
`
`
`
`
`
`It is another object to provide a system and apparatus
`
`
`
`
`
`
`for providing an indication when the dosage delivered
`during any increment of motion of the source falls
`
`
`
`
`
`
`
`
`below a predetermined level.
`
`
`
`It is still another object to provide a system and appa-
`
`
`
`
`
`
`
`
`ratus for producing an indication when the speed at
`
`
`
`
`
`
`
`which the source traverses any increment of motion
`
`
`
`
`
`
`
`falls below a predetermined value.
`
`
`
`
`It is a further object to provide a system and appara-
`
`
`
`
`
`
`
`tus for providing an indication if the dosages delivered
`
`
`
`
`
`
`
`during any increment of motion is significantly greater
`
`
`
`
`
`
`then the desired dosage.
`
`
`
`
`It is a another object to provide a system and appara-
`
`
`
`
`
`
`
`tus for providing an indication of an unacceptable
`
`
`
`
`
`
`
`
`amount of radiation during the time the source is in-
`
`
`
`
`
`
`
`
`tended to be inactivated.
`
`
`It is an additional object to provide a system and ap-
`
`
`
`
`
`
`
`
`
`
`
`
`
`paratus which includes flexibility in selecting different
`speeds of movement of the source and/or different dose
`
`
`
`
`
`
`
`rates of the source.
`
`
`
`SUMMARY OF THE INVENTION
`
`
`
`This invention relates to a system for metering the
`
`
`
`
`
`
`
`
`amount of radiation which is delivered to a target area
`
`
`
`
`
`
`of a subject by means of a radiation source which is
`
`
`
`
`
`
`
`
`movable along a particular path with respect to the sub-
`
`
`
`
`
`
`
`
`ject. ln the preferred embodiment of this invention, the
`
`
`
`
`
`
`
`
`path of motion of the radiation source is along a circu-
`
`
`
`
`
`
`
`lar or arcuate course. The system incorporates drive
`
`
`
`
`
`
`
`
`means for propelling the source along its path at a con-
`
`
`
`
`
`
`
`trollable speed. Also included is a sensor for generating
`
`
`
`
`
`
`
`a signal indicative of the position of the source along
`
`
`
`
`
`
`
`
`
`
`the path. Additionally, the apparatus included within
`
`
`
`
`
`
`
`the system comprises a counter which emits a signal
`
`
`
`
`
`
`
`whenever the position of the source changes by a pre-
`
`
`
`
`
`
`
`determined amount, this amount being 2° in one pre-
`
`
`
`
`
`
`
`ferred embodiment.
`'
`
`
`
`The radiation source is provided with an ionization
`
`
`
`
`
`
`
`chamber in the path of emitted radiation, along with
`
`
`
`
`
`
`
`‘ associated circuitry to render the chamber an accurate
`65
`
`
`
`
`
`
`
`sensor’ of the amount of radiation passing from the
`
`
`
`
`
`
`
`source toward the subject. The circuitry generates a
`
`
`
`
`
`
`
`signal corresponding to the amount of sensed radiation.
`
`
`
`
`
`
`
`45
`
`
`
`50
`
`S5
`
`
`
`
`
`Page 6 of 14
`
`Page 6 of 14
`
`
`
`3,906,233
`
`3
`
`
`A counter cumulatively records the sensed radiation.
`
`
`
`
`
`
`
`Means is provided for independently presetting a signal
`
`
`
`
`
`
`
`
`
`
`
`corresponding to a particular given maximum radiation
`which is desired to be permitted during the traversal by
`
`
`
`
`
`
`the source of any one increment of motion.
`'
`
`
`
`
`
`
`
`This signal, and the signal representing the amount of
`
`
`
`
`
`
`
`
`radiation sensed by the ionization chamber,‘ are
`
`
`
`
`
`
`
`brought together in a comparator. The comparator is
`
`
`
`
`
`
`
`
`
`
`
`
`
`designed to emit a stop signal whenever the total
`amount of radiation accumulating during any given in-
`
`
`
`
`
`
`crement equals or exceeds the value of the quantity of
`
`
`
`
`
`
`
`radiation which is independently presented as indicated
`
`
`
`
`
`above. The stop signal V turns off the‘ source. The
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`counter of radiation, which is connected to the radia-
`
`
`
`
`
`
`
`
`tion sensor, is reset by the occurrence of the stop sig-
`nal. Thus, the counter reinitiates the count every time
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`the source completes the generation of its predeter-
`I
`mined maximum_ radiation for one_ increment.
`
`
`
`
`
`
`
`The disablement of the source continues until it has
`
`
`
`
`
`
`
`
`
`
`
`
`
`completed’ its traversal through that particular incre-
`ment of motion for which the radiation had been
`
`
`
`
`
`
`
`
`counted, and during which the predetermined amount
`
`
`
`
`
`
`
`of radiation had been delivered.
`
`
`
`
`
`The inherent consequence of this configuration of
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`apparatus and circuitry is, that, for any given increment
`of motion, there is established a predetermined maxi-
`
`
`
`
`
`
`mum value of radiation which substantially cannot be
`
`
`
`
`
`
`exceeded during any of the increments of motion.
`
`
`
`
`
`
`When the source begins to traverse a subsequent in-
`
`
`
`
`
`crement of motion, it is reactuated to begin delivering
`
`
`
`
`
`radiation toward the subject once more.
`
`
`
`
`
`
`Note that, as mentioned above, the counter itself is
`
`
`
`
`
`
`
`
`reset to zero upon the issuance of the stop signal from
`
`
`
`
`
`
`
`
`
`the comparator which effects the disablement of the
`
`
`
`
`
`
`
`source when the radiation for the particular increment
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`being traversed equals or exceeds the predetermined
`' value which is preset. The reason for thisis to enable
`
`
`
`
`
`
`
`
`
`the counter to correctly record the incidence of any
`
`
`
`
`
`
`
`
`spurious or accidental radiation which may be emitted
`
`
`
`
`
`
`by the source. The occurrence of any such radiation is
`
`
`
`
`
`
`
`
`thus taken into account in governing the amount of ra-
`
`
`
`
`
`
`
`diation administered in the succeeding increment of
`
`
`
`
`
`motion. Thus, this system possesses the flexibility of
`
`
`
`
`
`
`
`
`compensating for inaccuracies in the control of the
`
`
`
`
`
`
`
`source itself.
`
`
`The system, as can be seen, measures the amount of
`
`
`
`
`
`
`
`radiation delivered to the subject during each and
`
`
`
`
`
`
`
`
`every increment of motion and limits that amount to a
`
`
`
`
`
`
`
`prespecified maximum. The total amount of radiation
`
`
`
`
`
`
`delivered can thus be limited very precisely. Addition-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`ally, the system maintains uniformity in the delivery of
`radiation from various directions as the source moves
`
`
`
`
`
`
`
`along its path of motion.
`-
`
`
`
`
`Several interlocks are built into the system of this in-
`
`
`
`
`
`
`
`
`vention in order to provide an indication when a basic
`
`
`
`
`
`
`malfunction occurs, and to, where warranted, disable
`
`
`
`
`
`
`the radiation delivery apparatus. For example, a special
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`counter is provided which is actuated only during those
`periods in which the radiation source has been theoreti-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`cally disabled by the stop signal from the comparator.
`This counter is programmed such that it emits a signal
`
`
`
`
`
`
`
`when a predetermined amount of radiation escapes
`
`
`
`
`
`from the radiation source during a time when it is sup-
`
`
`
`
`
`
`
`
`
`posedly turned off. If such a condition occurs, a fault
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`signal is generated, which disables the entire system by
`cutting off the power supply.
`’
`
`
`
`
`
`
`
`5
`
`10
`
`15
`
`20
`
`25
`
`
`
`30
`
`
`
`
`
`40
`
`
`
`45
`
`
`50
`
`55
`
`
`60
`
`
`65
`
`
`
`Page 7 of 14
`
`
`
`4
`
`
`
`
`
`
`A second interlock senses the time required for the
`
`
`
`
`
`
`
`
`
`source to traverse a particular increment of motion. If
`
`
`
`
`
`the time required for such traversal is excessive, a simi-
`
`
`
`
`
`
`
`
`lar fault signal is generated.
`
`
`
`
`Two other types of interlocks generate a fault signal
`
`
`
`
`
`
`
`if it appears that the radiation administered during an
`
`
`
`
`
`
`
`increment is less or morethan the desired amount.
`
`
`
`
`
`
`Note that, in the utilization of this system, the output
`
`
`
`
`
`
`
`
`dose rate of the radiation source is normally at a rate
`
`
`
`
`
`
`
`which, if the source were allowed to traverse its entire
`
`
`
`
`
`
`
`
`course or path in the activated state, would result in an
`
`
`
`
`
`
`
`overdose of radiation. Since the system of this inven-
`
`
`
`
`
`
`
`tion has the flexibility of interrupting the dosage of ra-
`
`
`
`
`
`
`
`diation whenever the dosage given in any one incre-
`
`
`
`
`
`
`
`
`ment is sufficient, it is possible to assure in this way that
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`the dosage given over the entire path will cumulatively
`be sufficient’. At the same time the system permits se-
`
`
`
`
`
`
`
`
`
`lection of traversal speed and/or dose rate of the source
`
`
`
`
`
`
`
`
`so that the desired dose per increment can be adminis-
`
`
`
`
`
`
`
`
`
`tered over almost the entire path of each increment.
`
`
`
`
`
`
`
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`
`
`
`FIG. 1 is a‘ block schematic diagram illustrating the
`
`
`
`
`
`
`
`components of the system of this invention;
`
`
`
`
`
`FIG. 2 is a portion of the schematic diagram illustrat-
`
`
`
`
`
`
`
`
`
`
`
`
`
`ing in greater detail the components of the system of
`this invention;
`
`
`FIG. 3 is another portion of the schematic diagram
`
`
`
`
`
`
`
`
`
`
`
`
`
`showing in detailed fashion the elements of the inven-
`'
`tion; and
`
`
`
`FIG. 4 is a block diagram disclosing a further em-
`
`
`
`
`
`
`bodiment of the invention.
`
`
`
`
`
`DESCRIPTION _OF THE PREFERRED
`EMBODIMENT
`
`FIG. 1 enables a concise understanding of the system
`
`
`
`
`
`
`of this invention. A conventional radiation source 5 is
`
`
`
`
`
`
`mounted on the arm of a U-shaped member 6 and de-
`
`
`
`
`
`
`livers X-rays along an axis 7 toward a subject or patient
`
`
`
`
`
`
`
`8 positioned on a couch 9. The U-shaped support in-
`
`
`
`
`
`
`cluding source 5 is mounted on a housing 10 for rota-
`
`
`
`
`
`
`
`tion about an axis 11. Drive means such as a variable
`
`
`
`
`
`
`
`
`speed motor 12 and gears 13 and 14 drive the source
`
`
`
`
`
`
`
`
`
`for rotation about axis 11. The X-ray beam emerging
`
`
`
`
`
`
`
`
`
`from the source passes through a convention ionization
`
`
`
`
`
`
`
`chamber or radiation sensor 15. Integrator 20 emits a
`
`
`
`
`
`
`
`
`
`
`
`
`digital signal which is proportional to the quantity of
`radiation delivered by the source 5. Integrator 20 re-
`
`
`
`
`
`
`ceives its input from the ionization chamber (radiation
`
`
`
`
`
`
`
`sensor) 15 located in the path of radiation from the
`
`
`
`
`
`
`
`
`source 5. The ionization chamber. 15 contains a gas
`
`
`
`
`
`
`such as air which ionizes in the presence of radiation
`
`
`
`
`
`
`
`incident thereon such that electrodes positioned in the
`
`
`
`
`
`
`
`chamber and connected together through a load de-
`
`
`
`
`
`
`
`velop a current flowing between them which is a func-
`
`
`
`
`
`
`
`tion of the radiation incident upon the chamber. The
`
`
`
`
`
`
`
`
`current from said electrodes is delivered to integrator
`
`
`
`
`
`
`20. The particular structure of integrator 20 and ioniza-
`
`
`
`
`
`
`
`tion chamber 15 does not constitute a part of this in-
`
`
`
`
`
`
`
`
`vention, and hence is not described in greater detail.
`
`
`
`
`
`
`
`The signal from integrator‘ 20 passes to divider 30.
`
`
`
`
`
`
`
`Integrator 20 emits a signal which indicates units of
`
`
`
`
`
`
`
`
`decirads in a preferred embodiment. As will be ex-
`
`
`
`
`
`
`plainedhereinbelow, the motion of the source will be
`
`
`
`
`
`
`
`calibrated in two degree increments in a preferred em-
`
`
`
`
`
`bodiment. Therefore, in order toderive a signal from
`
`
`
`
`
`
`divider 30 which is indicative of the radiation delivered
`
`
`
`
`
`
`
`Page 7 of 14
`
`
`
`5
`
`per degree of arc, divider 30 produces an output signal
`
`
`
`
`
`
`
`at one output which is divided by two. Obviously, if mo-
`
`
`
`
`
`
`
`tion of the source 5 is calibrated in one degree incre-
`
`
`
`
`
`
`
`ments, the output signal would not be divided by two.
`
`
`
`
`
`
`
`
`The signal which is divided by two is input to counter
`
`
`
`
`
`
`
`40, which will be described below.
`
`
`
`
`
`
`A second output of divider 30 produces a signal
`
`
`
`
`
`
`
`
`which is divided by a factor of 10, and presented as an
`
`
`
`
`
`
`input to a display apparatus associated with the main
`
`
`
`
`
`
`
`console (not shown) within view of the operator of the
`
`
`
`
`
`
`
`
`system, in order to present an instantaneous viewing of
`
`
`
`
`
`the quantity of radiation having been administered in
`
`
`
`
`
`
`rads.
`
`The signal corresponding to the amount of radiation
`
`
`
`
`
`
`accumulated (divided by two) is input to counter 40.
`
`
`
`
`
`
`
`Counter 40 stores this integrated amount of radiation
`
`
`
`
`
`
`as it accumulates.
`
`
`Presetting switch 50 is adapted to generate a radia-
`
`
`
`
`
`
`tion limit signal which is a function of a quantity of ra-
`
`
`
`
`
`
`diation which may be manually preset into presetting
`
`
`
`
`
`
`
`switch 50. The format of the radiation limit signal
`
`
`
`
`
`
`
`
`
`thereby generated corresponds to the format in which
`
`
`
`
`
`
`the accumulated radiation signal is stored in counter
`
`
`
`
`
`
`40; that is, decirads desired per one degree increment.
`
`
`
`
`
`
`
`
`The accumulated radiation signal and the radiation
`
`
`
`
`
`
`
`limit signal are each directed as inputs to comparator
`
`
`
`
`
`
`
`60. Comparator 60 produces an output signal when-
`
`
`
`
`
`
`ever the stored radiation signal in counter 40 equals or
`
`
`
`
`
`
`
`exceeds the radiation limit signal input from presetting
`
`
`
`
`
`
`
`
`switch 50.
`
`
`This stop signal is input to switch 70. Switch 70 is
`
`
`
`
`
`
`
`connected to the radiation source in such a way that it
`
`
`
`
`
`
`
`is responsive to the occurrence of the stop signal from
`
`
`
`
`
`
`
`
`comparator 60 to disable the source to prevent it from
`
`
`
`
`
`
`emitting any further radiation.
`
`
`
`
`The radiation source 5, together with the other appa-
`
`
`
`
`
`
`
`
`ratus, such as counterweights, which are movable
`
`
`
`
`
`
`
`therewith, form the U-shaped member 6 and are com-
`
`
`
`
`
`
`
`
`monly known as the gantry of the radiation system. For
`
`
`
`
`
`
`
`
`example, see U.S. Pat. No. 3,720,817. The U-shaped
`
`
`
`
`
`
`
`
`member of gantry 6 is provided with position sensor 80,
`
`
`
`
`
`
`
`which is connected thereto, and which produces a sig-
`
`
`
`
`
`
`
`nal which is a function of the rotational position of the
`
`
`
`
`
`
`
`gantry. This position signal is directed as an input to
`
`
`
`
`
`
`
`traversal sensor 90. Traversal sensor 90 produces an
`
`
`
`
`
`
`
`
`output pulse whenever the gantry rotates through a two
`
`
`
`
`
`
`
`
`degree increment. The signal output from traversal sen-
`
`
`
`
`
`
`
`
`sor 90 represents an enabling signal directed to switch
`
`
`
`
`
`
`70. The occurrence of this enabling signal resets switch
`
`
`
`
`
`
`
`
`70 such that the radiation source is re-enabled to begin
`
`
`
`
`
`
`
`
`once more to emit radiation.
`
`
`
`
`Comparator 60 is connected to counter 40 such that
`
`
`
`
`
`the occurrence of the stop signal produced by the com-
`
`
`
`
`
`
`
`
`parator, in addition to disabling the radiation source,
`
`
`
`
`
`
`
`also resets counter 40 to zero to begin cumulatively
`
`
`
`
`
`
`counting the radiation which is delivered by the source
`
`
`
`
`
`
`
`toward the subject.
`
`
`
`It is thus evident that this system limits the amount of
`60
`
`
`
`
`
`
`
`
`
`radiation delivered by the source toward the subject
`
`
`
`
`
`
`
`
`during each two degree increment of rotation of the
`
`
`
`
`
`
`
`
`gantry to that quantity of radiation which is preset into
`
`
`
`
`
`
`
`presetting switch 50. When that quantity is reached
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`during any two degree increment, comparator 60 actu-
`ates switch 70 to turn off the radiation source. The ra-
`
`
`
`
`
`
`
`
`diation source remains in the off state until it is turned
`
`
`
`
`
`
`
`
`
`on again by the passage of the gantry into a subsequent
`
`
`
`
`
`
`
`
`
`25
`
`
`
`30
`
`
`
`35
`
`40
`
`
`
`
`
`45
`
`
`
`50
`
`
`
`55
`
`
`
`
`
`Page 8 of 14
`
`3,906,233
`
`5
`
`10
`
`15
`
`20
`
`
`
`6
`
`
`
`
`
`
`
`two degree increment of rotation, at which point the
`
`
`
`
`
`
`
`source is reactuated.
`
`
`As noted above, the occurrence of the stop signal
`
`
`
`
`
`
`
`
`from comparator 60 resets counter 40. This can occur
`
`
`
`
`
`
`
`
`before the end of the traversal of the gantry over a par-
`
`
`
`
`
`
`
`
`
`ticular two degree increment. Thus, counter 40 can cu-
`
`
`
`
`
`
`
`
`mulatively count radiation which may occur after the
`
`
`
`
`
`
`
`
`radiation source is supposedly turned to the off state by
`
`
`
`
`
`
`
`the stop signal. The reason for this is that integrator 20
`
`
`
`
`
`
`
`
`
`does not produce a signal corresponding to the amount
`
`
`
`
`
`
`
`of radiation instantaneously with the occurrence of that
`
`
`
`
`
`
`
`radiation. Thus, even though the source may be turned
`
`
`
`
`
`
`
`
`off, there will be registered at the output of integrator
`
`
`
`
`
`
`
`
`20 additional radiation shortly after the instant at
`
`
`
`
`
`
`
`
`which the source is turned off. It is clearly desirable to
`
`
`
`
`
`
`
`
`incorporate this delayed count of additional radiation
`
`
`
`
`
`
`
`
`
`
`
`
`
`in order to precisely control the quantity of radiation
`incident on the subject.
`
`
`
`Several interlocks are provided in the system of this
`
`
`
`
`
`
`invention for indicating various types of malfunctions
`
`
`
`
`
`of the system or of the associated apparatus.
`
`
`
`
`
`
`The first of these interlocks comprises an additional
`
`
`
`
`
`
`counting means 100. Counter 100 receives the same
`
`
`
`
`
`
`
`
`input of accumulated radiation which is delivered to
`
`
`
`
`
`
`counter 40. Alternatively, as a double check, counter
`
`
`
`
`
`
`
`100 can be fed with a divided signal from an indepen-
`
`
`
`
`
`
`
`
`dent integrator which receives its input from additional
`
`
`
`
`
`
`
`electrode means in the ionization chamber. In either
`
`
`
`
`
`
`case, counter 100 is actuated to record its count only
`
`
`
`
`
`
`
`when the radiation source is programmed by the stop
`
`
`
`
`
`
`
`signal to be in its off state. Counter 100 senses that the
`
`
`
`
`
`
`
`
`
`radiation source is in its off state by means of switch
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`20, switch 120 being responsive to the stop signal to
`emit an off signal which is input to counter 100 to en-
`
`
`
`
`
`
`
`
`able it to count. Counter 100 is reset to zero when tra-
`
`
`
`
`
`
`
`
`versal sensor 90 signals that two degrees of rotation
`
`
`
`
`
`
`
`
`
`have been completed, at which time the source is reac-
`
`
`
`
`
`
`
`
`tivated.
`
`Counter 100 is programmed to emit a fault signal if,
`
`
`
`
`
`
`during the off state of the radiation source, a predeter-
`
`
`
`
`
`
`
`
`mined amount of radiation is detected and counted at
`
`
`
`
`
`
`counter 100. This fault signal is delivered as an input
`
`
`
`
`
`
`
`
`to OR gate 110. OR gate 110, in response to the input
`
`
`
`
`
`
`
`of a fault signal from counter 100, produces an output
`
`
`
`
`
`
`
`
`signal which is directed to a supplemental disabling
`
`
`
`
`
`
`means for the radiation source. In this preferred em-
`
`
`
`
`
`
`
`
`
`bodiment,
`that supplemental disabling means com-
`
`
`
`
`
`
`prises a means responsive to an output from OR gate
`
`
`
`
`
`
`110 to cut off the entire high power supply from the en-
`
`
`
`
`
`
`
`
`
`
`tire system, and thus deactivate the radiation source
`
`
`
`
`
`
`
`
`and the gantry drive motor. Low voltage to controls
`
`
`
`
`
`
`
`
`
`and monitoring devices remains on. When the high
`
`
`
`
`
`
`
`
`voltage system thus shuts down, the subject is protected
`
`
`
`
`
`
`
`
`from additional radiation, and the operator is free to
`
`
`
`
`
`
`
`
`correct the difficulty and restart the system.
`
`
`
`
`
`
`
`A second fault interlock comprises timer 130. Timer
`
`
`
`
`
`
`
`
`130 is connected to receive the pulses generated by tra-
`
`
`
`
`
`
`
`versal sensor 90 whenever the gantry moves through
`
`
`
`
`
`
`
`
`one two-degree increment of rotation. Timer 130 is
`
`
`
`
`
`
`programmed to emit an output fault signal to OR gate
`
`
`
`
`
`
`1 10 whenever the gantry fails to traverse one of the two
`
`
`
`
`
`
`
`
`
`degree increments within a predetermined amount of
`
`
`
`
`
`time. In this preferred embodiment, the maximum time
`
`
`
`
`
`
`
`permitted for traversal of a two degree increment is
`
`
`
`
`
`
`
`0.08 minutes. If the gantry fails to make that traversal
`
`
`
`
`
`
`
`
`
`in the prespecified time period, the output signal from
`
`
`
`
`
`
`
`
`
`
`Page 8 of 14
`
`
`
`
`
`8
`
`
`the rotation of the gantry when the preset position limit
`
`
`
`
`
`
`
`is reached, or to the high voltage supply.
`
`
`
`
`
`
`FIGS. 2 and 3 illustrate in schematic form the princi-
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`pal components of the system of this invention. FIGS.
`2 and 3 are interconnected as indicated by the lettered
`
`
`
`
`
`
`
`lines at the right of FIG. 2 and the left of FIG. 3. More
`
`
`
`
`
`
`
`
`
`specifically line A of FIG. 2 is connected to line A of
`
`
`
`
`
`FIG. 3, line B is connected to line B, etc. It is noted that
`
`
`
`
`
`
`
`
`
`
`
`
`
`many of the components of this specific preferred em-
`bodiment are made up, in whole or in part, by inte-
`
`
`
`
`
`
`
`
`grated circuit elements as shown in FIGS. 2 and 3 as
`
`
`
`
`
`
`
`
`
`
`
`
`bearing its particular identifying integrated circuit
`number. These numbers are standardized among those
`
`
`
`
`
`
`
`of skill in the art dealing with such integrated circuit
`
`
`
`
`
`
`
`
`
`
`components. The drawings do not show more than a
`
`
`
`
`
`
`
`schematic rendition of the radiation source and related
`
`
`
`
`
`
`
`mechanism for driving the source around a patient
`
`
`
`
`
`
`
`couch since these are well known in the art, as shown
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`
`for example in U.S. Pat. Nos. 3,582,650 and 3,720,817.
`Although the invention is described for use in treat-
`
`
`
`
`
`
`
`ment of a patient with X-ray radiation, it is useful