Radiotherapy monitoring apparatus

1. A radiotherapy monitoring apparatus for monitoring a treatment state by irradiation of radiations on a treatment region, comprising:

a detecting unit configured to detect the radiations transmitted through the treatment region at least in two places;

a comparing unit configured to compare a relative value of the transmitted radiations in the two places with a reference relative value; and

a control signal generating unit configured to generate, when the relative value exceeds the reference relative value, a control signal for stopping the irradiation of the radiations, the relative value being at least one of a ratio of transmitted doses in the at least two places and an absolute value of a difference between the transmitted doses.

2. A radiotherapy monitoring apparatus according to claim 1 , wherein the detecting unit is a flat panel detector.

3. A radiotherapy monitoring apparatus according to claim 1 , wherein the detecting unit directly converts the radiations into electric signals.

4. A radiotherapy monitoring apparatus according to claim 1 , wherein a position in the treatment region is included in the two places.

5. A radiotherapy monitoring apparatus according to claim 1 , wherein a position in the treatment region and a position outside the treatment region are included in the two places.

6. A radiotherapy monitoring apparatus according to claim 1 , wherein the control signal generating unit generates the control signal when at least one of the ratio of the transmitted doses and the absolute value of the difference exceeds the reference relative value.

7. A radiotherapy monitoring apparatus according to claim 1 , wherein, when it is assumed that a dose in a position in the treatment region is DT, a dose in a position outside the treatment region and in a critical organ region having relatively high sensitivity to radiations is DC, and a dose in an external position of a patient is DS, the relative value is calculated by |DT/DS−DC/DS|.

8. A radiotherapy monitoring apparatus according to claim 1 , wherein the control signal corresponds to display of a message for urging an operator to reexamine a treatment plan.

9. A radiotherapy monitoring apparatus for monitoring a treatment state by irradiation of radiations on a treatment region, comprising:

a reference value calculating unit configured to calculate at least one of a ratio of exit doses in at least two places in an irradiation range of the radiations and an absolute value of a difference between the exit doses as a reference value on the basis of a planned dose distribution;

a detecting unit configured to detect the radiations transmitted through the treatment region;

a measured value calculating unit configured to calculate at least one of the ratio of the exit doses in the two places and the absolute value of the difference between the exit doses as a measured value on the basis of an output of the detecting unit;

a comparing unit configured to compare the measured value with the reference value; and

a control signal output unit configured to output a control signal corresponding to a result obtained by comparing the measured value with the reference value.

10. A radiotherapy monitoring apparatus according to claim 9 , wherein the control signal corresponds to urgent stop of the irradiation of the radiations.

11. A radiotherapy monitoring apparatus according to claim 9 , wherein the control signal corresponds to display of a message for urging an operator to reexamine a treatment plan.

12. A radiotherapy monitoring apparatus according to claim 9 , wherein one of the two places is set in a target center position region and the other of the two places is set in a comparative observation position region.

13. A radiotherapy monitoring apparatus according to claim 9 , wherein one of the two places is a place where an exposure dose indicates a minimum in a target center position region and the other of the two places is a place where an exposure dose indicates a maximum in a comparative observation position region.

14. A radiotherapy monitoring apparatus according to claim 9 , further comprising an operation unit with which an operator performs operation for designating the two places.

15. A radiotherapy monitoring apparatus according to claim 9 , wherein the control signal output unit generates the control signal when the ratio of the exit doses calculated by the measured value calculating unit exceeds the ratio of the exit doses calculated by the reference value calculating unit.

16. A radiotherapy monitoring apparatus according to claim 9 , wherein the control signal output unit generates the control signal when the absolute value of the difference between the exit doses calculated by the measured value calculating unit exceeds the absolute value of the difference between the exit doses calculated by the reference value calculating unit.

17. A radiotherapy monitoring apparatus according to claim 9 , wherein the control signal output unit generates the control signal when at least one of a state in which the ratio of the exit doses calculated by the measured value calculating unit exceeds the ratio of the exit doses calculated by the reference value calculating unit and a state in which the absolute value of the difference between the exit doses calculated by the measured value calculating unit exceeds the absolute value of the difference between the exit doses calculated by the reference value calculating unit occurs.

18. A radiotherapy monitoring apparatus according to claim 9 , wherein the detecting unit has plural detecting elements arrayed in a two-dimensional shape for directly converting the radiations into electric signals.

19. A radiotherapy monitoring apparatus according to claim 9 , further comprising a data storing unit that stores data of the measured value together with a measurement date and time.

20. A radiotherapy monitoring apparatus for monitoring a treatment state by irradiation of radiations on a treatment region, comprising:

a detecting unit configured to detect the radiations transmitted through the treatment region;

a calculating unit configured to calculate at least one of a ratio of exit doses in at least two places in an irradiation range of the radiations and an absolute value of a difference between the exit doses as a measured value on the basis of an output of the detecting unit;

a comparing unit configured to compare the measured value with a predetermined value; and

a signal output unit configured to output a control signal corresponding to a result of the comparison of the measured value with the predetermined value.