Radiotherapy planning apparatus and radiotherapy system

A radiotherapy planning apparatus 3, comprising:

• processing circuitry configured to:
• obtain a medical image relating to a patient,
• obtain a number of beams and beam directions of a plurality of radiation beams applied substantially simultaneously to an irradiation area of the patient, and
• generate a total dose rate distribution, which is a spatial distribution of total values of predicted dose rates of the plurality of radiation beams to be applied to the patient, based on the obtained medical image and the obtained number and the beam directions of the plurality of radiation beams, wherein
• the processing circuitry is further configured to calculate a first ratio or a second ratio, the first ratio is a ratio of a second time length for which all the plurality of radiation beams are simultaneously applied to a first time length for which at least one radiation beam of the plurality of radiation beams is applied, the second ratio being a ratio of a third time length to the first time length, and the third time length being acquired by subtracting the second time length from the first time length, and
• the processing circuitry is further configured to output a second determination result relating to whether the first ratio is smaller than a first threshold and/or whether the second ratio is larger than a second threshold.

A radiotherapy system, comprising:

• a radiotherapy planning apparatus producing a radiotherapy plan relating to radiotherapy in which a plural number of radiation beams are applied in a plurality of beam directions to a patient substantially simultaneously with a high dose and for a short time;
• and
• a radiotherapy apparatus applying the plural number of the radiation beams in the plurality of beam directions to the patient substantially simultaneously with a high dose and for a short time in accordance with the radiotherapy plan,
• wherein the radiotherapy planning apparatus;
• obtains a medical image relating to the patient,
• obtains the number of beams and the plurality of beam directions of the radiation beams applied substantially simultaneously to an irradiation area of the patient, and
• generates a total dose rate distribution, which is a spatial distribution of total values of predicted dose rates of the radiation beams to be applied to the patient, based on the obtained medical image and the number and the beam directions of the radiation beams, and
• wherein the radiotherapy planning apparatus further specifies a first internal area in which a FLASH effect is acquired and/or a second internal area in which no FLASH effect is acquired, based on the generated total dose rate distribution, and displays the first internal area and/or the second internal area in a visually distinguishable manner in the medical image.