Section 410IAC5-7-3. Teletherapy

 

                                (a) Equipment.

(1) The housing shall be so constructed that, at 1 meter from the source, the maximum exposure rate does not exceed 10 milliroentgens per hour when the beam control mechanism is in the "off" position. The average exposure rate measured at a representative number of points about the housing, each 1 meter from the source, shall not exceed 2 milliroentgens per hour.

(2) For teletherapy equipment installed after the effective date of 410 IAC 5, the leakage radiation measured at 1 meter from the source when the beam control mechanism is in the "on" position shall not exceed 0.1 percent of the useful beam exposure rate.

(3) Adjustable or removable beam-defining diaphragms shall allow transmission of not more than 5 percent of the useful beam.

(4) The beam control mechanism shall be of a positive design capable of acting in any orientation of the housing for which it is designed to be used. In addition to an automatic closing device, the mechanism shall be designed so that it can be manually returned to the "off" position with a minimum risk of exposure.

(5) The closing device shall be so designed as to return automatically to the "off" position in the event of any breakdown or interruption of the activating force and shall stay in the "off" position until activated from the control panel.

(6) When any door to the treatment room is opened, the beam control mechanism shall automatically and rapidly restore the unit to the "off" position and cause it to remain there until the unit is reactivated from the control panel.

(7) There shall be at the housing and at the control panel a warning device that plainly indicates whether the beam is "on" or "off."

(8) The equipment shall be provided with a locking device to prevent unauthorized use.

(9) The control panel shall be provided with a timer that automatically terminates the exposure after a preset time.

(10) Provision shall be made to permit continuous observation of patients during irradiation.

                                (b) Operation. No individual shall be in the treatment room during irradiation unless that individual is the patient. Mechanical restraining or supporting devices shall be used for positioning the patient, if necessary.

                                (c) Testing for Leakage and Contamination. Teletherapy sources shall be tested for leakage and contamination in accordance with the procedures described in 410 IAC 5-7-2(b). Tests of leakage may be made by wiping accessible surfaces of the housing port or collimator while the source is in the "off" position and measuring these wipes for transferred contamination.

                                (d) Calibration and Physical Decay Determinations.

(1) Calibration measurements shall be performed by a qualified radiation therapy physicist on each teletherapy unit:

(i) Prior to the first use of the unit for treating humans;

(ii) Prior to treating humans;

(A) Whenever spot-check measurements indicate that the output value differs by more than 5 percent from the value obtained at the last calibration corrected mathematically for physical decay;

(B) Following replacement of the radiation source or following reinstallation of the teletherapy unit in a new location; and

(C) Following any repair of the teletherapy unit that includes removal of the source or major repair of the components associated with the source exposure assembly; and

(iii) At intervals not exceeding 1 year.

(2) Calibration measurement shall include determination of:

(i) The exposure rate or dose rate to an accuracy within 3 percent for the range of field sizes and for the range of distances or for the axis distance, used in radiation therapy;

(ii) The congruence between the radiation field and the field indicated by the light beam localizing device;

(iii) The uniformity of the radiation field and its dependence upon the orientation of the useful beam;

(iv) Timer accuracy; and

(v) The accuracy of all distance measuring devices used for treating humans.

(3) The exposure rate or dose rate values shall be corrected mathematically for physical decay at intervals not exceeding 1 month.

(4) Calibration measurements and physical decay corrections shall be performed by a qualified radiation therapy physicist in accordance with 410 IAC 5-7-3(g).

                                (e) Spot-Check Measurements

(1) Spot-check measurements shall be performed on each teletherapy unit at intervals not exceeding 1 month.

(2) Spot-check measurements shall include determination of:

(i) Timer accuracy;

(ii) The congruence between the radiation field and the field indicated by the light beam localizing device;

(iii) The accuracy of all distance measuring devices used for treating humans;

(iv) The exposure rate, dose rate or a quantity related in a known manner to these rates for one typical set of operating conditions; and

(v) The difference between the measurements made in 410 IAC 5-7-3(e)(2)(iv) and the anticipated output expressed as a percentage of the anticipated output. The anticipated output is the value obtained at the last calibration corrected mathematically for physical decay.

(3) Spot-check measurements shall be performed in accordance with procedures established by a qualified radiation therapy physicist in accordance with 410 IAC 5-7-3(g)(1). A qualified radiation therapy physicist need not actually perform the spot-check measurements. If a qualified radiation therapy physicist does not perform the spot-check measurements, the results of the spot-check measurements shall be reviewed by a qualified radiation therapy physicist within 15 days.

                                (f) Dosimetry System Calibration

(1) Calibration measurements shall be performed using a dosimetry system that has been calibrated by the National Bureau of Standards or by a Regional Calibration Laboratory accredited by the American Association of Physicists of Medicine. The dosimetry system shall have been calibrated within the previous 2 years and after any servicing that may have affected system calibration.

(2) Spot-check measurements shall be performed using a dosimetry system that has been calibrated in accordance with 410 IAC 5-7-3(f)(1). Alternatively, a dosimetry system used solely for spot-check measurements may be calibrated by direct intercomparison with a system that has been calibrated in accordance with 410 IAC 5-7-3(f)(1). This alternative calibration method shall have been performed within the previous 1 year and after each servicing that may have affected system calibration. Dosimetry systems calibrated by the alternative method shall not be used for teletherapy calibration measurements.

                                (g) Records. The licensee or registrant shall maintain, for inspection by the board, records of the measurements, tests, corrective actions, and instrument calibrations.

(1) Records of teletherapy calibration measurements and calibration of the instruments used to make these measurements shall be preserved for 5 years after completion of the teletherapy calibration.

(2) Records of spot-check measurements and corrective actions and calibration of instruments used to make spot-check measurements shall be preserved for 2 years after completion of the spot-check measurements and corrective actions.

(Indiana State Department of Health; Rule HRH-2, PT G, Sec G.3; filed May 26, 1978, 3:30 pm: 1 IR 222; filed Feb 29, 1984, 10:10 am: 7 IR 968; readopted filed Jul 11, 2001, 2:23 p.m.: 24 IR 4234; readopted filed May 22, 2007, 1:44 p.m.: 20070613-IR-410070141RFA; readopted filed Sep 11, 2013, 3:19 p.m.: 20131009-IR-410130346RFA)