Doses monitoring in radiology: calibration of air kerma-area product (P<sub>KA</sub>) meters

Terini, Ricardo Andrade; Campelo, Maria Carolina de Santana; Almeida Jr., José Neres de; Herdade, Silvio Bruni; Pereira, Marco Aurélio Guedes

doi:10.1590/S0100-39842013000600008

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Sumário

Original Articles • Radiol. Bras. 46 (6) • Nov-Dec 2013 • https://doi.org/10.1590/S0100-39842013000600008 copy

Doses monitoring in radiology: calibration of air kerma-area product (P_KA) meters^* * Study developed in the Laboratory of Ionizing Radiations Metrology at Instituto de Energia e Ambiente da Universidade de São Paulo (IEE-USP) - São Paulo, SP, Brazil.

Authorship SCIMAGO INSTITUTIONS RANKINGS

Objective

The authors have sought to study the calibration of a clinical P_KA meter (Diamentor E2) and a calibrator for clinical meters (PDC) in the Laboratory of Ionizing Radiation Metrology at Instituto de Energia e Ambiente - Universidade de São Paulo.

Materials and Methods

Different qualities of both incident and transmitted beams were utilized in conditions similar to a clinical setting, analyzing the influence from the reference dosimeter, from the distance between meters, from the filtration and from the average beam energy. Calibrations were performed directly against a standard 30 cm³ cylindrical chamber or a parallel-plate monitor chamber, and indirectly against the PDC meter.

Results

The lowest energy dependence was observed for transmitted beams. The cross calibration between the Diamentor E2 and the PDC meters, and the PDC presented the greatest propagation of uncertainties.

Conclusion

The calibration coefficient of the PDC meter showed to be more stable with voltage, while the Diamentor E2 calibration coefficient was more variable. On the other hand, the PDC meter presented greater uncertainty in readings (5.0%) than with the use of the monitor chamber (3.5%) as a reference.

Kerma; Meters; Calibration; Dosimetry; Radiology; X-rays

RQR	kVp_mean (kV)	PPV (kV)	Current (mA)	M_c,ref (Gy /h)	HVL₁ (mmAl)	h	Aditional filtration (mmAl)
2	39.2(3)	40.0(1)	14.3	0.89(2)	1.4(1)	0.81(7)	2.176(5)
3	49.4(3)	50.0(1)	12.0	1.41(4)	1.8(1)	0.75(7)	2.174(5)
4	59.6(4)	60.0(1)	11.5	1.91(4)	2.2(1)	0.72(7)	2.334(5)
5	69.4(4)	70.0(1)	13.2	2.71(6)	2.6(1)	0.71(5)	2.583(5)
6	79.6(5)	80.0(2)	11.5	2.99(6)	3.0(1)	0.67(5)	2.684(5)
7	89.8(5)	90.1(2)	10.2	3.27(7)	3.5(2)	0.68(5)	2.792(5)
8	99.6(6)	99.9(2)	11.5	4.25(9)	4.0(2)	0.67(5)	2.967(5)
9	119.6(7)	119.9(3)	12.5	6.03(13)	5.1(2)	0.68(5)	3.353(5)
10	150.2(9)	149.9(2)	11.0	7.64(17)	6.5(3)	0.70(5)	3.695(5)

RQR	Incident beams			Transmitted beams
RQR	P_KA,DE2 (µGy.m² /s)	P_KA,ref (µGy.m² /s)	N_PKA,DE2	P_KA,DE2 (µGy.m² /s)	P_KA,ref (µGy.m² /s)	N_PKA,DE2
2	1.01(6)	1.48(5)	1.46(9)	8.04(8)	9.16(25)	1.14(4)
3	1.88(6)	2.51(8)	1.34(6)	15.39(7)	16.52(44)	1.07(4)
4	2.63(6)	3.24(10)	1.23(5)	20.66(7)	21.09(25)	1.02(3)
5	3.93(5)	4.60(14)	1.17(4)	30.54(9)	30.51(81)	1.00(3)
6	4.43(6)	5.09(15)	1.15(4)	34.20(8)	34.01(88)	0.99(3)
7	4.91(7)	5.55(17)	1.13(4)	37.60(12)	37.44(97)	1.00(3)
8	6.19(3)	6.90(21)	1.11(4)	46.88(11)	47.0(13)	1.00(3)
9	9.22(9)	10.22(31)	1.11(4)	72.63(13)	74.2(19)	1.02(3)
10	11.47(9)	12.94(40)	1.13(4)	86.22(14)	91.7(24)	1.06(4)

PPV (kV)	N_PKA,DE2 incident RQR	N_PKA,DE2 transmitted RQR	N_PKA,DE2 transmitted 3 mmAl
40	1.46(9)	1.14(4)	1.13(4)
50	1.34(6)	1.07(4)	1.06(4)
60	1.23(5)	1.02(3)	1.01(3)
70	1.17(4)	1.00(3)	0.99(3)
80	1.15(4)	0.99(3)	0.99(3)
90	1.13(4)	1.00(3)	0.99(3)
100	1.11(3)	1.00(3)	1.00(3)
120	1.11(4)	1.02(3)	1.02(3)
150	1.13(4)	1.06(4)	1.06(4)

PPV (kV)	N_PKA,PDC-ref RQR	N_PKA,PDC-ref 1,5 mmAl + 0,9 mmCu	N_PKA,PDC-ref 4 mmAl + 0,2 mmCu	N_PKA,PDC-ref 3 mmAl + 0,1 mmCu
50	1.03(6)	1.36(8)	1.15(7)	1.09(7)
80	1.01(6)	0.99(6)	1.04(6)	1.06(6)
100	0.99(6)	0.95(6)	1.01(6)	1.04(6)
120	0.98(6)	0.93(5)	1.00(6)	1.04(6)

PPV (kV)	N_PKA,DE2-PDC RQR	N_PKA,DE2-PDC 1,5 mmAl + 0,9 mmCu	N_PKA,DE2-PDC 4 mmAl + 0,2 mmCu	N_PKA,DE2-PDC 3 mmAl + 0,1 mmCu
50	1.08(6)	0.86(6)	1.00(6)	1.01(6)
80	1.01(6)	0.94(6)	0.93(6)	0.96(6)
100	1.00(6)	1.04(6)	0.98(6)	1.00(6)
120	1.03(6)	1.12(7)	1.03(6)	1.05(6)

Component^* * Standard uncertainty components: 1. standard ionization chamber calibration coefficient; 2. reading of the air kerma meter; 3. reading of the PDC PKA meter; 4. PDC calibration coefficient against the 30 cm3 standard chamber; 5. reading of the DE2 PKA meter; 6. correction for the inverse square of distance; 7. reference collimator aperture size; 8. correction factor for standard air density for the reference chamber (kTP,ref); 9. correction factor for standard air density for the PKA DE2 meter (kTP,DE2.); 10. calibration coefficient of the monitor chamber against the 30 cm3 standard chamber (Nmon-ref).	1	2.h	2.c	2.b	2.g
1	0.5%	-	-	0.5%	-
2	3.0%	-	-	3.0%	-
3	-	0.5%	5.0%	-	5.0%
4	-	6.0%	-	-	6.0%
5	0.01%	0.01%	0.01%	0.01%	0.01%
6	2.0%	2.0%	2.0%	2.0%	2.0%
7	1.3%	1.3%	1.3%	1.3%	1.3%
8	0.15%	-	0.07%	0.15%	-
9	0.15%	0.07%	0.07%	0.15%	0.07%
10	-	-	3.5%	-	-
Total relative uncertainty	3.9%	8.2%	6.2%	3.9%	8.2%

Series	Voltage (kV)	P_KA,IBA (µGy.m²)	P_KA,PDC (µGy.m²)	N_PKA,med-PDC (para P_KA)
1(25 × 25 cm² field)	50	48.0(17)	52.6(46)	1.10(10)
	60	78.5(27)	77.5(58)	0.99(8)
	70	111.2(39)	112.2(83)	1.01(8)
	80	145.0(51)	152(11)	1.05(9)
	90	183.6(64)	198(14)	1.08(9)
	100	222.5(78)	250(18)	1.12(9)
	110	262.8(92)	296(21)	1.13(9)
	120	345(25)	305(23)	1.13(9)
2(20 × 20 cm² field)	50	23.3(8)	22.0(22)	0.94(10)
	60	37.6(13)	38.3(30)	1.02(9)
	70	70.7(25)	54.8(41)	1.02(9)
	80	70.7(25)	75.5(56)	1.07(9)
	90	89.1(31)	97.9(72)	1.10(9)
	100	108.0(38)	123(90)	1.14(9)
	110	128.1(45)	147(11)	1.15(9)
	120	155.1(54)	170(17)	1.10(9)
3(15 × 15 cm² field)	50	13.1(5)	13.8(16)	1.05(13)
	60	21.1(7)	20.7(19)	0.98(9)
	70	30,0(11)	31.0(25)	1.03(9)
	80	39.9(14)	42.7(33)	1.07(9)
	90	50.6(18)	55.5(42)	1.10(9)
	100	61.2(21)	69.7(52)	1.14(9)
	110	72.0(25)	82.9(61)	1.16(9)
	120	84.0(29)	96.2(71)	1.15(9)

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[1] Dr. Ricardo Andrade Terini. Rua Marquês de Paranaguá, 111, Consolação. São Paulo, SP, Brazil, 01303-050. E-mail: rterini@pucsp.br.

1	Incident beam, RQR series, against 30 cm³ chamber
2	Beam transmitted through the DE2 meter itself
2.a	RQR series against the 30 cm³ chamber
2.b	With 3 mmAl fixed filtration against 30 cm³ chamber
2.c	With 3 mmAl fixed filtration against monitor chamber
2.d	With 3 mmAl fixed filtration against PDC meter
2.e	With 3 mmAl + 0.1 mmCu fixed filtration against PDC
2.f	With 4 mmAl + 0.2 mmCu fixed filtration against PDC
2.g	With fixed 1.5 mmAL + 0.9 mmCu filtration, against PDC
2.h	RQR series against PDC
3	Transmitted beams, with 3 mmAl fixed filtration, for two distances between chamber and meter

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Doses monitoring in radiology: calibration of air kerma-area product (PKA) meters* * Study developed in the Laboratory of Ionizing Radiations Metrology at Instituto de Energia e Ambiente da Universidade de São Paulo (IEE-USP) - São Paulo, SP, Brazil.

Objective

Materials and Methods

Results

Conclusion

Doses monitoring in radiology: calibration of air kerma-area product (P_KA) meters^* * Study developed in the Laboratory of Ionizing Radiations Metrology at Instituto de Energia e Ambiente da Universidade de São Paulo (IEE-USP) - São Paulo, SP, Brazil.