Abstraction:
Craniospinal irradiation is considered an of import component of the multidesplinary attack in the intervention of medulloblastoma. It is a complex radiation therapy technique, patients who are treated successfully normally live long periods. Every attempt should be done to diminish the radiation therapy related side effects, particularly with the presently available 3D conformal radiation therapy planning system in our section.
This dosimetric survey is taking to describe the consequences of analysis of doses received by mark volumes and variety meats outside the mark volumes during intervention of medullblastoma patients. Besides taking at comparing the doses making to the eyes and the lens with the usage of different screening methods.
Ten kids recent diagnosing of high hazard medulloblastoma ( big residuary & gt ; 1.5 centimeter, M0 ) were included in the survey after reexamining the pathology. All of them were subjected to MRI encephalon and spine together with CSF cytology three hebdomads after surgery. They were subjected to arrested development, conventional simulation, followed by CT simulation. The scans will be transferred to the intervention planning system. The encephalon, spinal canal, and different normal tissue will be outlined.
For the cranial Fieldss, parallel opposed Fieldss were used with the isocentre of the Fieldss in the mid-plan in the Centre of the encephalon, and behind the eyes. For the spinal field, the full length was opened to the desired place to handle the spinal column by asymmetric jaws. The inferior boundary line of the cranial field was matched to the superior boundary line of the spinal field utilizing collimator and couch rotary motion of the cranial field. Sensitive tissues near to the mark volume was shielded utilizing either MLCS or blocks.
The dosage prescribed was 36 Gy/20 fractions for cranial and spinal parts. The mention point was placed in the Centre of the cranial and spinal Fieldss. The upper limit, lower limit and intend dosage to each anatomic construction were computed utilizing dose volume histograms by summing the cranial and spinal intervention programs. All patients gave informed consent that we can analyze their program and do research on it
Introduction
Medulloblastoma constitutes 15-20 % of all childhood cardinal nervous system tumours. The average age at diagnosing is normally 6 old ages. The most common site of beginning is the vermis and the 4th ventricle. The presence of big residuary tumour & gt ; 1.5 centimeter or cerebro-spinal metastasis identifies high hazard patients ( 1 ) .
Reduced-dose ( 23.4 Gy ) craniospinal irradiation ( CSI ) in combination with hebdomadal Oncovin, followed by a boosting of the dosage to the buttocks fossa up to 55.8 Gy followed by accessory systemic chemotherapy in the signifier of Oncovin, CCNU, and cisplatin output a Progression-free endurance of 79 % at 5 old ages and is considered the province of art for standard hazard medulloblastoma patients. ( 2 )
Higher radiation therapy dosage to the CSI 36-39 Gy is normally considered for M0 instances ( & gt ; 1.5 centimeter residuary without cranio-spinal metastasis ) . ( 2 )
Craniospinal axis irradiation ( CSI ) is considered the corner rock in the intervention of medulloblastoma. It is a complex technique with really irregular clinical mark volume ( CTV ) . It is executed in two stages, the whole encephalon and neuraxis are treated in the initial stage. The site of the 1ry tumour is boosted in the 2nd stage ( 3 ) .
A figure of techniques are applied to better dose homogeneousness across the junction between the cranial and the spinal Fieldss ; including either direct abutment of the Fieldss or the debut of a spread with or without a traveling junction. Effort had been made to diminish the dosage to the lens, thyroid, bosom, GIT, and sex glands and to diminish the possible late effects of radiation therapy in those long life patients.
Several new modes and techniques are now available taking at more precise coverage of the mark volume ( spinal canal & A ; encephalon ) and more sparing of the variety meats at hazard, including the usage of CT simulators, better arrested development installations, the usage of conformal radiation therapy and IMRT. ( 4 )
Since the debut of our new additive gas pedal ( Elekta ) and intervention planning system ( Precise Elekta ) with many exposing and rating package tools 5 old ages ago in our section we became more able to give better radiation therapy to those patients.
Aim of this survey:
This dosimetric survey is taking at describing the consequences of analysis of doses received by mark volumes and variety meats at hazard ( OAR ) during intervention of high hazard medullblastoma patients. Besides we will compare the dose stretch to the lens with the usage of different screening methods.
Materials and methods:
Ten kids with recent diagnosing of high hazard medulloblastoma ( big residuary & gt ; 1.5 centimeter, M0 ) were included in the survey after reexamining the pathology. All of them were subjected to MRI encephalon and spine together with CSF cytology three hebdomads after surgery. All of these patients were planned to have whole craniospinal irradiation ( CSI ) accompaniment with hebdomadal vincristin get downing 4 hebdomads after surgery. All patients gave informed consent that their program will be studied and will be subjected to research.
All patients received craniospinal irradiation ( CSI ) with a sidelong analogue opposed Fieldss to the caput and a matched posterior spinal column field, with moving of the junction 1cm every 7 fractions ( The place of the lower cranial boundary line and upper spinal field were shifted ) .
The cranial Fieldss were treated iso-centrically while the spinal field was treated at fixed SSD.
An immobilisation mask was fabricated from thermoplastic stuff for each patient. The patients were simulated from the top of the caput to the mid-pelvis utilizing CT scan. During simulation, patients were placed in prone place with cervix extended so that a posteriorly oriented spine field could go out below the lower jaw.
CT spacing was 3mm for the encephalon and 5mm for the spinal column. Patients were marked with sagittal and sidelong optical maser lines during the confirmation, simulation and subsequent intervention.
The CT scans were so transferred to Precise Elekta intervention planning system where spinal canal and encephalon were contoured as the mark volumes. Variety meats at hazard and other normal tissues were besides contoured. They include lenses, eyes, ocular nervousnesss, bosom, lung, liver and kidneys. Care was taken to guarantee that the encephalon contour included the cribriform home base. Then the intervention Fieldss were designed for intervention.
The energies of the photon beams were 4MV & A ; 6MV for cranial and spinal Fieldss severally.
For the braincase, parallel opposed Fieldss were used with two isocenters for each patient one behind the oculus and the other in the Centre of the encephalon. The cranial Fieldss include whole encephalon and extended caudally every bit long as the shoulder permits with 1 centimeters above shoulder to let traveling junction. In order to bring forth the field aperture for the cranial Fieldss, the multi-leaf collimator was automatically positioned with the inside corner of the aperture 0.5cm from the contoured encephalon so MLC foliages were adjusted.
Because the inferior divergency of the cranial Fieldss may overlap into the spinal cord, a couch rotary motion of 6-80 was added to extinguish such divergency. Besides a collimator rotary motion of 8-100 on the sidelong cranial Fieldss was done to fit the divergency of the superior spinal field border.
So couch and collimator rotary motion in sidelong cranial Fieldss were applied to efficaciously hold all three field borders from both sidelong encephalon ports and the posterior spinal column port to run into at the cervical junction as a individual plane. So the dose homogeneousness at the craniospinal junction was achieved.
For the spinal field, a individual buttocks long thin spinal field was used. It should cover the whole spinal column. The posterior spinal column field was simulated ; the superior boundary line of the spinal field touches the inferior boundary line of the cranial field. The full length was opened to the desired place to handle the spinal column by asymmetric jaws. If the distance from 2nd cervical vertebra to the base of the spinal column ( 2nd sacral vertebra ) was more than 39cm so the intervention was carried out at drawn-out SSD. SSD was 100cm in 8 patients and 110cm and 120cm in two other patients.
For the cranial Fieldss, the averaged field size was 20x20cm. For the spinal field, the length ranged from 26cm -38cm. The breadth of the spinal field ranged from 4-8cm.
MLCS and or cerrobend screening blocks were used to screen eyes, lenses and other sensitive tissues near to the mark volume as kidneys and lungs. For each patient, four planes were created ; Plan 1, the isocenter of the cranial Fieldss was placed in the centre of the encephalon and MLCs were used to screen the eyes and lenses. In Plan 2 the isocenter was behind the eyes and MLCs were used to screen the eyes and lenses. In Plan 3 the isocenter was behind the eyes and screening block was used to screen the eyes and lenses. In Plan 4 the isocenter was in the centre of the encephalon and screening block was used to screen the eyes and lenses.
The dosage prescribed was 36 Gy/20 fractions for braincase and spinal column parts. For cranial dose prescription, the dosage was normalized to the Centre of the encephalon. For spinal cord dosage prescription the dosage was normalized to the Centre of the field at the anterior surface of the spinal cord to accomplish good coverage ( 95 % ) as the dosage is low at the anterior surface of the spinal cord. The delivered MU of the spinal Fieldss ranged from 190-300 and for the cranial field ranged from 95-108Mu.
For each plane of each patient the added dosage program map was used to look into the dose coverage of the combined cranial and spinal dosage programs. Then the four programs for each patient were compared utilizing ocular review of the dose distribution, dose volume histogram and dose volume histogram parametric quantities. These parametric quantities were listed and analyzed statistically utilizing excel sheet and SPSS ( version11 ) Wilcoxon signed Ranks trial
Consequences:
Radiation doses to aim volumes and variety meats at hazard during CSI ( Table 1 ) :
By reexamining the intervention planning and dose volume histograms of all 10 patients, the followerss were the consequences as respects the dose distribution of the mark volumes ( encephalon & A ; spinal canal ) and organs at hazard:
As respects the mark volumes ;
Brain was covered in all instances by 95 % of the dosage. The lower limit dosage received by any of the treated patients was 34.2 Gy while the maximal dose received was 40.3Gy ( still within the encephalon tolerance ) .
The spinal cord was covered in all instances by 95 % of the dosage. The lower limit dosage received by the spinal cord in any of the treated patients was 34.2 Gy, while the maximal dosage was 41.4Gy ( still within spinal cord tolerance ) .
As respects variety meats at hazard ( OARs ) :
The norm of the mean dosage received by the whole liver for all patients was 18 % of the prescribed dose i.e. 641 cGy, with a dose scope from 504-828cGy.
The norm of the mean dosage received by any of the kidneys was 8 % of the prescribed dose i.e. 280 cGy with a dose scope from 72-612 cGy.
The norm of the maximal dosage received by the bosom of the treated patients was 94.5 % of the prescribed dose i.e. 34Gy, with the dose scopes from 33-34.9 cGy
The norm of the dosage that 20 % of the lungs received is 10 % of the prescribed dose i.e. 360cGy with the dose scopes from 180cGy-540cGy.
The norm of the maximal dosage of ocular nervus was 98.5 % of the prescribed dose i.e. 36Gy, with the dose scopes from 34-37Gy. The maximal dosage is still below the maximal point dosage for the ocular nervus.
The norm of the organic structure maximal dosage was 118 % of the prescribed dose i.e 42Gy, with the dose scopes from 40 and 45 Gy ; this maximal point was in the back musculuss ( still within the tolerance of the musculus ) .
Table 1: Radiation doses in per centum for mark volumes and variety meats at hazard during CSI:
Patients
Brain min
Brain soap
Cord min
Cord soap
Liver intend
R. k. mean
L. k. mean
Heart soap
Heart mean
Lung D20 %
Ocular soap
Body soap.
1
96
107
95
115
16
5
5
97
51
10
99
124
2
95
109
96
113
18
5
10
92
54
10
99
115
3
96
106
97
115
17
8
7
95
50
8
101
117
4
95
110
96
111
14
9
7
95
55
8
101
117
5
95
111
95
110
20
4
4
92
39
15
100
113
6
95
112
95
113
16
3
5
95
49
8
95
119
7
95
112
95
115
22
14
2
93
51
5
95
125
8
95
109
95
110
23
11
13
95
54
12
104
112
9
95
106
98
113
17
14
17
97
56
15
97
119
10
95
110
96
109
15
8
8
94
50
9
97
118
min
95
106
95
109
14
3
2
92
39
5
95
112
soap
96
112
98
115
23
14
17
97
56
15
104
125
mean
95.2
109.2
95.8
112.4
17.8
8.1
7.8
94.5
50.9
10
98.8
117.9
Median
95.5
109.5
96.5
111
17.5
8
7.5
94
50.5
9.5
99.5
117.5
Average = mean of the agencies.
Table 2.Radiation doses in cGy for mark volumes and variety meats at hazard during CSI
Patients
Brain min
Brain soap
Cord min
Cord soap
Liver intend
R. k. mean
L. k. mean
Heart soap
Heart mean
Lung D20 %
Ocular soap
Body soap.
1
3456
3852
3420
4140
576
180
180
3492
1836
360
3564
4464
2
3420
3924
3456
4068
648
180
360
3312
1944
360
3564
4140
3
3456
3816
3492
4140
612
288
252
3420
1800
288
3636
4212
4
3420
3960
3456
3996
504
324
252
3420
1980
288
3636
4212
5
3420
3996
3420
3960
720
144
144
3312
1404
540
3600
4068
6
3420
4032
3420
4068
576
108
180
3420
1764
288
3420
4284
7
3420
4032
3420
4140
792
504
72
3348
1836
180
3420
4500
8
3420
3924
3420
3960
828
396
468
3420
1944
432
3744
4032
9
3420
3816
3528
4068
612
504
612
3492
2016
540
3492
4284
10
3420
3960
3456
3924
540
288
288
3384
1800
324
3492
4248
Minute
3420
3816
3420
3924
504
108
72
3312
1404
180
3420
4032
Soap
3456
4032
3528
4140
828
504
612
3492
2016
540
3744
4500
mean
3427
3931
3448.8
4046
640.8
291.6
280.8
3402
1832
360
3556.8
4244
Median
3438
3942
3474
3996
630
288
270
3384
1818
342
3582
4230
Average = mean of the agencies
As regard eyes & A ; lenses:
The dosage received by the eyes and lenses utilizing two different screening techniques and utilizing two different positioning for encephalon isocenters:
Four programs were carried out, they are
Plan 1 isocenter is in the centre of the encephalon with utilizing MLCs shielding.
Plan 2 isocenter is behind the eyes with utilizing MLCs screening
Plan 3 isocenter is behind the eyes with utilizing block shielding.
Plan 4 isocenter is in the centre of the encephalon with utilizing block shielding
The mean dosage received by the right and left eyes and the maximal dosage received by the right and left lens were listed and compared for the four programs. ( Tables 3-6 ) :
Plan 1 & A ; 2:
Plan 2 shows lower doses to eyes and lenses compared to be after 1
In program 2, the norm of the mean dosage of the right and left eyes was 46 % & A ; 45 % compared with 53 % & A ; 52 % in program 1 ( table 3 ) . In program 2 the norm of the maximal dosage of the right and left lens was 38 % & A ; 41 % compared with 44 % & A ; 48 % in plan1 ( table 5 ) . So utilizing MLCs to screen the eyes & A ; lenses with seting the isocenter behind the eyes shows lower doses than seting the isocenter in the centre of the encephalon.
Plan 3 & A ; 4: program 4 shows lower doses to eyes and lens compared to be after 3
In program 3, the norm of the mean dosage of the right and left eyes was 32 & A ; 31.5 % compared with 30.5 % & A ; 30 % in program 4 ( table 3 ) . The norm of the maximal dosage of the right and left lens was 15.5 % & A ; 11 % compared with 13 % & A ; 11 % in program 4 ( table 5 ) . So utilizing block to screen the eyes with seting isocenter behind the eyes or in the centre of the encephalon shows no important difference ( both show low doses to eyes and lenses )
Plan 2 & A ; 3: program 3 shows lower doses to eyes and lenses compared to be after 2
In program 2, the norm of the mean dosage of the right and left eyes was 46 % & A ; 45 % compared with 32 % & A ; 31.5 % in program 3 ( table3 ) . The norm of the maximal dosage of the right and left lens was 38 % & A ; 41 % compared with 15.5 % & A ; 11 % in program 3 ( table5 ) . So seting the isocenter behind the eyes with block screening shows low doses to eyes and lenses than seting the isocenter behind the eyes with utilizing MLCs shielding.
Plan 1 & A ; 3: Plan 3 shows lower doses to eyes and lenses compared to be after 1
In program 1, the norm of the mean dosage of the right and left eyes was 53 % & A ; 52 % compared with 32 % & A ; 31.5 % in program 3 ( table 3 ) . In program 1, the norm of the maximal dosage of the right and left lens was 44 % & A ; 48 % compared with 15.5 % & A ; 11 % in program 3 ( table5 ) . so seting the isocenter behind the eyes with block shielding shows lower doses than seting the isocenter in the centre of the encephalon with utilizing MLCs screening
Plan 1 & A ; 4: program 4 shows lower doses to eyes and lenses compared to be after 1
In program 1, the norm of the mean dosage of the right and left eyes was 53 % & A ; 52 % compared with 30.5 % & A ; 30 % in program 4 ( table 3 ) . The norm of the maximal dosage of the right and left lens was 44 % & A ; 48 % compared with 13 % & A ; 11 % in program 4 ( table 5 ) . So seting the isocenter in the centre of the encephalon with utilizing block shielding shows lower doses than seting the isocenter in the centre of the encephalon with utilizing MLCs shielding.
The mean dosage to both eyes and the maximal point dosage to both lenses for these programs were assessed and analyzed statistically utilizing Wilcoxon signed rank trial. We found that there is a important difference in saving the eyes and the lenses between program 1 & A ; 2, between program 2 & A ; 3, between plan1 & A ; 3 and between program 4 & A ; 1 ( P values & lt ; 0.05 for all ) . On the other manus, there is no important difference between program 3 & A ; 4. Both show low doses to eyes and lenses ( P values & gt ; 0.05 ) .
Table 3, The mean dosage received by the oculus in % for four different planes utilizing two different encephalon isocenters and different shielding methods
Rt oculus
mean dosage
Lt oculus
mean dosage
patients
program 1
plan2
plan3
plan4
program 1
plan2
plan3
plan4
1
31
31
12
12
33
23
12
13
2
70
56
36
32
57
41
21
19
3
77
68
46
48
60
55
32
35
4
46
41
30
24
50
42
36
30
5
65
64
50
49
51
47
34
30
6
33
32
17
18
24
26
15
11
7
38
20
18
11
37
27
19
13
8
62
57
46
49
75
72
59
60
9
43
38
29
25
61
52
37
40
10
65
55
37
37
74
61
50
47
min %
31
20
12
11
24
23
12
11
max %
77
68
50
49
75
72
59
60
mean
53
46.2
32.1
30.5
52.2
44.6
31.5
29.8
Median
46
41
30
25
54
44.5
33
32.5
Average = mean of the agencies
Table 4, The mean dosage received by the oculus in cGy for four different planes utilizing two different encephalon isocenters and different shielding methods
Rt oculus
mean dosage
Lt oculus
mean dosage
patients
program 1
plan2
plan3
plan4
program 1
plan2
plan3
plan4
1
1116
1116
432
432
1188
828
432
468
2
2520
2016
1296
1152
2052
1476
756
684
3
2772
2448
1656
1728
2160
1980
1152
1260
4
1656
1476
1080
864
1800
1512
1296
1080
5
2340
2304
1800
1764
1836
1692
1224
1080
6
1188
1152
612
648
864
936
540
396
7
1368
720
648
396
1332
972
684
468
8
2232
2052
1656
1764
2700
2592
2124
2160
9
1548
1368
1044
900
2196
1872
1332
1440
10
2340
1980
1332
1332
2664
2196
1800
1692
min
1116
720
432
396
864
828
432
396
soap
2772
2448
1800
1764
2700
2592
2124
2160
mean
1908
1663.2
1155.6
1098
1879.2
1605.6
1134
1072.8
Median
1656
1476
1080
900
1944
1602
1188
1170
Average = mean of the agencies.
Table 5 ; The upper limit dosage received by the lenses in % for 4 different planes utilizing two different isocenters and different screening methods:
Rt lens
soap dosage
Lt lens
soap dosage
patients
program 1
plan2
plan3
plan4
program 1
plan2
plan3
plan4
1
24
29
12
12
41
33
12
13
2
69
59
10
11
37
23
10
11
3
93
80
53
28
75
54
12
12
4
23
17
23
20
77
60
10
10
5
53
56
12
12
60
45
12
11
6
18
19
6
7
38
46
10
10
7
17
17
7
10
9
12
7
9
8
34
29
11
11
62
68
23
17
9
36
30
11
11
20
19
9
7
10
70
46
10
8
60
49
9
8
min %
17
17
6
7
9
12
7
7
max %
93
80
53
28
77
68
23
17
mean
43.7
38.2
15.5
13
47.9
40.9
11.4
10.8
Median
35
38
11
11
41
45.5
10
10.5
Average = mean of the agencies.
Table 6 ; the upper limit dosage received by the lenses in cGy for 4 different planes utilizing two different isocenters and different shielding methods
Rt lens
Max. dose
Lt lens
Max dosage
patients
program 1
plan2
plan3
plan4
program 1
plan2
plan3
plan4
1
864
1044
432
432
1476
1188
432
468
2
2484
2124
360
396
1332
828
360
396
3
3348
2880
1908
1008
2700
1944
432
432
4
828
612
828
720
2772
2160
360
360
5
1908
2016
432
432
2160
1620
432
396
6
648
684
216
252
1368
1656
360
360
7
612
612
252
360
324
432
252
324
8
1224
1044
396
396
2232
2448
828
612
9
1296
1080
396
396
720
684
324
252
10
2520
1656
360
288
2160
1764
324
288
min
612
612
216
252
324
432
252
252
soap
3348
2880
1908
1008
2772
2448
828
612
mean
1573.2
1375.2
558
468
1724.4
1472.4
410.4
388.8
Median
1260
1368
396
396
1476
1638
360
378
Discussion:
This dosimetric survey was conducted to describe the consequences of analysis of doses received by mark volumes and variety meats at hazard during intervention of 10 kids with high hazard medullblastoma treated with craniospinal irradiation accompaniment with chemotherapy at our section. Besides we compared the dosage making to the eyes and the lens with the usage of two different screening methods and two different places for encephalon isocenter.
As respects the mark volume ; the lower limit dosage received by the encephalon in any of the treated patients was 34.2Gy and the maximal dose received was 40.3Gy. The median of the maximal dosage received by the encephalon was 39.4 Gy while the median of the lower limit dosage received by the encephalon was 34.38 Gy.
The lower limit dosage received by the spinal cord by any of the treated patients was 34Gy, and the maximal dosage was 41.4Gy, The median of the maximal dosage received by the cord was 39.96 Gy while the median of the lower limit dosage received by the encephalon was 34.74 Gy.
These consequences are closely related to the consequences published by Darunee Tongwan in his dosimetric analysis of craniospinal irradiation in the supine place comparing four different techniques, where the average dosage received by the encephalon was 36.91Gy and the average dosage received by the spinal column was 38.12 Gy. ( 5 )
As respects variety meats at hazard, get downing with the liver, the average dosage received by the whole liver for all patients was 17.5 % of the prescribed dose i.e. 630 cGy, with a dose scopes between 504-828cGy. This was similar to darunee ‘s survey in which the dosage to the liver ranged from 533-698 cGy with a average dosage of 576 cGy.
Sing the kidneys, the average dosage received by the right and left kidneys were 8 and 7.5 % of the prescribed dose i.e. 288 and 270 cGy to the right and left kidney severally with a dose scope between 72-612 cGy, which is about indistinguishable to the average dosage received by the kidneys in darunee ‘s survey.
In the present survey, the upper limit dosage received by the bosom in any of the treated patients was 34.9Gy, with the mean dosage ranged between 14.04 Gy and 20.16 Gy. This is in agree with, the dosage received by the bosom in darunee ‘s survey, which ranged from 14,00-19,00 Gy.
In darunee ‘s survey, the lungs received a dose runing from 413-565 cGy with a average dosage of 476 cGy. This is about the same in our survey where the dosage received by 20 % of the lungs ranged from 180-540 cGy with a average dosage of 342 cGy.
In this survey, the norm of the mean dosage received by the right and left eyes was 53 % and 52 % of the prescribed dose when utilizing program 1 ( MLC and isocenter in the centre of the encephalon ) , this was improved to 46 % and 45 % for both right and left eyes when the isodose was moved to merely behind the eyes and maintaining utilizing of MLCs for screening ( program 2 ) . On the other manus, utilizing blocks for shielding was associated with dramatic betterment in the mean dosage making the eyes i.e. 32 % , 31.5 % to right and left eyes severally when utilizing ( program 3 ) & A ; 30.5 % , 30 % severally when utilizing ( program 4 ) .
So, by utilizing blocks for screening alternatively of MLCs there was a dramatic lessening in the dosage making the eyes. The mean dosage to the eyes was reduced by up to 42 %
In the present survey, the norm of the maximal dosage received by the right and left lens was 44 % and 48 % of the prescribed dose when utilizing program 1 ( MLC used and the isocenter is in the centre of the encephalon ) , this was improved to 38 % and 41 % for both right and left lens when the isocentre was moved to merely behind the eyes and maintaining utilizing of MLCs for screening ( program 2 ) . On the other manus, utilizing blocks for shielding was associated with dramatic betterment in the maximal dose making the lens i.e. 15.5 % , 11 % to right and left lenses severally when utilizing ( program 3 ) & A ; 13 % , 11 % severally when utilizing ( program 4 ) . The soap. dose to the lens was reduced by 70 % & A ; 77 % for the right & A ; left lens severally.
Our consequences were similar to the consequences obtained by Kalapurakal et Al in his survey measuring the inauspicious consequence of the usage of multileaf collimator on the dosage received by the lens in kids with leukaemia having cranial irradiation where the dosage to the lens was increased by approximately 64 % and 72 % when utilizing MLC without screening blocks ( 6 ) .
The fact that the usage of MLCs was associated with addition the dosage to the lens was besides recognized by vijay et Al ( 7 ) measuring shielding of the whole encephalon by three different methods in 10 kids having whole encephalon irradiation and making the decision that the usage of conformal planning and screening utilizing MLCs will take to better coverage of the PTV by the 95 % isodose curves but higher dosage to the eyes and lenses
The dosage to the lens was besides evaluated in the survey done by Cochran et Al ( 8 ) measuring the dosage to the lens during craniospinal irradiation utilizing protons and demoing that angling the cranial proton beam 15-20 grade posteriorly will take to significant lessening in the dosage received by the lens by about 50 % .
But still our consequences were off from the consequences shown by pakisch et Al ( 9 ) who showed that the dosage to the lens was reduced to 4 % merely from the described midplan dose with usage of combination of angulation of the sofa, arrangement of extra oculus blocks near to the surface, and angulation of the gauntry during contraceptive cranial irradiation and with the usage of 8 MV photon beams.
Decision:
From the above motioned survey we can reason that, the dosage of radiation received by the mark volume and the variety meats at hazard during craniospinal irradiation of kids with high hazard medulloblastoma with the usage of our new additive gas pedal and intervention planning system Elekta & A ; Precise Elekta is about indistinguishable to other surveies and is making its mark ( OARs are within normal tissue tolerance ) .
As respects the dosage to the lenses, utilizing block shielding shows lower doses to eyes and lenses irrespective to the place of isocenter, on the other manus, with the usage of MLCs for screening, the isocenter should be behind the oculus non in the centre of the encephalon as this shows lower doses to eyes and lenses. If we use the isocenter in the encephalon so we should utilize block.
