Original Article - Onkologia i Radioterapia ( 2021) Volume 15, Issue 5

Dosimetric evaluation of patient setup errors due to uncertainties during IMRT for head and neck cancer cases

Marwa Abdel Razek1*, Khaled Elshahat2, Ehab Khalil1 and Wafaa Khalil3
 
1Department of Radiotherapy, NCI, Cairo University, Egypt
2Department of Clinical Oncology, Faculty of Medicine, Al Azhar University, Egypt
3Department of Biophysics, Faculty of Sciences, Cairo University, Egypt
 
*Corresponding Author:
Marwa Abdel Razek, Department of Radiotherapy, NCI, Cairo University, Egypt, Email: [email protected]

Received: 02-Feb-2021 Accepted: 25-Mar-2021 Published: 15-Apr-2021

Abstract

Background: IMRT become popular because dose escalation to the target can be done while sparing adjacent normal tissues. Intensity-modulated radiation therapy tends to produce steep absorbed-dose gradients between the target volume and the OAR. This study was done to determine the error during RT on positioning displacement for patients treated for head and neck cancer. We tried to find the magnitude of daily setup errors to determine the set up error cases. The results can help physicians to determine the most suitable margin for head and neck cases. Results: Data from 20 patients calculated. The Right/Left direction as X direction, Anterior/Posterior direction as Y shift and Up/Down direction as Z shift. Average shift for all fractions calculated to be 0.05 cm, 0.08 cm and -0.02 cm as RT/LT, Ant/Post and Up/Down shifts. Conclusions: To reduce setup errors in patients with H&N cancer receiving RT. The use of on-line image-guided radiotherapy is recommended to increase accuracy.

Keywords

Adaptive Radiotherapy,Head and Neck Cancer; Image-guided Radiotherapy; Setup Error; IMRT

Introduction

Radiation Therapy (RT) is commonly used as part of multiple modality treatment for prostate cancer. Intensity-Modulated Radiation Therapy (IMRT) has become increasingly popular because dose escalation to the target can be done while sparing adjacent normal tissues. Several factors such as the accuracy of the immobilization device change in body contours, and tumor regression could lead to setup uncertainties during RT, all of these factors need to be minimized with the use of special approaches. Image-Guided Radiation Therapy (IGRT) can be used to correct and quantify geometrical uncertainties for daily setup [1].

IMRT target contours in three dimensions, often with six independent values~anterior, posterior, medial, lateral, superior, inferior [2]. Intensity-modulated radiation therapy tends to produce steep absorbed-dose gradients between the target volume and the OAR. Having realistic margins for both the tumor volume and any OAR. Factors affecting margin requirements to define the PTV include uncertainty of patient positioning, mechanical uncertainty of the equipment (e.g. gantry sagging), dosimetric uncertainties (e.g. penetration of the beam), the use of motion management techniques such as gating, image transfer errors from CT and simulator to the treatment unit, and human factors. These factors will vary from center to center, and, within a given center, from machine to machine and from patient to patient. The use of patient immobilization devices, the application of quality-assurance programs, and the skill and experience of the radiographers/radiotherapists are also important and must be taken into account. Additionally, the use of different image-guidance systems or other uncertaintyreduction techniques can significantly alter the size of the required margins.

An error is defined as; The difference between the measured (observation) value and the actual (true) value [3-12].

Errors can be divided into three categories:

• Personal Error

• Systematic Error

• Random Error

Systematic Error

The type of error arises due to defect in the measuring device or its data handling system, or because the instrument is wrongly used by the experimenter. Generally, it is called "ZERO ERROR". It may be positive or negative error and can be removed by correcting measurement device. [13-14].

Systematic errors may be of four kinds:

• Instrumental: For example, a poorly calibrated instrument such as a thermometer that reads 1020C when immersed in boiling water and 20C when immersed in ice water at atmospheric pressure. Such a thermometer would result in measured values that are consistently too high.

• Observational: For example, parallax in reading a meter scale.

• Environmental: For example, an electrical power that causes measured currents to be consistently too low.

• Theoretical: Due to simplification of the model system or approximations in the equations describing it. For example, if your theory says that the temperature of the surrounding will not affect the readings taken when it actually does, then this factor will introduce a source of error [13].

Random Error

The error produced due to sudden change in experimental conditions. For example: During sudden change in temperature, change in humidity, fluctuation in potential difference (voltage). It is an accidental error and is beyond the control of the person making measurement. Random errors are positive and negative fluctuations that cause about one-half of the measurements to be too high and one-half to be too low. Sources of random errors cannot always be identified. Possible sources of random errors are as follows:

• Observational. For example, errors in judgment of an observer when reading the scale of a measuring device to the smallest division.

• Environmental. For example, unpredictable fluctuations in line voltage, temperature, or mechanical vibrations of equipment.

Random errors, unlike systematic errors, can often be quantified by statistical analysis; therefore, the effects of random errors on the quantity or physical law under investigation can often be determined. The precision is limited by the random errors. It may usually be determined by repeating the measurements.

Random errors are errors which fluctuate from one measurement to the next. They yield results distributed about some mean value. They can occur for a variety of reasons. They may occur due to lack of sensitivity. For a sufficiently a small change an instrument may not be able to respond to it or to indicate it or the observer may not be able to discern it. They may occur due to noise. There may be extraneous disturbances which cannot be taken into account. They may be due to imprecise definition. They may also occur due to statistical processes such as the roll of dice [9,12].

This study was done to determine the error during RT on positioning displacement for patients treated for Head and Neck. We tried to find the magnitude of daily setup errors to determine the set up error cases. The results can help physicians to determine the most suitable margin for H&N cases.

Methods

Patients

We used data from 20 patients treated for Head and Neck at Our radiotherapy center. All patients received IGRT with daily on-line kilovoltage imaging with weekly Cone Beam Computed Tomography (CBCT) to correct the treatment position. No patients had ART planning before a prescribed dose of (70) Gy.

Treatment Planning

To enhance the accuracy of the daily irradiated position, simulation using a Computed Tomographic (CT) scan simulator (GE ct) was made. The scans consisted of a protocol with a 2.5-mm-slice thickness, and Marks on the patients’ skin were drawn using setup lasers to facilitate an accurate daily position.

For patients receiving definitive RT, the Clinical Target Volume (CTV) was defined as the gross tumor volume plus a margin of 7 mm posteriorly, and 10 mm in all other directions. All patients underwent IMRT plans and all plans were carried out using a commercial radiation treatment planning system (Elekta).

Treatment verification

All patients were treated with IGRT with linear accelerator equipped with an on-line On-Board Imaging (OBI) function including two-dimensional (2D) kilovoltage (kV) images and three-dimensional (3D) CBCT. The technicians set up the patients on a couch in the simulation room according to the marks drawn on their bodies. On-line OBI images (2D kV images daily and 3D CBCT weekly) were taken and sent to the station where they could be registered to digitally reconstructed radiographs from the treatment planning images. Two technicians compared these paired images by correlating the bony anatomy and corrected the difference by shifting the couch translationally before treatment. Then, physician confirmed the corrected on-line images. Anatomic reference landmarks included at least three visible bony structures.

Setup displacement

After image registration, quantification of alignment data for daily OBI in the Superior-Inferior (SI), Anterior-Posterior (AP), and Medial-Lateral (ML) directions, and Couch Rotation (CR) for all patients were collected. For each direction, the recorded setup displacements were composed of two components, Systematic Errors (SE) and Random Errors (RE). The SE was the deviation between the simulated patient position and the average patient position, while the RE was that which occurred between different fractions.

Results

Setup errors are modelled as shifts of the beam isocenter. A shift of the beam isocenter leads to a non-rigid shift of the dose distribution. Small setup errors might thus lead to large displacements of spots that travel close to and in parallel with steep density gradients, such as along bone edges.in our study average data from 20 patient during all fractions calculated in table (1).The Right/Left direction as X direction, Anterior/Posterior direction as Y shift and Up/Down direction as Z shift as shown. Then drawing the relation between X, Y and Z shift as a function of no. of fractions then average shift for all fractions calculated to be (0.05) cm, ( 0.08) cm and (-0.02) cm as RT/LT , Ant./Post. And Up/Down shifts.

Discussion

Several studies have investigated setup uncertainty in H&N cancer patients [8]. According to the International Commission on Radiation Units and Measurements report 62 [5], an inappropriate definition of the CTV-PTV margin, accounting for organ motion and setup uncertainties, may yield an under-dose to the CTV. Organ motion could be neglected, while variability due to inadequate setup or deformity must be carefully considered. In clinical practice, use of daily IGRT is not always possible because of limited facilities in some countries as well as concerns about increased daily doses to patients [4]. Because of RT treatment for H and N cancer, anatomical modifications due to tumor regression led to geometric change of tumor volume and organs at risk and Margins in the three translation directions should be done.

Generally, our study record shifts during all fractions (shown in Tables 1-33).

Table 1. Bet Shifts and no. of fractions. Shifts were found that it range from 1 mm to 4 mm in X- direction and from 1 mm to 2 mm in Y and from 2 mm to 5 mm in Z direction (between + and in all directions) . Then we applied shifts to plan on planning system and recording differences occurred on DVH’s of targets and critical organs

No. Xavg Yavg Zavg
1 0.39 -0.07 0.04
2 -0.04 0.04 -0.12
3 -0.05 0 -0.0 1
4 -0.0 1 0.04 0.23
5 -0.03 0 .11 -0.14
6 0.08 0 .11 -0.1
7 -0.0 1 0.13 0.0 1
8 0.07 0.15 -0.15
9 0.1 0.15 -0.23
10 0.07 0.19 -0.07
11 0.03 0.08 -0.03
12 0.03 0.13 -0 .10
13 0.03 0.12 -0.13
14 0.06 0.1 -0 .07
15 0.05 0.12 -0.04
16 0.1 0.23 -0.1
17 0.03 0.12 -0.11
18 0.04 0 .11 -0.11
19 0.07 0 .11 -0.04
20 0.07 0.15 -0.04
21 0.03 0.07 0.0 1
22 0.07 -0.03 -0.1
23 0.08 0.0 1 0.03
24 0.05 0.06 0.02
25 0 0.06 -0.05
26 0 0.03 0
27 0.0 1 0.07 0.07
28 0.05 0.09 0.0 1
29 0.05 0.04 0.48
30 0.05 0.05 0.03
31 0.06 0.03 0.02
32 0.04 0.02 0.0 1
33 0.03 0.04 0.03
34 0.1 0.02 0.0 1
35 0.05 0.0 1 -0.0 1

Table 2. Changes occurred to dose delivered to 98% volume of PTV45 with different shifts

  PTV54Gy 98%  
Shift dose X dose Y dose Z
1 50.877 50.766 50.878
2 50.887 50.148 50.814
3 50.775 49.521 50.585
4 50.704 48.849 50.398
5 50.323 47.453 50.358
6 50.09 45.515 49.88
7 49.801 41.556 49.575
8 49.251 38.581 49.195
-1 50.651 50.881 50.833
-2 50.622 50.626 50.617
-3 50.368 50.258 50.442
-4 50.211 49.839 50.197
-5 49.9 49.391 49.653
-6 49.499 49.072 49.096
-7 49.067 48.446 48.566
-8 48.594 47.811 47.924

Table 3. Changes occurred to dose delivered to 98% volume of PTV60 with different shifts

  PTV60Gy 98%  
Shift Dose X Dose Y Dose Z
1 55.661 56.07 55.574
2 55.228 56.059 55.287
3 54.526 55.965 54.89
4 53.73 55.614 54.156
5 52.545 55.248 53.25
6 51.185 54.696 52.314
7 49.7 53.992 51.38
8 48.118 53.267 50.179
-1 55.506 55.193 55.714
-2 54.939 54.485 55.425
-3 54.07 53.649 54.904
-4 64.754 52.196 54.494
-5 51.407 50.62 53.78
-6 49.74 48.922 52.985
-7 57.891 47.437 52.156
-8 45.739 45.268 51.238

Table 4. Changes occurred to dose delivered to 98% volume of PTV70 with different shifts

  PTV70Gy 98%  
shift dose X dose Y dose Z
1 64.408 64.925 63.979
2 64.299 65.127 63.39
3 63.957 64.943 62.569
4 63.36 64.656 61.401
5 62.208 64.251 60.512
6 61.513 63.624 59.426
7 59.905 62.905 58.138
8 58.205 62.351 56.817
-1 64.322 63.746 65.025
-2 64.132 63.034 64.977
-3 63.365 62.144 64.94
-4 62.7 60.594 64.628
-5 61.124 59.544 64.226
-6 59.481 58.339 63.363
-7 57.891 57.56 62.542
-8 55.793 56.431 61.652

Table 5. Changes Max dose of LT lens with different shifts

  It lens 11.93GY  
shift Max dose Max dose Y Max dose Z
1 11.887 14.616 12.956
2 12.318 18.333 12.959
3 11.993 21.774 12.839
4 12.472 23.395 12.643
5 12.282 25.196 13.765
6 12.725 27.55 13.018
7 12.688 30.325 13.234
8 13.331 31.743 13.754
 -1 12.495 10.77 11.97
-2 11.784 9.408 11.766
-3 11.729 7.703 11.936
-4 12.381 5.8 11.667
-5 12.108 5.149 11.679
-6 11.542 4.169 11.719
-7 10.959 4.427 11.45
-8 10.872 4.035 11.667

Table 6. Changes occurred to Max dose of RT lens with different shifts

  Rt lens 5.492 GY  
shift lllax dose lllax dose lllax dose
1 5.213 6.331 5.107
2 5.485 7.724 5.5
3 5.302 8.7 5.225
4 5.187 10.367 6.079
5 5.25 10.44 5.993
6 4.908 12.508 5.681
7 5.194 15.007 6.057
8 5.434 17.473 5.708
 -1 5.624 5.09 5.678
-2 6.027 4.733 5.578
-3 5.712 4.214 5.777
-4 5.305 3.524 5.609
-5 6.499 3.77 5.936
-6 6.566 3.539 5.397
-7 5.853 3.927 5.518
-8 6.227 3.085 5.506

Table 7. Changes occurred to Max dose of Optic Chiasm with different shifts

  optic chiasm 35.97 GY  
shift Max dose X Max dose Y Max dose Z
1 35.257 40.796 35.884
2 36.394 48.758 34.347
3 35.797 51.74 33.358
4 36.405 53.457 33.121
5 35.329 56.585 32.5
6 34.644 58.335 32.544
7 34.218 59.904 32.449
8 37.179 59.958 29.524
-1 36.28 31.255 36.102
-2 35.08 27 .848 36.553
-3 35.804 24.333 36.743
-4 36.559 20.367 37.535
-5 34.425 18.204 37.309
-6 35.884 16.471 37.698
-7 33.829 15.847 37.756
-8 34.841 13.338 38.717

Table 8. Changes occurred to Max dose of Brain stem with different shifts

  Brain stem 51.476 GY  
shift Max dose X Max dose Y I/lax dose
1 51.033 51.413 51.213
2 51.266 51.78 49.893
3 51.744 52.131 49.453
4 54.656 52.48 49.458
5 54.648 52.909 49.655
6 54.4 53.118 48.344
7 55.876 53.558 48.126
8 55.915 54.742 47.992
-1 51.327 53.683 51.254
-2 52.087 51.841 52.767
-3 53.902 51.65 53.098
-4 54.455 51.602 54.192
-5 55.176 50.448 55.52
-6 56.864 50.392 57.59
-7 58.499 50.064 59.458
-8 59.813 49.592 60.72

Table 9. Changes occurred to Max dose of Spinal cord with different shifts

  spinal cord 39.516GY  
shift Max dose X ax dose \/lax dose
1 39.953 39.88 39.453
2 41.217 40.281 38.59
3 43.131 39.985 36.991
4 43.554 39.764 36.808
5 45.131 39.836 36.79
6 46.495 42.752 36.234
7 47.607 40.312 35.479
8 49.161 41.485 35.196
-1 41.093 40.191 41.116
-2 41.453 40.519 42.919
-3 41.119 40.602 45.022
-4 42.64 39.919 47.207
-5 43.938 41.707 48.363
-6 45.044 42.066 49.213
-7 45.117 41.436 50.289
-8 47.221 41.665 53.792

Table 10. Changes occurred to Max dose of optic chiasm PRV with different shifts

  Optic chiasm PRV 34 Gy
Shift Max dose X Max dose Max dose Z
1 36.882 41.729 36.372
2 36.394 49.672 35.185
3 36.023 51.842 34.591
4 36.405 54.931 33.298
5 35.916 58.258 34.4
6 35.467 58.849 33.842
7 34.802 61.59 33.977
8 38.27 61.197 30.738
-1 36.28 32.268 36.971
-2 35.841 28.971 36.349
-3 35.804 25.866 36.916
-4 36.684 20.848 38.199
-5 35.108 18.204 37.309
-6 36.352 17.285 37.698
-7 34.87 16.25 38.967
-8 35.763 13.872 38.895

Table 11. Changes occurred to Max dose of Brain stem PRV with different shifts

  B S.PRV 45.6 Gy  
Shift \/lax dose fi/lax dose \/lax dose
1 55.444 54.46 1 54.059
2 56.763 55.12 1 52.819
3 55.937 56.145 51.913
4 57.057 56.663 51.458
5 58.347 57.942 51.158
6 60.711 58.035 50.305
7 62.574 61.039 49.788
8 62.764 60.852 50.65
-1 54.177 53.822 55.658
-2 55.823 53.857 56.914
-3 58.35 53.779 58.502
-4 58.955 53.722 59.74
-5 60.527 52.636 63.105
-6 62.401 52.589 64.788
-7 65.043 53.287 63.783
-8 67.232 54.344 64.363

Table 12. Changes occurred to Max dose S.C. PRV with different shifts

  S.C.PRV 49.9GY  
Shift Max dose Max dose Max dose
1 50.282 49.159 48.046
2 52.184 48.399 47.596
3 53.176 48.53  1 44.38
4 54.685 47.983 44.108
5 54.536 47.746 42.577
6 57.125 49.087 40.573
7 59.731 48.98 39.647
8 58.396 48.569 38.95
-1 49.157 49.726 51.042
-2 50.817 51.092 51.484
-3 51.076 50.343 53.242
-4 53.061 51.125 54.535
-5 53.857 51.834 56.308
-6 56.933 51.633 61.403
-7 56.416 50.405 61.255
-8 58.762 51.567 63.104

Table 13. Changes occurred to Max dose of LT. Parotid with different shifts

  Lt Parotid Mean 25 Gy
Shift Dose X Dose Y Dose Z
1 27.595 26.237 26.436
2 29.488 26.824 26.844
3 31.315 27.195 27.393
4 33.341 27.502 28.095
5 35.428 27.99 1 28.752
6 37.597 28.413 29.489
7 39.612 29.017 30.379
8 41.882 29.624 31.234
  -1 24.345 25.656 25.627
-2 22.743 25.578 25.472
-3 21.365 25.235 25.32
-4 20.074 24.973 25.182
-5 18.95 24.825 25.207
-6 17.838 24.582 25.298
-7 16.957 24.609 25.507
-8 16.046 24.466 25.697

Table 14. Changes occurred to Max dose of RT. Parotid with different shifts

  RT parotid 25.3GY  
Shift Max Dose Max Dose Max Dose
1 24.297 26.25 26.366
2 22.805 26.792   26.96
3 21.545 27.244 27.602
4 20.154 27.72   28.16
5 18.895 28.336 29.011
6 17.89 28.828 29.739
7 16.907 29.49  130.622
8 15.994 30.018 31.246
-11 27.38 25.258 25.285
-2 29 24.803 24.806
-3 30.646 24.399 24.482
-4 32.304 24.082 24.189
-5 33.959 23.623 23.859
-6 35.7 23.311 23.796
-7 37.45 23 1 23.73
-8 39.178 22.743 23.773

Table 15. Changes occurred to Mean dose of LT. Cochlea with different shifts

Lt coch lea mean 26.9 Gy<45
Shift Dose X Dose Y Dose Z
1 27.895 27.592 26.075
2 30.316 30.82 25.808
3 32.448 33.476 24.966
4 35.475 34.57 1 24.639
5 37.859 37.309 24.228
6 38.97 40.127 23.123
7 42.462 46.016 23.02
8 43.021 50.14 23.711
 -1 25.225 25.77 27.507
-2 24.664 26.077 28.843
-3 24.345 26.113 29.139
-4 25.252 26.065 30.747
-5 24.71 25.506 31.586
-6 24.431 26.337 32.662
-7 25.501 26.26 1 34.268
-8 25.484 27.122 35.478

Table 16. Changes occurred to Mean dose of RT. Cochlea with different shifts

Rt Cochlea 42 Gy  
Shift Dose X Dose Y Dose Z
1 39.249 43.052 42.22
2 37.369 44.969 41.235
3 37.308 46.934 40.955
4 36.109 47.565 40.342
5 35.122 50.062 40.07
6 34.088 53.054 38.986
7 34.029 56.644 39.013
8 33.184 58.154 37.529
 -1 43.546 41.769 41.483
-2 45.458 41.559 41.598
-3 48.136 40.816 42.103
-4 48.563 39.964 41.937
-5 51.193   39.73 1 42.578
-6 52.523  38.92 42.989
-7 52.402 39.247 42.777
-8 52.595 39.142 43.585

Table 17. Changes occurred to Max dose of Mandible with different shifts

  Mandible 70 Gy  
Shift Dose X Dose Y Dose Z
1 70.443 71.084 71.076
2 69.827 70.557 71.256
3 71.264 68.992 70.351
4 70.715 72.218 70.024
5 70.811 71.352 72.473
6  72.82 70.321 70.941
7 73.1 69.697 71.085
8 74.055 70.91 70.962
 -1 70.052 69.865 71.08
-2 69.616 69.02 69.672
-3 69.577 69.68 70.86
-4 69.991 71.36 69.675
-5 68.743 68.404 68.571
-6 69.352 69.143 68.556
-7 69.136 69.026 68.994
-8 69.535 66.973 66.8

Table 18. Changes occurred to Max dose of Lt.Temp.with different shifts

  Lt Temp 59.3 Gy  
Shift Dose X Dose Y Dose Z
1 59.884 59.89 59.775
2 62.287 60.876 58.143
3 61.268 62.334 58.515
4 61.925 63.638 57.838
5 62.071 63.576 55.5
6 63.143 64.044 55.996
7 62.941 62.357 55.885
8 63.252 64.011 52.58
-1 61.129 59.446 60.117
-2 58.444 58.887 60.29
-3 58.355 57.707 61.783
-4 56.259 55.826 62.22
-5 55.878 57.763 63.274
-6 55.569 56.698 64.911
-7 54.96 52.997 63.539
-8 53.756 52.942 62.672

Table 19. Changes occurred to Max dose of RT. Temp with different shifts

  Rt Temp 59 Gy  
Shift Dose X Dose Y Dose Z
1 61.96 60.265 60.188
2 60.457 61.111 61.303
3 57.958  61.5 59.114
4 57.342 63.218 59.889
5 56.753 64.083 58.195
6 55.213 64.35 58.163
7 54.224   64.6 58.023
8 52.399  66.342 58.917
  -1 60.538  62.228 61.112
-2 64.064  59.324 61.718
-3 61.688  58.93  161.32
-4 62.364  57.562  63
-5 61.708  58.362 62.543
-6 63.547  56.536 61.952
-7 63.148 56 63.457
-8 64.203  55.122 62.953

Table 20. Changes occurred to Max dose of Lt .Eye with different shifts

  LT Eye 48 Gy  
Shift Dose X Dose Y Dose Z
1 49.33 51.196 51.49
2 51.012 53.328 49.833
3 50.488 53.358 50.568
4 51.101 56.145 54.947
5 51.156 54.779 54.195
6 51.208 58.32 54.625
7 51.902 55.738 53.512
8 51.372 58.4 53.129
-1 48.008 47.025 47.557
-2 45.831 45.382 45.913
-3 45.301 43.542 44.929
-4 44.558 39.304 44.682
-5 43.405 38.584 43.116
-6 41.14 35.227 42.48
-7 40.781 35.129 42.147
-8 39.221 31.59 41.096

Table 21. Changes occurred to Max dose of RT Eye with different shifts

  Rt Eye 27.5Gy  
Shift Dose X Dose Y Dose Z
1 25.553 31.444 27.816
2 26.012 36.865 29.768
3 25.243 38.46 29.717
4 22.954 41.132 32.998
5 22.185 43.974 31.796
6 20.905 45.087 32.18
7 21.506 47.015 32.162
8 21.449 48.588 32.305
-1 28.709 25.323 26.597
-2 29.107 23.302 25.778
-3 29.442 20.852 25.273
-4 30.66 15.872 24.12
-5 31.475 13.664 23.3
-6 32.046 11.502 23.78
-7 31.66 1 11.274 22.595
-8 31.59 1 8.945 22.378

Table 22. Changes occurred to max dose of LT optic nerve with different shifts

LT Optic Nerve 38Gy  
Shift  Dose X Dose Y Dose Z
1 38.468 41.899   36.95
2 37.23 147.345  36.9
3 38.402 51.182  36.227
4 37.475 52.393 35.699
5 37.718 54.413 35.957
6 39.357 56.603 36.105
7 38.668 59.258 35.199
8 37.889 61.62 36.89
-1 38.556 33.776 38.469
-2 36.54 30.619 37.84
-3 36.926 27.664 39.98
-4 37.367 21.323 40.335
-5 37.417 19.764 38.332
-6 36.475 15.88 38.513
-7 36.209 14.186 39.578
-8 36.508 12.258  40.4

Table 23. Changes occurred to Max dose of RT Optic Nerve with different shifts

Rt Optic Nerv 32 Gy  
Shift Dose X Dose Y Dose Z
1 31.097 38.036 32.299
2 31.79 47.338 31.642
3 31.375 48.664 34.853
4 30.142 52.028 32.954
5 30.272 53.753 34.312
6   30.44 54.946 32.85
7 31.056 57.88 33.088
8 29.345 59.509 32.58
-1 32.819 27.319  33.15
-2 34.553 26.87 33.916
-3 33.372 21.68 31.938
-4 33.113 18.287 32.003
-5 34.682 16.846 31.186
-6 33.818 15.278 31.379
-7 34.136 14.09  132.217
-8 35.408 13.272 31.622

Table 24. Changes occurred to Max dose of LT TMJ with different shifts

  LTTMJ 69 Gy  
Shift Dose X Dose Y Dose Z
1 69.087 72.423 68.638
2 69.299 68.692 69.984
3 69.234 71.458 72.068
4 70.151 69.666 68.022
5 70.289 70.161 67.092
6 71.586 70.679 70.456
7 73.394 72.707 68.928
8 71.934 71.162 67.834
 -1 69.739 67.478 68.159
-2 66.332 66.968 67.805
-3 68.364 66.321 68.791
-4 68.062 62.82 68.011
-5 65.243 60.664 67.895
-6 64.393 57.36 68.57
-7 62.148 55.866 66.769
-8 59.736 52.004 66.901

Table 25. Changes occurred to Max dose of RT TMJ with different shifts

  RTTMJ 65 Gy  
Shift Dose X Dose Y Dose Z
1 64.223 67.173 63.641
2 63.891 66.94 66.618
3 59.44 66.8 63.005
4 58.77 72.07 64.119
5 58.107 69.614 62.941
6 52.846 71.024 63.547
7 50.865 70.904 62.062
8 47.48 69.608 62.014
-1 66.388 65.361 66.138
-2 70.02 63.395 64.624
-3 67.289 61.542 65.01
-4 68.788 59.19 64.654
-5 68.401 55.572 66.617
-6 70.995 51.764 63.441
-7 68.994 50.018 63.364
-8 69.814 48.455 62.909

Table 26. Changes occurred to Mean dose of Thyroid gland with different shifts

Thyroid Glani 43.5Gy 43.5Gy  
Shift Dose X Dose Y Dose Z
1 45.523 45.633 44.615
2 45.886 45.902 45.885
3 46.07 46.255 46.237
4 46.211 46.841 46.608
5 46.259 47.27 46.756
6 46.281 47.504 46.95
7 46.232 47.801 47.115
8 46.203 48.52 47.348
-1 45.004 45.061 46.881
-2 44.649 44.791 44.47
-3 44.169 44.347 44.082
-4 43.808 44.25 43.453
-5 43.152 44.195 43.22
-6 42.621 44.101 42.71
-7 42.273 43.926 42.385
-8 41.995 43.667 41.944

Table 27. Changes occurred to Mean dose of Esophageal inlet with different shifts

  Esophageal Inlet 42 Gy Mean
Shift Dose X Dose Y Dose Z
 1 40.919 42.328 42.012
2 40.381 42.024 41.604
3 39.498 42.523 41.455
4 38.964 42.604 41.649
5 38.453 43.449 41.114
6 37.454 43.509 41.262
7 37.467 43.263 40.571
8 37.048 44.197 40.824
 -1 43.26 42.159 41.88
-2 44.107 41.567 42.026
-3 44.783 40.504 42.153
-4 46.28 40.821 41.451
 -5 47.193 40.57 41.333
-6 48.138 40.406 41.225
-7 48.965 40.224 41.031
-8 50.518 39.373 40.536

Table 28. Changes occurred to Mean dose of Cervical Esophagus with different shifts

  Cervical Esophagus 39.22Gy Mean
Shift Dose X Dose Y Dose Z
1 38.67 38.925 38.897
2 38.196 38.3 38.653
3 37.779 37.9 1 38.554
4 37.313 37.772 38.164
5 37.043 37.386 37.768
6 36.745 36.882 37.634
7 36.375 36.088 37.322
8 36.292 35.703 37.155
-1 39.837 39.733 39.517
-2 40.485 39.715 39.884
-3 40.907 39.833 40.049
-4 41.265 40.319 40.192
-5 41.997 40.474 40.268
-6 42.375 40.717 40.605
-7 42.88  140.653 41.026
-8 43.473 40.724 41.162

Table 29. Changes occurred to Mean dose of Base of tongue with different shifts

Base Of Tongue 45Gy  
Shift Dose X Dose Y Dose Z
1 45.492 45.376 45.6
2 45.506 59.502 45.732
3 45.568 45.453 46.032
4 45.876 45.643 46.227
5 46.294  45.54 46.493
6 46.447 45.488 46.708
7 46.825 45.432 47.118
8 41.385 45.25 147.426
-1 45.256 45.162 45.223
-2 45.529 44.724 44.86
-3 45.716 44.694 44.579
-4 45.822 44.643 44.534
-5 46.36 44.376 44.256
-6 46.453 44.376 44.298
-7 47.035 44.293 44.284
-8 47.605 44.345 44.322

Table 30. Changes occurred to Mean dose of Lt Carotid with different shifts

  LT Carotid 60.5Gy  
Shift Dose X Dose Y Dose Z
1 60.431 60.334 60.202
2 60.307 59.746 59.739
3 60.243 59.323 59.515
4 60.149 59.255 59.41
5 59.736 58.885 58.999
6 59.338 58.601 58.471
7 59.037 58.111 57.999
8 58.399 57.901 57.508
-1 60.461 60.709 60.725
-2 60.31 60.837 60.674
-3 60.078 61.142 60.583
-4 59.968 61.704 60.59
-5 59.761 61.826 60.783
-6 59.598 62.244 60.974
-7 59.039 62.124 60.757
-8 58.959 62.274 60.833

Table 31. Changes occurred to Mean dose of Rt Carotid with different shifts

RT Carotid 64.3Gy  
Shift Dose X Dose Y Dose Z
1 65.155 64.474 64.573
2 65.155 64.513 64.534
3 65.155 64.479   64.57
4 65.155 64.394 64.484
5 65.155 64.298 64.233
6 65.155 64.199 63.886
7 65.155 64.066 63.4
8 65.155 63.822 62.97
 -1 64.317 64.634 64.496
-2 63.93 164.597 64.294
-3 63.506 64.464 64.047
-4 63.183 64.748 64.04
-5 62.653 64.544 63.876
-6 61.903 64.605 63.752
-7 61.269  64.34 63.386
-8 60.634 64.379 63.277

Table 32. Illustrate Changes occurred in critical organs according to shifts

  Lt lens Rt lens Optic Chiasm B.S. S.C. Lt parotid RT parotid Lt cochlea Rt cochlea Mandibe Lt Temp Rt temp
X +direction Const. variated
X  -direction variated variated variated
Y +direction variated variated
Y -direction variated variated variated
Z +direction variated variated
Z -direction variated variated const

Table 33. Illustrate changes occurred in critical organs according to shifts

  Lt eye Rt eye Lt O.N Rt O.N. Lt TMJ Rt TMJ Thyroid Eso. inlet Cervical Eso. Base of tongue Lt carotid Rt carotid
X +direction variated variated Almost const.
X  -direction
Y +direction variated variated Almost const. Almost const.
Y -direction Almost const.
Z +direction variated variated variated variated
Z -direction variated variated variated Almost const.

This study recommends on-line IGRT for patients receiving RT to deliver more accurate dose to tumor and avoid extra dose to organs at risk due to anatomical change also according to (11-12) shifts in all direction reduced when using on line image guided leading to reduce margins in all direction surrounding the tumor and saving critical organs.

The primary objective of the study was to measure inter-fraction setup variation in head and neck cancer patients undergoing. Displacements of portal images from CT images, set as reference images, were measured for calculating errors are related to any accidental error during setup, due to mis-positioning of the patient in the mask, movements of the patient or organ motion in the period between positioning and start of irradiation or during irradiation. Naiyanet, N. et al [10] reported the L-R, S-I and A-P axes. While our study has shown the errors along the L-R, S-I and A-P axes) that 0.05 mm, 0.08 mm and -0.02 mm. Large systematic errors lead to a large under-dosage.

The secondary objective of the present study was to define adequate CTV-to-PTV margin for IMRT of head and neck cancer in our department. Ideally, the CTV-to-PTV margin should be determined solely by the magnitudes of the uncertainties involved. In practice, the clinician usually also considers abutting healthy tissues when deciding on the size of the CTV-to-PTV margin.

Generally, our study record shifts during all fractions (shown in Tables 1) & then illustrated the differences occurred in target and critical organs according to shifts that applied to plan on planning system. We found that all targets dose reduced with increasing shifts.

Conclusion

In this examine, the scientific effectiveness of planned and delivered dose distributions of IMRT technique for head-andneck cancer became evaluated the usage of both physical and dose constraints criteria. The distinction between the “one-toall” and “cascade” dose distributions became small, statistically insignificant, and really near the values of the corresponding treatment plans. However, for a fraction of the sufferers and given OAR, the differences among the added and deliberate doses had been mainly large. These findings aid the necessity of the correct affected person setup earlier than the treatment the usage of IGRT, as a result minimizing dose inaccuracy mistakes. We recommend reducing setup errors in patients with Head and Neck cancer receiving RT, the use of on-line image-guided radiotherapy is recommended to increase accuracy.

List of Abbreviations

Abbreviation Symbol
Three Dimensional Radiation Therapy 3D CRT
Intensity Modulated Radiation Therapy IMRT
Dynamic Multi Leaf Collimator DMLC
Static Multi Leaf Collimator SMLC
Dose Volume Histogram DVH
Mega Volt MV
Clinical Target Volume CTV
Planning Target Volume PTV
Organ at Risk OAR
Gray Gy
Fraction Fr
Computed Tomography CT
Treatment Planning System TPS
Linear Accelerators LINAC
Electronic Portal Imager Device EPID
Digitally Reconstructed Radiograph DRR
Prostate-Specific Antigen PSA
Beam Eye View BEV
Right Rt
Left Lt
Monitor Unit MU
Clock Wise CW
Counter Clock Wise CCW
Dose Maximum Dmax

References

Editors List

  • S.SREEDHAR

    Submitted PhD thesis in Biotechnology at GITAM University, Vizag.

  • Yousef Alomi

    Yousef Alomi
    The Past Head, General Administration of Pharmaceutical Care at Ministry of Health,
    Saudi Arabia Critical Care/TPN
    Clinical Pharmacist Ministry of Health,
    Riyadh, Saudi Arabia.

  • Osamu Tanaka

    Osamu Tanaka
    Assistant Professor,
    Department of Radiation Oncology
    Asahi University Hospital
    Gifu city, Gifu, Japan

  • Maher Abdel Fattah Al-Shayeb

    Department of Surgical Sciences, Ajman University, UAE

  • Andrzej Zdziennicki

    Institute of Gynecology and Obstetrics, Medical University of Lodz, I Clinic of Gynecology and Gynecological Oncology (Lodz, Poland)

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