Co esponding au ho : Adekunle Job
Copy igh © 2025 Au ho (s) e ain he copy igh o his a icle. This a icle is published unde he e ms o he C ea i e Commons A ibu ion Liscense 4.0.
Simula ion o ITV and GTV doses in SBRT ea men o lung cance
Adekunle Job *
Depa men o Radio he apy, Kuopio Uni e si y Hospi al, Puijonlaakson ie 2,70210 Kuopio, A ilia e o Uni e si y o
Eas e n Finland.
Wo ld Jou nal o Ad anced Resea ch and Re iews, 2025, 26(01), 3601-3612
Publica ion his o y: Recei ed on 14 Ma ch 2025; e ised on 21 Ap il 2025; accep ed on 23 Ap il 2025
A icle DOI: h ps://doi.o g/10.30574/wja .2025.26.1.1345
Abs ac
Backg ound: S e eo- ac ic body adia ion he apy (SBRT) has eme ged as a highly e ec i e ea men o ea ly-s age
non-small cell lung cance (NSCLC) and me as a ic lung umo s. I s abili y o deli e high doses o adia ion p ecisely o
he umo while spa ing su ounding heal hy issue makes i a p e e ed op ion o inope able cases. Accu a e dose
dis ibu ion assessmen is c i ical o op imizing ea men plans and minimizing oxici y isks.
Objec i e: This s udy aims o analyze he dose dis ibu ion o SBRT in lung cance ea men using Mon e Ca lo
simula ions and expe imen al e i ica ion. By e alua ing dose accu acy and i s impac on su ounding issues, he s udy
seeks o imp o e ea men p ecision and pa ien sa e y.
Me hods: We employed Mon e Ca lo-based simula ions o model adia ion dose dis ibu ions o lung umo s ea ed
wi h SBRT. The simula ed dose dis ibu ions we e compa ed wi h expe imen al measu emen s using ioniza ion
chambe s and ilm dosime y in a lung-equi alen phan om. Key pa ame e s, including dose he e ogenei y, umo
co e age, and o gan-a - isk (OAR) exposu e, we e analyzed o alida e he ea men planning sys em (TPS).
Resul s: P elimina y indings indica e ha Mon e Ca lo simula ions p o ide highe accu acy in p edic ing lung dose
dis ibu ions compa ed o con en ional algo i hms. Di e ences in calcula ed s. measu ed doses highligh he need o
imp o ed he e ogenei y co ec ions in TPS.
Conclusion: Mon e Ca lo simula ions o e a eliable app oach o e alua ing SBRT dose dis ibu ions in lung cance
pa ien s. Thei in eg a ion in o clinical wo k lows could enhance ea men planning accu acy, ul ima ely imp o ing
he apeu ic ou comes while minimizing oxici y isks.
Keywo ds: SBRT; PTV; GTV; ITV; VMAT; 4DCT; DCA; PlanningCT; MAXCT; MEANCT
1. In oduc ion
The in oduc ion o ype B and C dose calcula ion algo i hms o clinical ea men planning so wa e has signi ican ly
imp o ed dose p edic ion accu acy in low-densi y ma e ials such as lungs. Howe e , imp o ed calcula ion accu acy has
c ea ed new challenges o he use o mode n in e se planning echniques and he concep o dose no maliza ion when
a ge olume includes densi y inhomogenei ies.
To a oid c ea ing o e ly complica ed and non- obus ea men s con en ional ype A algo i hms a e ecommended in
he op imiza ion o in ensi y-modula ed adio he apy ea men o lung umo s. A e op imiza ion, he dose
dis ibu ion is calcula ed using he ype b (o c) algo i hm and he dose is no malized ypically o 95% co e age o PTV.
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Howe e , due o he in insic di e ences in dose calcula ion algo i hms, PTV no maliza ion has been epo ed o cause
inconsis en and excessi e GTV doses in lung umo s. Fu he mo e, ype A algo i hms a e no a ailable in all ea men
planning so wa e. Thus, a i icially inc easing he densi y o low-densi y a eas wi hin he PTV a ea is used o inc ease
he obus ness o he ea men plans. Howe e , he e a e no gene al guidelines on how elec on densi y o e ides
should be used.
Finally, o a oid he c ea ion o o e ly complex ea men plans, con o mal a cs wi h limi ed modula ion migh be mo e
sui ed o lung SBRT ea men s han VMAT echnique. Howe e , o a ge s loca ed close o c i ical s uc u es such as
a hea o a ibcage accep able ea men plan quali y migh no be eached wi h con o mal echniques. The aim o his
wo k is o in es iga e he e ec o ea men planning echniques and planning CT densi y o e ides on ITV and GTV
dose on he simula ed SBRT ea men o lung umo s.
2. Me hods
2.1. T ea men se up
Fou lung cance pa ien s ea ed o lung cance we e selec ed o he s udy. Fo each pa ien planning CT and 4D CT
a e acqui ed in ee b ea hing. GTV is delinea ed on one b ea hing phase on he 4D CT, and he con ou is p opaga ed
o o he b ea hing phases. ITV is de e mined as a union o he b ea hing phase speci ic GTV s uc u es. Subsequen ly,
PTV is c ea ed as an ou e ma gin a ound he ITV s uc u e.
Th ee planning CTs a e c ea ed o each pa ien o he ea men planning ask. Elec on densi ies wi hin PTV a e illed
o 0.8 o c ea e “Plannings”, and a maximum and mean in ensi y p ojec ions a e calcula ed based on 4D CT o c ea e
“MAXCT” and “MEANCT”, espec i ely. Subsequen ly, olume ic modula ed a c (VMAT), dynamic con o mal a c (DCA),
and con o mal a c (3DCA) ea men plans a e c ea ed o each planning CT and i s p ojec ions in Monaco ea men
planning so wa e. The ea men plans a e ca ied ou wi h he ac iona ion o 5 x 11 Gy.
Lung ea men is simula ed using MIM Su eCalc™ Mon e Ca lo algo i hm. C ea ed ea men plans a e ecalcula ed in o
each b ea hing phase in 4D CT and inal dose is accumula ed in o ITV and GTV. Subsequen ly, he simula ed dose is
compa ed wi h he planned o iginal dose o e alua e he obus ness o he ea men . Finally, he consis ency o GTV,
ITV and PTV doses among he pa ien s a e e alua ed.
The compa ison be ween planned o iginal and simula ed plans is pe o med using minimum dose, mean dose,
maximum dose and D95 alue o a dose olume his og am (DVH), whe e D95 is he minimum dose ha is deli e ed o
95 % o he umo olume.
2.2. Film measu emen s
To e alua e he accu acy o he me hod used o simula e he pa ien ea men s, a ea men planning p ocess desc ibed
abo e is epea ed o 4D lung phan om CIRS Dynamic Tho ax Phan om wi h an inse o Ga ch omic EBT III ilms.
C ea ed VMAT ea men plans o all di e en CTs (PlanningCT, MAXCT, MEANCT) o he phan om a e i adia ed in o
he mo ing 4D phan om wi h a 6 MV pho on beam.
To compa e he esul s, a ba ch o Ga ch omic ilms a e calib a ed in RW3 slab phan om (PTW) in he dep h o i e
cen ime e s and wi h he o al hickness o he phan om being 30 cen ime e s. Films we e ma ked wi h pen p io o
i adia ion o indica e he posi ions o he ilms. Calib a ion ilms we e i adia ed wi h an Elek a In ini y linac, SSD o 95
cm, gan y angle o ze o, a 6 MV pho on beam and wi h doses o 0 MU, 100 MU, 400 MU, 700 MU and 1000 MU. Films
we e used o de e mine op ical densi y o i adia ed and non-i adia ed ilms. A ull Ga ch omic ilm slab was scanned
o co ec scanne inhomogenei ies. I adia ed and con olled ilms in bo h cases, calib a ion and phan om i adia ion,
we e scanned 24 hou s a e he ini ial i adia ion wi h an Epson pe ec ion 750 p o scanne and he ed channel was
selec ed o analysis.
To con e ilm op ical densi y o dose he images o he scanned ilms we e p ocessed and calib a ed wi h Ma lab using
a single channel ilm dosime y me hod desc ibed in he pape by And e Micke e al. [1]. The calib a ion cu e o he
g aph used o analyze he ilms is shown in Figu e 1. A e he p ocessing, he esul s o he ilm measu emen s a e
compa ed wi h calcula ed dose dis ibu ions o e i y he accu acy o he ea men simula ions.
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Figu e 1 The dose calib a ion cu e o he ilms
3. Resul s
3.1. Dose o ITV
T ea men echnique speci ic and CT speci ic mean alues o he pa ame e s (min, mean, max, D95) ac oss all he
pa ien s a e lis ed in Table 1 o o iginally calcula ed plans and Table 2 o simula ed plans. The dose olume his og ams
(DVH) o all pa ien s, ea men echniques and CTs can be ound in Figu es 5-8 in Appendix 1.
When compa ing pa ame e s o ea men echniques lis ed in Table 1, i can be no iced ha all he a e aged alues
o DCA plans a e consis en ly highe han co esponding pa ame e s o VMAT o CA plans. Howe e , pa ame e s o
VMAT a e lowe han hose o CA plans, apa om minimum dose and D95. The same a e age alues o di e en CTs
(Table 1) show lowes alues o PlanningCT, whils MAXCT and MEANCT ha e simila alues ac oss all he pa ame e s.
Table 1 A e age alues o o iginally calcula ed plans in ITV
min
mean
max
D95
VMAT
56.065 ± 6.074
62.596 ± 3.756
67.187 ± 3.125
59.608 ± 4.786
DCA
57.047 ± 3.775
65.286 ± 3.145
70.715 ± 4.261
60.998 ± 3.154
CA
54.868 ± 5.139
64.578 ± 3.362
70.445 ± 5.055
59.141 ± 3.847
PlanningCT
54.920 ± 5.943
62.894 ± 4.190
69.008 ± 4.363
58.215 ± 5.299
MAXCT
56.068 ± 5.357
64.787 ± 2.854
69.127 ± 3.276
61.061 ± 3.022
MEANCT
56.992 ± 3.712
64.778 ± 3.353
70.212 ± 5.582
60.470 ± 2.750
A e age alues o simula ed plans a e lis ed in Table 2. Also, in his case o ea men echniques, he esul s a e
simila o o iginally calcula ed case. DCA has he highes alues h oughou all pa ame e s. VMAT has lowe mean and
maximum alues, bu highe minimum and D95 alues, compa ed o CA. Fo CT speci ic alues, MAXCT yields he lowes
alues o all pa ame e s, while MEANCT alues, on he o he hand, a e consis en ly highe han hose o o he CTs.
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Table 2 A e age alues o simula ed plans in ITV
min
mean
max
D95
VMAT
56.030 ± 5.963
62.069 ± 3.531
66.012 ± 3.710
59.295 ± 4.310
DCA
57.175 ± 3.393
64.709 ± 2.779
69.458 ± 3.687
60.496 ± 2.481
CA
55.058 ± 4.879
64.121 ± 3.783
69.065 ± 4.861
58.950 ± 3.761
PlanningCT
55.707 ± 5.538
63.464 ± 3.983
68.240 ± 4.301
59.166 ± 4.529
MAXCT
54.957 ± 5.374
62.713 ± 2.734
66.938 ± 2.899
58.860 ± 3.429
MEANCT
57.600 ± 3.119
64.722 ± 3.621
69.357 ± 5.353
60.716 ± 2.427
The di e ences be ween he o iginally calcula ed alues and simula ed alues in ITV can be seen in Table 3. Fo
ea men echnique ypes, VMAT ends o gene a e lowe minimum and maximum alues and CA lowe mean and D95
alues. DCA ends o gene a e he highes mean and D95 alues, while CA gene a es he highes minimum and maximum
alues.
The CT which s ands ou he mos , when compa ing he di e ence o o iginal and simula ed plan alues in Table 3, is
MAXCT, which alues a e isibly highe han hose o PlanningCT and MEANCT. When compa ing PlanningCT and
MEANCT, i can be no iced ha MEANCT alues ha e gene ally smalle di e ences when i comes o compa ing he
simila i y be ween o iginal and simula ed plans, apa om maximum dose.
Table 3 A e aged di e ences be ween o iginally calcula ed and simula ed plans in ITV
min
mean
max
D95
VMAT
0.035 ± 1.372
0.527 ± 1.774
1.175 ± 1.814
0.313 ± 1.818
DCA
-0.128 ± 1.386
0.576 ± 1.620
1.257 ± 0.964
0.502 ± 1.814
CA
-0.190 ± 1.289
0.457 ± 1.531
1.380 ± 0.634
0.190 ± 2.230
PlanningC
T
-0.787 ± 1.046
-0.570 ± 1.097
0.768 ± 0.768
-0.950 ± 1.347
MAXCT
1.112 ± 0.748
2.074 ± 1.097
2.188 ± 0.971
2.201 ± 1.013
MEANCT
-0.608 ± 1.201
0.056 ± 1.245
0.855 ± 1.315
-0.245 ± 1.677
Wi h hese esul s, i seems ha he simula ions made wi h a combina ion o MEANCT o PlanningCT, ega dless o he
ea men echnique, would yield he mos consis en esul compa ed o he o iginally calcula ed plans. The wo s
combina ion would on he o he hand be ea men echnique plans wi h MAXCT.
3.2. Dose o GTV
In igu es 9-12 in Appendix 2, DVH cu es o en indi idual GTV delinea ions and hei a e age is shown o all
ea men echniques and CTs o all pa ien s. Maximum and minimum dose alues o each CT o all ea men
echniques a e shown in Table 4.
Fo VMAT plans MAXCT yields he lowes and MEANCT he highes minimum alues. Meanwhile, he lowes maximum
alue can be seen o MEANCT and he highes o PlanningCT o VMAT plans. Fo DCA plans, he highes and lowes
minimum alues a e ound in PlanningCT and MEANCT, espec i ely. Fo maximum alues he highes can be ound in
PlanningCT and he lowes in MAXCT. Fo CA plans, he lowes minimum alue is o MAXCT and highes o MEANCT.
The lowes maximum alue is o MAXCT and highes o MEANCT.
Wi h hese esul s VMAT plans seem o gene a e he lowes minimum and maximum dose alues in GTV ega dless o
he CT used. DCA and CA echniques on he o he hand seem o be consis en wi h each o he .
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Table 4 Simula ed dose ange o GTV s uc u es o all ea men echniques and CTs
min
max
VMAT
PlanningCT
57.81 ± 5.68
67.63 ± 4.46
MAXCT
56.79 ± 4.31
66.06 ± 2.19
MEANCT
58.93 ± 4.22
65.05 ± 16.13
DCA
PlanningCT
60.85 ± 4.55
71.14 ± 5.41
MAXCT
59.95 ± 3.89
70.10 ± 3.71
MEANCT
59.40 ± 4.20
70.61 ± 3.33
CA
PlanningCT
59.28 ± 3.60
68.82 ± 2.52
MAXCT
58.27 ± 4.12
67.49 ± 1.95
MEANCT
62.10 ± 4.36
70.59 ± 13.38
3.3. Dose o PTV
T ea men echnique speci ic and CT speci ic a e aged alues o he pa ame e s (min, mean, max, D95) ac oss all he
pa ien s a e lis ed in Table 5 o o iginally calcula ed plans and Table 6 o simula ed plans.
When compa ing he ea men echniques o he o iginal plans in Table 5, he pa ame e s o DCA echnique a e highe
han hose o he es o he plans, apa om mean alue. The lowes alues can be seen wi h VMAT plans consis en ly
h oughou he pa ame e s. When compa ing he CTs o he o iginal plans, i can be no iced ha MEANCT has he
highes alues and PlanningCT has he lowes . The esul s a e simila o he dose o ITV esul s.
Table 5 A e age alues o o iginal plans in PTV
min
mean
max
D95
VMAT
46.92 ± 3.03
59.31 ± 2.65
67.30 ± 3.29
52.58 ± 1.86
DCA
49.57 ± 1.63
61.43 ± 1.54
70.72 ± 4.26
54.59 ± 0.37
CA
47.45 ± 4.07
61.50 ± 3.01
70.45 ± 5.06
53.63 ± 3.37
PlanningCT
47.10 ± 3.68
59.85 ± 3.33
69.10 ± 4.45
52.93 ± 3.11
MAXCT
47.39 ± 3.71
61.01 ± 1.73
69.14 ± 3.25
53.53 ± 2.40
MEANCT
49.46 ± 1.35
61.39 ± 2.52
70.21 ± 5.58
54.34 ± 0.84
Table 6 A e age alues o simula ed plans in PTV
min
mean
max
D95
VMAT
46.93 ± 2.93
59.07 ± 2.45
66.31 ± 3.67
52.62 ± 1.67
DCA
49.85 ± 1.64
61.19 ± 1.45
69.46 ± 3.69
54.66 ± 0.45
CA
47.54 ± 4.12
61.33 ± 3.39
69.07 ± 4.86
53.73 ± 3.4
PlanningCT
47.33 ± 3.60
60.27 ± 3.06
68.40 ± 4.22
53.32 ±2.84
MAXCT
47.38 ± 3.80
59.74 ± 1.92
67.04 ± 2.79
53.07 ± 2.53
MEANCT
49.62 ± 1.5
61.58 ± 2.85
69.39 ± 5.34
54.63 ± 0.91
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Fo simula ed plans in Table 6, he esul s a e simila o he calcula ed o iginal plans. VMAT echnique achie es he
lowes alues, while highes alues can be seen o DCA plans, apa om mean alue, which is highes o CA plans. Fo
di e en CTs, alues o MEANCT a e consis en ly highe , while alues o MAXCT a e gene ally lowe han hose o he
PlanningCT, apa om he minimum alue. In his case, he esul s a e also simila o he esul s seen o ITV.
The di e ence be ween o iginal calcula ed plans and simula ed plans can be seen in Table 7. VMAT echnique gene a es
he lowes minimum, maximum and D95 alues, while he lowes mean alue is c ea ed by CA. The highes minimum
alue can be seen wi h DCA plans, he highes maximum and D95 wi h CA plans, and VMAT and DCA ha e he highes
mean alue.
The di e ence in alues o CTs in Table 7, shows he lowes minimum alue o MAXCT, lowes mean and D95 alues
o MEANCT, and he lowes maximum alue o PlanningCT. On he o he hand, he highes minimum alue is o
PlanningCT, and he highes mean, maximum and D95 alues o MAXCT.
Wi h hese esul s in PTV, i seems ha he simula ions made wi h a combina ion o MEANCT o PlanningCT, oge he
wi h VMAT, would yield he mos consis en esul compa ed o he o iginally calcula ed plans. The wo s combina ion
would on he o he hand be plans made wi h ea men echnique DCA o CA wi h MAXCT.
Table 7 A e aged di e ences be ween o iginally calcula ed and simula ed plans in PTV
min
mean
max
D95
VMAT
-0.01 ± 0.44
0.24 ± 1.29
0.98 ± 1.76
-0.04 ± 0.60
DCA
-0.28 ± 0.39
0.24 ± 1.07
1.26 ± 0.96
-0.07 ± 0.55
CA
-0.09 ± 0.36
0.17 ± 1.07
1.38 ± 0.63
-0.10 ± 0.64
PlanningCT
-0.23 ± 0.36
-0.43 ± 0.76
0.70 ± 0.73
-0.39 ± 0.5
MAXCT
0.01 ± 0.44
1.27 ± 0.87
2.10 ± 0.98
0.46 ± 0.40
MEANCT
-0.16 ± 0.40
-0.19 ± 0.88
0.82 ± 1.31
-0.29 ± 0.43
3.4. Film measu emen s
Figu e 2 The dose dis ibu ion o he ilm, PlanningCT, VMAT, phan om
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Figu e 3 The dose dis ibu ion o he ilm, MAXCT, VMAT, phan om
Figu e 4 The dose dis ibu ion o he ilm, MEANCT, VMAT, phan om
The esul s o he ilm measu emen s o phan om VMAT plans o PlanningCT, MAXCT and MEANCT can be seen in
Figu es 2, 3 and 4, espec i ely. I adia ed cu es o ilms ha e been escaled ~12 % below he alues o
measu emen s and p o iles ha e been plo ed as middle as possible.
When compa ing simula ion and measu ed dose dis ibu ions o le - igh (LR) and an e io -pos e io (AP) posi ion,
he dis ibu ion o bo h di ec ions seem o be compa able, especially in he MAXCT in le side in Figu e 3. Fo he ilm,
which was posi ioned supe io -in e io (SI) and AP, he esul s a e mo e inconsis en . La ges di e ences can be seen
in in e io and pos e io sides o he ilm.
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All he lines a e no consis en be ween simula ed dose and i adia ed dose, which could be a sign ha he simula ion
does no co espond o eali y. The 12 % le el di e ence is unknown.
4. Discussion
Fo ITV, all he ea men echniques yield simila esul s when compa ing he consis ency be ween o iginally
calcula ed and simula ed plans, and bes combined wi h PlanningCT o MEANCT.
Fo GTV, All he echnique and CT combina ion pass he minimum dose equi emen s because o he scaling used o
co e PTV. To a oid high maximum doses wi h VMAT plans, MEANCT seems o be he bes pai ing op ion, while
PlanningCT he wo s . Wi h DCA plans, he di e ences be ween MEANCT and MAXCT a e minimal, bu bo h a e s ill
be e han hose wi h PlanningCT. Wi h CA plans, on he o he hand, MEANCT seems o be he wo s pai ing op ion,
and MAXCT he bes . O e all, minimum doses close o he p esc ibed o al dose o 55 Gy and lowes maximum alues
can be achie ed wi h VMAT plans.
Fo PTV, he di e ence o o iginally calcula ed and simula ed plans, VMAT plans seem o be simula ed he mos
accu a ely. Mos a ia ion can be ound wi h DCA and CA alues. The di e ences o CTs a e he highes in MAXCT, and
lowes in MEANCT.
Abb e ia ions
• SBRT: S e eo- ac ic Body Radia ion The apy
• PTV: Planning Ta ge Volume
• GTV: G oss Tumo Volume
• ITV: In e nal Ta ge Volume
• VMAT: Volume ic Modula ed A c The apy
• 4DCT: 4 Dimensional Compu ed Tomog aphy
• DCA: Dynamic Con o mal A c
• PlanningCT: Planning Compu ed Tomog aphy
• MAXCT: Maximum Compu ed Tomog aphy
• MeanCT: Mean Compu ed Tomog aphy
5. Conclusion
O e all, he esul s o di e en ea men echnique ypes and CTs a e su p isingly simila . The e is no enough da a
o de e mine a de ini e conclusion based on hese measu emen s. The hypo hesis in he beginning was ha he
co esponding simula ion o an o iginally calcula ed ea men plan would be he mos consis en wi h he combina ion
o DCA and MEANCT, while plans wi h VMAT and/o PlanningCT would ha e yielded wo se esul s. One explana ion o
his migh be he simplici y o he VMAT plans, which due o he lack o modula ion esembles plans c ea ed wi h DCA.
Wi h mo e complica ed VMAT plans, he e could be mo e di e ences in luence calcula ions, which would lead o la ge
di e ences be ween o iginal and simula ed plans.
Re e ences
[1] Micke, And e e al. “Mul ichannel ilm dosime y wi h non-uni o mi y co ec ion.” Medical physics ol. 38,5
(2011): 2523-34. doi:10.1118/1.357610
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Appendix 1
Figu e 5 O iginal and simula ed plans o all ea men echniques and CTs o pa ien 4
Figu e 6 O iginal and simula ed plans o all ea men echniques and CTs o pa ien 5
