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https://doi.org/10.1177/25898892221145226
Journal of Current Oncology
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DOI: 10.1177/25898892221145226
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Article
Step-by-Step Stereotactic Radiotherapy
Planning of Brain Metastasis: A Guide
to Radiation Oncologists—the ROSE
Case (Radiation Oncology from
Simulation to Execution)
Kanhu Charan Patro1, Ajitesh Avinash2, Arya Pradhan3, Rakesh Reddy Boya4,
Chittaranjan Kundu1, Partha Sarathi Bhattacharyya1, Venkata Krishna Reddy Pilaka1,
Mrutyunjayarao Muvvala1, Arunachalam Chithambara Prabu5,
Ayyalasomayajula Anil Kumar5, Srinu Aketi5, Parasa Prasad5,
Venkata Naga Priyasha1, Veera Surya Premchand Kumar Avidi1,
Mohanapriya Atchaiyalingam1 and Keerthiga Karthikeyan1
Abstract
Brain metastasis is seen in 10% to 20% of all adult cancer patients. One of the main modalities of treatment is stereotactic
radiosurgery (SRS). Here, we describe the step by step procedure for stereotactic planning of brain metastasis by using a
clinical scenario. The management of brain metastasis starts with the clinical evaluation of the patient followed by imaging and
SRS treatment in the present case. The paper highlights the sequential process of radiation planning for SRS—starting from
simulation, planning, evaluation of plan, and treatment.
Keywords
Brain metastasis, radiotherapy planning, SRS
3 Department of Medical Oncology, Gujarat Cancer and Research Institute,
Ahmedabad, Gujarat, India
4 Department of Medical Oncology, Mahatma Gandhi Cancer Hospital and
Research Institute, Vishakhapatnam, Andhra Pradesh, India
2 Department of Radiation Oncology, SUM Ultimate Medicare, Bhubaneswar,
Odisha, India
1 Department of Radiation Oncology, Mahatma Gandhi Cancer Hospital
and research Institute, Visakhapatnam, Andhra Pradesh, India
Corresponding author:
Kanhu Charan Patro, Department of Radiation Oncology, Mahatma Gandhi
Cancer Hospital and Research Institute, Visakhapatnam, Andhra Pradesh
530017, India.
E-mail: drkcpatro@gmail.com
Introduction
The incidence of brain metastasis is 10 times more than the
primary brain tumors. MRI of brain is the best imaging
modality for diagnosis of brain metastasis. The treatment
options for brain metastasis include surgery, whole brain
radiotherapy, stereotactic radiation in the form of stereotactic
radiosurgery (SRS) or stereotactic radiotherapy, or best
supportive care depending on the general condition of
patient or number of brain metastasis.1 In this paper, the
various steps of radiation planning for SRS have been
illustrated in an easy way for the beginners who are planning
for SRS in a case of brain metastasis.
Case History
A 70-year female, with a history of triple negative breast
cancer (TNBC) post modified radical mastectomy post
chemotherapy and radiotherapy after 6 months of follow up,
presented with the chief complaints of headache and
giddiness for 1 month.
Imaging
Contrast Enhanced Magnetic resonance imaging (CE-MRI)
of the brain revealed a well-defined lesion measuring
2.2cm×2.2cmintheleftoccipitallobewithringenhancement
and minimal edema, no mass effect or midline shift (Figure 1).
The Positron Emission Tomography Computed Tomography
(PET-CT) scan showed increased uptake in brain with
multiple lung nodules. The above features were suggestive of
left occipital lobe brain metastasis in a treated case of triple
negative carcinoma breast.
Brain Metastasis Prognostic Index
All patients with brain metastasis should undergo disease
specific Graded Prognostic Assessment (GPA).2 This GPA
5 Department of Medical Physics, Mahatma Gandhi Cancer Hospital and
Research Institute, Vishakhapatnam, Andhra Pradesh, India

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takes into account various factors such as primary tumor type,
molecular profile of tumor, and number of brain metastasis. It
helps the physician as well as the patient to choose the
appropriate treatment.
In the current case, details of patient such as age of
patient at the time of diagnosis of brain metastasis,
Karnofsky Performance Status of the patient, number of
brain metastasis, tumor type, and molecular subtype were
used to calculate the GPA to be 1.5 with median survival
of 7.7 months.
Treatment Decision by the Tumor Board
The patient details were put in the tumor board for decision
regarding the line to treatment. After group discussion with
neurosurgeon, radiation oncologist, and medical oncologist,
board decided to plan for stereotactic radiosurgery followed
by chemotherapy.
Treatment Decision by the Radiation
Tumor Board
TNBC being an aggressive histology, a TNBC patient with
brain metastasis would benefit from whole brain radiation
with simultaneous integrated boost to the solitary lesion. But
basing on the advanced age of the patient, ie 70 years, and in
order to prevent development of radiation induced
neurological toxicity and deterioration of quality of life, the
radiation tumor board opined for SRS. In the present case,
there was a single brain metastasis of diameter 2.2 cm, the
radiation tumor board decided for single fraction SRS with 18
Gy marginal dose as per RTOG 9005.3
RT Planning
Here we describe the steps of treatment of brain metastasis
from simulation to plan execution
Step 1: CT Simulation
During simulation, patient was set up in the supine
position with neutral neck position and immobilization
was done using FRAXION thermoplastic mask and
stereotactic frame with mouth bite (Figure 2a). Fiducials
were placed on the thermoplastic mask after proper
alignment with the lasers. Intravenous contrast was given
at a dose of 1 mL per kg body weight. Then, CT scan was
taken from the vertex to neck with CT slice thickness of
1 mm as is depicted in Table 1 (Figure 2b). After
simulation, the DICOM CT, images were sent to our
Oncentra server which was then imported for delineation
of target and organ at risk (OAR).
Figure 1. MRI Images of Patient With Single Lesion at the Left
Occipital Region With Ring Enhancement and Minimal Edema.
Table 1. Showing CT Simulation and MRI Protocol to Be Followed
for Brain Metastasis.
CT Simulation Protocols for Simulation
Supine position
Immobilization using stereotactic thermoplastic mask
Intravenous contrast at a rate of 1 mg/kg
CT scan taken from vertex to neck 15 minutes after contrast
administration
1 mm slice thickness
MRI Protocol Utility
T1/T2/FLAIR sequence Usual sequence
3D FSPGR sequence Normal anatomy
512 × 512 matrix
1 mm slice thickness
No gap
No tilt
Neutral neck
Figure 2. Immobilization of the Patient Using the Stereotactic
Thermoplastic Mask and Frame During CT Simulation in (2a), the
Planning CT Scan in (2b), and Fusion of MRI of the Patient With
Planning CT Scan in (2c).

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Patro et al. 3
Step 2: MRI Protocol
MRI of brain of the patient was done using 512 × 512 matrix in the
neutral neck position similar to that of CT scan during simulation
with no gap, no tilt, and 1 mm slice thickness as depicted in
Table 1. The MRI should include the usual T1, T2, FLAIR
sequences. In addition, the 3D FSPGR was used to view the
normal anatomy.4 If dedicated MR simulator is available, MR
simulationcanbedoneusingthis MRIprotocolandthesimulation
process being same as the CT simulation mentioned above.
Step 3: Image Fusion
This acquired MRI sequences were fused with the planning CT
scan by contouring the eyes, lens, basilar artery, sinuses, and
calcification and matching was done using the auto-fusion
technique to help in target and OAR delineation (Figure 2c).
Step 4: Target Delineation
The gross tumor seen on the CT images that was fused with
the MRI images to consider the exact extension of tumor was
delineated as Gross Tumor Volume (GTV) (Figures 3a,b).
There is no necessity of Clinical Target Volume margin in
case of SRS brain metastasis. The Planning Target Volume
(PTV) was drawn taking 1 mm around the GTV (Figure 3c).
Smoothing of the contour was done from the adjacent bone.
Multi-planar evaluation, ie evaluation of both the GTV and
PTV, were done in all the three planes—axial, coronal, and
sagittal.
In the present case, the GTV volume was 4.65 cc and the
PTV volume was 5.75 cc.
Step 5: Organs at Risk (OAR) Delineation
The OARs for delineation included both the cochlea,
brainstem, hippocampus, optic chiasma, and optic apparatus.
The cochlea was contoured in the bone window setting while
other OARs, ie brainstem, hippocampus, optic chiasma, and
optic apparatus, were contoured using the MRI that was fused
with the planning CT. Also Brain-GTV was also drawn as an
OAR (Figure 4a).
Step 6: RT Technique
Radiation planning can be done using any of the RTtechniques
such as Intensity Modulated Radiotherapy (IMRT),
Volumetric Modulated Arc Therapy (VMAT), Dynamic
Conformal Arc Therapy (DCARC), or 3-Dimensional
Conformal Radiotherapy (3DCRT) according to convenience
of radiation physicist and physician.
In the present case planning was done using the VMAT
technique.
Step 7: Plan Evaluation
After the completion of planning by the physicist, the
evaluation for the treatment plan was done using the following
indices.
PTV Coverage Index
Following planning, the coverage of the PTV need to be seen.
The prescription isodose level was such that not 100% of
the prescribed dose covered 100% of the PTV. Often 95% of
the prescription dose covered 95% or higher percentage of the
PTV, otherwise 100% of the prescription dose covered 95%
or higher percentage of the PTV.5
In the present case, 95% of the prescription dose covered
99.9% of the PTV and 100% of the prescription dose
covered 99.15% of the PTV which satisfied the above-
mentioned parameter for the PTV coverage as depicted in
the Table 2.
Intracranial Organ at Risk (OAR) Index
Keeping in mind the desirable dose constraints to the OAR
we need to check the dose to individual OARs.6
Figure 3. The Delineation of GTV (Pink) in Planning CT Is Shown in 3a, Delineation of GTV (Pink) in MRI Is Shown in 3b and PTV (Cyan)
Is Generated by Taking 1 mm Margin Around GTV Shown in 3c.

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The dose desirable and dose achieved for all the OARs in
the present case is depicted in Table 3.
Whole Brain-GTV Dose
Korytko et al have stated that while treating Non-AVM
tumors with Gamma Knife, in order to reduce the risk of
symptomatic radiation induced necrosis of brain, the dose to
12 Gy volume of Brain-GTV should be limited to <10 cc.7
This data can be extrapolated while treating patients with
single fraction SRS.
In the current case, the 12 Gy volume of Brain-GTV was
10.765 cc.
Conformity Index: To note the conformity index of the
SRS, here we used 2 types of conformity indices, ie the
RTOG conformity index and the Paddick conformity
index.5,8
RTOG Conformity index (CIRTOG) was calculated using
the following formula.
CIRTOG = Volume of prescription isodose / PTV volume
In this case of VS, the RTOG conformity index was 1.18
(Table 2).
Paddick conformity index (CIPaddick) was calculated
using the following formula:
CIPaddick = (Volume of prescription isodose in the area of
interest ie PTV)2 / PTVvolume ×Volume of prescription isodose
Here in the current case, the Paddick conformity index
was 0.82 (Table 2).
Homogeneity Index
It was calculated using the formula:
Homogeneity index = Maximum dose / Prescription dose
In this case the homogeneity index was 1.27 (Table 2).
Dose Fall Off
The dose fall off observation is very much needed in the plan
evaluation under the heading of gradient index. For this we
need to calculate the difference between various isodose
lines. In order to calculate the difference between the isodose
lines we need to calculate the equivalent radius.
Equivalent Radius Calculation
To evaluate the dose gradient, we have to find out the
difference between radius of various isodose lines. But none
of the isodoses are spherical. So, we use the following formula
to calculate the equivalent radius.
Figure 4. Showing the Brain-GTV in 4a and Beam Arrangement in Axial (4b), Cronal (4c), and Sagittal View (4d).

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Patro et al. 5
Table 3. Organs at Risk With Their Desirable Dose and Dose Achieved in the Current Case.
Organ Desirable Dose Achieved Dose
Right eye DMax < 8 Gy <1 Gy
Left eye DMax < 8 Gy <1 Gy
Right optic nerve DMax < 8 Gy <1 Gy
Left optic nerve DMax < 8 Gy <1 Gy
Optic chiasma DMax < 8 Gy 1.88 Gy
Left hippocampus 5 Gy
Right hippocampus 9 Gy
Brain stem DMax < 8 Gy 3.83 Gy
Right cochlea DMean < 9 Gy <1 Gy
Left cochlea DMean < 9 Gy <1 Gy
Table 2. The Various Indices of Plan Evaluation of Brain Metastasis in the Current Case.
Parameter Value Desirable
Dmax 22.89 Gy –
D95% 18.82 Gy –
D100% 16.62 Gy –
V95% 99.93% –
V25Gy (V100%) 99.15% –
V110% 81.01% –
V120% 17.97% –
V130% 0 –
PTV volume 5.755 cc –
Volume of prescription isodose 6.811 cc –
Volume of prescription isodose within the
PTV
5.706 cc –
Maximum dose 22.89 Gy –
Prescription dose 18 Gy –
RTOG conformity index 1.18 1–2
Paddick conformity index 0.82 0.85–1
Homogeneity index 1.27 1.1-1.3
Parameter Volume Radius
100% isodose line 6.811 cc 1.18 mm
80% isodose line 11.00 cc 1.38 mm
60% isodose line 17.14 cc 1.6 mm
50% isodose line 22.05 cc 1.74 mm
40% isodose line 30.09 cc 1.93 mm
First: Find out the specified isodose volume
Second: Calculate the radius of the isodose volume by
using the formula:
V = 4/3 π r3
r = (3V/4 π)1/3
The calculation of volume and radius of various isodose
lines in the present case is shown in Table 2.
Gradient Index
The formula for calculating gradient index is as follows.

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Gradient index = Equivalent radius of 50% isodose –
Equivalent radius of prescription isodose. Ideally the gradient
index should be between 0.3 mm and 0.9 mm.
In the current case, the gradient index was 1.74 mm – 1.18
mm = 0.56 mm which was close to ideal gradient index.
Gradient index can also be calculated as the ratio of
the volume enclosed by half of the prescription isodose
divided by the prescription isodose volume. The ideal
value is < 3.5
In the present case, the gradient index was calculated by
9 Gy volume / 18 Gy volume, ie 22.2/6.8 = 3.2.
Distance BetweenVarious Isodose Lines
The ideal difference between 80% and 60% isodose lines
should be < 2 mm.9
In the current case it was 0.22 mm.
The ideal difference between 80% and 40% isodose lines
should be < 8 mm.
In present case, it was 0.55 mm.
Beam Arrangement
The arrangement of the beams (Figures 4b-d) was done such
that there is adequate coverage of the target while giving less
dose to the OARs. It should be noted that the beams should
not pass through the ipsilateral eye.
Step 8: Quality Assurance (QA)
Mechanical isocenter check was done using the Winston Lutz
test and the point dose verification was done keeping the
tolerance as 1 mm.10
Step 9: Dry Run
Treatment verification consists of setup reproduction,
isocenter verification, and clinically verifying each treatment
field—check beam clearance, check any interlock—MLC
interlock and potential monitor unit problems. Then clearly
mark the immobilization devices after successful dry run.
Step 10: Premedication Protocol
Prior to start of treatment premedication was delivered in the
form of tablets as described further—all starting the day
before start of RT treatment:
Tablet Dexamethasone 8 mg—thrice daily
Tablet Ondansetron 8 mg—thrice daily
Tablet pantoprazole 40 mg—once daily
If the patient is diabetic, proper diabetic care needs to be done.
Step 11: Set up Verification and Treatment Delivery
It includes cone beam CT correction (Figures 5a-c) and
hexapod corrections (Figure 5d). After all the corrections
been done treatment was delivered.
Step 12: Post Medication
It is an optional protocol that usually includes anti emetics, proton
pump inhibitors, and tapering the dose of steroid over a week.
We also provide the Brain Metastasis SRS Plan Evaluation
sheet as a supplementary file that will help in proper and
accurate plan evaluation for every SRS case of brain
metastasis.
Figure 5. Depicting the Treatment Verification by CBCT Correction of the Patient During the Treatment in Coronal (5a), Sagittal View
and (5b), Axial (5c), and the Hexapod Correction of the Same Patient During the Treatment in 5d.

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Patro et al. 7
Conclusion
This paper conceptualizes and acts as an easy guide for the
beginners for the stereotactic radiation planning for brain
metastasis.
Declaration of Conflicting Interests
The authors declared no potential conflicts of interest with respect to
the research, authorship, and/or publication of this article.
Funding
The authors received no financial support for the research,
authorship, and/or publication of this article.
Statement of Informed Consent and Ethical
Approval
Necessary ethical clearances and informed consent was received and
obtained respectively before initiating the study from all participants.
Appendix
BRAIN METASTASIS SRS PLAN EVALUATION CHECK LIST
1. NAME UMR
2. DIAGNOSIS
3. PRIOR TREATMENT
4. DISEASE SPECIFIC GRADED PROGNOSTIC ASSESSMENT SURVIVAL
5. PRIOR WBRT YES NO DOSE INTERVAL
6. PRIOR SRS YES NO DOSE INTERVAL
7. NUMBER OF METASTASIS/CAVITY
8. LOCATION SIDE SIZE max [mm] PTV MARGIN VOLUME-CC DOSE
1. GTV PTV
2. GTV PTV
3. GTV PTV
4. GTV PTV
5. GTV PTV
9. PLAN TYPE-[3DCRT/VMAT/DCR/IMRS]
10. PRESCRIBED MARGINAL ISODOSE
LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
D MAX LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
D95% LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
D100% LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
V95% LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
V100% LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
V120% LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
V130% LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
DISTANCE BETWEEN 80% ISODOSE AND 60% ISODOSE-[<2mm]
LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
DISTANCE BETWEEN 80% ISODOSE AND 40% ISODOSE-[<8mm]
LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
CONFIRMITY INDEX [IDEAL 1]VOLUME OF PRESCRIPTION ISODOSE/VOLUME OF PTV
LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
HOMOGENITY INDEX [BETWEEN 1.1-1.3] MAX DOSE/ PRESCRIPTION DOSE
LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
(Appendix continued)

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BRAIN METASTASIS SRS PLAN EVALUATION CHECK LIST
GRADIENT INDEX[BETWEEN 0.3-0.9][RADIUS OF PRESCRIPTION ISODOSE - RADIUS OF HALF
PRESCRIPTION ISODOSE]
LESION 1 LESION 2 LESION 3 LESION 4 LESION 5
11. 1. BRAIN-GTV[12Gy volume] <10cc and D50% <5Gy
2. BRAIN-GTV[4Gy volume] <20CC-MULTIPLE FRACTION
12. OAR SINGLE FRACTION 5 FRACT. [ALT. DAY] ACHIEVED
1. RIGHT EYE MAX<8Gy MAX <22.5Gy
2. LEFT EYE MAX<8Gy MAX <22.5Gy
3. RIGHT OPTIC NERVE MAX<8Gy MAX <22.5Gy
4. LEFT OPTIC NERVE MAX<8Gy MAX <22.5Gy
5. OPTIC CHIASM MAX<8Gy MAX <22.5Gy
6. BRAIN STEM MAX <15Gy MAX <31Gy
7. RT.HIPPOCAMPUS
8. LT.HIPPOCAMPUS
9. RT.COCHLEA MEAN <9Gy MEAN <25Gy
10. LT.COCHLEA MEAN <9Gy MEAN <25Gy
(Appendix continued)
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