Planning of Radiotherapy Installation and Brachytherapy Facility: Site Selection, Layout, Shielding, Maze Design and Radiation Safety
Radiotherapy is an essential component of modern cancer treatment. The safe and effective delivery of radiation therapy depends not only on the treatment machine and treatment planning system but also on the proper planning and design of the radiotherapy facility.
A radiotherapy installation must be designed to provide adequate radiation protection for patients, radiation workers, other hospital staff, and members of the public while maintaining an efficient clinical workflow.
This article provides a comprehensive overview of teletherapy and brachytherapy facility planning, including site selection, area requirements, shielding calculations, maze-wall design, door location, wall openings, construction considerations, high-energy LINAC installations, and brachytherapy facility planning.
1. Introduction to Radiotherapy Facility Planning
Planning a radiotherapy facility is a multidisciplinary activity involving radiation oncologists, medical physicists, radiotherapy technologists, architects, engineers, equipment manufacturers, and radiation safety professionals.
The fundamental objectives of facility planning are:
To provide adequate radiation protection.
To ensure safe treatment delivery.
To provide efficient patient and staff workflow.
To accommodate treatment equipment and accessories.
To provide adequate space for maintenance and future requirements.
To minimize radiation exposure to workers and the public.
To comply with applicable radiation safety requirements.
Radiation safety should receive the highest priority during facility planning, followed by economy and convenience.
A properly planned facility should follow the principle of ALARA: As Low As Reasonably Achievable.
The design should ensure that radiation exposure outside controlled areas remains within the applicable regulatory limits.
2. Planning of a Teletherapy Facility
Teletherapy refers to external beam radiation therapy in which radiation is delivered to the patient from a treatment unit positioned outside the body.
Teletherapy facilities may contain equipment such as:
Cobalt-60 teletherapy units
Medical linear accelerators
High-energy photon treatment units
Electron-capable linear accelerators
The treatment room, or bunker, is the principal radiation-controlled area.
The design of the bunker depends on:
Machine type
Maximum radiation energy
Workload
Treatment techniques
Beam orientation
Use factor
Occupancy factor
Distance to occupied areas
Shielding material
Surrounding building structure
3. Site Selection for a Teletherapy Facility
Site selection is one of the first steps in radiotherapy facility planning.
The treatment facility should preferably be located in a controlled area with minimum unnecessary public movement.
The site should be selected after considering the location of surrounding rooms, floors, buildings, corridors, offices, waiting areas, and other occupied spaces.
Important considerations include:
3.1 Controlled Location
The treatment room should preferably be located in an area where unnecessary public access and occupancy are minimized.
This helps reduce the potential exposure of members of the public.
3.2 Proximity to Related Facilities
The teletherapy facility should be reasonably close to associated radiotherapy facilities such as:
Simulator room
Examination room
Doctor's room
Medical physicist's room
Patient waiting area
Dressing area
This improves patient movement and departmental workflow.
3.3 Ground Floor or Basement
Depending on the facility design and structural requirements, the treatment room may be located on the ground floor or basement.
Basement installation can be advantageous because surrounding soil and structural mass may contribute to radiation protection and may reduce occupancy concerns in adjacent areas.
However, the final location must be determined by the overall shielding and architectural design.
3.4 Future Requirements
The selected site should also consider:
Equipment replacement
Maintenance access
Future upgrades
Expansion of the radiotherapy department
Transportation of large equipment
Good site planning prevents significant structural problems during future equipment replacement.
4. Area Requirements for a Teletherapy Facility
The required area depends on the treatment machine and the treatment techniques to be performed.
The treatment room should provide sufficient space for:
Treatment machine movement
Patient positioning
Gantry rotation
Couch movement
Staff movement
Patient transfer
Radiation protection structures
Equipment maintenance
In addition to the treatment bunker, supporting spaces may include:
Patient waiting area
Dressing room
Examination room
Doctor's room
Medical physicist's room
Control room
The exact room dimensions should always be based on the actual equipment manufacturer's specifications and the approved facility design rather than applying one standard room size to every machine.
5. Shielding Requirements for Teletherapy
Radiation shielding is a central component of treatment-room design.
The objective of shielding is to attenuate radiation so that people occupying areas outside the treatment room do not receive radiation doses above the applicable limits.
For teletherapy installations, barriers are generally considered as:
Primary Barriers
Primary barriers are barriers that may receive the direct treatment beam.
They require substantial shielding because the primary radiation beam has a high radiation intensity.
The required barrier depends on:
Workload
Use factor
Distance
Permissible dose
Beam energy
Field size
Barrier material
Secondary Barriers
Secondary barriers protect against radiation other than the primary beam, particularly:
Leakage radiation from the treatment head
Scattered radiation from the patient
Scattered radiation from walls and other structures
Secondary barriers therefore require a different shielding assessment from primary barriers.
6. Shielding Calculation
A basic shielding calculation considers several important parameters.
Workload — W
Workload represents the amount of radiation delivered by the treatment unit over a specified period.
For teletherapy calculations, it may be expressed in terms such as radiation exposure per week at a specified distance.
Use Factor — U
The use factor represents the fraction of the workload during which the primary beam is directed toward a particular barrier.
For example, a barrier that receives the primary beam frequently will require greater consideration than one that rarely receives the primary beam.
Occupancy Factor — T
The occupancy factor represents the fraction of time that the area beyond a barrier is occupied.
A continuously occupied office requires more protection than an area that is rarely occupied.
Distance — d
Distance is measured from the radiation source or relevant radiation origin to the point of interest.
Because radiation intensity decreases with increasing distance, distance is an important component of shielding design.
Permissible Dose — P
The permissible dose represents the design dose constraint for the protected area.
7. Protective Barrier Transmission Factor
The transmission factor of a protective barrier can be represented by:
Where:
B = transmission factor of the barrier
P = permissible exposure
d = distance from source to point of interest
W = workload
U = use factor
T = occupancy factor
The calculated transmission factor is then used with appropriate attenuation data to determine the required shielding thickness.
The final shielding design should be evaluated by a qualified medical physicist or radiation protection professional using the applicable standards and regulatory requirements.
8. Maze Wall in a Radiotherapy Treatment Room
A maze is commonly incorporated into radiotherapy treatment-room designs to reduce radiation exposure at the entrance.
The primary purpose of the maze is to prevent a direct line of sight between the radiation source and the treatment-room entrance.
Radiation entering the maze undergoes scattering and attenuation as it travels through the maze.
This significantly reduces the radiation level near the entrance.
Functions of the Maze
A properly designed maze:
Reduces direct radiation reaching the entrance.
Increases the radiation travel distance.
Reduces scattered radiation levels.
Can reduce the shielding requirement for the entrance door.
Improves radiation safety for workers and the public.
For high-energy LINAC installations, maze design requires particular attention because both leakage and scattered radiation must be considered.
9. Door Location
The treatment-room door should be carefully positioned to minimize radiation exposure.
Ideally, the entrance should be located through the maze rather than directly opposite the radiation source.
The design should avoid a direct radiation path from the treatment position to the entrance.
A well-designed maze can substantially reduce the radiation level reaching the door.
Depending on the calculated radiation level, the door may require additional shielding.
A lead-lined door may be used when required, but heavy doors can create practical difficulties during routine operation.
The treatment-room door should also have an appropriate safety interlock.
The interlock should prevent operation of the treatment unit when the door is open.
10. Openings in the Treatment Room Walls
Wall openings require careful consideration because they can become potential radiation leakage paths.
Possible openings include:
Viewing windows
Cable conduits
Air-conditioning openings
Service penetrations
Electrical conduits
Viewing Arrangement
The operator must be able to monitor the patient during treatment.
This may be achieved through:
A radiation-protected viewing window
CCTV monitoring
A backup viewing method may also be considered so that patient observation remains possible if the CCTV system fails.
Cable Conduits
Conduits may be provided to allow measurement cables or other required services to pass between the control room and treatment room.
The conduit design must not create a significant radiation leakage pathway.
Air-Conditioning Openings
Air-conditioning openings should be designed with suitable shielding or baffling arrangements.
The purpose is to maintain ventilation while preventing radiation from travelling directly through the opening.
11. Construction Restraints
Large radiotherapy machines create significant architectural and engineering challenges.
The machine may be too large or heavy to pass through a completely finished treatment room.
Therefore, the construction plan should consider equipment transportation before the bunker is completed.
In some situations:
Portions of the wall may be completed after machine installation.
Portions of the ceiling may be completed after equipment placement.
Temporary access routes may be required.
Special lifting or transportation arrangements may be necessary.
The equipment manufacturer's installation requirements should therefore be considered during the architectural planning stage.
12. Other Requirements for Teletherapy Facilities
A radiotherapy bunker requires more than just shielding walls.
The following should be incorporated into the design:
Primary and Secondary Barriers
The shielding design should consider the location of the isocentre and the complete range of gantry rotation.
Primary Barrier Width
The width of a primary barrier should account for:
Maximum field size
Beam divergence
Distance from the isocentre
Gantry movement
Electrical Requirements
Electrical services should be planned before installation, including:
Electrical wiring
Power requirements
Conduits
Equipment connections
Control systems
Equipment Access
A suitable access route or ramp may be required for transporting the machine into the treatment room.
Adequate access should also be maintained for:
Maintenance
Equipment replacement
Component replacement
Future upgrades
13. High-Energy Teletherapy Machines
High-energy radiotherapy installations require additional attention to shielding and facility design.
Examples include high-energy medical linear accelerators capable of producing photon beams at energies such as 15 MV.
When planning two radiation installations close to one another, their relative positions can sometimes be optimized to allow structural barriers to serve both facilities where appropriate.
The facility should also consider the possibility of occupancy above the treatment room.
If future occupancy above the treatment room is unlikely, the architectural design can potentially be optimized accordingly.
However, these decisions must be based on the approved shielding design and actual building use.
14. Planning a 6 MV Linear Accelerator Facility
A typical 6 MV LINAC facility includes:
Treatment bunker
LINAC
Isocentre
Primary barriers
Secondary barriers
Maze
Control room
Patient entrance
Conduits
Safety interlock
Patient monitoring system
The isocentre acts as the central reference point for treatment geometry.
The bunker dimensions shown in a typical layout are not universal values.
The actual dimensions depend on the selected accelerator model, treatment techniques, shielding calculations, equipment clearances, and building conditions.
15. Planning a 15 MV Linear Accelerator Facility
A 15 MV LINAC requires careful consideration of radiation shielding because of its higher photon energy.
The bunker design should consider:
Maximum photon energy
Workload
Use factor
Occupancy factor
Distance
Primary beam directions
Leakage radiation
Patient scatter
Maze geometry
Ceiling and floor shielding
The typical 15 MV layout includes a treatment room, control room, maze, structural barriers, conduits, and the treatment isocentre.
The dimensions shown in a sample layout are specific to that design and should not be treated as universal construction dimensions.
16. Door Location in a 15 MV LINAC Bunker
The door location in a 15 MV LINAC bunker is closely related to the maze design.
The entrance should generally be positioned so that there is no direct radiation path from the treatment position to the outside.
The maze increases the distance and changes the direction of scattered radiation before it reaches the entrance.
Door shielding and maze geometry must therefore be considered together.
The final design should ensure that radiation levels outside the bunker remain within the applicable limits.
17. Section Z-Z and Maze Wall of a 15 MV LINAC
The Section Z-Z drawing illustrates the maze arrangement of the 15 MV LINAC bunker.
The maze forms an indirect route between the treatment room and entrance.
Its function is to:
Prevent direct radiation from reaching the entrance.
Increase the radiation travel distance.
Reduce scattered radiation.
Reduce radiation levels near the entrance.
Improve radiation protection for personnel and the public.
For high-energy installations, the maze should be evaluated for both scattered radiation and leakage radiation.
The final dimensions must be obtained from a detailed shielding calculation rather than from a generic drawing.
18. Shielding Calculation for a 15 MV LINAC
Shielding calculation for a 15 MV LINAC requires systematic evaluation of the radiation environment around the bunker.
Important parameters include:
Photon energy
Workload
Use factor
Occupancy factor
Distance
Permissible dose
Barrier type
Leakage radiation
Patient-scattered radiation
Primary barriers are evaluated for direct beam exposure.
Secondary barriers are evaluated for leakage and scattered radiation.
The calculated transmission factor is then used to determine the necessary attenuation and barrier thickness using appropriate shielding data.
Higher-energy beams and increased workloads can increase shielding requirements, so the shielding design must be based on the actual machine and clinical workload.
19. Introduction to Brachytherapy
Brachytherapy is a form of radiation therapy in which sealed radioactive sources are placed inside or close to the tumour.
Because the radioactive source is positioned close to the target, a high radiation dose can be delivered to the tumour while reducing radiation exposure to surrounding normal tissues.
Brachytherapy can be used in different anatomical sites and clinical situations depending on the treatment technique.
The treatment requires careful coordination between the radiation oncologist, medical physicist, radiotherapy technologist, nursing staff, and other members of the clinical team.
20. Brachytherapy Planning
Brachytherapy planning involves:
Selection of the radioactive source
Selection of the applicator
Treatment technique
Source positioning
Dwell positions
Dwell times
Dose prescription
Dose distribution
Protection of organs at risk
Treatment planning must consider the tumour location, tumour size, prescribed dose, and nearby critical organs.
Modern brachytherapy may use manual afterloading or remote afterloading systems.
Techniques may include:
LDR
MDR
HDR
Commonly used radionuclides include:
Iridium-192
Cobalt-60
Caesium-137
The exact source depends on the treatment system and clinical application.
21. Site Selection for a Brachytherapy Facility
A brachytherapy department should preferably be located in a suitable controlled area of the hospital.
It should be reasonably close to the radiotherapy department and associated facilities.
This supports:
Patient transfer
Clinical coordination
Staff workflow
Equipment utilization
Emergency response
The site should have appropriate radiation shielding and should minimize unnecessary occupancy of surrounding areas.
Areas above, below, and adjacent to the treatment room should be considered during shielding design.
Where both teletherapy and brachytherapy facilities are present, their relative locations may be planned to make effective use of structural shielding where appropriate.
22. General Layout of a Brachytherapy Facility
The general layout depends on whether the facility uses manual or remote afterloading.
Manual Brachytherapy
A basic facility may include:
Source storage and preparation room
Minor surgery or procedure room
Nurses' station
Patient ward
Recovery area
Treatment and examination facilities
Full-Fledged Brachytherapy Department
Additional facilities may include:
Radiation oncologist's room
Medical physicist's room
Patient examination room
Reception and records room
Waiting area
Treatment planning area
Source storage
Emergency facilities
Patient monitoring facilities
Remote Afterloading
For LDR, MDR, or HDR remote afterloading systems, a dedicated shielded treatment room is required.
Important safety features include:
Control area outside the treatment room
CCTV monitoring
Intercom
Emergency stop system
Source retraction system
Radiation warning indicators
Door interlocks
23. Shielding Requirements for Brachytherapy
Radiation shielding is essential in brachytherapy to protect radiation workers, patients, the public, and people in surrounding areas.
The shielding requirement depends on:
Type of radionuclide
Source strength
Number of patients
Number of sources
Workload
Treatment duration
Distance
Occupancy
Construction material
Material density
Unlike teletherapy, where the beam is highly collimated, brachytherapy sources emit radiation in multiple directions.
Therefore, shielding requirements must consider radiation in a broader range of directions.
24. Shielding of Different Areas in Brachytherapy
In a teletherapy room, barriers are commonly divided into primary and secondary barriers because of the highly collimated treatment beam.
In a brachytherapy ward or treatment room, radiation can be emitted in multiple directions.
Therefore:
Walls require consideration as protective barriers.
Floors require consideration.
Ceilings require consideration.
Adjacent occupied areas require evaluation.
The radiation contribution from patients and sources must be included in the shielding assessment where relevant.
25. Workload Calculation in Brachytherapy
Workload is an important component of brachytherapy shielding design.
A simplified relationship can be expressed as:
Where:
W = workload
S = source strength
RHM = relevant radiation exposure or dose-rate constant
Treatment time = total duration of source use
If more than one patient is treated or multiple radiation sources contribute to exposure, the radiation contribution from each source or patient must be considered.
Accurate workload estimation is important because an underestimated workload can result in inadequate shielding design.
26. Radiation Safety in Facility Planning
Radiation safety should be incorporated into the facility from the earliest planning stage rather than added after construction.
Important safety measures include:
Access Control
The treatment area should have appropriate access restrictions.
Door Interlocks
Treatment should not be possible when the treatment-room door is open where an interlock is required.
Patient Monitoring
CCTV and communication systems should allow continuous observation and communication with the patient.
Warning Systems
Appropriate radiation warning indicators should be provided.
Emergency Systems
Emergency procedures and equipment should be incorporated into the facility design.
Shielding Verification
Radiation levels should be verified after installation and commissioning according to applicable requirements.
27. Importance of Medical Physics in Facility Design
Medical physicists play a central role in radiotherapy facility planning.
Their responsibilities may include:
Shielding calculations
Radiation survey planning
Workload assessment
Evaluation of use and occupancy factors
Equipment commissioning
Radiation protection assessment
Quality assurance
Verification of treatment-room safety systems
Architectural and engineering plans should therefore be developed in consultation with qualified radiation protection and medical physics professionals.
28. Key Points to Remember
When planning a radiotherapy facility, remember the following sequence:
1. Select the site
Consider occupancy, accessibility, workflow, and radiation safety.
2. Define the equipment
Know the exact machine model, energy, geometry, and manufacturer's requirements.
3. Establish the workload
Estimate expected clinical use accurately.
4. Identify radiation sources
Consider primary radiation, leakage radiation, patient scatter, and brachytherapy source radiation.
5. Determine use and occupancy factors
Evaluate how barriers and surrounding spaces will be used.
6. Calculate shielding
Determine the required transmission factor and barrier thickness.
7. Design the maze and entrance
Minimize radiation reaching the entrance.
8. Plan wall openings
Include viewing systems, conduits, air-conditioning, and other services without compromising shielding.
9. Plan equipment installation
Consider transportation, lifting, access, maintenance, and future replacement.
10. Verify the completed facility
Radiation protection must be assessed and the installation commissioned before clinical operation.
Conclusion
Planning a radiotherapy facility is much more than constructing a room around a radiation-treatment machine. It requires integration of clinical workflow, radiation physics, engineering, architecture, equipment specifications, and radiation protection.
For teletherapy and LINAC installations, the design must address primary and secondary barriers, workload, use factor, occupancy factor, distance, maze geometry, door location, wall openings, and equipment access.
For high-energy machines such as a 15 MV LINAC, particular attention must be given to the shielding requirements associated with high-energy photon radiation, including primary radiation, leakage radiation, and scattered radiation.
Brachytherapy facilities require a different approach because radioactive sources are positioned inside or close to the patient and radiation can be emitted in multiple directions. Consequently, walls, floors, ceilings, adjacent occupancy, source strength, workload, and treatment duration must all be considered.
The central principle throughout facility planning is radiation protection. A well-designed facility should provide adequate shielding, efficient workflow, patient safety, staff protection, and appropriate access for maintenance and future development.
Most importantly, the dimensions and shielding values shown in educational layouts should not be directly adopted for construction. Actual radiotherapy facilities must be designed using the specifications of the selected equipment, detailed shielding calculations, applicable regulatory requirements, and assessment by appropriately qualified professionals.
In short: good radiotherapy facility planning means safe radiation protection, practical workflow, reliable equipment operation, and a sustainable clinical environment.