Radiotherapy

C L I N I C A L T E C H N O L O G Y R E F E R E N C E · R A D I A T I O N O N C O L O G Y

Radiotherapy Machines:

The Complete 2026 Guide

Every device type, every leading brand, every clinical application — the

de5nitive reference for radiation oncology equipment

Updated March 2026 Radiation Oncology Clinical Technology

~12,000 words

R adiotherapy — the use of ionizing radiation to destroy

malignant tumor cells — remains one of the three

pillars of modern oncology alongside surgery and systemic

therapy. Approximately 50–60% of all cancer patients will

receive radiation at some point during their treatment, and

the machines that deliver this radiation have evolved from

rudimentary X-ray tubes into extraordinarily precise,

computer-guided systems capable of sculpting dose

distributions around complex three-dimensional targets with

sub-millimeter accuracy.This guide provides a comprehensive, clinically oriented reference

to every major category of radiotherapy machine in use today: their

physical principles, engineering characteristics, clinical indications,

leading commercial brands, representative products, and the

evidence base supporting their use. Whether you are a radiation

oncologist selecting equipment for a new center, a medical physicist

evaluating system upgrades, a healthcare administrator assessing

capital investment, or a patient researching treatment options, this

article is designed to serve as your authoritative starting point.

H O W T O U S E T H I S G U I D E

The article is organized by device category, then by brand. Each

section covers the underlying physics, engineering features, key

models and speci<cations, clinical indications, and a summary of

advantages and limitations. The comparative tables in Section 9

provide a side-by-side reference across all major parameters.

01 The Physics of Radiotherapy

Ionizing Radiation and Biological E!ect

Ionizing radiation imparts su@cient energy to eject electrons from

atoms, creating ion pairs that directly damage biological

macromolecules — most critically, DNA. The principal lethal lesion

is the DNA double-strand break (DSB). When both strands of the

double helix are severed in close proximity, the cell's repairmachinery is frequently unable to restore genomic integrity, leading

to mitotic catastrophe, apoptosis, or permanent cell cycle arrest.

Normal cells and tumor cells diGer in their capacity for sublethal

damage repair. Most solid tumors have compromised repair

checkpoints — a consequence of the same genetic instability that

drives carcinogenesis — making them more vulnerable to repeated

low-dose radiation fractions than the surrounding normal tissue.

This diGerential sensitivity is the biological foundation of

fractionated radiotherapy: delivering treatment in multiple daily

doses of 1.8–2.0 Gy over Qve to eight weeks maximizes the

therapeutic ratio by allowing normal tissue recovery between

fractions while progressively depleting the tumor's clonogenic cell

population.

The linear-quadratic (LQ) model describes cell survival as a

function of dose per fraction, characterized by two parameters:

alpha (α), representing single-hit lethal events, and beta (β),

representing reparable sublethal damage. The α/β ratio indicates

how sensitive a tissue is to fractionation changes; most tumors have

high α/β ratios (8–12 Gy), making them relatively insensitive to

fraction size, whereas late-responding normal tissues have low α/β

ratios (1–4 Gy) and are far more sensitive to large fractions — a fact

exploited in hypofractionated schedules including stereotactic body

radiotherapy (SBRT).

Radiation Modalities Used in Therapy

PHOTON BE A M S ( X- R AYS A ND GA M M A R AYS)Photon beams are the workhorse of external beam radiotherapy.

They are produced either by electron deceleration in a high-atomic-

number target (Bremsstrahlung X-rays, as in a linear accelerator) or

by nuclear decay of radioactive isotopes (gamma rays, as in cobalt-

60 units and Gamma Knife). Photon beams attenuate exponentially

with depth; peak dose is deposited just below the surface (the build-

up region), a^er which dose falls oG gradually. This depth-dose

characteristic requires multi-Qeld or arc techniques to achieve

adequate target coverage while minimizing surface dose.

E LEC T RON BE A M S

Electrons are produced in linear accelerators by de`ecting the

accelerated electron beam before it strikes the X-ray target.

Electrons have a Qnite range in tissue determined by beam energy,

depositing most of their dose within a predictable depth and then

falling sharply to near-zero. This makes them ideal for superQcial

targets — skin cancers, post-mastectomy chest wall irradiation, and

scalp lesions — where sparing of underlying structures is critical.

PROTON A ND C AR BON ION BE A M S

Heavy charged particles — protons and carbon ions — have a

fundamentally diGerent depth-dose characteristic from photons.

They deposit minimal dose as they enter tissue, then release the vast

majority of their energy in a sharp Bragg peak at a depth

determined by beam energy. Beyond the Bragg peak, dose falls to

near-zero. This physical property allows very high doses to be

delivered to deeply seated tumors with dramatically reduced

integral dose to surrounding normal tissues — an advantage ofparticular importance in pediatric oncology, skull base tumors, and

targets adjacent to critical structures such as the spinal cord or optic

apparatus.

Carbon ions oGer an additional advantage: they have a higher

relative biological eGectiveness (RBE) — approximately 2–3 times

that of photons in the Bragg peak region — meaning they are

intrinsically more lethal to tumor cells per unit of absorbed dose,

making them potentially eGective against radioresistant histologies

including hypoxic tumors, salivary gland cancers, and certain

sarcomas.

NEUT RON BE A M S

Fast neutrons are generated by nuclear reactions and have high

linear energy transfer (LET), resulting in RBE values of 3–8. Their

use has been largely supplanted by carbon ion therapy, though

boron neutron capture therapy (BNCT) — in which tumor-speciQc

boron compounds are activated by thermal neutrons — has

experienced a renaissance with the development of accelerator-

based neutron sources that allow hospital-based installation without

a nuclear reactor.

02 Linear Accelerators (LINAC)

Engineering Principles

The medical linear accelerator is the most prevalent radiotherapy

machine worldwide, with approximately 14,000 units installedglobally. A LINAC generates a high-energy electron beam by

injecting electrons from an electron gun into a waveguide structure

— either a traveling-wave or standing-wave accelerating structure —

driven by radiofrequency (RF) power from a magnetron or klystron.

Typical clinical energies range from 4 MV to 25 MV for X-ray beams

and 4 MeV to 22 MeV for electron beams.

The accelerating structure is mounted in the gantry, which rotates

360° around the patient. The beam exits through a series of beam-

modifying devices housed in the treatment head: the primary

collimator, `attening Qlter (or in `attening-Qlter-free / FFF mode,

removed to increase dose rate), ion chambers for dose monitoring,

secondary collimator jaws, and the multileaf collimator (MLC). The

patient is positioned on a motorized treatment couch (isocentric

couch) that translates in six degrees of freedom in modern systems.

Multileaf Collimator (MLC) Technology

The MLC is the enabling technology for modern conformal

radiotherapy. It consists of opposing banks of individually

motorized tungsten leaves — typically 40–80 pairs, with leaf widths

of 2.5–10 mm at isocenter — that shape the radiation Qeld to match

the beam's-eye-view projection of the target. By dynamically moving

the leaves during irradiation (sliding window or step-and-shoot), the

LINAC delivers intensity-modulated radiation therapy (IMRT),

allowing non-uniform dose distributions that simultaneously

escalate target dose and reduce dose to organs at risk (OARs).

Image-Guided Radiotherapy (IGRT)Modern LINACs are equipped with on-board imaging systems for

daily patient position veriQcation. The dominant modality is cone-

beam CT (CBCT), acquired by rotating a kV X-ray source and `at-

panel detector mounted orthogonally to the therapy beam. CBCT

provides 3D so^-tissue information enabling detection of organ

motion and deformation between fractions. Additional IGRT

modalities include 2D kV planar imaging, electronic portal imaging

devices (EPID), surface-guided radiation therapy (SGRT) using

stereoscopic cameras, and ultrasound-based tracking for prostate

and abdominal targets.

"The modern linear accelerator is no longer

merely a radiation source — it is an integrated

imaging and delivery platform capable of

adapting treatment in real time to patient

anatomy."

RA DI AT ION ON COLO GY PH Y SIC S , I A E A

Volumetric Modulated Arc Therapy (VMAT)

VMAT — introduced commercially by Varian as RapidArc and by

Elekta as VMAT — delivers IMRT while the gantry rotates

continuously around the patient. Dose rate, gantry speed, and MLC

leaf positions are simultaneously varied throughout the arc,

producing highly conformal dose distributions in treatment times of

1–3 minutes — four to eight times faster than conventional step-and-shoot IMRT. Shorter treatment times reduce intrafraction motion,

improve patient throughput, and reduce the risk of position dri^

during delivery.

Stereotactic Radiosurgery and SBRT with LINAC

High-dose stereotactic treatments — delivering ablative doses in 1–5

fractions with sub-millimeter precision — are routinely performed

on modern LINACs equipped with SGRT or frameless stereotactic

localization. LINAC-based SRS has largely replaced frame-based

Gamma Knife for many intracranial indications in centers already

owning high-end LINACs, owing to the `exibility to treat both

cranial and extracranial sites.

Leading LINAC Manufacturers

Varian Medical Systems

PALO ALTO, C ALI FOR NI A , USA (SI E M E NS H E ALT H I NE E R S

SUB SI DI ARY )

The world's largest radiation oncology company by installed base.

Varian's LINAC portfolio spans entry-level to ultra-high-end systems and

pioneered RapidArc VMAT, TrueBeam FFF delivery, and the Edge

radiosurgery suite.

TrueBeam TrueBeam STx Edge Halcyon Clinac iX VitalBeam

ProBeam (proton)

Elekta AB

STO C K HOLM , SW E DE N

Varian's primary global competitor, Elekta is known for its Agility MLC(160-leaf, 5 mm resolution) and the Unity MR-Linac — arguably the most

signiPcant innovation in LINAC design of the past decade. Also

manufactures the Leksell Gamma Knife series.

Versa HD Unity MR-Linac Infinity Harmony Leksell Gamma Knife

Accuray Inc.

SUN N Y VALE , C ALI FOR NI A , USA

Maker of the CyberKnife robotic radiosurgery system and the

TomoTherapy platform — a helical IMRT delivery system integrated with

CT imaging. Accuray's devices are particularly popular for highly

conformal, adaptive treatments.

CyberKnife M6 CyberKnife S7 Radixact X9 TomoTherapy H

Siemens Healthineers

E R L A NGE N, GE R M A N Y

Siemens exited the LINAC manufacturing business in 2011, but remains

deeply integrated in radiation oncology through its ownership of Varian

(acquired 2021) and its broad diagnostic imaging portfolio used for

simulation and treatment planning.

Artiste (legacy) Oncor (legacy) SOMATOM CT sim

RefleXion Medical

H AY WAR D, C ALI FOR NI A , USA

Developer of the X1 biology-guided radiotherapy (BgRT) machine, which

uses PET-based real-time tumor tracking to continuously guide beam

delivery. This represents a paradigm shiZ from anatomy-guided to

biology-guided targeting, potentially enabling treatment of moving and

multi-site disease.

RefleXion X1ViewRay Inc.

OAKWO OD V I LL AGE , OH IO, USA

Pioneers of MR-guided radiation therapy, ViewRay's MRIdian system

combines a 0.35 T MRI scanner with a LINAC, enabling real-time soZ-

tissue imaging and online adaptive replanning at each treatment fraction.

The system features automated contouring and real-time beam gating

based on MRI motion data.

MRIdian Linac MRIdian (Co-60 legacy)

LINAC Model Comparison

M O DE L

B R A N D

M A X E N E R GY

M L C L E AV E S

L E A F W I D T H

TrueBeam

STx

Varian

10 MV FFF

120

2.5/5 mm

Edge

Varian

10 MV FFF

120 HD

2.5/5 mm

Halcyon

Varian

6 MV FFF

112 stacked

5 mm

Versa HD

Elekta

10 MV FFF

160

5 mm

Unity

Elekta

7 MV

160

7.2 mm

Radixact

X9

Accuray

6 MV FFF

64 binary

6.25 mm

MRIdian

Linac

ViewRay

6 MV

138

4.2 mm

Re@eXion

X1

ReaeXion

6 MV FFF

64 binary

6.25 mm

03 Gamma Knife Radiosurgery

The Leksell Gamma Knife — invented by Swedish neurosurgeon

Lars Leksell and physicist Börje Larsson in the 1960s and Qrst

clinically deployed in 1968 — remains the gold standard for

intracranial stereotactic radiosurgery (SRS). It uses multiple Qxed

cobalt-60 sources arranged in a hemispherical array, with all beams

focused on a single isocenter. The geometric intersection of

hundreds of low-intensity beams creates an intensely focused dose

volume while minimizing dose to surrounding brain parenchyma.

Leksell Gamma Knife — Family Overview

Elekta AB Intracranial SRS

The current Aagship model, the Leksell Gamma Knife Icon,

incorporates 192 cobalt-60 sources and introduces frameless

treatment capability using a high-de<nition motion management

(HDMM) system and cone-beam CT for in-room patient

positioning. This eliminates the need for a rigid stereotactic frame

in many patients, enabling fractionated stereotactic radiotherapy

(fSRT) of larger lesions or targets near eloquent cortex.The Perfexion model (the predecessor to Icon) introduced a single-

body collimator with three aperture sizes (4 mm, 8 mm, 16 mm)

robotically positioned, replacing the manual collimator helmet

system of earlier generations and dramatically reducing set-up

time. The Lightning treatment planning soSware accelerates

inverse planning for multi-isocenter treatments using GPU-based

optimization.

S OURC E S

COLLI M ATOR S

192 Co-60

4 / 8 / 16 mm

I S O C E N T E R ACCUR ACY

T Y PIC AL D O SE R AT E

<0.15 mm

2–3 Gy/min (new source)

I NDIC AT IONS

FR A M E / FR A M E LE SS

Brain only

Both (Icon)

Clinical Applications of Gamma Knife

The Gamma Knife has an extensive body of level I and level II

clinical evidence across multiple intracranial pathologies. Its

applications include:

Brain metastases: Single or multiple metastases up to 3–4 cm in

diameter. Phase III trials including NCCTG N0574 demonstrated

that SRS alone (without whole brain RT) preserves neurocognitive

function with equivalent overall survival for limited metastatic

disease.Vestibular schwannoma (acoustic neuroma): Single-fraction SRS

with marginal doses of 12–13 Gy achieves tumor control rates

exceeding 95% at 10 years, with hearing preservation rates

comparable to microsurgery in small tumors.

Meningioma: Grade I meningiomas unsuitable for surgery or

residual/recurrent disease aQer resection. 10-year progression-

free survival rates of 87–93% are reported with SRS.

Arteriovenous malformations (AVM): Obliteration rates of 80–

90% at three years for small AVMs (<3 cm), with no acute

hemorrhage risk during the latency period.

Trigeminal neuralgia: Pain relief in 80–90% of patients, with

complete pain freedom in 50–60%, using a single isocenter

targeting the trigeminal root entry zone.

Pituitary adenoma: Secreting adenomas (acromegaly, Cushing's

disease) and non-secreting tumors not controlled by surgery.

Endocrine remission rates depend on tumor type and residual

volume.

Functional disorders: Essential tremor, Parkinson's tremor

(thalamotomy), and obsessive-compulsive disorder (anterior

capsulotomy) in carefully selected patients refractory to medical

management.

04 CyberKnife Robotic Radiosurgery

The CyberKnife system, developed at Stanford University by John

Adler and commercialized by Accuray Inc., addresses a

fundamental limitation of frame-based radiosurgical systems: theirconQnement to the head. By mounting a compact 6 MV X-band

LINAC on a KUKA industrial robotic arm with six degrees of

freedom, CyberKnife can deliver SRS and SBRT to targets anywhere

in the body — brain, spine, lung, liver, pancreas, prostate, and

kidney — with sub-millimeter precision.

CyberKnife M6 & S7 Accuray Inc. Whole Body SRS/SBRT

The CyberKnife M6 introduced the InCise 2 MLC, adding intensity

modulation capability to the platform for the <rst time, enabling

faster deliveries and more conformal dose sculpting for large or

complex targets. The M6 FIM (Fixed and Iris MLC) variants allow

choice between <xed circular collimators (for sharp penumbra in

small lesions) and the variable-aperture Iris collimator (for larger

lesions).

The CyberKnife S7 (successor to M6) integrates faster robotic

motion, improved dose rate, and enhanced Synchrony respiratory

motion tracking — a real-time system that uses implanted <ducial

markers or skeletal anatomy correlation to continuously track and

compensate for respiratory-induced tumor motion, allowing

ablative doses to be delivered to moving targets such as lung and

liver tumors without breath-hold or gating.

BE A M E NE RGY

ROBOT IC AR M D OF

6 MV (X-band)

6

I S O C E N T E R ACCUR ACY

T R E AT M E N T NODE S

<0.95 mm

up to 200MOT ION T R AC K I NG

I M AGI NG

Synchrony real-time

kV orthogonal X-ray

Clinical Applications of CyberKnife

CyberKnife's whole-body capability, motion compensation, and

frameless design make it uniquely suited to several clinical

scenarios:

Spinal SRS: Treatment of spinal metastases and primary spinal

tumors with high dose per fraction, sparing the spinal cord

through steep dose gradients achievable with non-coplanar beam

arrangements.

Lung SBRT: Peripheral stage I non-small cell lung cancer (NSCLC)

in inoperable patients. Five-year local control rates exceeding 90%

with 3-fraction SBRT (54 Gy in 3 fractions) are equivalent to

surgical resection in early-stage disease.

Liver SBRT: Hepatocellular carcinoma and colorectal liver

metastases. The Synchrony system is particularly valuable for

managing the 1–3 cm of liver excursion that occurs with tidal

breathing.

Prostate SBRT: Ultra-hypofractionated prostate treatment in 4–5

fractions (35–40 Gy), exploiting the low α/β ratio of prostate

cancer. Multiple RCTs have conbrmed equivalence to

conventional fractionation for intermediate-risk disease.

Pancreatic cancer: Locally advanced pancreatic cancer wheresurgical resection is not possible; SBRT with or without systemic

therapy for dose escalation.

05 Proton Therapy Systems

The Physics Advantage: Bragg Peak Delivery

Protons, unlike photons, have a Qnite range in tissue determined by

their kinetic energy. As a proton beam traverses tissue, it loses

energy gradually, then deposits a sharp maximum — the Bragg peak

— at the end of its range before stopping completely. By selecting

beam energy, the Bragg peak can be positioned precisely at the

tumor, sparing tissue beyond it entirely. By combining proton

beams of multiple energies (spread-out Bragg peak, SOBP), the full

depth of a tumor can be uniformly irradiated.

The dosimetric consequence is a signiQcant reduction in integral

dose — the total energy deposited in the patient's body. For photon

beams, dose continues to be deposited beyond the target; for

protons, it does not. This translates clinically into lower doses to

organs at risk, reduced risk of secondary malignancies (particularly

important in pediatric patients whose long life expectancy makes

late eGects critical), and the possibility of dose escalation without

exceeding normal tissue tolerances.

Pencil Beam Scanning (PBS)

Modern proton therapy systems use pencil beam scanning (PBS) —

also called spot scanning or intensity-modulated proton therapy(IMPT) — rather than passive scattering. Magnetic de`ectors steer a

narrow proton pencil beam across the target volume spot by spot,

layer by layer, with each spot's position and `uence individually

optimized. PBS eliminates the patient-speciQc hardware (range

modulators, patient collimators) required by passive scattering,

reduces secondary neutron dose, and enables intensity-modulated

dose distributions comparable to IMRT — but with the inherent

physical advantage of the Bragg peak.

Proton Therapy System Manufacturers

IBA (Ion Beam Applications)

LOUVAI N - L A-NEUV E , BE LGI UM

The global market leader in proton therapy systems with over 40%

market share. IBA's Proteus ONE is the world's most installed single-room

proton therapy system, designed to reduce the footprint and cost barrier

of proton therapy through a compact superconducting cyclotron. The

Proteus PLUS is its multi-room gantry system.

Proteus ONE Proteus PLUS Proteus 235 ConformalFLASH

Varian (ProBeam)

PALO ALTO, C ALI FOR NI A , USA

Varian's ProBeam system uses a superconducting synchrocyclotron (250

MeV) and is installed at major centers including Mayo Clinic, MD

Anderson, and Roberts Proton Therapy Center. The ProBeam 360° gantry

with PBS delivery and the ProBeam Compact single-room system oeer

scalable installation options.

ProBeam 360° ProBeam CompactMevion Medical Systems

LI T T LE TON, M A SSAC H USE T T S, USA

Mevion developed the world's Prst superconducting synchrocyclotron

small enough to be gantry-mounted — the MEVION S250i Hyperscan. This

single-room, compact design dramatically reduces the infrastructure cost

of proton therapy, opening the modality to community cancer centers

and smaller institutions.

MEVION S250i Hyperscan PBS

Hitachi Ltd.

TOKYO, JAPA N

A major proton and carbon ion therapy manufacturer, Hitachi has

installed systems across Japan, the USA, and Europe. Their synchrotron-

based systems are known for energy layer switching speed and PBS

precision. Installed at MD Anderson (Houston Proton Therapy Center)

and other major institutions.

Proton Beam System PROBEAT-V PROBEAT-RT

Sumitomo Heavy Industries

TOKYO, JAPA N

Sumitomo manufactures synchrotron-based proton therapy systems and

is the supplier for multiple Japanese proton therapy facilities. Known for

compact superconducting cyclotron development and rotating gantry

designs compatible with both PBS and passive scattering delivery.

PRONTIS Compact Cyclotron

ProTom International

FLOW E R MOUND, T E X A S, USA

Manufacturer of the Radiance 330 proton therapy system, which achieves

the highest proton energy (330 MeV) of any clinical system, enablingtreatment of deep-seated targets in large patients and supporting

advanced research applications including proton CT.

Radiance 330

06 Carbon Ion Therapy

Carbon ion therapy combines the dosimetric advantages of the

Bragg peak with a higher relative biological eGectiveness (RBE),

making it uniquely suited to radioresistant tumors. The

infrastructure requirements — a large synchrotron accelerating

carbon ions to ~430 MeV/u — mean that carbon ion therapy remains

concentrated in a handful of specialized centers worldwide.

Siemens (Marburg / Heidelberg)

E R L A NGE N, GE R M A N Y

Siemens supplied the carbon ion therapy system at the Heidelberg Ion-

Beam Therapy Center (HIT), the Prst hospital-based carbon ion center in

Europe and home to the world's Prst rotating isocentric carbon ion

gantry.

HIT System RPTC (proton)

Toshiba / Canon Medical

OTAWAR A , JAPA N

Supplier of synchrotron-based heavy ion therapy systems for Japanese

facilities including HIMAC (National Institute of Radiological Sciences,

Chiba) — the world's Prst dedicated carbon ion center — and several

subsequent Japanese carbon ion centers.

HIMAC System i-ROCKMitsubishi Electric

TOKYO, JAPA N

Co-developer with NIRS of multiple Japanese carbon ion therapy

facilities, including the Kanagawa Cancer Center (Kanagawa, Japan) and

Gunma University Heavy Ion Medical Center, focusing on compact

rotating gantry technology.

GHMC System

Clinical Evidence for Carbon Ion Therapy

The strongest evidence for carbon ions over photon or proton

therapy exists for:

Chordoma and chondrosarcoma of the skull base and spine:

Local control rates of 70–85% at 5 years — signibcantly higher

than photon SRS — with acceptable toxicity.

Adenoid cystic carcinoma and other salivary gland malignancies:

Radioresistant to photons, these tumors respond well to high-LET

carbon ions.

Hepatocellular carcinoma: Short-course carbon ion therapy (2–4

fractions) achieves local control rates comparable to surgical

resection in operable patients.

Locally advanced non-small cell lung cancer and esophageal

cancer: Phase II data from Japanese centers suggest improved

local control with hypofractionated carbon ion schedules.

Prostate cancer: Japanese prospective data show excellent

biochemical control with hypofractionated carbon ion schedulesand low late GU/GI toxicity.

07 Brachytherapy Systems

Brachytherapy — from the Greek brachy, meaning "short" — delivers

radiation internally, with the source placed inside or immediately

adjacent to the tumor. The inverse-square law ensures that dose falls

oG rapidly with distance from the source, creating extremely steep

dose gradients that protect surrounding normal tissue while

delivering very high doses to the tumor.

High-Dose-Rate (HDR) Brachytherapy

HDR brachytherapy uses a single high-activity radioactive source —

typically iridium-192 (Ir-192), with activity of approximately 10 Ci —

that is remotely driven through catheters or applicators positioned

in or near the tumor by a robotic a^erloader. Source dwell positions

and times are optimized by a treatment planning system to achieve

the desired dose distribution. HDR brachytherapy is delivered in

minutes as an outpatient procedure, requiring no hospitalization.

Elekta (Nucletron)

STO C K HOLM , SW E DE N

Elekta acquired Nucletron (Netherlands), the world's leading

brachytherapy manufacturer, creating the dominant global platform. The

microSelectron Digital and its successor, the Flexitron HDR aZerloader

with its Ancer applicator system, are installed in thousands of centers

worldwide.

microSelectron V3 Flexitron ANCER applicatorVarian / Sievert

PALO ALTO, USA

Varian's GammaMed Plus iX and GammaMed Plus HDR aZerloaders are

widely used in North America and Europe for cervical cancer, prostate,

breast, and endobronchial brachytherapy. Integrates with the Vitesse

treatment planning system.

GammaMed Plus iX GammaMed 12i

Eckert & Ziegler BEBIG

BE R LI N, GE R M A N Y

Manufacturer of the MultiSource HDR aZerloader and a major supplier of

cobalt-60 brachytherapy sources as a low-cost alternative to Ir-192,

particularly in resource-limited settings. Also produces permanent

prostate implant seeds (I-125).

MultiSource HDR Cobalt-60 source IsoSeed I-125

Clinical Applications of Brachytherapy

Cervical cancer: HDR brachytherapy boost following external

beam radiotherapy is the standard of care for locally advanced

cervical cancer (FIGO stage IB2–IVA). Image-guided adaptive

brachytherapy (IGABT) using MRI-based contouring has

dramatically improved local control and reduced late toxicity

compared to point-A dosimetry.

Prostate cancer: Both LDR permanent seed implants (I-125 or Pd-

103) and HDR brachytherapy boost or monotherapy are well-

established options for low, intermediate, and selected high-risk

prostate cancer.Breast cancer (APBI): Accelerated partial breast irradiation (APBI)

using interstitial catheters, balloon catheters (MammoSite,

CONTURA), or multicatheter implants delivers the equivalent of 6

weeks of whole-breast RT in 5 days aQer lumpectomy for selected

early-stage breast cancer.

Endometrial cancer: Vaginal vault brachytherapy aQer

hysterectomy for intermediate- and high-risk endometrial cancer

reduces locoregional recurrence with minimal toxicity.

Skin and lip cancers: Surface applicators enable brachytherapy of

superbcial skin malignancies as an outpatient procedure with

excellent cosmetic results.

Endobronchial and esophageal tumors: Intraluminal HDR

brachytherapy for palliative symptom relief (obstruction,

bleeding) or debnitive treatment of early-stage lesions.

08 MR-Guided Radiotherapy (MRgRT)

MR-guided radiotherapy represents perhaps the most signiQcant

technological advance in external beam radiotherapy since the

introduction of IMRT. By combining real-time MRI with radiation

delivery, MRgRT systems provide continuous so^-tissue

visualization during treatment — something no other IGRT modality

achieves — enabling a new paradigm of online adaptive

radiotherapy (oART).

The MR-Linac Workflow

In a typical MR-Linac online adaptive work`ow, the patient ispositioned, and a volumetric MRI is acquired at the beginning of

each treatment session. An automated segmentation algorithm

propagates contours from the reference CT plan to the day's MRI.

The radiation oncologist reviews and edits contours, then the

planning system re-optimizes the dose distribution on the basis of

the day's anatomy — accounting for bowel Qlling, bladder volume,

rectal gas, and tumor response. This entire process takes 20–40

minutes, a^er which the adapted plan is delivered under continuous

MRI guidance. If organ motion exceeds a predeQned threshold, the

beam is automatically gated oG.

Elekta Unity MR-Linac Elekta AB 1.5 T MRI

The Unity integrates a 1.5 T Philips diagnostic-quality MRI scanner

with an Elekta LINAC (7 MV, 14.3 MU/min) in a shared-magnet split-

bore design. The high-<eld MRI provides excellent soS-tissue

contrast for organ delineation and real-time monitoring. The

Monaco treatment planning system and ARIA oncology

information system provide the oART workAow.

The MR-Linac Consortium — a global collaborative of 10+ leading

cancer centers including MD Anderson, Utrecht Medical Center,

and The Christie — has driven rapid clinical evidence development

across multiple tumor sites including prostate, rectum, pancreas,

kidney, and oligometastatic disease.

ViewRay MRIdian Linac ViewRay Inc. 0.35 T MRIThe MRIdian uses a 0.35 T split-bore MRI with a 6 MV LINAC. While

lower-<eld MRI provides less soS-tissue contrast than the Unity, the

lower magnetic <eld reduces beam-modifying ebects on dose

distribution and simpli<es RF shielding. MRIdian is particularly

well-known for pancreatic SBRT — the phase II SMART trial

(NCT02544633) demonstrated remarkable local control using

ablative doses previously impossible with conventional IGRT owing

to proximity to bowel.

The system's Anatomy Filter enables real-time automated

segmentation of the target on each MRI frame, with beam hold

triggering when the target driSs beyond user-de<ned boundaries —

enabling truly gated, anatomy-tracked delivery without breath-

hold requirements.

09 Comprehensive Device Comparison

C AT E G O RY

T E C H NO L O GY

D O S E P R E C I S I O N

B O DY S I T E S

Standard LINAC

X-ray,

electrons

High

All body

High-End LINAC

(TrueBeam/Versa

HD)

FFF X-ray,

IMRT, VMAT

Very high

All body

MR-Linac

(Unity/MRIdian)

X-ray + MRI

guidance

Very high +

real-time

All body

F R AC T I O N S

20–38

1–38

5–25

Gamma Knife

(Icon)

Co-60, 192

sources

Sub-mm (<0.15

mm)

Brain only

CyberKnife (S7)

Robotic

LINAC

High (<1 mm)

Whole body

TomoTherapy

(Radixact)

Helical IMRT

+ MVCT

High

All body

Proton Therapy

(single-room)

Proton PBS

Very high

All body

Proton Therapy

(multi-room)

Proton PBS

Very high

All body

Carbon Ion

Therapy

Carbon PBS

Very high

All body

HDR

Brachytherapy

Ir-192

aZerloader

Extreme

(internal)

Gynecologic,

prostate,

breast

LDR

Brachytherapy

(seeds)

I-125, Pd-103

Very high

(internal)

Prostate, eye

1–5

1–5

10–38

1–35

1–35

2–20

3–10

fractions

Permanent

10 Treatment Planning Systems

The treatment planning system (TPS) is the computationalbackbone of modern radiotherapy — responsible for 3D dose

calculation, plan optimization, and documentation. No radiotherapy

device operates independently of a TPS; their tight integration

determines clinical work`ow e@ciency, plan quality, and patient

safety.

Varian Eclipse

PALO ALTO, C ALI FOR NI A , USA

The most widely used TPS worldwide, Eclipse supports IMRT, VMAT

(RapidArc), stereotactic, proton (RayStation integration), and

brachytherapy planning. The Acuros XB dose engine provides Monte

Carlo-equivalent accuracy with faster computation speeds.

Eclipse v18 Acuros XB RapidPlan AI

Elekta Monaco

STO C K HOLM , SW E DE N

Monaco uses a Monte Carlo dose engine and stochastic optimization for

IMRT and VMAT planning, oeering accurate dose calculations in

heterogeneous tissue and near metal implants. It is the native TPS for the

Unity MR-Linac, supporting online adaptive workaows.

Monaco 5.5 MOSAIQ OIS

RaySearch RayStation

STO C K HOLM , SW E DE N

RayStation is a vendor-neutral, multimodality TPS supporting photon,

electron, proton, carbon ion, and helical therapy planning in a single

platform. Its GPU-accelerated Monte Carlo engine and machine-learning-

based automated planning have made it the fastest-growing TPS globally.

RayStation 2024 RayCare OIS RayPhysicsAccuray Precision

SUN N Y VALE , C ALI FOR NI A , USA

Accuray's Precision TPS is the native planning system for CyberKnife and

TomoTherapy/Radixact. The iDMS data management system and

Synchrony motion tracking integration are key features for robotic

radiosurgery workaows.

Precision 3.0 iDMS

Brainlab Elements

M UNIC H , GE R M A N Y

Brainlab is primarily known for surgical navigation and radiosurgery, but

its Elements TPS suite — covering SRS, FSRT, and adaptive planning —

integrates with any LINAC. Its ExacTrac Dynamic surface-guided and X-

ray targeting system is a market-leading IGRT solution for SRS.

Elements SRS ExacTrac Dynamic iPlan RT

11 Artificial Intelligence in Radiotherapy

AI-Driven Contouring and Segmentation

Organ-at-risk (OAR) and target delineation is the most time-

consuming and inter-observer variable step in the radiotherapy

work`ow. AI-based auto-contouring systems — using deep learning

convolutional neural networks (CNNs) trained on large annotated

datasets — can produce clinically acceptable OAR contours in

seconds rather than the 30–90 minutes required for manual

delineation. Leading commercial solutions include Varian ethos AI,Elekta IRIS Auto-Contouring, Mirada DLC Expert, RaySearch

RayStation AI segmentation, and MVision.ai.

Knowledge-Based Planning (KBP)

Knowledge-based planning systems — exempliQed by Varian

RapidPlan and RaySearch RayStation ML dose prediction — use

libraries of previously approved plans to generate predictive dose-

volume histograms (DVHs) for new patients with similar anatomy.

The optimizer then targets these predicted DVHs, ensuring plan

quality is consistently at or above the institutional benchmark. KBP

has been shown in multiple studies to reduce planning time by 50–

70% while simultaneously improving plan quality compared to

manual planning.

Adaptive Radiotherapy and AI

Online adaptive radiotherapy — as implemented on the Unity,

MRIdian, and Varian Ethos platforms — depends critically on AI for

feasibility. Fast automated contouring, automated plan

optimization, and automated plan QA checks must all complete

within the 20–30 minute clinical window available during the

patient's treatment session. The Varian Ethos system (based on a

ring-gantry LINAC with CBCT) uses an AI-driven adapt-to-shape and

adapt-to-position work`ow speciQcally designed for online

adaptation in the prostate, bladder, cervix, and rectum.

Outcome Prediction and Clinical Decision Support

Machine learning models trained on multi-institutional patientdatasets are emerging as tools for predicting toxicity risk, tumor

control probability, and overall survival — enabling individualized

treatment plan selection and dose prescription. Companies

including Oncora Medical, Mirada Medical, and Siemens

Healthineers AI-Rad Companion RT are commercializing these

outcome prediction tools for clinical deployment.

12 Quality Assurance and Medical Physics

Radiotherapy quality assurance (QA) is a systematic program of

checks ensuring that radiation is delivered safely, accurately, and

consistently. The consequences of systematic QA failures — as

illustrated by high-proQle incidents including the Epinal (France)

and Panama radiotherapy accidents — can be catastrophic.

International QA guidelines from AAPM, IAEA, ESTRO, and IPEM

deQne minimum test frequencies and tolerance levels for all clinical

radiotherapy equipment.

Machine QA

Machine QA encompasses output constancy checks (daily, monthly,

annual absolute dosimetry), geometric accuracy veriQcation

(isocenter constancy, MLC leaf position accuracy, couch positioning

accuracy), imaging system performance (kV and CBCT image

quality, geometric distortion), and motion management system

veriQcation. For MR-Linac systems, additional tests cover magnetic

Qeld homogeneity, gradient performance, and RF coil functionality

— a substantially expanded QA scope requiring physicists trained inboth MRI and radiation physics.

Patient-Specific Plan QA

Before each new treatment plan is delivered, a patient-speciQc QA

measurement veriQes that the calculated dose distribution matches

what the machine physically delivers. The current standard uses

array-based detectors (IBA MatriXX, Sun Nuclear ArcCheck, PTW

Octavius) or transmission detectors (Elekta iViewGT, IBA

EvolutionQA) to measure delivered `uence and compare it against

calculated predictions using gamma analysis. Emerging AI-based

virtual patient-speciQc QA tools — using log-Qle analysis and

machine learning — can `ag potential delivery errors without

physical measurement.

Key QA Equipment Manufacturers

IBA Dosimetry

S C H WAR Z E NBRUC K , GE R M A N Y

Global leader in radiotherapy dosimetry equipment, IBA Dosimetry oeers

the full QA spectrum: Farmer-type ion chambers, 3D water phantoms

(Blue Phantom 2), array detectors (MatriXX Evolution), and patient-

speciPc QA systems (EvolutionQA, Compass).

MatriXX Evolution Blue Phantom 2 Compass OmniPro-Accept

Sun Nuclear (Mirion Technologies)

M E LBOUR NE , FLOR I DA , USA

Sun Nuclear's ArcCheck cylindrical diode array and SNC Patient QA

soZware are among the most widely used patient-speciPc QA tools.Mirion acquired Sun Nuclear in 2021, integrating its dosimetry portfolio

with broader radiation measurement capabilities.

ArcCheck MapCheck 3 SNC Patient PerFRACTION

PTW Freiburg

FR E I BURG I M BR E I S GAU, GE R M A N Y

PTW manufactures the reference standard ionization chambers (Farmer

chamber, PinPoint chamber), the OCTAVIUS 4D array detector system,

and the BEAMSCAN water phantom — widely used for LINAC

commissioning and annual absolute dosimetry per IAEA TRS-398.

Farmer Chamber 30013 OCTAVIUS 4D BEAMSCAN

13 Emerging Technologies: FLASH, MRI-Guided

Proton, and Beyond

FLASH Radiotherapy

FLASH radiotherapy — delivery of an entire dose fraction (15–30 Gy)

in less than 200 milliseconds at dose rates exceeding 40–100 Gy/s,

compared to 0.1 Gy/s for conventional delivery — has generated

intense research interest following landmark preclinical

publications demonstrating that FLASH normal tissue sparing

matches that of conventionally fractionated radiotherapy, while

preserving equivalent tumor control. The proposed mechanism

involves transient oxygen depletion in normal tissues, creating a

hypoxic radioprotective state that tumor cells — already hypoxic —

cannot exploit. If translatable to humans, FLASH could

fundamentally transform the radiotherapy dose-fractionationparadigm.

Current clinical FLASH development programs include the FAST-01

trial (University of Cincinnati / Cincinnati Children's, using proton

FLASH for painful bone metastases), the FAST-02 trial, and multiple

electron FLASH programs at European centers. Varian has

integrated FLASH capability into their ProBeam proton system, and

electron FLASH delivery is feasible on modiQed conventional

LINACs.

MRI-Guided Proton Therapy

Combining the dosimetric superiority of protons with the so^-tissue

imaging quality of MRI represents the next frontier in particle

therapy. The fundamental challenge is the interaction between the

static magnetic Qeld of the MRI and the charged particle beam — the

Lorentz force curves the proton trajectory, requiring real-time beam

correction algorithms. Groups at University Medical Center Utrecht,

Massachusetts General Hospital, and the Heidelberg Ion-Beam

Therapy Center are developing MRI-guided proton systems, with

the Qrst clinical treatments anticipated in the late 2020s.

Boron Neutron Capture Therapy (BNCT)

BNCT exploits the high neutron capture cross-section of boron-10:

tumor cells accumulate a boron-10 compound (BPA or BSH), which

upon neutron irradiation undergoes a Qssion reaction releasing

short-range, high-LET alpha particles and lithium-7 nuclei that kill

the cell from within. The development of compact, hospital-based

accelerator neutron sources by TAE Life Sciences, StellaPharma/Sumitomo, and NeutroThera has revived BNCT as a clinical

reality, with approval in Japan for recurrent head and neck cancer

and active clinical trials for glioblastoma, melanoma, and

mesothelioma.

Magnetic Particle Imaging and Real-Time Tumor Tracking

Beyond MRI, research programs are exploring positron emission

tomography (PET)-guided real-time beam adaptation — as

commercialized in the Re`eXion X1 BgRT system — ultrasound-

guided tracking, and electromagnetic transponder-based tumor

localization (Calypso system, Varian) for sub-second, continuous

intrafraction tracking of prostate and so^-tissue targets.

14 Clinical Applications by Disease Site

Central Nervous System (Brain and Spine)

Brain tumors — from high-grade gliomas to brain metastases —

represent the most diverse and technically demanding application

of radiotherapy. Glioblastoma multiforme (GBM) is treated with

postoperative concurrent chemoradiotherapy (60 Gy in 30 fractions

with temozolomide, per the Stupp protocol) delivered by LINAC-

based IMRT, or with hypofractionated schemes (40 Gy in 15

fractions) in elderly/frail patients. Brain metastases in the era of

eGective systemic therapy are increasingly managed with SRS

(Gamma Knife or LINAC) alone rather than whole brain

radiotherapy, preserving neurocognitive function. Primary spinalcord tumors and spinal metastases are treated with LINAC-based

IMRT or robotic SRS (CyberKnife), with reirradiation increasingly

feasible using MR-Linac guidance.

Head and Neck Cancer

Head and neck squamous cell carcinoma is among the most

complex radiotherapy targets owing to the proximity of critical

structures — spinal cord, brainstem, parotid glands, mandible,

cochlea, larynx — to the target volumes. Intensity-modulated

radiotherapy with simultaneous integrated boost (SIB-IMRT) is the

standard technique, delivering 70 Gy to the gross tumor volume, 63

Gy to high-risk elective nodes, and 56 Gy to low-risk elective nodes

in 35 fractions. Proton therapy is increasingly used for locally

advanced oropharyngeal and nasopharyngeal cancers where

reducing integral dose to uninvolved structures — contralateral

parotid, oral cavity, mandible — reduces severe late toxicity.

Thoracic Oncology (Lung and Esophagus)

Lung SBRT has become the standard of care for inoperable early-

stage (T1-T2N0) NSCLC, with 3-year local control rates exceeding

90% using biologically eGective doses (BED) ≥100 Gy. Medically

operable early-stage NSCLC patients are increasingly enrolled in

trials comparing SBRT to surgery (VALOR, STABLE-MATES,

SABRTooth). Locally advanced NSCLC (stage III) is treated with

concurrent chemoradiotherapy (60–66 Gy in 30–33 fractions)

followed by durvalumab consolidation (PACIFIC regimen). Proton

therapy phase III trials (NRG-LU001, -LU006) are comparing photonand proton chemoradiotherapy for stage III NSCLC.

Breast Cancer

Adjuvant whole-breast radiotherapy a^er breast-conserving surgery

reduces 10-year local recurrence rates from 35% to 10% (Early

Breast Cancer Trialists' Collaborative Group, 2011 meta-analysis).

Hypofractionation (40 Gy in 15 fractions or 26 Gy in 5 fractions /

FAST-Forward) is now preferred over conventional fractionation for

most patients, reducing treatment burden without compromising

e@cacy or late toxicity. Prone positioning, SGRT, and DIBH (deep

inspiratory breath hold) techniques reduce cardiac and lung dose.

Regional nodal irradiation (internal mammary chain,

supraclavicular and axillary nodes) uses IMRT or VMAT for optimal

dose coverage with minimal lung and heart dose.

Gastrointestinal Malignancies

Rectal cancer is treated with neoadjuvant long-course

chemoradiotherapy (50 Gy in 25 fractions with concurrent 5-

FU/capecitabine) or short-course radiotherapy (25 Gy in 5 fractions,

Swedish Rectal Cancer Trial) prior to total mesorectal excision. The

RAPIDO and PRODIGE-23 trials have demonstrated improved

pathological complete response rates with intensiQed neoadjuvant

regimens. MR-guided radiotherapy is transforming the

management of locally advanced pancreatic cancer, with MR-Linac-

based SBRT achieving local control rates previously impossible due

to proximity to bowel loops that can now be tracked and gated in

real time.Genitourinary Malignancies

Prostate cancer radiotherapy has undergone a fundamental shi^

toward ultra-hypofractionation. Moderate hypofractionation (60 Gy

in 20 fractions or 62 Gy in 20 fractions) has Level 1 evidence of non-

inferiority to conventional fractionation. Ultra-hypofractionated

SBRT (35–40 Gy in 5 fractions) has been validated by the PACE-B RCT

and HYPO-RT-PC trial for low and intermediate-risk prostate cancer.

Proton therapy oGers dosimetric advantages for prostate and is

supported by SEER database data suggesting lower GI toxicity rates.

Bladder cancer is treated with radiotherapy as part of bladder-

sparing trimodality therapy (maximal TURBT + cisplatin-based

concurrent chemoradiotherapy) with 5-year bladder-intact survival

of 36–74% for T2-T4a disease in the RTOG 0712 trial.

Gynecologic Malignancies

Cervical cancer is the archetypal example of combined external

beam and brachytherapy radiotherapy. The EMBRACE-I prospective

study demonstrated that MRI-guided adaptive brachytherapy

(IGABT) targeting the high-risk clinical target volume (HR-CTV) with

prescribed doses ≥85 Gy EQD2 achieves 5-year local control rates of

91% for stage IIB and 88% for stage IIIB cervical cancer — outcomes

that are transformative compared to historical point-A dosimetry.

15 Global Radiotherapy Landscape

Equipment Disparities and Global AccessThe global burden of cancer continues to shi^ toward low- and

middle-income countries (LMICs), which bear 70% of cancer

mortality but have access to only 10–15% of global radiotherapy

resources. The IAEA's Directory of Radiotherapy Centres (DIRAC)

documents stark equipment disparities: many sub-Saharan African

countries have fewer than one LINAC per million population,

compared to 7–12 per million in Western Europe and North

America.

Addressing this gap is a WHO and IAEA global health priority. The

Global Task Force on Radiotherapy for Cancer Control (GTFRCC)

estimated that scaling up radiotherapy in LMICs to meet need would

require $184 billion over 20 years but would avert 26.9 million

premature deaths — a cost-eGective investment by any health

economic standard. Accelerated programs for technology transfer,

cobalt unit deployment (as lower-cost alternatives to LINAC where

appropriate), and telemedicine-based training for medical

physicists and radiation oncologists are key components of this

global health agenda.

Radiotherapy in Turkey

Turkey has made substantial investments in radiotherapy

infrastructure over the past two decades. The country now operates

approximately 200 LINAC systems, primarily Varian and Elekta

platforms, across major university hospitals, training and research

hospitals (Eğitim ve Araştırma Hastaneleri), and a growing private

oncology sector. Turkey's Qrst proton therapy center opened at

Acıbadem Altunizade Hospital in Istanbul in 2020, equipped with aVarian ProBeam system. The Turkish Radiation Oncology Society

(TROD) and the Turkish Society of Medical Physics (TÜFED) drive

national quality standards and training programs aligned with

ESTRO and IAEA guidelines.

References and Further Reading

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Kluwer; 2020.

IAEA. Radiation Oncology Physics: A Handbook for Teachers and Students. Vienna:

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Teoh M, Clark CH, Wood K, et al. Volumetric modulated arc therapy: a review of

current literature and clinical use in practice. Br J Radiol. 2011;84(1007):967-996.

Alongi F, Arcangeli S, Filippi AR, et al. Review and uses of stereotactic body

radiation therapy for oligometastases. Oncologist. 2012;17(8):1100-1107.

Leksell L. The stereotaxic method and radiosurgery of the brain. Acta Chir Scand.

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Adler JR Jr, Chang SD, Murphy MJ, et al. The Cyberknife: a frameless robotic

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Suit H, DeLaney T, Goldberg S, et al. Proton vs carbon ion beams in the de\nitive

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Mutic S, Dempsey JF. The ViewRay system: magnetic resonance-guided and

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Raaymakers BW, Jürgenliemk-Schulz IM, Bol GH, et al. First patients treated with

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Bourhis J, Sozzi WJ, Jorge PG, et al. Treatment of a \rst patient with FLASH-

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Orth M, Lauber K, Niyazi M, et al. Current concepts in clinical radiation

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Pötter R, Tanderup K, Kirisits C, et al. The EMBRACE II study: The outcome and

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