IMRT 2017

IMRT and other conformal techniques Madrid, Spain April 9-13, 2017

Current status of IMRT at H.U. HM Sanchinarro

Carmen Rubio MD PhD Radiation Oncology H. U. HM Sanchinarro- Puerta del Sur http://radioterapiahm.com

HM Hospitales

2

Private Group of University Hospitals

4

2010

1991

2015

2007

2008

San Pablo CEU- University

HM Sanchinarro Clara Campal Cancer Center (Radiation Oncology)

Residents Programme Radia8on Oncology

HM Puerta del Sur (Radiation Oncology)

Hospital de Madrid

HM Sanchinarro Clara Campal Cancer Center C.I.O.O.C. Diagnosis Treatment Pathology

Radiation Oncology

Multidisciplinary Teams Tumours Committees

Radiology

Surgery

Nuclear Medicine

Medical Oncology

3 Teslas RMI

PET-CT PET-MRI

Radiation Oncology and Medical Physics Department

HM Sanchinarro September 2007

HM Puerta del Sur January 2015

(1)

Radiation Oncologists 8 Medical Phycicists

4 Residents

4 Dosimetrits 14 Technicians 4 Nurses

HM Sanchinarro 2007 HM Sanchinarro- Equipment

2 Oncor Siemens

1 Novalis Brainlab & Varian

1 CT Simulator

Siemens Somaton Open CT 82 cm wide Gantry diameter

6MV LINAC Micro MLC 3mm Stereotactic Radiosurgery & HFSRT SBRT & SBRT with Gating IGRT based on Orthogonal RX- Exactrac system

Multienergetic 6-15 MV LINAC 82 -160 MLC 3 D Conformal RT IMRT IGRT based on MV CBCT

HM Sanchinarro- Equipment

HDR- Iridium-192 Brachytherapy and IORT Programme

Ginecology tumors

Real Time Planification system -ELEKTA

Prostate Cancer

LDR Iodine-125 seeds

Intraopera)ve and Inters))al Brachytherapy

HDR & Electrons

HM Sanchinarro- Equipment

1 VERSA HD (Elekta)

1 CT Simulator

HM Puerta del Sur January 2015

Multienergetic LINAC Photons: 6,10 and 15 MV Fla$ening filter free beams ( 6 and 10 FFF) Agility 160 MLC 5 mm Hexapod Couch 6D IGRT: KV Cone beam CT Simmetry 4D Conebeam /ABC/Clarity

Toshiba Aquilon (LB) 82 cm gantry bore opening 4D CT acquisi:on mode RPM ABC “Active Breathing Coordinator”

HM Sanchinarro- Equipment Treatment planification systems (TPS)

iPlan (Brainlab )

RayStation (Raysearch)

XiO Planning - Focal Contouring Systems (Elekta)

From 2007 3D –Conformal RT Arc conformal therapy (static or dynamic) Static IMRT : Step and shoot Dinamyc IMRT: sliding Windows Montecarlo ( from 2011 )

From 2007 to 2014 3D –Conformal RT Static IMRT : Step and shoot

From 2014 3D Conformal RT sIMRT & dIMRT VMAT

HM Sanchinarro- Equipment

Pa9ent management informa9on system Registration and Verfication System

LANTIS (Siemens)

• Single interface / Single database • Workflow management • Integrated informa9on • Accessible by mul9-disciplinary teams across mul9ple loca9ons

2014- MOSAIQ (ELEKTA)

ARIA (Brainlab )

HM Sanchinarro Radiation Oncology Department

The same Radiation Oncology Department “The same team”

Mosaiq (R & V) i (

V)

Ray Station (TPS) Servers Mosaiq (R & V) Servers

Ray Station (TPS) Ray Station (TPS)

HM Puerta del Sur

Integrate with treatment planning system and linear accelerators

CLINICAL EXPERIENCE ON IMRT FOR OLIGOMETASTATIC PATIENTS WITH SBRT

OVIDIO HERNANDO REQUEJO MD. PhD. RADIATION ONCOLOGY HM HOSPITALES.

Si es ta is F or bi d

Introduction

• • • • • • • • •

IMRT SRS SBRT

Oligometastases IMRT + SRS/SBRT

Clinical Experience with IMRT

SRS SBRT

INTRODUCTION

Radiation Oncology development.

Sofis:cated IMRT-IGRT

First xRay treatments

200 0

1897

1950

1980

1990

2005

2016

Protons & HP

3D RT

IMRT

Xrays discovery and radiac:vity discovery

Cobalt Units

2D RT

Adap:ve RT

IGRT

Stereotac:c Radiosurgery

Linear Acelerators

MR-Linac

SBRT

IMRT

IMRT

QA program

Inverse planning

Dose distribution conform much more closely to the PTV

SLOW

Static IMRT

Step and Shoot

-

Dynamic IMRT

Sliding Windows

-

Volumetric Modulated Radiotherapy - VMAT - Rapid Arc

FAST

IMRT

SRS

SBRT

RADIOSURGERY

1950- Radiosurgery was born 2000- Technological advances

GK treatments LINAC treatments Experience Gained

Frameless RS&SHRT (IMRT)

SINGLE DOSE 15-24 Gy HYPOFRACIONATION 3-5Fx to 21-35Gy

FRAMELESS

FRAMELESS • End to end process over a hidden target test (radiopaque sphere, Ø 5 mm) provided by BrainLAB to evaluate the accuracy of IGRT positioning system . • Irradiation with a conical collimator (Ø 7,5 mm) • Gantry 0º & 90º • The center to center deviations are below 0.7 ± 0.3

FRAMELESS

Allows us to perform SRS with IMRT and Hypofractionated RT

SBRT It´s a modern radiotherapy technique, SBRT = Stereotactic Body Radiation Therapy High precision technique that allow to administer high doses in few fractions Requires highly conformal dosimetry, high dose gradient and image guided radiotherapy. Including movement control methods for moving targets.

SRS/SBRT VS CONVENTIONAL RT

Conventional RT

SRS/SBRT

Dose per fraction Number of fractions

1,8-3Gy

6-30Gy

10-30

1-8

Target

GTV à CTV If possible Not necessary

GTV

Motion management

Mandatory (if needed)

Daily IGRT

Mandatory

AAPM Task Group 101

Radiobiology

10 x 2 Gy

Tumoral cells alive

1x 20 Gy

5 x 4 Gy

Radiobiology

The SBRT is based on the Lineal Quadratic Model to compare doses to targets and organs at risk with the doses used in conventional fractionation using the biologically equivalent dose (BED) formulae:

There are some doubts about the use of the LQM in SBRT treatments:

• The LQM in vitro demonstrated fiability to doses up to 15 Gy per fraction. • In vivo the LQM predictions are consistent up to 2-20 Gy.

Radiobiology

The lethal effect of the SBRT is bigger than predicted from the LQM.

At high dose per fraction (> 8-10 Gy), to the DNA lesive effect we have to add the effect in the vascular endothelial (ASMase pathway).

Abscopal Effect: Systemic Effect of radiotherapy. The tumoral cell destruction generate antigens that favors the production of antibodies. Those antibodies stimulate the immune system to attack distant areas of disease. Radiobiology

SBRT = CHANGE IN TREATMENT INTENTION

Oligometastastic patients & Radiotherapy evolution

Palliative Radiotherapy

SBRT (curative intent)

Modern treatment units

Tumor motion control

Better tumor localization

TUMOR MOTION CONTROL

Moving targets

Compensation Gating / Tracking (fidutial markers)

Restrictive Methods

Body-Fix

4DCT + ITV

Dampening

ABC

OLIGOMETASTATIC PATIENT •

Samuell Hellman (1995) defines an oligometastatic patient as an intermediate state in the development of metastatic disease:

- -

Range from 1 to 5 metastases Limited number of organs

• They achieve longer survival and could have long periods with no evidence of disease after treatment. • Local treatments of the oligometastases could play an important role on the major survival of these patients.

OLIGOMETASTATIC PATIENT Primary Tumor

Primary tumor treated

Primary tumor + oligometastases ± oligo-recurrences

New metastases

Oligometastases

Oligo-recurrence

Anticancer Research September 2015 vol. 35 no. 9 4903-4908

INDICATIONS Oligometastases:

• • • • • •

Brain Metastases Lung metastases Liver metastases

Bone metastases (spine & other bones)

Adrenal gland metastases Lymph node metastases

IMRT & SRS/SBRT

Site

IMRT

Reason

-Allows to treat tumors near OARs

CNS

Recommended

Lung Liver

-Better conformity -Allows to treat tumors near OARs

Lymph nodes Adrenal gland Bones

Recommended

Spine Pancreas Prostate

-OARs within the target volume

Mandatory

Introduction IMRT SRS SBRT

Oligometastases IMRT + SRS/SBRT Clinical Experience with IMRT SRS SBRT

SRS

SRS Started on 2008 in HM Sanchinarro • Novalis LINAC • Frameless • Mostly 3-D, Dynamic conformal arcs • IMRT (Sliding Windows if needed) • ExacTrac xRays (inter/intrafraction)

SRS Started on 2015 in HM Puerta del Sur • Versa HD • Frameless • VMAT • CBCT (+ intrafraction CBCT)

BRAIN METASTASES SRS 15-24 Gy

BRAIN METASTASES

SHRT 5-10 Fx, 30-50 Gy

Surgical bed

Large Mts

BENIGN TUMORS

IMRT Sliding Windows Meningioma hypofractionated

VMAT Pituitary Adenoma SRS

BENIGN TUMORS IMRT Sliding Windows Acoustic Neuroma SRS

IMRT Sliding Windows AVM hypofractionated

SBRT

SBRT IN HM HOSPITALES

Started on 2008 on HM Sanchinarro

• • • •

Novalis (Adaptive Gating ± IMRT Steep & Shoot)

Started on January 2015 on HM Puerta del Sur

Versa HD (ABC/Dampening + VMAT)

IMRT IN HM HOSPITALES

127%

474%

201 6

2007

2008

2009

2010 2011 2012 2013 2014 2015

IMRT-VMAT

4

90

190

185

190

270

325

380 328 456

Tecnicas especiales IMRT- VMAT Tenicas especiales sin IMRT

9

18

30

37

44

53

47 124 223 115 158 192

0

80

125

120

144

130

132

TUMOR MOTION CONTROL

Moving targets

Compensation Gating / Tracking (fidutial markers)

Restrictive Methods

Body-Fix

4DCT + ITV

Dampening

ABC

EXACTRAC ADAPTIVE GATING

ADAPTIVE GATING

ABC & DAMPENING

GATING ABC

GATING ABC

CBCT & treatment in inspiration phase

DAMPENING (+ 4D-CT) Body-Fix

Dampening

4DCT + ITV

Residual movement = ITV

T

Dampening

T

DAMPENING (+ 4D-CT)

Dampening + 4DCT

4D-CBCT IGRT

LUNG METASTASES VMAT can achieve better dose conformity and make treatment faster.

LUNG METASTASES VMAT can achieve better dose conformity and protect the OARs

LUNG METASTASES Shared isocenter for nearby tumors

LUNG SBRT RESULTS

Numer of fractions

Dose per fraction 15-20 Gy 10-12 Gy

Total Dose

3 5

45-60 Gy 50-60 Gy

LOCAL CONTROL 12 m

PFS Median 16 m

94% 92% 85%

12 m 24 m 36 m

57% 39% 14%

24 m 36 m

LIVER METASTASES IMRT can avoid dose in nearby OARs Step and Shoot IMRT for Segment II liver Mts

LIVER METASTASES IMRT can avoid dose in nearby OARs VMAT for HCC in Child A patient

LIVER METASTASES A) Multiple Isocenter - Step and Shoot-IMRT B) Shared isocenter for nearby tumors - VMAT A B

LIVER SBRT RESULTS

Numer of fractions

Dose per fraction

Total Dose

3 5

12-15-20 Gy 36-45-60 Gy

10 Gy

50 Gy

Local Control 12 m

PFS Median 16 m

93% 81% 64%

12 m 24 m 36 m

57% 39% 14%

24 m 36 m

SPINE METASTASES

SPINE METASTASES

Novalis Sliding-Windows/ Step & Shoot ExacTrac

Versa VMAT CBCT (intraFx)

SPINE METASTASES

Novalis

Versa

SPINE METASTASES

Novalis

Versa

SPINE METASTSES Multiple metastases 3x8 Gy

SPINE IGRT It is mandatory to have intrafraction control when high dose IMRT- SBRT is applied to spine metastases. IGRT Start treatment

IGRT IGRT

Finished

SPINE VMAT EXAMPLE VMAT and FFF beams results in faster treatments.

SPINE RESULTS

• • • • • •

Single Dose 18 Gy Faster pain relief Local Control in 85%

Local control

Median pain pre SBRT(VAS=4,26) Median pain post SBRT (VAS=0,69)

Wilcoxon p<0,01

BONE SBRT

BONE SBRT

ADRENAL METASTASES

LYMPH NODE METASTASES

The IMRT allows us to preserve the ureter, which, as a OARs can develop stenosis after SBRT.

MESSAGES TO TAKE HOME

SRS & SBRT are consolidated radiation techniques

• • •

Indications are rapidly growing although no clinical trials are available. IGRT: is as important as the treatment technique when high doses are administered • IMRT (whatever the modality): plays an important role in CNS, liver, lung and adrenal SRS / SBRT. • IMRT (whatever the modality): is mandatory for spine SRS / SBRT.

CLINICAL EXPERIENCE ON IMRT FOR GASTROINTESTINAL AND GENITOURINARY TUMORS DR. EMILIO SÁNCHEZ HOSPITAL UNIVERSITARIO SANCHINARRO

• Gastrointestinals Tumors • Pancreatic Cancer • Rectal Cancer • Anal canal Cancer • Genitourinay Tumors • Cervical Cancer

RECTAL CANCER

RECTAL CANCER

NCCN • IMRT should only be used in the setting of a clinical trial or unique clinical situations or anatomical situations • NEOADJUVANT • 45 to 50.4 Gy to the pelvis in 25-28 fractions • Followed by boost of 5.4 Gy in 3 fractions to the tumor bed • ADJUVANT

NEOADJUVANT • Preoperative CRT (compared with postoperative chemoradiation):

• Improvement of locoregional tumor recurrence (6 vs. 13%) • Improvement of acute toxicity (27 vs. 40%) • Downstaging effect of the tumor in more than half of the patients

NEOADJUVANT

• Standard chemoradiation with 5-Fu:

• Complete pathological responses (ypCR): 15%

• Grade 3 Diarrhea and Proctitis: 15-40%

NEOADJUVANT

• Multidisciplinary GI Tumors Board

• cT2-4 N0/+ cM0 tumors

NEOADJUVANT

• DIAGNOSIS

• Colonoscopy and biopsy • Echoendoscopy

• Computed tomography (CT) imaging. • Positron emission tomography PET-CT • Pelvic magnetic resonance imaging (MRI) • PET-MRI

NEOADJUVANT

• Radiation therapy simulation

• Somatom Sensation Open Siemens CT or Biograph PET-CT scanner (Siemens®, Germany)

• BellyBoard (CIVCO®, USA) device (prone) • Helicoidal CT images: 3 mm reconstruction • Oral and intravenous contrast agents

NEOADJUVANT

PET-CT SIMULATION

NEOADJUVANT

• Radiation therapy • 4.5 weeks with a total of 23 fractions. • PTV1 (pelvic nodes + 0.5 cm): 46 Gy • PTV2 (gross tumor and affected nodes + 0.5 cm): 57.5 Gy Concomitant Boost 2.5 Gy per fraction BED 71.8 Gy; Eq2 Gy/f 70 Gy

NEOADJUVANT • Treatment Verification: Image-guided radiation therapy (IGRT) • MV Cone-Beam

NEOADJUVANT • Automatic calculation of movements

NEOADJUVANT

• IGRT: Kv Cone-Beam • Better image quality in soft tissues

NEOADJUVANT

SUPINE POSITION

NEOADJUVANT

• 74 patients • July 2008 – December 2012 • Median Follow up was 17 months

NEOADJUVANT

• Radiation therapy

• 4.5 weeks with a total of 23 fractions. • PTV1 (pelvic PTV) 46 Gy • PTV2 (gross tumor and affected nodes) 57.5 Gy with concomitant boost • Capecitabine • Surgery • Median time from the end of radiation therapy to surgery was 67.6 days. • Low anterior resection in 56 (77.7%) • Abdominoperineal resection in 16 patients (22.2%).

NEOADJUVANT • Primary tumor downstaging was achieved in 55 out of 72 patients (76.38%)

• Nodal downstaging was achieved in 34 patients (47.2%)

NEOADJUVANT

• Acute Gastrointestinal Toxicity 9.5% • Standard Treatment 15-40%

NEOADJUVANT

• 22/72 patients (30.6%) achieved ypRC

• 21 patients (29.2%) had near complete regression

• 17 (23.6%) moderate regression

• 12 patients (16.7%) minimal regression

• Circunferencial Resection Margin was free of tumor in 70 (97.2%) of 72

NEOADJUVANT

• 3-year estimated OS 95.4%

• 3-year estimated DFS 85.9%

• No local relapse was found

• 10 patients (13.8%) developed distant metastases

NEOADJUVANT

• 30.6 % ypCR achieved (standard radiotherapy 15%)

• pT downstaging to pT0-2 had better DFS (p 0.013)

• cN0 tumors had higher rates of ypCR than patients presenting with cN1/2 tumors (p 0.007)

NEOADJUVANT • Anastomosis leakage has been previously reported with rates of 11% ; in our experience there were only two cases (2.7%)

ADJUVANT

• Radiation therapy • 5.5 weeks with a total of 28 fractions. • PTV1 (pelvic PTV) 50.4 Gy

• Capecitabine

PANCREATIC CANCER

PANCREATIC CANCER Role of Radiation Therapy

ADJUVANT Local control: Large tumors ≥ 3 cms Lymph node involvement Affected surgical margins

UNRESECTABLE Local Relapse in RT-QT group

NEOADJUVANT Increase the rate of complete resections R0 (R1 prognostic factor of lower survival) Benefit in survival

PANCREATIC CANCER

• NEOADJUVANT/RADICAL • Standard Treatment: IMRT with concomitant Boost • Stereotactic Body Radiation Therapy (SBRT)

• ADJUVANT

PANCREATIC CANCER

• NCCN

• NEOADJUVANT/RADICAL

• STANDARD TREATMENT • 45 to 54 Gy in 1.8 Gy-2.0 Gy fractions. (Consider doses > 54 Gy, if clinically appropriate) • SBRT:

• 30 to 45 Gy in 3 fractions • 25 to 45 Gy in 5 fractions

• ADJUVANT • 45 to 46 Gy in 1.8-2.0 Gy fractions (tumor bed, adjacent lymph nodes, and surgical anastomoses).

IMRT and other conformal techniques in practice

PHYSICS PERSPECTIVE ON IMRT TREATMENTS

Daniel Zucca Aparicio Medical Physicist Hospital Universitario HM Sanchinarro

3DCRT and IMRT require of some kind of collimation to adapt the beam ’ s shape to the geometry of the target as seen from the beam ’ s eye view ( BEV ) RATIONALE OF IMRT

Nevertheless , while 3DCRT shows an uniform fluence pattern , on IMRT such fluence pattern is modulated in order to achieve some dose constraints under the beam delivery . RATIONALE OF IMRT

RATIONALE OF IMRT

4 fields box 3DCRT

7 fields 3DCRT

7 fields IMRT

IMRT allows improvements in PTV coverage or OAR sparing compared to 3DCRT

RATIONALE OF IMRT

The IMRT technique is a requirement for the treatment of targets with large irregular shapes that have concavities around OAR that 3DCRT can not achieve .

Mesothelioma 180 c G y x 30 fx

10 sIMRT Beams ONCOR @ 160 MLC 88 segments

RATIONALE OF IMRT

The IMRT technique is a requirement for the treatment of targets with large irregular shapes that have concavities around OAR that 3DCRT can not achieve .

Pleuro - pulmonay Blastoma 180 c G y x 28 fx

8 sIMRT Beams ONCOR @ 160 MLC 113 segments

RATIONALE OF IMRT

IMRT presents an intensity variation of the beam within the treatment field by dividing a large beam into many small beamlets . Dose constraints are assigned to both the PTV and OAR and inverse optimization is performed to find the individual weights of this large number of beamlets.

The computer adjusts the intensities of these beamlets according to the required planning dose objectives. The optimized intensity patterns are then decomposed into a series of deliverable MLC shapes ( segments ) in the sequencing step.

IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING IMRT requires the addition of these small fields ( segments ) delivered with irregular shapes and non - equilibrium conditions to treat target volumes using optimization routines. These segments are commonly off-axis and with overlapping penumbra over the treatment volume.

There is no clear consensus definition as to what constitutes a small field , but in practice, field sizes lower than or equal to 3 cm x 3 cm present dosimetry issues that require special attention (Das et al ., 2008) There are some questions that must be of concern for an appropriate dosimetry (dose measurement and beam modelling in treatment planning system) whose effect in narrow beams is more critical (Das et al ., 2008, IPEM 2010)

These dosimetric challenges are, • the lack of lateral charged particle equilibrium (CPE) • the partial occlusion of the primary source due to overlapping penumbra from opposing collimating borders. • variations of electron spectrum inducing changes in stopping power ratios. IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING

( Das et al ., Med Phys. 2008 )

The graph provides the information of penumbra ranges in water across a collimating edge for different beam energies, specified by their quality index TPR20/10, and serves to set the dimensions of when small field conditions apply based on overlapping electron distribution zones from different field edges . (Nyholm et al . 2006) IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING

( Das et al ., Med Phys. 2008 )

By collimating a beam from a source of finite width, it is clear that below a certain field size, only a part of the source area can be viewed from a detector’s point of view. The output will then be lower than compared to field sizes at which the entire source can be viewed from the detector’s field of view. IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING

complete view of the source • absorbed dose from primary radiation fully received • penumbra defined from source perimeter to collimating edges without overlapping

partial blocking of the source • absorbed dose reduction from primary radiation • penumbra overlapping from opposing collimating edges

( Aspradakis et al ., Med Dosim. 2005 )

Small fields require a careful beam modelling in the treatment planning system (TPS) in order to shape accurately the behaviour of the radiation beam in such circumstances. Wider values for the source dimensions will cause an overestimation of beam penumbra , while output factors calculated would be underestimated compared to those measured. IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING

( Aspradakis et al ., Med Dosim. 2005 )

IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING

The sources dimensions for the primary and scattered components , and also the electron contamination , are modelled as gaussian distribution with different widths .

IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING

comparison of calculated vs measured for a 12 mm x 12 mm dose profile for MLC edges

IMRT CONCERNS ON SMALL FIELD DOSIMETRY AND BEAM MODELLING comparison of calculated vs measured output factors for rectangular and square fields

IMRT REQUIREMENTS: MULTILEAF COLLIMATORS AND SEQUENCERS SIEMENS ONCOR EXPRESSION ( from September 2007 ) BrainLAB NOVALIS ( from February 2008 ) VERSA HD ( from January 2015 )

6 MV , 15 MV sIMRT

6 MV sIMRT , dIMRT VMAT ( constant dose rate )

6 MV , 10 MV , 15 MV 6 FFF MV , 10 FFF MV sIMRT , dIMRT , VMAT

160 MLC @ width 0 . 5 cm single focused rounded leaves

52 m MLC @ width 0 . 3 cm single focused rounded leaves

160 MLC @ width 0 . 5 cm single focused rounded leaves

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE Beamlet Based Optimization divides a large beam into many small beamlets of the leaf size which intensities are adjusted according to the required planning dose objectives and constraints . Once the optimal fluence map is decided upon there is a further leaf sequencing step. The optimized intensity patterns are decomposed into a series of deliverable MLC shapes made up of a number of basic beamlets with mathematically related intensities.

Beamlet Based Optimization ( 22 segments )

Direct Aperture Optimization ( 12 segments )

82 MLC @ 1 . 0 cm width

160 MLC @ 0 . 5 cm width

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE Direct Aperture Optimization ( DAO ) is another IMRT optimization engine where the apertures are selected based on a few initial iterations and then the dose distribution is calculated for all fields. A large number of candidate apertures are sampled and either accepted or rejected depending on whether the plan is improved by adding the new aperture. Beamlet Based Optimization ( 22 segments ) Direct Aperture Optimization ( 12 segments )

82 MLC @ 1 . 0 cm width

160 MLC @ 0 . 5 cm width

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

G000

G285

G075

G225

G135

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

In converting the fluence optimized plan from the computer generated solution to deliverable segments , the dose distribution will degrade from that originally decided.

RayStation 40 segments 5 sIMRT Beams @ 160 MLC

XiO 100 segments 5 sIMRT Beams @ 160 MLC

XiO 97 segments 5 sIMRT Beams @ 82 MLC

Direct Aperture Optimization Beamlet Based Optimization Beamlet Based Optimization

The degradation in quality of the beamlet based optimized plan is solely attributable to the sequencing step as the plan quality prior to sequencing of the beamlet based plan is equal or less than the DAO plan . IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

RayStation 40 segments 5 sIMRT Beams @ 160 MLC

XiO 100 segments 5 sIMRT Beams @ 160 MLC

XiO 97 segments 5 sIMRT Beams @ 82 MLC

Direct Aperture Optimization Beamlet Based Optimization Beamlet Based Optimization

DAO differs from beamlet based optimization in that it does not rely on the use of a segmentation routine ( sequencing step ) to select the initial leaf sequence as this step is incorporated into the original optimization. Therefore, with DAO the treatment plan is optimized using a deliverable treatment solution . IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

RayStation 40 segments 5 sIMRT Beams @ 160 MLC

XiO 100 segments 5 sIMRT Beams @ 160 MLC

XiO 97 segments 5 sIMRT Beams @ 82 MLC

Direct Aperture Optimization Beamlet Based Optimization Beamlet Based Optimization

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

This avoids the plan degradation which can occur during the conversion of the ideal intensity map into a deliverable one at the end of optimization.

RayStation 40 segments 5 sIMRT Beams @ 160 MLC

XiO 100 segments 5 sIMRT Beams @ 160 MLC

XiO 97 segments 5 sIMRT Beams @ 82 MLC

Direct Aperture Optimization Beamlet Based Optimization Beamlet Based Optimization

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

The main purpose of DAO is to reduce the number of segments and MU required to treat a complex arrangement of targets and surrounding structures.

RayStation 40 segments 5 sIMRT Beams @ 160 MLC

XiO 100 segments 5 sIMRT Beams @ 160 MLC

XiO 97 segments 5 sIMRT Beams @ 82 MLC

Direct Aperture Optimization Beamlet Based Optimization Beamlet Based Optimization

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

Reducing the number of segments in a beamlet based optimization plan could compromise the target coverage or increase the dose delivered over critical structures.

RayStation 40 segments 5 sIMRT Beams @ 160 MLC

XiO 100 segments 5 sIMRT Beams @ 160 MLC

XiO 97 segments 5 sIMRT Beams @ 82 MLC

Direct Aperture Optimization Beamlet Based Optimization Beamlet Based Optimization

IMRT INVERSE PLANNING OPTIMIZATION: THE IMPORTANCE OF THE OPTIMIZATION ENGINE

RS 160 MLC

XiO 160 MLC

XiO 82 MLC

IMRT DELIVERY TECHNIQUES

sIMRT : static IMRT beam ON when leaves are set @ each segment position less leakage radiation and transmission over critical structures (OAR) allows max dose rate delivery (treatment time reduction) step-dose gradients are easier to obtain (hotspots inside target are common) – – – –

dIMRT : dynamic IMRT

beam ON during all the sliding segment sequence leakage radiation increases due to continuous beam delivery dose rate is limited to allow max leaf speed fluence modulation is, in general, softer

IMRT DELIVERY TECHNIQUES

sIMRT : static IMRT

dIMRT : dynamic IMRT

IMRT and other conformal techniques in practice

Quality Assurance on IMRT at HM

Juan M Pérez Medical Physicist HM Hospitals Group

1

Q. Assurance or Q. Control? QA: is a way of preventing mistakes or defects in manufactured products and avoiding problems when delivering solutions or services to customers; which ISO 9000 defines as “part of quality management focused on providing confidence that quality requirements will be fulfilled”

2

Q. Assurance or Q. Control? QC: Process by which entities review the quality of all factors involved in production. ISO 9000 defines quality control as “A part of quality management focused on checking that a final product fulfills quality requirements”

3

Q. Assurance or Q. Control? Today's quality assurance systems emphasize catching (potential) defects before they get into the final product: a looking forward approach.

QC is the most basic level of quality. It started with activities whose purpose is to control the quality of products or services by finding problems and defects

4

IMRT treatments

“Final product”: treated patient

5

QA affects to all RT stages

Diagnosis

Imaging

6

QA affects to all RT stages

Simulation

Image registration and contouring

7

QA affects to all RT stages

• • •

PTV’s (Dose/fx) Tissue tolerances

Prescription

Constraints

Treatment Planning

8

QA affects to all RT stages

Evaluation

Plan approval, export and review

9

QA affects to all RT stages

Plan measurement in phantom

Patient setup before/during each fx

10

QA affects to all RT stages Most steps of all this QA process are not exclusive to IMRT treatments

Implementation of QA on technical factors involved in IMRT/VMAT treaments at HM Hospitals Group

11

QA of prescription Automatically generated prescription sheet attached to EMR-OIS

12

QA of prescription

Patient data Location

Fx scheme

Target volumes and doses

Dose limits

13

QA of prescription

Dose limits include two types of dose restrictions to OARs: • OARs tolerances (QUANTEC, TG-101, NRG-BR001, …) • Constraints/Objetives

• • •

Target volume, dose and number of fx

Location

“Dosimetric quality”

Treatment technique

Many times what is achievable is (much) lower than is tolerable (ALARA)

14

How far can I get with my TPS? QA of prescription / Planning

Know very well TPS (optimization tips,weak points, limitations, etc)

15

QA of prescription / Planning

10 fx of 3-4 Gy

Conventional 2Gy/fx

16

QA of prescription / Planning

Low/med risk prostate in 21 fx

Prostate with pelvic nodes at conventional fx

17

QA of plan evaluation Every prescription sheet has a corresponding evaluation template in TPS: easier and faster evaluation and no risk of missing OARs

18

QA of TPS calculation accuracy and plan delivery

Alternative dose calculation

Plan measurement

19

QA: secondary dose calculation • Single point dose calculation algorithms/software could be poor for many IMRT treatments (“ASHARA” criterion) • True independence of calculation: minimal user interference in calculation parameters (beam data/modeling)

20

QA: secondary dose calculation

• Full 3D Collapsed Cone calculation • Using planning CT, RT Structures, RT Plan and RT Dose, exported from TPS to a server • Based on gold standar machine beam models • No errors coming from low quality beam model/measurement

21

QA: secondary dose calculation Only one input data: linac calibration cGy/MU

22

QA: secondary dose calculation No beam customization using own data (PDDs, Ofs, etc)

23

QA: secondary dose calculation Full 3D analysis of TPS vs Alternative calculation

24

QA: secondary dose calculation Full 3D analysis of TPS vs Alternative calculation

25

QA: secondary dose calculation

26

QA: secondary dose calculation Full 3D analysis of TPS vs Alternative calculation

27

QA: plan measurement • Phantom+dosimeter are irradiated with clinical plan • More than one measurement system (detector limitations, dosimeter recalibration, etc)

28

QA: plan measurement

• 2D Array 729

o Oncor: SIMRT (white polystirene) o Novalis: DIMRT and DCA (Octavius phantom)

• Pretreatment EPID dosimetry: Oncor SIMRT • Octavius4D + 2D Array 1500: Versa HD VMAT • Gafchromic EBT3: all cases (small fields)

29

• Only one measurement per plan • All detectors are cross calibrated to Dw • Cross calibration is checked before every plan measurement: 10x10 cm2 before plan irradiation • Usually, no single point measurement using IC QA: plan measurement

30

Oncor (SIMRT): 2D Array 729 @ 95-5 (SSD-depth) setup, gantry 0º QA: plan measurement

31

Oncor (SIMRT): 2D Array 729 @ 95-5 (SSD-depth) setup, gantry 0º γ 2%-2mm QA: plan measurement

32

Novalis (DIMRT, DCA and VMAT): Octavius + 2D Array 729 QA: plan measurement

33

QA: plan measurement

Novalis (DIMRT, DCA and VMAT): Octavius + 2D Array 729

In static gantry treatments, nominal gantry angles are used with two avoided sections: 90º/270º ± 20º

34

QA: plan measurement

Novalis (DIMRT, DCA and VMAT): Octavius + 2D Array 729

γ 2%-2mm

35

QA: plan measurement

Pretreatment EPID dosimetry: Oncor SIMRT

In house calibration software, compatible with PTW software

• cF : EPID conversion factor signal/cGy • G(trad) : ghos9ng correc9on • Graw(x,y) : EPID raw image • BP(x,y) : uniformity correc9on • kG : radia9on sca>er kernel inside EPID. • kD : radia9on sca>er kernel in water

36

QA: plan measurement

Pretreatment EPID dosimetry: Oncor SIMRT

γ 2%-2mm

37

Research: 3D dose calculation in patient’s anatomy using pretreatment EPID dosimetry (Oncor SIMRT) QA: plan measurement

38

Research: 3D dose calculation in patient’s anatomy using pretreatment EPID dosimetry (Oncor SIMRT) QA: plan measurement

39

Research: 3D dose calculation in patient’s anatomy using pretreatment EPID dosimetry (Oncor SIMRT) QA: plan measurement

RTPlan, RTStructures and RTDose from TPS

List of EPID images for selected patient

TPS vs measurement DVH for Volume of Interest (PTV or OAR)

Evaluation of mean, max and %coverage for a isodose level for selected Volume of Interest

40

Gafchromic EBT3: small field sizes and/or high dose gradients in small regions QA: plan measurement

41

QA: plan measurement

Octavius4D + 2D Array 1500: Versa HD VMAT

Time resolved measurement: Multiple frames 1 frame – 1 gantry position (inclinometer) Detector (ic) always perpendicular to beam axis

• • •

42

QA: plan measurement

Octavius4D + 2D Array 1500: Versa HD VMAT

3D measurement:

•

Every dose frame is projected, acording to inclinometer reading Projection using user measured PDD’s @ 85 cm SSD Sum of all frames projected

•

•

43

QA: plan measurement

Octavius4D + 2D Array 1500: Versa HD VMAT

3D measurement

3D evaluation

γ 2%-2mm and 3%-3mm

Axial, coronal and sagital planes

Sorted and/or arranged by dose levels

44

Octavius4D + 2D Array 1500: Versa HD VMAT QA: plan measurement

45

Octavius4D + 2D Array 1500: Versa HD VMAT QA: plan measurement

46

Octavius4D + 2D Array 1500: Versa HD VMAT QA: plan measurement

47

Octavius4D + 2D Array 1500: Versa HD VMAT QA: plan measurement

48

Octavius4D + 2D Array 1500: Versa HD VMAT • Greater uncertainty than in “classical” 2D verification using 2D Array Seven29 • Additional step (projection of measurement dose plane) • PDDs (unc. in depth dose distribution meas.) • Inclinometer (accuracy and sync. with array meas.) • Angular discretization of TPS calculation Know very well your LINAC, TPS and Measurement Devices (weak points, limitations, etc) QA: plan measurement

49

Thank you for your attention. Enjoy Madrid and visit its Temples and Museums

50

IMRT - a physician‘s view (As if physician‘s, physicists and RTs should have different views of the world…..)

One's own experience has the advantage of absolute certainty - Schopenhauer

No man's knowledge (here) can go beyond his own experience - Locke

Stupid is as stupid does - Gump

Some VERY SUBJECTIVE COMMENTARIES!!

Disclosure

Research and Training Agreement, Expert Testimony and Travel Grants with Elekta/IBA/C-Rad Board Member of C-Rad Stock holdings Imuc

Drivers of IMRT

Thing‘s weren‘t perfect prior to IMRT Need to avoid Toxicity Conveniece / Economical Factors / Simplification of established paradigms Evolution of Technology / IGRT / Online Adaptation Chronification of Disease/Oligometastases Expanding Indications for SBRT (e.g. Prostate with the need for dose shaping) Potentially a new Paradigm in Combination with Immunotherapy

Technical Basis

Radiotherapy Treatment Planning

3-D

Simulator

2-D

Treatment Delivery

IMRT

Conventiona l

Conformal

Inverse Planning

Inverse Planning (IP) User enters port/arc layout, and treatment objectives, computer optimizes beam modulation

www.nomos.com

Requirements

1. 2. 3. 4. 5.

IMRT-Capable Delivery System Inverse Planning System Record & Verify / Console Module

QA Protocols

Training / On-Site

Consultations

www.nomos.com

Prescription

The Key to Inverse Planning is a prescription tool that easily and efficiently captures the physician’s most critical clinical judgements

Clinically relevant tissue types provide quantum leap in optimization quality

Numerical and/or graphical entry of dose/volume goals

www.nomos.com

On-screen optimization guidance

Everything works fine up to here

But: How much time you spend everyday planning? How many of you are using autoplanning?

Optimization

A “cost function” trades off different portions of the CDVH curves in order to arrive at a composite “ Optimal Result ”

www.nomos.com

Optimization Strategies

Gradient vs. Stochastic

www.nomos.com

IMRT-Capable Delivery System

Basic treatment techniques

K. Bratengeier In: Kiricuta, Definition of Target Volumes, 2001

2 “Slices” Treated per Rotation

www.nomos.com

Couch Indexing

Ok, everything is almost perfect up to this point

But: How much time you spend everyday contouring? How many of you are using autocontouring?

Clinical Application of IMRT