Angelo F. Monti Ospedale “S. Anna” – Como e-mail: amonf@iole-mail: [email protected] Rapporto...

I Sessione: IMRT nella pratica quotidiana

I documenti di riferimento:ISTISAN – ICRU 83

Angelo F. MontiOspedale “S. Anna” – Comoe-mail: [email protected]

Rapporto ISTISAN 08/12 (2008)“Indicazioni per l’assicurazione di qualità nella radioterapia ad intensitàmodulata”

Rapporto ISTISAN 05/14 (2005)“Strumenti di lavoro in radioterapia con fasci ad intensità modulata”

Rapporto ISTISAN 08/12

• Sono considerate tutte le modalità di erogazione dell’IMRT


•Criteri per l’uso dell’IMRT

•Vantaggi e svantaggi clinico-dosimetrici•Indicazioni clinico-tecniche all’uso dell’IMRT

(cervico-facciale, prostata, mammella, paraspinali)

•Aspetti fisici

•Commissioning e AQ di “LINAC” e TPS


•Aspetti fisici


•Aspetti fisici

•Assicurazione di qualità dei pazienti

γ


•Aspetti fisici

•Test dosimetrici•Indice γ mancanza di uniformità

•Accettabili valori del 3÷5% per l’accordo in dose e 2÷3 mm per la “distance to agreement” (DTA)

•Nessuna indicazione sulla percentuale di punti soddisfacenti la condizione γ ≤ 1


•Aspetti fisici

•Indicazioni e suggerimenti sulla scelta dei dosimetri per IMRT

•Analisi del processo IMRT

•Posizionamento e immobilizzazione (IGRT)•Immagini: (passo 3÷7 mm, mezzo di contrasto, multimodalità)•Contornamento (ICRU)


•Aspetti fisici



•Posizionamento e immobilizzazione (IGRT)•Immagini: (passo 3÷7 mm, mezzo di contrasto, multimodalità)•Contornamento (ICRU)•Prescrizione della dose (ICRU: 50, 62)


•Aspetti fisici



•Posizionamento e immobilizzazione (IGRT)•Immagini: (passo 3÷7 mm, mezzo di contrasto, multimodalità)•Contornamento (ICRU)•Prescrizione della dose (ICRU: 50, 62)•Criteri di ottimizzazione fisici (dose, dose/volume)


•Aspetti fisici



•Posizionamento e immobilizzazione (IGRT)•Immagini: (passo 3÷7 mm, mezzo di contrasto, multimodalità)•Contornamento (ICRU)•Prescrizione della dose (ICRU: 50, 62)•Criteri di ottimizzazione fisici (dose, dose/volume)•Criteri di ottimizzazione biologici (g Effective Uniform Dose)


•Criteri di accettabilità del piano e “reporting” della dose (ICRU)


•…Criteri di accettabilità del piano e “reporting” della dose (ICRU)


•Risorse

1993 1999 2004

INTERNATIONAL COMMISSION ONRADIATION UNITS ANDMEASUREMENTS

Prescribing, Recording, and Reporting Electron Beam Therapy (Report 71)Journal of the ICRU Vol. 4 No. 1

… The Report extends the concepts and recommendations for photons contained in ICRU Reports 50 and 62 to electron beam therapy. Reflecting the similarities between electron and photon treatments, the section on volumes in the present Report is very similar to the section on volumes in Reports 50 and 62, but evolutionary clarifications applicable to both modalities are presented. The concepts of Gross Tumor Volume (GTV), Clinical Target Volume (CTV), Planning Target Volume (PTV), Organs at Risk (OARs) and Planning Organ at Risk Volume (PRV) are recalled, or refined, and new examples are given to illustrate these concepts …

ICRU volumes

291978 Target Volume

501993 GTV CTV PTV Organ at risk

621999 GTV CTV ITV PTV OR PRV

ICRU volumes

29 Target Volume

50 GTV CTV PTV Organ at risk


T N MGTV-T CTV-T ITV-T PTV-T

712004 GTV-N CTV-N ITV -N PTV-N OAR PRV

GTV-M CTV-M ITV -M PTV-M

-T-T-T-T

Cosa cambia ?

•Revisione nella classificazione dei volumi di trattamento

•Prescrizione della dose mediante DVH

•Nuove definizioni di dose “minima” e “massima”

•Nuovo concetto di “punto” ICRU

•Richiesta di QC “paziente – specifici”

•Ridefinizione di “Accuratezza del trattamento”

Cosa cambia ?

•Revisione nella classificazione dei volumi di trattamento,

Cosa cambia ?

•Revisione nella classificazione dei volumi di trattamento:definizionizioni ICRU 71 valide, ma si deve indicare:

• procedura di definizione del volume (visita, CT, MR, PET, US …)

• momento temporale della definizione (rispetto at0 = 0 Gy)

• GTV-X (p,t) ; CTV-X (p,t) ; PTV-X (p,t)

ICRU 83 volumes


GTV-T CTV-T ITV-T PTV-T71 GTV-N CTV-N ITV -N PTV-N OAR PRV


GTV-T (clin, 0 Gy) : tumor GTV evaluated clinically before the start of the radiotherapy

832010GTV-T (MRI-T2, 30 Gy): tumor GTV evaluated with a

T2-weighted MRI scan after an absorbed dose of 30 Gy ofexternal beam irradiation.

ICRU 83 volumes

GTV-T CTV-T ITV-T PTV-T71 GTV-N CTV-N ITV -N PTV-N OAR PRV


GTV-T (clin, 0 Gy) : tumor GTV evaluated clinically before the832010 start of the radiotherapy

GTV-T (MRI-T2, 30 Gy): tumor GTV evaluated with a T2-weighted MRI scan after an absorbed dose of 30 Gyof external beam irradiation.

But: “…The use of terminology such as “biological target volume”, “proliferative target volume”, and “hypoxic target volume” is not recommended and is not discussed in this Report…”

ICRU 83 volumesOAR PRV

• For so-called “parallel-like organs,” the whole organ should be entirely delineated.

• For so-called “serial like organs,” those parts of the organ that could receive a high dose should be delineated in a consistent way.

• Especially for a serial-like organ, a planning organ at riskvolume (PRV) should be delineated around the OAR.

ICRU 83 volumesRemaining Volume at Risk

RVR

• Tissues not included in the CTV/PTV or not delineated as dose limiting OARs, should still be specifically delineated and named the Remaining Volume at Risk (RVR).

• Dose–volume constraints applied to the RVR avoid unsuspected regions of high dose.

ICRU 83 volumesRVR

ICRU 83 volumes

Dose-reporting recommendations are adapted to IMRT

•From “single-point” to “volume-based” absorbed-dose specification (DVH)

•Minimum and maximum absorbed doses not recommended for reporting (GTV, CTV, PTV):

•Replaced by “Near-Minimum” (D98 %),and “Near-Maximum” (D2 %)

•The ICRU reference point is not recommended:

•The Median Absorbed Dose, D50 %, should be reported(Mean dose is permitted)


• OAR absorbed-dose specification: Dm, VD, D2%(and Dmax = D0%)

•…these criteria do not replace visual inspection of the calculated dose distribution to determine if there is significantly higher or lower dose to a small fraction of the volume irradiated


•Appropriate patient-specific QA is necessary to ensure that the patient receives the prescribed dose:

•(1) verification that the intensity-modulated field boundary matches the planning boundary, which is commonly done for 3D-CRT;•(2) through an independent calculation, verification that the machine instructions driving the leaves produce the planned absorbed-dose distribution;•(3) comparison of the absorbed-dose distribution in a phantom with that calculated by the treatment planning computer for the same irradiation condition;•(4) comparison of the planned leaf motions with that recorded on the MLC log files;•(5) confirmation of the initial and final positions of the MLC for each field by a record-and-verify system;•(6) in vivo absorbed-dose measurements.


•The old ICRU recommendation of 5 % absorbed-dose accuracy is now replaced:

•In low-gradient situations, (∆D < 20 %/cm in any direction): 85 % of target-volume absorbed-dose samples within 5 %.

•In high-gradient situations, (∆D ≥ 20 %/cm in any direction): 85 % of absorbed dose samples within 5 mm of the intended position (DTA).

•A new definition for Homogeneity Index (HI) is suggested:

B.1 Squamous-Cell Carcinoma of the Supra-Glottic Larynx

B.2 Squamous-Cell Carcinoma of the Lung

B.3 Adenocarcinoma of the Prostate

F i n e

Angelo F. Monti Ospedale “S. Anna” – Como e-mail: amonf@iole-mail: [email protected] Rapporto...

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