RapidArc in Bergen Britt Nygaard, Harald Valen and Ellen Wasbø Haukeland University Hospital, Bergen, Norway.

RapidArc in Bergen

Britt Nygaard, Harald Valen and Ellen Wasbø

Haukeland University Hospital, Bergen, Norway

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• 2007: – Trilogy with RapidArc option

• 2008: – Scandidos Delta4 QA tool– Aria upgrade: RapidArc on the Trilogy and 23iX

• Autumn 2009: – Course in Bellinzona and Zug– Stay-and-learn in Copenhagen– Eclipse AAA configuration– Machine QA and patient QA procedures

• 2010:– Decisions, decisions.. Which category of patients?– Learning RapidArc doseplanning in Eclipse– 1st patient on 14th of June – 2nd on 22nd of November

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Quality control

• Commisioning tests as suggested by Memorial Sloan-Kettering CC and Varian– A picket fence test during RapidArc– 7 adjacent fields with varying Dose rate & Gantry

speed– 4 adjacent fields with varying MLC speed & Gantry

speed

– Possible to study combined effect of • dose rate and gantry speed• dynamic MLC and variable dose rate

C. C. Ling et. al: Commissioning and Quality Assurance of RapidArc Delivery System. Radiotherapy, Int. J. Radiation Oncology Biol. Phys., Vol. 72, No. 2, pp. 575–581, 2008.

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MLC speed variation during RapidArc

Dose rate and Gantry speed variation during RapidArc

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Analyse results

• MLC speed variation (”Test3”)

• Dose rate and Gantry speed variation (”Test2”)

Clinac 23EX (2004): T2 & T3

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Trilogy (2007): T2 & T3

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Clinac 23iX (2005): T2 & T3

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TrueBeam (2011): T2 & T3

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Analyse results• Dynalog files

– Log planned and actual leaf positions and leaf speed vs. time

– Log gantry speed vs. Time– How TrueBeam

• Tool: ”Analyse Dynalog”– In-house developed (EW)– Language: IDL

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Patient QA

• Delta4– Daily dose correction– Run and measure Verification plan– Pass / Fail criteria

• Dose deviation– > 85% within ±3% deviation

• Distance to agreement– > 98% with DTA ≤ 3mm

• Gamma index 3%, 3mm– > 95% with index ≤ 1

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1 arc, 135° to 225°, TrueBeam 6MV photons

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Clinac 23EX (2004), RapidArc in 2011: Failed T2 & T3 commissioning tests

Patient QA Dose dev. within ±3%

DTA < 3mm γ < 1 (3%, 3mm)

PAB 90,7% 100% 100%

GB 83,7% 100% 100%

TER 95,8% 100% 99,4%

GDG 85,5% 100% 100%

EKGP 85,9% 100% 100%

MS 83,0% 100% 100%

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More patient QA

• Independent dose calculation

• Point check of dose• Control of monitor units

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Treatment planning, Autumn 2010:

• 5 years experience with IMRT– head and neck– prostate with and without lymph nodes (LN)– ani (and gyn) with LN – Sarcoma, lymphoma and other

• RA configuration and acceptance tests OK • RA installed on 2 Clinacs • Patient start up

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Which patient groups?

• Increased efficiency for the department – Prostate with LN, 7 splitted fields

• Patients unable to keep the supine position for 10-15 min– Head and neck

• Less MU and less risk for secondary cancer• A category that is easy to create acceptable and

standardized plans for– Prostate intermediate risk

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Which patient groups?

• Increased efficiency for the department – Prostate with LN, 7 splitted fields

• Patients unable to keep the supine position for 10-15 min– Head and neck

• Less MU and less risk for secondary cancer• A category that is easy to create acceptable and

standardized plans for– Prostate intermediate risk

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Prostate intermediate risk, criteria:• Treatment of prostate and seminal vesicles

• Equal plan or better than IMRT (PTV and rectum)

• We made two plans, one IMRT (backup) and one RA, 1 arc 135-225° (avoid couch slides) for the 10 first patients

• PTV 95%-107%, median 100%,

• Rectum: max 10ml >60 Gy and less than 50 Gy to half the circumference

• Delta4 measurements OK; • Gamma index 3%, 3mm

– > 95% with index ≤ 1

• Dose deviation– > 85% within ±3% deviation

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5 fields IMRT: 574 MU (2.15 Gy x 35) RA: 1 arc 135-225° 494 MU (2.15 Gy x 35)

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5 fields IMRT: 574 MU (2.15 Gy x 35 = 75.25) RA: 1 arc 135-225° 494 MU (2.15 Gy x 35)

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5 fields IMRT: RA: 1 arc 135-225°

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IMRT

RA

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RA today: (2.4 Gy sem.ves. and integrated boost 2.7 Gy prostate) x 25 = 67.5 Gy (EQD2= 81 Gy if α/β=1.5)

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Gamma: 2mm 2%

Measured with Delta4

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7 field-IMRT

1499 MU (2.7 Gy)

555 MU/Gy

(calibration factor 130MU/Gy)

2 full arc RA

611 MU (2.7 Gy)

Prostate high risk: 2 Gy to the lymph nodes, integrated boost; 2.4 Gy sem.ves. and 2.7 Gy prost, 25 fractions

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IMRT RA

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IMRT RA

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Dose to rectum

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IMRT

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Future:

• We would like to treat our high risk protate with LN with two arcs– Prerequisite: RA plan equal or better than IMRT (PTV and

rectum)

• This autumn we have been focusing on commissioning TrueBeam..