Antolín San Martín, E.

Bertomeu Padín, M.

Fayos Ferrer, F.

Palazón Cano, I.

Simón de Blas, R.

Elsevier - Publisher Connector 

Rapid Arc vs IMRT of prostate plans: A dosimetric comparison 

S382 reports of practical oncology and radiotherapy 1 8 ( 2 0 1 3 ) S378–S385
Patient-speciﬁc treatment veriﬁcation in lung stereotactic body radiotherapy (SBRT)
A. Ribalta Poyatos, A. Lloret Gudin˜a, M. Ciudad Rivas
Clínica Puerta de Hierro, Radiofísica y Protección Radiológica, Spain
Introduction. Helical Tomotherapy (HT) is a modality for delivering intensity modulated radiation therapy (IMRT) treatments
using a rotating linear accelerator mounted on a continuously moving slip ring gantry in synchrony with the couch motion.
HT allows performing stereotactic radiotherapy treatments without ﬁducial markers due to its 3D imaged guided system. Lung
SRBT treatments has been selected as a routine treatment in our facility. Effects of respiratory motion are reduced using an
abdominal compression paddle to restrict tumormotion and normal tissue irradiation.Moreover, HT achieves very homogeneous
dose distributions, leading to local tumor control and survival results comparable to surgery. These IMRT treatments require
patient-speciﬁc veriﬁcation previous to the irradiation, as routine in other IMRT modalities.
Purpose. The aim of this work is to describe the quality assurance (QA) protocol for the veriﬁcation of lung SBRT treatments
performed on HT.
Materials and methods. Prescription doses to PTV were between 45 and 60Gy on 3 fractions. Treatment plans were recalculated
using a solid water cylindrical phantom (Tomophantom) that allows simultaneous measurements with Exradin A1SL cylindrical
ionization chamber (i.c.) in 29 different positions as well as radiochromic EBT2 ﬁlm irradiation, usually located in a coronal plane.
Dose measurements were compared to values from the HT treatment planning system (TPS). Film analysis was performed with
OmniProm I’mRT software and gamma pass rate was evaluated.
Results. Dose differences between TPS calculations and i.c. measurements were mostly within +3%, with −0.7% mean value,
ranged from −3% to 2%. Gamma analysis evaluation showed an agreement superior to 97% (95-100) for 3%,3mm criterium.
Conclusions. The QA protocol proved to be an effective method for veriﬁcation of lung SBRT treatments. Results showed good
agreement between calculated dose from TPS and measurements with i.c. and ﬁlm.
http://dx.doi.org/10.1016/j.rpor.2013.03.625
Positioning protocol image guided for radiotheraphy
J. Gómez Fervienza1, A. Corral García1, R. Márquez Parro1, M. Mancha Pescador1, N. Ferdandez de Romarategui1,
N. Martín Jorge1, V. Vázquez Camello1, N. Cantarero Valenzuela1, M. Alvarez Sánchez1, S. Carnicero Montoro1,
N. Gavela Robles1, A. Santiago Novillo1, A. Rodriguez Perez1, A. López Fernandez2, C. Rodríguez Rodríguez2,
R. Bermudez Luna2, G. Martín Martín2
1 Hospital de Fuenlabrada, Oncología Radioterápica, Spain
2 Hospital de Fuenlabrada, Radiofísica Hospitalaria y Protección Radiológica, Spain
Objective. To show the procedure we apply for our radiotheraphy treatments.
Material and methods. Linear accelerator ARTISTE SIEMENS. We check during the ﬁrst three days the patient position relative to
the treatment beams. We have determined by means of portal image or cone bean. We collect the movement X, Y, Z and the
absolute vertical position of the couch in a database. We calculate on the fourth day the average of the three days and modify the
initial SETUP. If with this corrected SETUP on the fourth day, no correction is necessary, we apply it for the rest of the treatment
and do weekly checks. If on the fourth day, a correction is required, we repeat on the ﬁfth and sixth day and on the seventh day
we calculate the average and apply. If the application of the average does not need any correction we apply this average for the
rest of the treatment. We have a weekly control check. If the average needs correction, we consider the patient unstable, and we
will do portal image or cone bean, daily.
Results. 1. ORTHOGONAL PORTAL IMAGE, 3 initials + week: Breast, palliative: – 10 sessions 2. CONE BEAN 3 initials + week: Lung,
otolaryngologist, Rectum, Cerebral, Lymph, Stomach, Pancreas, Esophagus 3. ORTHOGONAL PORTAL IMAGE + 1 week: Cranial
irradiation 4. DAILY PORTAL IMAGE: Palliative care: 5 sessions 5. DAILY CONE BEAN: Prostate.
Conclusions. We collect in a database the necessary information that we use for a good daily positioning, minimizing an error
that we could apply to the positioning of a patient every day.
http://dx.doi.org/10.1016/j.rpor.2013.03.626
Rapid Arc vs IMRT of prostate plans: A dosimetric comparison
I. Palazón Cano, M. Bertomeu Padín, F. Fayos Ferrer, R. Simón de Blas, E. Antolín San Martín
Hospital Ruber Internacional, Física Médica, Spain
Introduction. The arrival of Rapid Arc (RA) technique has gradually replaced IMRT treatments at our unit.
Objectives. To evaluate the dosimetric outcomes of prostate treatment plans and the possibility of reduction of peripheral dose
and treatment delivery time.
Material. Ten cases are planned to target a prescription dose of 78Gy of mean dose in PTV and D95>95%, in 2Gy/fraction, for
a 5 ﬁeld IMRT (G265◦, G312◦, G0◦, G47◦ and G95◦) and two full Rapid arcs, delivered with Varian Clinac iX, for a beam energy
of 6MV and a maximum dose rate of 600MU/min. The CBCT performance allows the acquisition of KV images for positioning
and evaluation of changes in bladder and rectum size. Treatment planning system used is Varian Eclipse 8.9.17 with inverse
reports of practical oncology and radiotherapy 1 8 ( 2 0 1 3 ) S378–S385 S383
optimization algorithm PRO-II and AAA absorbed dose calculation algorithm. Dosimetric veriﬁcation is mostly performed with
ArcCheck (Sun Nuclear Corp.), a cylindrical detector array.
Methods. Several parameters are analysed in the obtained data set: totalMU, treatment time andusual OAR limits values (Quantec)
are compared in key risk organs: rectum, bladder and femoral heads.
Results and conclusions. Neither the treatment time nor the values obtained for bladder and rectum (V50, V60, V65, V70, V80 and
mean dose) show statistically signiﬁcant differences. Nevertheless, we do ﬁnd them in D1cm3 femoral heads: 27±3.9Gy for RA
vs. IMRT 36.8±4.02Gy, D50% body: 520±155 cm3 for RA y 924±311 cm3 in IMRT and total MU: RA 553±30 vs. IMRT 824±70. RA
plans get better sparing dose values to D1 cm3 femoral heads and an assessable peripheral dose and total MU reduction.
http://dx.doi.org/10.1016/j.rpor.2013.03.627
Total body irradiation (TBI) 3-D treatment planning
A. Lloret Gudin˜a, M. Ciudad Rivas, C. Padilla Vaz
Clínica Puerta de Hierro, Radiofísica y Proteccion Radiologica, Spain
Introduction. TBI is often used in conditioning regimens prior to bone marrow transplantation.
Aim. We describe a 15 MV photon beam irradiation technique with customized lungs shields.
Methods. A total dose of 10Gy in 5 fractions on 3 consecutive days, with a gap of at least 6h between fractions, will be delivered to
the patient. The prescribed dose to the lungs is reduced to 8Gy. The patient undergoes one torax CT scan (3mm slice thickness) to
determine the lung shields andawhole bodyCTscan (1 cmslice thickness),whichwill beused to calculate thedosedistribution. In
our institution it has been established a two parallel opposed beams (AP/PA) treatment technique at extended SSD distance (4m),
applied in different fractions (the patient lying on his side and switching position). Treatment ﬁelds are centered at the height of
the pelvis. The reference point for dose speciﬁcation is deﬁned at mid-pelvis. Lungs are shielded during the PA irradiation. 3-D
treatment planning is performed using XiO Treatment Planning System (ELEKTA). A TBI-speciﬁc 15MV photon beam machine
has been commissioned for this purpose. The dose calculation algorithm is superposition. During the treatment delivery, in-
vivo dosimetry (OmniPro-InViDos) is performed to obtain an online dose veriﬁcation. Six or more detectors are attached to the
patient’s body surface at dose-relevant points (head, lungs and pelvis). Mid-point doses are computed based on the entrance and
exit doses.
Results. There is a good agreement between the planned dose and the mid-point doses obtained from the in-vivo measurements.
Conclusions. 3-D-TBI-planning guarantees a sufﬁciently homogeneous dose in the target volume under optimal sparing of the
lungs. A whole body dose distribution can be obtained, which allows more precise dose adjustments during the planning process.
http://dx.doi.org/10.1016/j.rpor.2013.03.628
Variation and reproducibility of SUV for use in radiotherapy contouring with PET/CT
C. Solera Moscardó1, B. Bordería Navarro1, J. Pamos Navas1, A. Vicedo González1, T. García Hernández1,
R. Sánchez Jurado2, J. Ferrer Rebolleda2, J. Roselló Ferrando1
1 Hospital General Universitario, Servicio de Radiofísica, Spain
2 Hospital General Universitario, Servicio de Medicina Nuclear, Spain
Objectives. The Standardized Uptake Value (SUV) is a useful tool to aid in the contouring in radiotherapy. Usually a SUV value of
2.5 or the 40% of the maximum value of SUV is used as background to contouring the lesion in the PET images. The SUV value
depends on various physical and biological effects. The aim of this work is to test the reproducibility of the different modes of SUV
calculation, its dependence with noise, reconstruction algorithm and concentration, to determine the most optimal parameter.
Materials and methods. We use a NEMA chest phantom with F-18 containing 6 spheres of volumes between 0.5 and 26.5ml, with
an initial background concentration of 0.5uCi/ml. The lesion-to-background ratio was 1/10. Acquisitions were taken on a PET-CT
Philips Gemini TF every two hours to see the change in SUV with noise and concentration. Studies were reconstructed using
different algorithms and different bed times.
Results. SUVmax and SUVpeak depend on noise and reconstruction algorithm, with differences up to 20%. The SUVmean depends
on selected volume with a variation of up to 15%. The SUVmedian shows less dependence on the selected volume, varying less
than 1.5%. Also its dependence on noise and reconstruction algorithm is much lower than that of SUVmax. Variations of up to
30% in SUVmax are present due to dead time effects in higher dose concentrations.
Conclusions. Is important to choose the most stable and reproducible SUV calculation in order to minimize the effects of its
possible variations. According to this study, the value that best meets these requirements is the SUVmedian.
http://dx.doi.org/10.1016/j.rpor.2013.03.629


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Rapid Arc vs IMRT of prostate plans: A dosimetric comparison

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