International Journal of Radiation Oncology � Biology � PhysicsS932

3828Direction Modulated Brachytherapy (DMBT) for Cervical CancerD. Han,1 M.J. Webster,1 D.J. Scanderbeg,1 C. Yashar,1 D. Choi,2 B. Song,2

S. Devic,3 A. Ravi,4 and W.Y. Song1; 1University of California, San Diego,

San Diego, CA, 2University of California, San Diego, CA, 3McGill

University, Montreal, QC, Canada, 4Sunnybrook Odette Cancer Centre,

Toronto, ON, Canada

Purpose/Objective(s): A new intra-uterine tandem design is proposed for

creating non-isotropic 192-Ir dose distribution and give unprecedented

dose conformality for treatment of cervical cancer.

Materials/Methods: A DMBT design was made of non-magnetic high

density tungsten alloy (18.0g/cc) cylinder with 6 peripheral grooves

running along the length for an 192-Ir HDR afterloader source to travel

along. The groove has 1.3mm in diameter and evenly distributed on the

tungsten alloy, which has a diameter of 5.4mm. The tungsten alloy is

enclosed in a total diameter of 6.4mm polyoxymethylene tube (1.41 g/

cc). For calculating dose distribution, 51 million decay events are

simulated on Monte Carlo simulation and resulting non-isotropic dose

distributions. 75 plans (5 fraction [fx] of 15 patient cases), clinically

treated with conventional tandem & ovoids (T&O) applicator, were re-

planned on an in-house development HDR brachytherapy planning

platform, which is intensity modulated planning capability using Simu-

lated Annealing and Constrained-Gradient Optimization algorithms. All

DMBT plan results were compared against the T&O clinically treated

plans, which were normalized to match the HRCTV V100 coverage.

Also all the plans were optimized with the same ovoids in place as the

conventional T&O plans.

Results: Generally, the plan qualities were markedly better using DMBT.

Among the 75 plans, an average bladder, rectum, and sigmoid dose (D2cc)

reduction were 0.59�0.87 Gy (8.5�28.7%), 0.48�0.55 Gy (21.1�27.2%),

0.10�0.38 Gy (40.6�214.9%) among the 75 plans, respectively. The

bladder dose, 3.20Gy (40.8%), was the best single plan reduction, due to

the horseshoe-like bladder around the CTV. The best sigmoid dose

reduction was 1.26Gy (27.5%) for endophytic growth type cervical cancer.

Overall, the most dose reduction was caused by the dose flexibility of

DMBT. The HRCTV D90 was similar with 6.55�0.96 Gy for T&O and

6.59�1.06 for DMBT.

Conclusions: The new tandem designs that advance the conformality of

image-guided cervix HDR were created in congruence with the current

trend of 3D image based planning to maximize the therapeutic ratio.

Author Disclosure: D. Han: None. M.J. Webster: None. D.J. Scander-

beg: None. C. Yashar: None. D. Choi: None. B. Song: None. S. Devic:

None. A. Ravi: None. W.Y. Song: None.

3829A Novel Proton Pencil Beam Scanning Technique forPostmastectomy Chest Wall IrradiationN. Depauw,1,2 E. Batin,1 J. Daartz,1 S. MacDonald,1 H. Kooy,1 and H. Lu1;1Massachusetts General Hospital, Boston, MA, 2University of Wollongong,

Wollongong, Australia

Purpose/Objective(s): Post-mastectomy radiation therapy treatment

(PMRT) is conventionally performed using a composition of photon and

electron fields. Including the internal mammary nodes is always a chal-

lenge in such treatment for patients with unfavorable cardiac anatomy and/

or breast implants. Furthermore, multi-field matching results in hot and

cold spots, as well as extended treatment time. We have developed a

PMRT technique using a single proton pencil beam scanning (PBS) field

that includes the whole chest wall and all nodal regions with complete

target coverage and reduced dose to cardiac and lung tissues.

Materials/Methods: The patients undergo a CT scan on an angled

breast board, as for regular photon/electron treatment, but with the

addition of a chin strap and hand grips to provide additional immobi-

lization and reproducibility. An in-house software, with multi-criteria

optimization (MCO) capability, is used for PBS treatment planning. A

single isocentric field, angled at 30 degrees from vertical, is used to

cover the whole chest wall and the potentially involved lymph nodes

(axillary, supraclavicular, internal mammary), all of which volumes are

combined into a single scanning target volume (STV) for the spot map

optimization. An 8 cm thick range shifter, made of Lucite, is used to

reduce the proton beam energy in order to appropriately cover the

superficial portion of the target volumes. The PBS field usually contains

less than 15 layers equally spaced about 5 mm, with a total number of

spots in the range of 1500 to 2000. For patients with breast implants,

the stopping power ratio of the implant materials was separately

measured, and the remaining range uncertainty is limited to that from

the chest wall only. Surface imaging, along with daily radiography, is

used for patient positioning in order to improve setup accuracy for the

largely superficial target volume and to monitor anatomical changes

during the course of treatment.

Results: Over 20 patients (mostly left sided) have been treated at the

institution using the described technique. A single PBS field proves to be

sufficient to deliver full and more homogeneous dose coverage of all the

target volumes as well as less dose to cardiac tissues compared to con-

ventional photon/electron treatment plans. All treatment fields pass QA

gamma test by more than 95% (3 mm / 3% of prescription dose). A

planning study, based on 4D CT, showed that the PBS dose distribution is

robust to patient’s breathing, as well as to patient’s setup uncertainties, 3

mm shifts and 2 � rotations.

Conclusions: A novel treatment technique for post-mastectomy chest wall

irradiation using proton PBS fields is currently offered by the institution.

While improving both target coverage and OAR sparing, this technique

also offers simpler planning and reduced treatment time.

Author Disclosure: N. Depauw: A. Employee; Massachusetts General

Hospital. E. Batin: A. Employee; Massachusetts General Hospital. J.

Daartz: A. Employee; Massachusetts General Hospital. S. MacDonald:

A. Employee; Massachusetts General Hospital. H. Kooy: A. Employee;

Massachusetts General Hospital. H. Lu: A. Employee; Massachusetts

General Hospital.

3830Real-Time Gall Bladder Motion and Deformation DuringFractionated Stereotactic Body Radiation TherapyD. Gupta, T. Kataria, A. Abhishek, S.S. Bisht, K.P. Karrthick,

V. Subramani, T. Basu, S. Goyal, A. Srivastava, K. Sharma,

and H.B. Govardhan; Medanta The Medicity, Gurgaon, India

Purpose/Objective(s): To analyze real time intra-fractional rotational and

translational motion of Gall bladder during cyber knife based stereotactic

body radiation therapy (SBRT).

Materials/Methods: We analyzed 1,500 alignment shifts in target posi-

tions during 15 treatment sessions in 5 consecutive gall bladder cancer

patients being treated with hypofractionated SBRT with CyberKnife using

synchrony model. The shifts were obtained by tracking 3-4 gold seeds

implanted via a pair of in-room kV X-ray imagers. Images were acquired

every 15 seconds for first 25 minutes of treatment. For each sequential pair

of images, the correction to the target position was calculated in six-de-

grees of motion (3 rotations and 3 translations). The threshold for trans-

lational and rotational motion were 10 mm and 3� respectively. Rigid body

error(RBE) was also analyzed for each patient to find out the deformation

during the course of treatment.

Results: The rotational mean and standard deviation for the intra-fraction

Gall bladder motion were 0.13� � 1.33, 0.87� � 1.49 and -0.27� � 2.09 in

roll, pitch and yaw directions respectively. The translational mean and

standard deviation for the intra-fraction Gall Bladder motion were

0.53mm� 4.34, -0.37mm� 2.63 and 0.87mm � 1.76 in the Left-right

(LR), anterior-posterior (AP), superior-inferior (SI) directions respectively.

Intra-fraction Gall Bladder motion of less than 3� was observed 95.67%,

89.9%, and 86.2%, while greater than 3� was only observed in 4.33%,

10.1% and 13.8% in the Roll, Pitch, and Yaw directions, respectively.

Intra-fraction Gall Bladder motion of less than 2mm was observed 34.6%,

78.6%, and 72.3%, in the LR, AP, and SI directions, respectively, and

47.4%, 88.2%, and 86.2%, in the LR, AP, and SI directions, respectively,