SU-E-T-225: A Comprehensive Evaluation of Real-Time Motion Tracking of a Surface Imaging System for Lung Treatment

PURPOSE

Applicability of the AlignRT surface imaging system was extensively investigated for real-time motion tracking in radiation therapy of lung cancer.

METHODS

A 4D computer-controlled motion phantom was employed to simulate a human breathing motion. An anthropomorphic thoracic phantom (a coronal cross-sectional area: ∼1,200 cm² ) was monitored during the 4D motion tracking. A breathing cycle from a healthy subject (breathing frequency: 0.2 Hz; maximum amplitude: vertical 7 mm, longitudinal 6 mm, and lateral 1.2 mm) was monitored and fed into the phantom control system. The real time monitoring was investigated by modifying a region of detection (the whole, a half, and a quarter of the area) and combination of 3 cameras (patient left, middle, and right).

RESULTS

The real-time tracking errors (detected breathing motion - the input of the subject's breathing) of the phantom motion using one camera (lateral, longitudinal, vertical) were (0.02±0.14 mm, -0.23±0.48 mm, -0.10±0.48 mm) with ipsilateral halves of the area (frame rate: 1.52 Hz), (0.06±0.10 mm, -0.30±0.30 mm, -0.03-0.35 mm) with ipsilateral quarters (frame rate: 1.95 Hz), and (0.19±0.96 mm, 0.29±1.50 mm, -0.46±1.58 mm) with contralateral quarters (frame rate: 3.04 Hz). The detection errors using 2-camera combinations (left-middle and right-middle) were (-0.06±0.06 mm, -0.43±0.21 mm, 0.00±0.22 mm) for the ipsilateral quarters and (-0.62±0.18 mm, -1.20±0.37 mm, 0.03±0.30 mm) for the contralateral quarters, respectively. The 3-camera tracking using halves of the area presented an error of (-0.04±0.12 mm, -0.69±0.35 mm, -0.08±0.38 mm) with a frame rate of 0.62 Hz.

CONCLUSIONS

To guarantee a sub-millimeter accuracy of realtime motion tracking in the lung treatment, combination of 2 cameras or less, a frame rate of greater than the Nyquist frequency (in this study fN = 2B (breathing frequency) = 0.4 Hz), and a tracking area of less than an ipsilateral half of thoracic area is highly recommended.

SU-E-J-214: Target Intrafraction Motion Dosimetric Impact on 5-Fraction Proton Prostate SBRT

PURPOSE

To investigate dosimetric impact of prostate intra-fraction motion to five fraction hypofractionated proton treatment with uniform scanning (US) and double scattering (DS) techniques using real-time prostate tracking data from electromagnetic transponder system.

METHODS

Prostate intra-fraction motion can have spatiotemporal interplay with proton treatment delivery. Five fraction (7.25Gy/fraction) prostate proton stereotactic body radiotherapy (SBRT) treatments were simulated for total 14 patients using in-house proton treatment simulation program. The US treatment was simulated by rigidly moving CTV through a series of temporal-spatial dose matrices indexed by energy layers, according to prostate motion traces. The CTV temporal doses of the whole treatment fraction were obtained and summed as final prostate CTV dose. The DS treatment was simulated by moving CTV through the energy layer summed dose matrix. For all patients, the fraction doses and the total dose to the CTV were presented for both DS and US treatments.

RESULTS

The CTV dose of different fractions indicated that its dose degradation depends on magnitude and direction of prostate intra-fraction motion and is patient specific. For one of the prostate motion traces investigated, only 70% of CTV received 100% prescribed dose for a simulated US treatment and 79% CTV had 100% dose for a DS treatment. Furthermore, DVH and isodose graphs of both treatments revealed that intra-fraction motion caused significant CTV cold and hot spots in US treatment whereas only cause CTV underdose in DS treatment.

CONCLUSIONS

Intra-fraction prostate motion causes dose uncertainty to CTV. In the 5 fraction prostate SBRT, prostate intra-fraction motion causes significant target dose degradation. In US treatment, spatiotemporal interplay between energy layers delivery and prostate motion leads to hot and cold spots in CTV for some patients with severe prostate intra-fraction motion. Further investigation of intra-fraction motion management and its impact on CTV dose is necessary.

The Interaction of Polymer Dispersions with Portland Cement Paste

Research has been done on the interaction of two types of polymer dispersions, a styrene acrylate (SA) and a polyvinylidene chloride (PVDLC), with portland cement by means of a COULTER particle size analyzer and a filtration technique. It was found that over 50% of the polymer SA particles were adsorbed onto the cement surface, the others did not adhere to cement grains and remained dispersed in the mixing water. However, the polymer dispersion PVDLC caused a quick flocculation and coagulation of cement grains and stiffening of the paste. Hardly any free polymer particles of this polymer were found in the liquid phase.

Gynandroblastoma with the symptoms of infertility and secondary amenorrhea: a case report

The case of a female patient who failed to get pregnant due to delayed menstruation is reported. Gynecological examination showed that the patient had a male pubic distribution, hypertrophic clitoris, unobstructed vagina and hypertrophic cervices with smooth and medium texture. B ultrasonic examination detected a 42 x 30 mm in size medium echo mass. This mass had irregular shape, smooth surface, relatively clear boundary and hard texture. Examination with paraffin-embedded section indicated that the tumor was composed of supporting cells and to a lesser amount of interstitial components. Some regions had particle-like cell differentiation. These results suggested that the tumor was gynandroblastoma. We found that the increased level of serum testosterone in the patient was the reason for amenorrhea and infertility. The diagnosis and treatment for patients with gynandroblastoma is also discussed.