For the case considered, the proposed(153)Gd-based I-RSBT system has the potential to lower the urethral dose relative to HDR-BT by 29%-44% if the clinician allows a urethral dose gradient volume of 0-5 mm around the urethra to receive a dose below the prescription. A multisource approach is necessary in order to deliver the proposed (153)Gd-based I-RSBT technique in reasonable treatment times.

No abstract

Background Recent incidence, treatment patterns and outcomes for node negative microscopically invasive breast cancer (MIBC) have not been reported. Methods State Health Registry of Iowa data identified women with ductal carcinoma in situ (DCIS), MIBC, and Stage I breast cancer excluding MIBC (Stage 1BC). Results From 2000–2013, 1,706, 193 and 4,514 women were diagnosed with DCIS, MIBC and Stage 1BC, respectively. MIBC increased at an annual percentage change of 2.1 (p=0.041). MIBC was more frequently human epidermal-growth-factor-receptor-2 positive than Stage 1BC (39.7% vs 9.6%, p<0.001). Mastectomy was performed more frequently in MIBC than DCIS (40.9% vs 30.6%, p=0.014) or Stage 1BC (40.9% vs 33.8%, p=0.119). Chemotherapy was given to 4.1% of women with MIBC. Survival for women with MIBC was intermediate between DCIS and Stage 1BC. Conclusions Management of MIBC is an increasingly frequent clinical scenario. Women with MIBC receive more aggressive local and systemic therapy than women with DCIS.

Since CNR scales with the square root of imaging dose, changing from TBL + LFB to IBL + LFB and IBL + LFB to IBL + SPA reduces the imaging dose required to obtain a given CNR by factors of 0.38 and 0.37, respectively. MTFs were comparable between imaging system configurations. IBL + SPA patient image quality was always better than that of the TBL + LFB system and as good as or better than that of the IBL + LFB system, for a given dose.

Purpose: To introduce a feasible interstitial rotating shield brachytherapy (I‐RSBT) system for treating prostate cancer. With I‐RSBT, the radiation sources are surrounded by catheters that contain shields to enable conformal avoidance of healthy tissues, potentially reducing complications relative to conventional high‐dose‐rate brachytherapy (HDR‐BT) techniques. Methods: The I‐RSBT system is based around ten control cartridges with 9.5 mm × 9.5 mm cross sections. Each control cartridge contains a rotational stepper motor, connected to a lead screw, which drives a platinum‐shielded nitinol catheter containing a 37 GBq Gd‐153 source. Gadolinium‐153 is generated by neutron irradiation of europium‐151 or Gd‐152 and is mass‐producible at reasonable cost. For I‐RSBT delivery, the cartridges are arranged in a box‐shaped magazine in a desired delivery pattern and aligned with a template containing implanted 16 gauge interstitial nitinol needles. Each source/catheter travels down a needle in a helical pattern during the dose delivery process. An I‐RSBT delivery using more than ten needles can be accomplished by dividing the treatment into multiple parts, each with a different cartridge arrangement in the magazine. Results: Treatment plans based on Monte Carlo dose calculations and optimized using the linear least squares technique demonstrated I‐RSBT reduced D1% (minimum dose to hottest 1%) for the urethra and rectum by 20% and 10% respectively, relative to conventional HDR‐BT. The prostate D97% was the same for I‐RSBT as for HDR‐BT. The I‐RSBT treatment time for a 20 Gy delivery would be 3 hours with fresh Gd‐153 sources. Since Gd‐153 has substantially lower gamma ray energies than iridium‐192, I‐RSBT treatments can occur in procedure rooms rather than conventional brachytherapy suites, reducing the disadvantage of the longer I‐RSBT delivery times. Conclusions: Treating prostate cancer with I‐RSBT is technically feasible in reasonable treatment times using platinum‐shielded Gd‐153 sources and the proposed delivery system. University of Iowa Research Foundation

Purpose: To demonstrate that megavoltage cone beam CT (MVCBCT) image quality can be significantly improved without increasing imaging dose or reducing spatial resolution for both head‐ and pelvis‐sized volumes. The improvement is achieved with the combination of an imaging beam line (IBL) with a low atomic number electron target and a novel sintered pixelated array (SPA) detector. Methods: Three Siemens Oncor linear accelerators were equipped with an IBL+SPA system, an IBL system with a conventional Kodak Lanex Fast B scintillator (IBL+LFB), and a 6 MV treatment beam line system with an LFB (TBL+LFB). Head‐ and pelvis‐sized phantom images were acquired with all three systems at imaging doses ranging from 2‐60 cGy. Contrast to noise ratio (CNR) and modulation transfer function (MTF) were calculated from the phantom images. Head and neck, prostate, and lung cancer patients were imaged with the three imaging systems at doses ranging from 2–15 cGy. Results: For head‐ and pelvis‐sized phantom images acquired at 5 cGy or above, the CNR average percentage increases for imaging system upgrades from TBL+LFB to IBL+LFB to IBL+SPA were 52% (p < 1E‐7) and 42% (p < 1E‐6), respectively. The MTFs do not change with imaging system by statistically significant percentages. Soft tissue contrast is generally more easily differentiated on IBL+SPA images than TBL+LFB and IBL+LFB in the patient images. Conclusions: Since CNR scales with the square root of imaging dose, each step in the TBL+LFB to IBL+LFB to IBL+SPA upgrade halves the imaging dose required to obtain a given CNR. No statistically significant change in spatial resolution was observed with any upgrade, suggesting that the pixelation of the SPA prevents a loss in spatial resolution. IBL+SPA patient image quality was always better than that of the TBL+LFB system and as good as or better than that of the IBL+LFB system. Sponsored partially by Siemens Oncology Care Systems.