Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – EU funding. Main funding source(s): H2020-FTI [Fast Track to Innovation] Pilot-2016 and MicroPort CRM Background Left ventricular (LV) lead positioning is an important contributor to cardiac resynchronization therapy (CRT) response. Multiple additional LV sites could be stimulated by passing a new ultra-thin (1.2 Fr, 0.4 mm) quadripolar microlead from one LV vein into another via venous collaterals. Purpose Study the acute and chronic stability and electrical pacing performance of a novel 1.2 Fr quadripolar microlead ("Axone 4LV"). Methods Seven healthy adult dogs underwent CRT defibrillator implantation, including a right ventricular lead and the microlead. The microlead was advanced into the coronary sinus network using a dedicated microguide catheter. The animals were followed up at 1, 15, 30 and 90 days post-implant to evaluate chronic stability and electrical pacing performance. Results Successful uncomplicated implantation was achieved in all cases. Despite the small diameter of the distal veins and collaterals, placement of the pacing electrodes in two different LV veins was feasible via available collateral passages. Lead position was stable in all cases and over the entire study period. Capture threshold and pacing impedance at 90 days post-implant were 1.7 ± 0.5 V with 1323 ± 245 Ω, respectively, at 0.5 ms pulse width. The mean pacing energy to get capture was 1.1 ± 0.5 µJ and less than 2 µJ in all cases (2 µJ ≈ 1.4 V @500 Ω, 0.5 ms). No phrenic nerve stimulation was observed during pacing. Conclusions The novel 1.2 Fr quadripolar microlead demonstrated adequate stability and good electrical performance allied to low energy consumption. This quadripolar microlead may extend pacing options while increasing device longevity in CRT. Changes in pacing parameters over time Post-implant Follow-up Pacing Threshold Pacing Impedance Pacing Energy 1 day 1.4 ± 0.7 V 1294 ± 270 Ω 0.8 ± 0.7 µJ 15 days 1.9 ± 0.9 V 1336 ± 274 Ω 1.8 ± 1.8 µJ 30 days 1.8 ± 0.7 V 1187 ± 303 Ω 1.5 ± 1.2 µJ 90 days 1.7 ± 0.5 V 1323 ± 245 Ω 1.1 ± 0.5 µJ

Postoperative intravaginal brachytherapy of endometrium carcinoma is usually performed with Ir192 HDR afterloading. A good alternative might be the treatment with a 50kV X-ray point source because of its low energy and the consequential steep dose gradient. Aim of the study is to create a homogeneous cylindrical energy deposition around an applicator, which is required for this treatment. A 50kV X-ray source (INTRABEAM system, Carl Zeiss Surgical GmbH, Oberkochen, Germany), which produces a spherical dose distribution around the tip of the probe, was used. For phantom measurements a cylindrical plastic vaginal applicator (PEI, Ø35mm) was used. To create a constant isodose layer (equidistant from the applicator along its length with the prescription depth being 5mm) the source was moved in steps of 17-21mm outward from the tip of the applicator. At each position (3-5 positions) an irradiation of a predetermined time was performed (depending on the prescribed total dose). The axial shift was established by a stepping mechanism (GfM mbH, Weiterstadt, Germany), which was mounted on a table support (B-K Medical, Herlev, Denmark). The total dose/dose distribution was determined by using film dosimetry (Gafchromic EBT films, ISP, New Jersey, USA) in a "solid water" phantom (GfM mbH, Weiterstadt, Germany). The films were evaluated with Mathematica 5.2 (Wolfram Research Inc. Champaign, IL, USA) and OmniPro-I'mRT (IBA Dosimetry GmbH, Schwarzenbruck, Germany). The results (dose D0/D5/D10 in 0/5/10mm tissue depth) were compared to an Ir192 HDR afterloading plan for multiple sampling points along the applicator. Three different dose distributions were created (l = length of the cylindrical dose distributions, t = irradiation time based on 5/7 Gy in 5mm tissue depth): - 3 positions, l = 3.5cm, t = 20/28min. The - 4 positions, l = 5.2cm, t = 25/34min. - 5 positions, l = 6.9cm, t = 30/40min. D0/D5/D10 (mean of the sampling points ± standard deviation) for both techniques (electronic brachytherapy = EB, afterloading = HDR) were: - D0 = 150%±1.6% (EB), D0 = 140%±1.3% (HDR). The - D5 = 100%±1.4% (EB), D5 = 100%±2.3% (HDR). - D10 = 67%±1.6% (EB), D10 = 74%±3.9% (HDR). The deviation for repeated measurements in the phantom was <7%. It is possible to create a homogeneous cylindrical dose distribution through superposition of multiple spherical ones by stepping a kV point source. The resulting dose distribution was similar to the one created with Ir192 HDR afterloading. Due to its low energy, electronic brachytherapy allows for flexible spatial use (minimal radiation protection). As a next step, the biological effect of kV radiation in this situation has to be modeled to determine a suitable correction factor for calculating physical kV doses that are biologically equivalent to Ir192 HDR doses.

PURPOSE:Permanent interstitial brachytherapy (IB) has become an increasingly appealing therapeutic option for localized prostate cancer (LPC) among physicians and patients because it involves short hospitalization and treatment and its postulated low degree of toxicity may reduce its impact on the patients' quality of life (QoL). The aim of this prospective study was to assess the impact of IB on the QoL of patients with LPC. METHODS AND MATERIALS:A validated self-completed questionnaire was administered to the patients before and after IB and then at yearly intervals. The items allowed the identification of seven subscales exploring physical well-being (PHY), physical autonomy (POW), psychological well-being (PSY), relational life (REL), urinary function (URI), rectal function (REC), and sexual function (SEX). RESULTS:The assessment of the QoL of 147 patients treated between May 2000 and February 2005 revealed no relevant differences in the PHY scale scores 1 month after IB or later, and the same was true of the POW, PSY, and REL scales. Urinary function significantly worsened after IB and returned to pretreatment levels only after 3 years; the impact of the treatment on the URI scale was greater in the patients with good baseline urinary function than in those presenting more urinary symptoms before IB. Rectal and sexual functions were significantly worse only at the post-IB evaluation. CONCLUSIONS:The results of the present study confirm that the impact of IB on the patients' QoL is low despite its transient negative effects on some function, and extend existing knowledge concerning QoL after IB.

4744 Background: When IB is planned as definitive treatment for LPC, HT is frequently prescribed to shrink the tumor mass and improve treatment outcomes. IB may produce per se a negative impact on ...

Background and purpose: The purposes of this multicentric study are (a) the evaluation of four different commercial ly available treatment planning systems (TPSs) and (b) to verify whether the dosimetric results are comparable, also when considering the inter-observer variabilities and the different scanning protocols used. This work is to be considered a first step to test the value of multicentric studies based on dosimetric evaluation of the quality of the implants.Patients and methods: Four different TPSs were used and the following tests were performed:1. Comparison of the parameters and mathematical algorithms used; comparison of the dose distributions generated by three different M geometries of sources based on 32 dose-points on each source geometry. An octagonal geometric phantom was used to compare volume algorithms and dose-volume histogram (DVH) calculations (V150(Gy), V100(cy), V50(Gy) and V25(Gy)).2. Comparison of the post-plan Source distribution performed on a prostate-phantom implanted with I-125 seeds. A CT scan of the phantom was obtained at each participating center. Both the geometrical coordinates (with respect to the most caudal one), and the spread of the gometrical distribution. were calculated. The volumes included within different isodoses were also collected.3. Comparison of the post-plan source distribution performed on an actual patient. Post-plan V100% and D90(Gy) derived from seed distributions obtained by different operators were calculated, using the same target delineation.Results:1. All the considered TPSs satisfied the AAPM dosimetric parameter recommendations. Point-dose examinations revealed differences smaller than 5%, except for one of the systems. Although the volume algorithm was not the same for all systems, no statistically significant difference was found in the volume measurements. The DVHs also presented differences smaller than 5%, except for one TPS.2. The distances between the seeds, based on the same CT images, showed a mean SD of 0.13 mm. The mean maximum difference of the position of each seed was 0.36 mm. The most significant errors were made in the cranio-caudal direction (mean maximal difference: 0.44 mm): here the size of the step between slices played an important role. The algorithm of source positioning of the different TPSs may also help explain this difference. The compiled DVHs showed differences smaller than 5%.3. Post-plans derived front different seed distributions showed a mild dependence upon operators. We obtained a mean value of 97.8 and 152.7 with a percentage of SD of 0.43 and 1.7, respectively, for V 100% and D90(Gy).Conclusions: Three-dimensional (3D) geometric reconstructions of seed distributions are slightly dependent upon the operators and the scanning protocols have little effect on the dosimetric evaluation. Some relevant discrepancies were found between one of the TPSs and the other three if few sources were used; increasing the number of seeds those differences became less pronounced. Multicentric studies on the quality of prostate implants based on post-implant dosimetry are feasible, provided an accurate step-wise evaluation of the procedure be performed. (C) 2004 Elsevier Ireland Ltd. All rights reserved.

A multicentric study involving eight Italian brachytherapy centers was performed to analyse to what extent the variations in the reconstructed seed distribution can affect the dosimetric parameters commonly used in post plan evaluations of permanent prostate brachytherapy. The geometrical seeds distributions were reconstructed by eight reviewers on CT and MR images of six implanted patients. Independently on the imaging modality, the geometric reconstruction of the seeds distribution showed little effect on quality dosimetric parameters D-90 and V-100 of the prostate implant. On the contrary a strong effect upon organs at risk (OARS) related parameters was found. The spread of the D-1 and V-150 values for the urethra calls into question the significance and the specificity of these parameters. Our preliminary results show the difficulty of collecting dosimetric data that could be correlated with biochemical relapse-free survival (RFS) or prostate specific antigen (PSA) and, particularly, with side effects. Nevertheless, in our opinion, prostate and OAR contouring remains the largest source of uncertainty in post plan evaluation.