Secondary Malignancy Risk Following Proton vs. X-ray Radiotherapy of Thymic Epithelial Tumors: A Comparative Modeling Study of Thoracic Organ-Specific Cancer Risk.

Background: Proton beam radiotherapy (PBT) offers physical dose advantages that might reduce the risk for secondary malignancies (SM). The aim of the current study is to calculate the risk for SM after X-ray-based 3D conformal (3DCRT) radiotherapy, intensity-modulated radiotherapy (IMRT), and active pencil beam scanned proton therapy (PBS) in patients treated for thymic malignancies.

Methods: Comparative treatment plans for each of the different treatment modalities were generated for 17 patients.

Secondary Malignancy Risk Following Proton vs. X-ray Treatment of Mediastinal Malignant Lymphoma: A Comparative Modeling Study of Thoracic Organ-Specific Cancer Risk.

Proton radiotherapy (PRT) is potentially associated with a lower risk for secondary malignancies due to a decreased integral dose to the surrounding organs at risk (OARs). Prospective trials confirming this are lacking due to the need for long-term follow-up and the ethical complexities of randomizing patients between modalities. The objective of the current study is to calculate the risk for secondary malignancies following PRT and photon-based intensity-modulated radiotherapy (IMRT).

Carbon ion and proton beam irradiation of a normal human TK6 lymphoblastoid cell line within a magnetic field of 1.0 tesla.

Background: Considering the increasing simultaneous application of magnetic resonance imaging (MRI) for more precise photon radiotherapy, it will be likely for particle radiotherapy to adopt MRI for future image guiding. It will then be imperative to evaluate the potential biological effects of a magnetic field (MF) on particle irradiation. This study explores such effects on the highly radiosensitive TK6 lymphoblastoid human cell line.

The influence of a magnetic field on photon beam radiotherapy in a normal human TK6 lymphoblastoid cell line.

Background: The implementation of magnetic resonance imaging (MRI) guided radiotherapy (RT) continues to increase. Very limited in-vitro data on the interaction of ionizing radiation and magnetic fields (MF) have been published. In these experiments we focused on the radiation response in a MF of the TK6 human lymphoblastoid cells which are known to be highly radiosensitive due to efficient radiation-induced apoptosis.

Feasibility of polymer gel-based measurements of radiation isocenter accuracy in magnetic fields.

For conventional irradiation devices, the radiation isocenter accuracy is determined by star shot measurements on films. In magnetic resonance (MR)-guided radiotherapy devices, the results of this test may be altered by the magnetic field and the need to align the radiation and imaging isocenter may require a modification of measurement procedures. Polymer dosimetry gels (PG) may offer a way to perform both, the radiation and imaging isocenter test, however, first it has to be shown that PG reveal results comparable to the conventionally applied films.

Prospective feasibility analysis of a novel off-line approach for MR-guided radiotherapy.

Background: The present work aimed to analyze the feasibility of a shuttle-based MRI-guided radiation therapy (MRgRT) in the treatment of pelvic malignancies.

Patients And Methods: 20 patients with pelvic malignancies were included in this prospective feasibility analysis. Patients underwent daily MRI in treatment position prior to radiotherapy at the German Cancer Research Center.

Long term results of postoperative Intensity-Modulated Radiation Therapy (IMRT) in the treatment of Squamous Cell Carcinoma (SCC) located in the oropharynx or oral cavity.

Background: To report our long-term results with postoperative intensity-modulated radiation therapy (IMRT) in patients suffering from squamous-cell carcinoma (SCC) of the oral cavity or oropharynx.

Methods: Seventy five patients were retrospectively analyzed. Median age was 58 years and 84 % were male.

SU-E-T-124: A Modified Winston Lutz Test Enabling Beam to Laser Angle Measurements.

Purpose: To present a modified Winston-Lutz-Test procedure able to measure beam and laser angles.

Methods: Room lasers have not only to indicate the isocenter spot but should also be aligned to the central beam axis. Therefore a modified WL test, based on a cube phantom made of low density foam material was developed.

Dosimetric integration of daily mega-voltage cone-beam CT for image-guided intensity-modulated radiotherapy.

Purpose: The goal of this work was to compare different methods of incorporating the additional dose of mega-voltage cone-beam CT (MV-CBCT) for image-guided intensity modulated radiotherapy (IMRT) of different tumor entities.

Material And Methods: The absolute dose delivered by the MV-CBCT was calculated and considered by creating a scaled IMRT plan (scIMRT) by renormalizing the clinically approved plan (orgIMRT) so that the sum with the MV-CBCT dose yields the same prescribed dose. In the other case, a newly optimized plan (optIMRT) was generated by including the dose distribution of the MV-CBCT as pre-irradiation.

4D-CT-based target volume definition in stereotactic radiotherapy of lung tumours: comparison with a conventional technique using individual margins.

Purpose: To investigate the dosimetric benefit of integration of 4D-CT in the planning target volume (PTV) definition process compared to conventional PTV definition using individual margins in stereotactic body radiotherapy (SBRT) of lung tumours.

Material And Methods: Two different PTVs were defined: PTV(conv) consisting of the helical-CT-based clinical target volume (CTV) enlarged isotropically for each spatial direction by the individually measured amount of motion in the 4D-CT, and PTV(4D) encompassing the CTVs defined in the 4D-CT phases displaying the extremes of the tumour position. Tumour motion as well as volumetric and dosimetric differences and relations of both PTVs were evaluated.

Radiobiological investigation of dose-rate effects in intensity-modulated radiation therapy.

Background And Purpose: Intensity-modulated radiation therapy (IMRT) has proven extraordinary capability in physical terms such as target conformity, dose escalation in the target volume, and sparing of neighboring organs at risk. The radiobiological consequences of the protracted dose delivery for cell survival and cell cycle progression are still unclear and shall be examined in this study.

Material And Methods: Human lymphoblasts (TK6) and human melanoma cells (MeWo) were irradiated with protocols of increasing dose protraction.

Influence of intra-fractional breathing movement in step-and-shoot IMRT.

Efforts have been made to extend the application of intensity-modulated radiotherapy to a variety of organs. One of the unanswered questions is whether breathing-induced organ motion may lead to a relevant over- or underdosage, e.g.

Intensity modulated radiotherapy (IMRT) for recurrent, residual, or untreated skull-base meningiomas: preliminary clinical experience.

Objective: To investigate the feasibility of using intensity modulated radiotherapy (IMRT) for complex-shaped benign meningiomas of the skull base and report clinical experience.

Methods: Twenty patients with benign skull-base meningiomas WHO degrees I (histopathologically proven in 16/20) were treated with IMRT between June 1998 and August 1999. Each tumor was complex in shape and adherent to, or encompassed, organs at risk (cranial nerves, optic apparatus, and brainstem).

Intensity-modulated radiotherapy of the female breast.

Current methods for intensity-modulated radiotherapy (IMRT) in breast cancer use forward planning based on equivalent radiological path length to design intensity modulated tangential beams. Compared to conventional tangential techniques, dose reduction of organs at risk is limited using these techniques. We developed a method for intensity modulation of multiple beams for adjuvant radiotherapy of breast cancer by application of a virtual bolus defined on CT for inverse optimization.

Conformational modulation of purified glycoprotein (GP) IIb-IIIa allows proteolytic generation of active fragments from either active or inactive GPIIb-IIIa.

This study characterized conformational states of platelet glycoprotein IIb-IIIa (GPIIb-IIIa) and regions of the molecule required for fibrinogen binding. Platelet lysates were passed sequentially over concanavalin A and aminoethylglycine (Aeg)RGDS affinity columns. Approximately 10% of the total GPIIb-IIIa bound to the Aeg-RGDS column.

Antisperm antibodies in women undergoing intrauterine insemination.

Intrauterine insemination is widely used for the treatment of infertility as a result of cervical or male factors or empirically before in vitro fertilization or gamete intrafallopian transfer. This study was designed to confirm or refute the theoretical concern that intrauterine insemination may induce antisperm antibodies in such women. Serum and cervical mucus were obtained at the first, fourth, and sixth intrauterine inseminations.

Effect of a synthetic platelet activating factor on steroidogenesis of cultured porcine granulosa cells.

An embryo-derived platelet activating factor has been demonstrated to play an important role in reproduction. This report examined the effect of various doses of a synthetic platelet activating factor on the production of progesterone by porcine granulosa cells in culture. Granulosa cells aspirated from ovarian follicles of prepubertal gilts were grown for 24 hours in Dulbecco's Modified Eagles Media: Ham's F-12 with 5% fetal bovine serum and 1 micrograms/ml insulin.