Two years experience with quality assurance protocol for patient related Rapid Arc treatment plan verification using a two dimensional ionization chamber array

<p>Abstract</p> <p>Purpose</p> <p>To verify the dose distribution and number of monitor units (MU) for dynamic treatment techniques like volumetric modulated single arc radiation therapy - Rapid Arc - each patient treatment plan has to be verified prior to the first treatment. The purpose of this study was to develop a patient related treatment plan verification protocol using a two dimensional ionization chamber array (MatriXX, IBA, Schwarzenbruck, Germany).</p> <p>Method</p> <p>Measurements were done to determine the dependence between response of 2D ionization chamber array, beam direction, and field size. Also the reproducibility of the measurements was checked. For the patient related verifications the original patient Rapid Arc treatment plan was projected on CT dataset of the MatriXX and the dose distribution was calculated. After irradiation of the Rapid Arc verification plans measured and calculated 2D dose distributions were compared using the gamma evaluation method implemented in the measuring software OmniPro (version 1.5, IBA, Schwarzenbruck, Germany).</p> <p>Results</p> <p>The dependence between response of 2D ionization chamber array, field size and beam direction has shown a passing rate of 99% for field sizes between 7 cm × 7 cm and 24 cm × 24 cm for measurements of single arc. For smaller and larger field sizes than 7 cm × 7 cm and 24 cm × 24 cm the passing rate was less than 99%. The reproducibility was within a passing rate of 99% and 100%. The accuracy of the whole process including the uncertainty of the measuring system, treatment planning system, linear accelerator and isocentric laser system in the treatment room was acceptable for treatment plan verification using gamma criteria of 3% and 3 mm, 2D global gamma index.</p> <p>Conclusion</p> <p>It was possible to verify the 2D dose distribution and MU of Rapid Arc treatment plans using the MatriXX. The use of the MatriXX for Rapid Arc treatment plan verification in clinical routine is reasonable. The passing rate should be 99% than the verification protocol is able to detect clinically significant errors.</p

Prolactinomas in Men

Prolactinomas in men have several peculiar features that distinguish them from female PRL-secreting tumors. They occur less frequently in the male gender but are usually larger, more frequently invasive, and more often aggressive than in women. Significantly higher prolactin concentrations are also observed in men as compared to women, especially in the case of macroprolactinoma. Sex differences in tumor behavior largely explain such characteristics, rather than the longer delay in making the diagnosis in men. The reasons for a more aggressive course of prolactinomas in men remain poorly understood, and some hypotheses will be discussed in this chapter. Striking differences also exist in the clinical presentation of prolactinoma. Most women will present with oligomenorrhea, infertility, and/or galactorrhea, while more than half of men initially complain from symptoms of mass effects. Male hypogonadism is often present but neglected, and the male reproductive axis appears to be less sensitive to hyperprolactinemia than the female one. Nonetheless, diagnosis of prolactinoma in men should rely on the same criteria as in women, and a similar therapeutic strategy should be used. Medical management with dopamine agonists (DA) is effective and should always be considered as the first-line therapy, also in men bearing very large and compressive tumors. Transsphenoidal surgery is indicated in patients who are either intolerant or resistant to dopamine agonists or who elect to undergo potential curative surgery. However, most male patients with a macroprolactinoma will require medical treatment to control prolactin hypersecretion after surger