Discriminator aided phase lock acquisition for suppressed carrier signals

A discriminator aided technique for acquisition of phase lock to a suppressed carrier signal utilizes a Costas loop which is initially operated open loop and control voltage for its VCXO is derived from a phase detector that compares the VCXO to a reference frequency thus establishing coarse frequency resolution with the received signal. Then the Costas loop is closed with the low-pass filter of the channel having a bandwidth much greater (by a factor of about 10) than in the I channel so that a frequency discriminator effect results to aid carrier resolution. Finally, after carrier acquisition, the Q-channel filter of the Costas loop is switched to a bandwidth substantially equal to that of the I-channel for carrier tracking

Intensity modulated radiotherapy (IMRT) in the treatment of children and Adolescents - a single institution's experience and a review of the literature

<p>Abstract</p> <p>Background</p> <p>While IMRT is widely used in treating complex oncological cases in adults, it is not commonly used in pediatric radiation oncology for a variety of reasons. This report evaluates our 9 year experience using stereotactic-guided, inverse planned intensity-modulated radiotherapy (IMRT) in children and adolescents in the context of the current literature.</p> <p>Methods</p> <p>Between 1999 and 2008 thirty-one children and adolescents with a mean age of 14.2 years (1.5 - 20.5) were treated with IMRT in our department. This heterogeneous group of patients consisted of 20 different tumor entities, with Ewing's sarcoma being the largest (5 patients), followed by juvenile nasopharyngeal fibroma, esthesioneuroblastoma and rhabdomyosarcoma (3 patients each). In addition a review of the available literature reporting on technology, quality, toxicity, outcome and concerns of IMRT was performed.</p> <p>Results</p> <p>With IMRT individualized dose distributions and excellent sparing of organs at risk were obtained in the most challenging cases. This was achieved at the cost of an increased volume of normal tissue receiving low radiation doses. Local control was achieved in 21 patients. 5 patients died due to progressive distant metastases. No severe acute or chronic toxicity was observed.</p> <p>Conclusion</p> <p>IMRT in the treatment of children and adolescents is feasible and was applied safely within the last 9 years at our institution. Several reports in literature show the excellent possibilities of IMRT in selective sparing of organs at risk and achieving local control. In selected cases the quality of IMRT plans increases the therapeutic ratio and outweighs the risk of potentially increased rates of secondary malignancies by the augmented low dose exposure.</p

Biological effects of exposure to magnetic resonance imaging: an overview

The literature on biological effects of magnetic and electromagnetic fields commonly utilized in magnetic resonance imaging systems is surveyed here. After an introduction on the basic principles of magnetic resonance imaging and the electric and magnetic properties of biological tissues, the basic phenomena to understand the bio-effects are described in classical terms. Values of field strengths and frequencies commonly utilized in these diagnostic systems are reported in order to allow the integration of the specific literature on the bio-effects produced by magnetic resonance systems with the vast literature concerning the bio-effects produced by electromagnetic fields. This work gives an overview of the findings about the safety concerns of exposure to static magnetic fields, radio-frequency fields, and time varying magnetic field gradients, focusing primarily on the physics of the interactions between these electromagnetic fields and biological matter. The scientific literature is summarized, integrated, and critically analyzed with the help of authoritative reviews by recognized experts, international safety guidelines are also cited

Amifostine protects against cisplatin-induced ototoxicity in children with average-risk medulloblastoma

PURPOSE: To determine the role of amifostine as a protectant against cisplatin-induced ototoxicity in patients with average risk (AR) medulloblastoma treated with craniospinal radiotherapy and 4 cycles of cisplatin-based dose-intense chemotherapy and stem cell rescue. PATIENTS AND METHODS: The primary objective was to determine whether, in patients with AR medulloblastoma (n=62), amifostine would decrease the need for hearing aids (defined as ≥ grade 3 ototoxicity in one ear) compared to a control group (n=35), one year from initiating treatment. (Figure 1) Ninety-seven patients received CSI (23.4 Gy) followed by 55.8 Gy to the primary tumor bed, using 3-D conformal technique and 4 cycles of high-dose cyclophosphamide (4000 mg/m(2) per cycle), cisplatin (75 mg/m(2) per cycle), and vincristine (two 1.5 mg/m(2) doses per cycle) and stem cell rescue. When used, amifostine (600 mg/m(2) per dose) was given as a bolus immediately prior to and 3 hours into the cisplatin infusion. RESULTS: The median age of the 97 patients was 8.7 years (range, 3.2–20.2 years). The study and control groups were similar in age and sex distribution. Amifostine was well-tolerated. One year after treatment initiation, 13 (37.1%) of the control-group versus 9 (14.5%; p=0.005 Chi-Square one-sided test) of the amifostine-treated patients had ≥ grade 3 ototoxicity, requiring hearing aid in at least one ear. CONCLUSION: Amifostine administered prior to and during the cisplatin infusion can significantly reduce the risk of severe ototoxicity in patients with AR medulloblastoma receiving dose-intense chemotherapy