Evaluation of geometric and dosimetric inaccuracies of stereotactic irradiation in the rat brain

OBJECTIVE: To evaluate geometric and dosimetric inaccuracies in the irradiation of the rat brain with the Leksell Gamma Knife. MATERIALS AND METHODS: Altogether three types of dosimeters were employed for these measurements: (a) a thermoluminescent dosimeter, (b) a semiconductor detector and (c) a polymer gel dosimeter. The thermoluminescent dosimeter and the semiconductor detector were calibrated using an ion chamber and then implanted in the brain of a rat cadaver and used for absolute dose determination. A special glass phantom mimicking exactly the shape of the rat body filled with the polymer gel was used for measurements of the relative dose distribution and evaluation of geometric inaccuracies during the stereotactic irradiation in the rat brain. RESULTS: Both thermoluminescent and semiconductor detectors, due to their size, measured mean doses. The observed results demonstrated that the Leksell GammaPlan can be employed for the calculation of absorbed doses in irradiation of experimental animals. In our case, it was necessary to apply a correction factor of 1.078 for the absolute absorbed dose to obtain reliable results. A comparison of calculated dose profiles using the treatment planning system in all three axes with those measured by the polymer gel dosimeter demonstrated a very good geometric agreement with the mean deviation in profile position of 0.5 mm. CONCLUSION: The results indicate that this technique can effectively check the geometric and dosimetric accuracy of stereotactic irradiation in the rat brain. The Leksell GammaPlan can be employed for the calculation of absorbed doses, but the correction factor of 1.078 had to be applied for the absolute dose calculations in our irradiation geometry.     

Treatment of suicidal and deliberate self-harming patients with borderline personality disorder using dialectical behavioral therapy: the patients' and the therapists' perceptions

The aim was to investigate patients and therapists perception of receiving and giving dialectical behavioral therapy (DBT). Ten deliberate self-harm patients with borderline personality disorder and four DBT-therapists were interviewed. The interviews were analyzed with qualitative content analysis. The patients unanimously regard the DBT-therapy as life saving and something that has given them a bearable life situation. The patients and the therapists are concordant on the effective components of the therapy: the understanding, respect, and confirmation in combination with the cognitive and behavioral skills. The experienced effectiveness of DBT is contrasted by the patient's pronouncedly negative experiences from psychiatric care before entering DBT.     

A patient questionnaire for radiation-induced brachial plexopathy

We analyzed the usefulness of a symptom questionnaire to screen for radiation-induced brachial plexopathy (RIBP) after breast cancer treatment. Four questions addressed distal and proximal paresis: impaired hand functions, problems raising the arm, carrying weights, and lifting objects from a high shelf. Eighty-one relapse-free patients were neurologically examined. Treatment was mastectomy (51%) or breast-conserving surgery (49%), radiotherapy to the supraclavicular +/- axilla with median 60 Gy maximum dose. Sixty-five subsequent control patients had breast-conserving surgery and radiotherapy to the breast only with 55 Gy median dose. Median follow up was 10 and 7.4 years, respectively. Sixteen patients had RIBP, 7 had Radiation Therapy Oncology Group (RTOG) grade 1, 4 grade 2, 3 grade 3, and 2 grade 4 RIBP. Thirty-seven patients had fibrosis and 32 had arm edema. Four patients with RIBP had no fibrosis (n = 2) or fibrosis of the axilla only (n = 2). Specificity of the question "impaired hand functions" for RIBP was 0.66 (95% confidence interval [CI], 0.51-0.78); sensitivity was 0.80 (95% CI, 0.52-0.96). Specificity of the question "raising the arm" was 0.98 (95% CI, 0.9-0.99) and sensitivity was 0.18 (95% CI, 0.04-0.45); the rate of false-positive control patients was 3%. In multivariate analysis, "impaired hand functions" and fibrosis were independent indicators of RIBP (P <0.005). Patients with breast irradiation only stated moderate/pronounced impaired hand functions; and problems carrying weights and lifting objects from a high shelf in 38%, 58%, and 77%, not significantly different from patients with RIBP or the patients with supraclavicular radiation. RIBP is not necessarily associated with fibrosis. The aim of the questionnaire was screening of a population at risk for RIBP. In this group, the question "problems raising the arm" detected severe RIBP with high specificity. Negation of "impaired hand functions" excludes RIBP. Both questions should be included in follow-up questionnaires.     

Daptomycin, a lipopeptide antibiotic in clinical practice

Gram-positive cocci are one of the leading causes of infections in clinical medicine. Since the invention of antibiotic substances, multidrug resistance is a major problem in the treatment of such infections. Methicillin-resistant Staphylococcus aureus (MRSA) is responsible for 60% of nosocomial infections in the US. The first-choice drug used in these cases is the glycopeptide vancomycin; however, vancomycin is associated with a significant number of adverse side effects, such as nephro- and ototoxicity. Thus, the discovery of new drugs against MRSA and other multidrug-resistant cocci is of utmost interest. Daptomycin, a lipopeptide, is one of these new drugs and has been successfully used in the treatment of complicated skin and skin-structure infections and right-sided endocarditis. Because of its potency and pharmacological profile, it is increasingly used for new indications not yet approved by the FDA. The purpose of this article is to provide an overview of daptomycin, with particular emphasis on potential new indications for which it could be used in the future.     

Pharmacokinetics of diltiazem and its metabolites in relation to CYP2D6 genotype

OBJECTIVES: Recently, it was shown in vitro that the polymorphic enzyme cytochrome P450 (CYP) 2D6 mediates O-demethylation of diltiazem. The aim of this study was to compare the pharmacokinetics of diltiazem and its major metabolites in healthy human volunteers representing different CYP2D6 genotypes. METHODS: Norwegians of Caucasian origin were screened for their CYP2D6 genotype on the LightCycler (Roche Diagnostics, Mannheim, Germany) by melting-curve analysis of allele-specific fluorescence resonance energy transfer probes hybridized to polymerase chain reaction-amplified deoxyribonucleic acid. The first 5 individuals identified with genotypes corresponding to a homozygous extensive, heterozygous extensive, or homozygous poor CYP2D6-metabolizing phenotype, respectively, were voluntarily enrolled in the pharmacokinetic study. The participants received diltiazem, 120 mg, as a single oral dose, and plasma samples were collected up to 24 hours after administration. Plasma samples were purified by solid phase extraction. Diltiazem and 7 phase I metabolites were analyzed by liquid chromatography-mass spectrometry. RESULTS: The pharmacokinetics of diltiazem was not significantly different between the subgroups. However, the systemic exposure of the pharmacologically active metabolites desacetyl diltiazem and N-demethyldesacetyl diltiazem was > or = 5 times higher in poor CYP2D6 metabolizers than in extensive CYP2D6 metabolizers (P <.01). CONCLUSIONS: CYP2D6 activity does not have a major impact on the disposition of diltiazem. In contrast, desacetyl diltiazem and N-demethyldesacetyl diltiazem are markedly accumulated in individuals expressing a deficient CYP2D6 phenotype. Because these metabolites exhibit pharmacologic properties of possible importance, individual CYP2D6 activity might be an aspect to consider in the clinical use of diltiazem.     

Recurrent laryngeal nerve palsy in patients with lung cancer: detection with PET-CT image fusion -- report of six cases

Positron emission tomography (PET) with fluorodeoxyglucose (FDG) was performed for preoperative staging of lung cancer. In six of 184 patients, there was an intense FDG accumulation in the lower anterior neck. Fusion of PET and computed tomographic images revealed that the focal FDG uptake was localized in the internal laryngeal muscles. This finding was a result of compensatory laryngeal muscle activation caused by contralateral recurrent laryngeal nerve palsy due to direct nerve invasion by lung cancer of the left mediastinum or lung apices. The knowledge of this pitfall is important to avoid false-positive PET results.