Measuring Stress Velocity Index Using Mean Blood Pressure: Simple yet Accurate?

The stress velocity index, or the relationship of the rate-corrected mean velocity of circumferential shortening (VCFc) to the end systolic wall stress (ESWS), is a sensitive, load-independent measure of left ventricular contractility. ESWS is technically difficult to obtain and requires simultaneous blood pressure measurement, carotid artery tracing, and phonocardiogram. We report our comparison of two simpler methods of measuring ESWS and, therefore, stress velocity index. Patients with normal cardiac anatomy who had completed anthracycline chemotherapy were evaluated. ESWS as measured by the standard method using a carotid artery tracing (ESWScar) was compared to ESWS obtained using mean arterial pressure (ESWSmap) or systolic blood pressure (ESWSsbp). The cohort included 63 patients, with 37 (59%) males and a median age of 13.1 years. The mean (±SD) ESWScar was 53.3±15.3 g/cm² (range, 26.3–94 g/cm²); ESWSmap, 53 ±13.4 g/cm² (range, 27.1–86.1 g/cm²); and ESWSsbp, 72.9 ± 18.2 g/cm² (range, 40.8–117.2 g/cm²). ESWSmap and ESWSsbp closely correlated with ESWScar (coefficient correlation r = 0.88 and r = 0.87, respectively). Using ESWSmap, all patients were correctly classified as having normal or abnormal contractility as defined by stress velocity index, whereas ESWSsbp detected only two of the six patients with impaired contractility. We conclude that ESWSmap is a simple, highly sensitive and specific method for assessing left ventricular contractility. ESWSmap correlates closely with ESWScar and can be incorporated into the monitoring of cardiac dysfunction in the anthracycline-treated population. Further studies are needed to determine if this simplified measure accurately assesses the ESWS in other cardiac disease states.     

Imaging of an invasive malignant thymoma on PET Scan: CT and histopathologic correlation

Thymomas are common primary mediastinal neoplasms. They can be benign or malignant. The diagnosis of malignant thymomas is based on capsular invasion, cellular atypia and distant metastases. We present a case of invasive malignant thymoma as diagnosed on PET and CT scan with histologic correlation and review of literature. A seventy year old Asian man presented with cough and dyspnea. A CT scan showed an anterior mediastinal mass, and a PET scan showed a hypermetabolic mass in the corresponding location. Resection of the mass revealed a minimally invasive thymoma based on evidence of capsular invasion. PET scan proved invaluable in correctly diagnosing, staging the lesion, and excluding any extramediastinal involvement.     

Classification of brain tumor type and grade using MRI texture and shape in a machine learning scheme

The objective of this study is to investigate the use of pattern classification methods for distinguishing different types of brain tumors, such as primary gliomas from metastases, and also for grading of gliomas. The availability of an automated computer analysis tool that is more objective than human readers can potentially lead to more reliable and reproducible brain tumor diagnostic procedures. A computer‐assisted classification method combining conventional MRI and perfusion MRI is developed and used for differential diagnosis. The proposed scheme consists of several steps including region‐of‐interest definition, feature extraction, feature selection, and classification. The extracted features include tumor shape and intensity characteristics, as well as rotation invariant texture features. Feature subset selection is performed using support vector machines with recursive feature elimination. The method was applied on a population of 102 brain tumors histologically diagnosed as metastasis ( 24 ), meningiomas ( 4 ), gliomas World Health Organization grade II ( 22 ), gliomas World Health Organization grade III ( 18 ), and glioblastomas ( 34 ). The binary support vector machine classification accuracy, sensitivity, and specificity, assessed by leave‐one‐out cross‐validation, were, respectively, 85%, 87%, and 79% for discrimination of metastases from gliomas and 88%, 85%, and 96% for discrimination of high‐grade (grades III and IV) from low‐grade (grade II) neoplasms. Multiclass classification was also performed via a one‐vs‐all voting scheme. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Androgen manipulation alters oxidative DNA adduct levels in androgen-sensitive prostate cancer cells grown in vitro and in vivo

Intracellular reactive oxygen species (ROS) may cause oxidative DNA damage, resulting in the formation of adducts such as 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) and the cyclic pyrimidopurinone N-1, N(2) malondialdehyde-2'-deoxyguanosine (M(1)dG). These adducts have been associated with carcinogenesis, genomic instability and clonal evolution. We tested two hypotheses in human prostate cancer cells grown in vitro and in a xenograft model: (1) treatment of androgen-sensitive cells with DHT increases levels of oxidative DNA adduct levels; (2) flutamide, a competitive androgen receptor antagonist, prevents DHT-induced changes. Levels of M(1)dG and 8-oxo-dG adducts were determined by immunoslot blot and liquid chromatography-tandem mass spectrometry. M(1)dG and 8-oxo-dG levels were significantly higher than control levels in LNCaP cells exposed to supra-physiological concentrations (25-100 nM) of DHT (both P<0.05 by ANOVA). Flutamide pre-treatment completely prevented this increase. In the xenograft model, tumour levels of M(1)dG were decreased by 46% (P=0.001 by Mann-Whitney Test) in flutamide-treated animals compared to controls. The changes demonstrated suggest that oxidative DNA adducts may serve as biomarkers of the efficacy of androgen manipulation in chemoprevention trials.