Merging Orthovoltage X-Ray Minibeams spare the proximal tissues while producing a solid beam at the target.

Conventional radiation therapy of brain tumors often produces cognitive deficits, particularly in children. We investigated the potential efficacy of merging Orthovoltage X-ray Minibeams (OXM). It segments the beam into an array of parallel, thin (~0.3 mm), planar beams, called minibeams, which are known from synchrotron x-ray experiments to spare tissues. Furthermore, the slight divergence of the OXM array make the individual minibeams gradually broaden, thus merging with their neighbors at a given tissue depth to produce a solid beam. In this way the proximal tissues, including the cerebral cortex, can be spared. Here we present experimental results with radiochromic films to characterize the method's dosimetry. Furthermore, we present our Monte Carlo simulation results for physical absorbed dose, and a first-order biologic model to predict tissue tolerance. In particular, a 220-kVp orthovoltage beam provides a 5-fold sharper lateral penumbra than a 6-MV x-ray beam. The method can be implemented in arc-scan, which may include volumetric-modulated arc therapy (VMAT). Finally, OXM's low beam energy makes it ideal for tumor-dose enhancement with contrast agents such as iodine or gold nanoparticles, and its low cost, portability, and small room-shielding requirements make it ideal for use in the low-and-middle-income countries.

Right heart failure after left ventricular assist device implantation in patients with chronic congestive heart failure.

BACKGROUND: Right heart failure (RHF) is not an infrequent complication of left ventricular assist device (LVAD) implantation. Few studies have examined outcomes for LVAD patients who subsequently develop RHF. This study details one center's experience with RHF in chronic congestive heart failure (CHF) patients. METHODS: One hundred eight patients with chronic CHF (>or=6 months) who underwent HeartMate LVAD implantation were identified during June 1996 to July 2004. Acute heart failure patients requiring LVADs were excluded to eliminate the impact of confounding non-cardiac factors. RHF was defined as the need for a subsequent right ventricular assist device (RVAD), >or=14 days of intravenous inotropes/pulmonary vasodilators, or both. Forty-two (38.9%) RHF patients were identified. Fourteen of these required RVAD insertion. Outcome parameters included early (

Intrathoracic pressure regulator during continuous-chest-compression advanced cardiac resuscitation improves vital organ perfusion pressures in a porcine model of cardiac arrest.

BACKGROUND: A novel device, the intrathoracic pressure regulator (ITPR), combines an inspiratory impedance threshold device (ITD) with a vacuum source for the generation of controlled -10 mm Hg vacuum in the trachea during cardiopulmonary resuscitation (CPR) while allowing positive pressure ventilation. Compared with standard (STD) CPR, ITPR-CPR will enhance venous return, systemic arterial pressure, and vital organ perfusion in both porcine models of ventricular fibrillation and hypovolemic cardiac arrest. METHODS AND RESULTS: In protocol 1, 20 pigs (weight, 30+/-0.5 kg) were randomized to STD-CPR or ITPR-CPR. After 8 minutes of untreated ventricular fibrillation, CPR was performed for 6 minutes at 100 compressions per minute and positive pressure ventilation (100% O2) with a compression-to-ventilation ratio of 15:2. In protocol 2, 6 animals were bled 50% of their blood volume. After 4 minutes of untreated ventricular fibrillation, interventions were performed for 2 minutes with STD-CPR and 2 minutes of ITPR-CPR. This sequence was repeated. In protocol 3, 6 animals after 8 minutes of untreated VF were treated with ITPR-CPR for 15 minutes, and arterial and venous blood gases were collected at baseline and minutes 5, 10, and 15 of CPR. A newer, leak-proof ITPR device was used. Aortic, right atrial, endotracheal pressure, intracranial pressure, and end-tidal CO2 values were measured (mm Hg); common carotid arterial flow also was measured (mL/min). Coronary perfusion pressure (diastolic; aortic minus right atrial pressure) and cerebral perfusion pressure (mean arterial minus mean intracranial pressure) were calculated. Unpaired Student t test and Friedman's repeated-measures ANOVA of ranks were used in protocols 1 and 3. A 2-tailed Wilcoxon signed-rank test was used for analysis in protocol 2. Fischer's exact test was used for survival. Significance was set at P<0.05. Vital organ perfusion pressures and end-tidal CO2 were significantly improved with ITPR-CPR in both protocols. In protocol 1, 1-hour survival was 100% with ITPR-CPR and 10% with STD-CPR (P=0.001). Arterial blood pH was significantly lower and Paco2 was significantly higher with ITPR-CPR in protocol 1. Arterial oxygen saturation was 100% throughout the study in both protocols. Paco2 and Pao2 remained stable, but metabolic acidosis progressed, as expected, throughout the 15 minutes of CPR in protocol 3. CONCLUSIONS: Compared with STD-CPR, use of ITPR-CPR improved hemodynamics and short-term survival rates after cardiac arrest.

Simplified placement of multiple artificial mitral valve chords.

BACKGROUND: The use of artificial chords for the replacement of diseased mitral valve chordae and the correction of anterior and posterior leaflet prolapse is well described, although it is infrequently applied because of technical challenges. METHODS: A simplified approach to attaching the new chords to a single papillary muscle base within the left ventricle has been reported, and we present a series of 13 patients with moderate-severe mitral regurgitation (MR) who underwent chordal replacement using this improved technique. RESULTS: The MR grade by echocardiogram improved from 3.7 +/- 0.4 preoperatively to 1.0 +/- 0.8 postoperatively. All patients were doing well at a mean follow-up interval of 285 +/- 62 days. CONCLUSION: Chordal replacement for both anterior and posterior leaflet prolapse is an effective treatment for MR when combined with standard mitral valve repair techniques. The authors' technique of determining proper chordal height and placing multiple chordae is also discussed.