Feasibility of real-time motion management with helical tomotherapy.

PURPOSE: This study investigates the potential application of image-based motion tracking and real-time motion correction to a helical tomotherapy system. METHODS: A kV x-ray imaging system was added to a helical tomotherapy system, mounted 90 degrees offset from the MV treatment beam, and an optical camera system was mounted above the foot of the couch. This experimental system tracks target motion by acquiring an x-ray image every few seconds during gantry rotation. For respiratory (periodic) motion, software correlates internal target positions visible in the x-ray images with marker positions detected continuously by the camera, and generates an internal-external correlation model to continuously determine the target position in three-dimensions (3D). Motion correction is performed by continuously updating jaw positions and MLC leaf patterns to reshape (effectively re-pointing) the treatment beam to follow the 3D target motion. For motion due to processes other than respiration (e.g., digestion), no correlation model is used - instead, target tracking is achieved with the periodically acquired x-ray images, without correlating with a continuous camera signal. RESULTS: The system's ability to correct for respiratory motion was demonstrated using a helical treatment plan delivered to a small (10 mm diameter) target. The phantom was moved following a breathing trace with an amplitude of 15 mm. Film measurements of delivered dose without motion, with motion, and with motion correction were acquired. Without motion correction, dose differences within the target of up to 30% were observed. With motion correction enabled, dose differences in the moving target were less than 2%. Nonrespiratory system performance was demonstrated using a helical treatment plan for a 55 mm diameter target following a prostate motion trace with up to 14 mm of motion. Without motion correction, dose differences up to 16% and shifts of greater than 5 mm were observed. Motion correction reduced these to less than a 6% dose difference and shifts of less than 2 mm. CONCLUSIONS: Real-time motion tracking and correction is technically feasible on a helical tomotherapy system. In one experiment, dose differences due to respiratory motion were greatly reduced. Dose differences due to nonrespiratory motion were also reduced, although not as much as in the respiratory case due to less frequent tracking updates. In both cases, beam-on time was not increased by motion correction, since the system tracks and corrects for motion simultaneously with treatment delivery.

Robust energy transfer mechanism via precession resonance in nonlinear turbulent wave systems.

A robust energy transfer mechanism is found in nonlinear wave systems, which favors transfers toward modes interacting via triads with nonzero frequency mismatch, applicable in meteorology, nonlinear optics and plasma wave turbulence. We emphasize the concepts of truly dynamical degrees of freedom and triad precession. Transfer efficiency is maximal when the triads' precession frequencies resonate with the system's nonlinear frequencies, leading to a collective state of synchronized triads with strong turbulent cascades at intermediate nonlinearity. Numerical simulations confirm analytical predictions.

High-dose MVCT image guidance for stereotactic body radiation therapy.

PURPOSE: Stereotactic body radiation therapy (SBRT) is a potent treatment for early stage primary and limited metastatic disease. Accurate tumor localization is essential to administer SBRT safely and effectively. Tomotherapy combines helical IMRT with onboard megavoltage CT (MVCT) imaging and is well suited for SBRT; however, MVCT results in reduced soft tissue contrast and increased image noise compared with kilovoltage CT. The goal of this work was to investigate the use of increased imaging doses on a clinical tomotherapy machine to improve image quality for SBRT image guidance. METHODS: Two nonstandard, high-dose imaging modes were created on a tomotherapy machine by increasing the linear accelerator (LINAC) pulse rate from the nominal setting of 80 Hz, to 160 Hz and 300 Hz, respectively. Weighted CT dose indexes (wCTDIs) were measured for the standard, medium, and high-dose modes in a 30 cm solid water phantom using a calibrated A1SL ion chamber. Image quality was assessed from scans of a customized image quality phantom. Metrics evaluated include: contrast-to-noise ratios (CNRs), high-contrast spatial resolution, image uniformity, and percent image noise. In addition, two patients receiving SBRT were localized using high-dose MVCT scans. Raw detector data collected after each scan were used to reconstruct standard-dose images for comparison. RESULTS: MVCT scans acquired using a pitch of 1.0 resulted in wCTDI values of 2.2, 4.7, and 8.5 cGy for the standard, medium, and high-dose modes respectively. CNR values for both low and high-contrast materials were found to increase with the square root of dose. Axial high-contrast spatial resolution was comparable for all imaging modes at 0.5 lp∕mm. Image uniformity was improved and percent noise decreased as the imaging dose increased. Similar improvements in image quality were observed in patient images, with decreases in image noise being the most notable. CONCLUSIONS: High-dose imaging modes are made possible on a clinical tomotherapy machine by increasing the LINAC pulse rate. Increasing the imaging dose results in increased CNRs; making it easier to distinguish the boundaries of low contrast objects. The imaging dose levels observed in this work are considered acceptable at our institution for SBRT treatments delivered in 3-5 fractions.

Building a statewide clinical trials network for cancer care in West Virginia.

In the United States, mortality rates have been declining for certain tumors, For the majority of advanced stage cancer types, cure is unattainable but treatment is still evolving. Advances in the treatment of cancer can be achieved by enrolling patients in cancer clinical trials. Presently, less than 3% of adult cancer patients participate on clinical trials in the United States. Providing cancer care and access to clinical trials are a challenge in a rural state, with a dispersed population base, such as West Virginia. Building upon recognition of barriers to clinical trials awareness and access, oncology leaders in the state are in the formative stages of developing a statewide cancer clinical trials network. Realization of this network will have an enormous impact on cancer care in our state and perhaps can serve as a model for other community and physician teams for other diseases.

Comprehensive hospital care improvement strategies reduce time to treatment in ST-elevation acute myocardial infarction.

BACKGROUND: Delay in treatment of patients with ST-elevation acute myocardial infarction (STEMI) has an adverse effect on patient outcomes. Limited data are available on the effectiveness of hospital care improvement strategies (HCIS) to reduce time to reperfusion by percutaneous coronary intervention (PCI). This study evaluated the combined effect of HCIS implementation to reduce door-to-balloon time in patients with STEMI. METHODS: Retrospective chart review was done for 95 consecutive patients with STEMI who underwent PCI at Charleston Area Medical Center. Patients with non-STEMI and patients transferred from other medical centers were excluded. Door-to-balloon time was defined as time from emergency department arrival to first PCI balloon inflation. A program of 3 HCIS was implemented: 1) a fast-track catheterization laboratory protocol, 2) feedback to cardiologists on their treatment times, and 3) a weekday 24-hour inhouse catheterization laboratory team. Patients were separated into groups before (n = 46), during (n = 18), and after (n = 31) HCIS implementation. RESULTS: Mean age was 60.3 +/- 13 years and 74% were male. The majority (64%) arrived by ambulance; 29% had a prehospital electrocardiogram done. Most patients presented during the day (68%) on weekdays (75%). Symptom onset-to-door time was 289 +/- 393 minutes. No significant differences were found between the groups for these variables. Door-to-PCI time in minutes was reduced in the group after versus the group before HCIS implementation (94.3 +/- 37 vs 133.5 +/- 53; P < 0.0001). CONCLUSION: Implementation of HCIS shortened door-to-PCI time for patients with STEMI by 39.2 +/- 10 minutes. Thus, HCIS may be effective in improving patient outcomes.

Helical tomotherapy radiation leakage and shielding considerations.

Leakage radiation and room shielding considerations increase significantly for intensity-modulated radiation therapy (IMRT) treatments due to the increased beam-on time to deliver modulated fields. Tomotherapy, with its slice by slice approach to IMRT, further exacerbates this increase. Accordingly, additional shielding is used in tomotherapy machines to reduce unwanted radiation. The competing effects of the high modulation and the enhanced shielding were studied. The overall room leakage radiation levels are presented for the continuous gantry rotations, which are always used during treatments. The measured leakage at 4 m from the isocenter is less than 3 x 10(-4) relative to calibration output. Primary radiation exposure levels were investigated as well. The effect of forward-directed leakage through the beam-collimation system was studied, as this is the leakage dose the patient would receive in the course of a treatment. A 12-min treatment was calculated to produce only 1% patient leakage dose to the periphery region. Longer treatment times might yield less patient dose if the field width selected is correspondingly narrower. A method for estimating the worst-case leakage dose a patient would receive is presented.

Sarcoma primário de duodeno com diagnóstico endoscópico pré-operatório / Duodenal primary sarcoma diagnosed preoperatively by upper endoscopy: case report

Os sarcomas de duodeno sao incomuns e estao associados a diagnostico tardio e mau prognostico.O objetivo do presente relato é descrever um caso de sarcoma duodenal diagnosticado pro-operatoriamente atraves da endoscopia digestiva. um homem de 40 anos procurrou assistencia medica devido a sintomas de hemorragia digestiva alta e dor abdominal. A investigacao endoscopica revelou tumor invadindo a segunda porcao duodenal, local de onde foram colhidas biopcias. O diagnostico apos estudo imunohistoquimico foi de sarcoma de alto grau. Na laparotomia foi observado extenso tumor duodenal, com invasao de colon transverso e ausencia de metastases hepaticas ou peritoneais. foram realizadas gastroduodenopancreatectomia e colectomia, com retirada em bloco do tumor. O exame histopatologico confirmou o diagnostico. O paciente teve boa evolucao, sem complicacoes pos-operatorias

Traqueostomia à beira do leito na UTI: estudo prospectivo de 70 casos / Bedside tracheostomy in the intensive care unit: prospective study of 70 cases

A traqueostomia apresenta uma série de vantagens em relação à entubação endotraqueal prolongada: conforto e maior possibilidade de comunicação para o paciente, diminuição da resistência respiratória, melhor controle de via aérea e facilidade de aspiração. No período de setembro de 1996 a dezembro de 1997 foram realizadas setenta traqueostomias à beira de leito na UTI, sob anestesia local, com tempo operatório médio de 30,5 minutos. A principal indicação foi ventilação mecânica prolongada, com uma média de 6,5 dias. Os pacientes foram acompanhados durante a internação por 1.494 dias. No terceiro dia de pós-operatório foi colhida cultura de secreção traqueal em 49 pacientes, predominando Pseudomonas aeruginosa em 40,8 por cento dos casos. Houve ll casos (15,7 por cento) de complicações maiores: uma fístula traqueoesofágica, uma fasciíte necrotizante, uma úlcera traqueal, duas infecções e seis sangramentos, que necessitaram reintervenção. Um óbito foi relacionado ao procedimento, devido à fasciíte necrotizante cervical. Tendo em vista a gravidade dos pacientes, a traqueostomia à beira de leito demonstrou ser um procedimento seguro e com baixo índice de complicações maiores. Além disso, evita o transporte de doente crítico dentro do hospital, e os custos são menores do que a traqueostomia no centro cirúrgico