SU-E-T-94: Multileaf Collimator Performance and Validation of Quality Control Tolerances.

PURPOSE: The automated quality assurance system (AQUA) is a centralized quality control (QC) software designed to automate QC tests. Statistical analysis of AQUA results was performed to assess the geometric accuracy and long-term reproducibility of a commercially available multileaf collimator (MLC) and examine the applicability of the American Association of Physicists in Medicine (AAPM) tolerances for MLC QC. METHODS: The MLC was first calibrated with AQUA by minimizing leaf-positioning errors on megavoltage images for 5 different leaf-bank positions (-60 to 100 mm from radiation isocenter). Leaf-positioning accuracy and reproducibility was assessed by repeating the AQUA test 5 times/week. The range of leaf-positioning error over leaf-bank positions and time was reported. Measured leaf-positioning errors were then separated into systematic and random error components. The systematic error corresponds to the variation (standard deviation) in mean positioning errors between leaves over leaf-bank positions and time. The random error quantifies the leaf position variations around its mean and is calculated as the root-mean-square of the individual leaf position standard deviations. RESULTS: To date, 2 different MLCs have been calibrated using AQUA and 9-18 datasets have been acquired to assess performance. For the unit with the longest follow up, the range of leaf-positioning errors was -0.62 to 0.85 mm and 98% of the measured leaf positions (n=7200) were within ±0.5 mm of the nominal position. The systematic error was the main error component (±0.15 to ±0.2 mm) and was attributed to the residual errors after calibration. The random error was ±0.07 mm for both units and demonstrated good leaf-positioning reproducibility and limited uncertainty of the AQUA measurements. CONCLUSIONS: Preliminary results show that after MLC calibration with AQUA, leaf-positioning errors on two different units are well within the AAPM-recommended ±1 mm tolerances. Additional MLC performance improvement is possible if residual errors after calibration can be reduced further as the MLC demonstrated high reproducibility. Funded in part by Elekta Inc.

Acute Effects of Acu-TENS on FEV1 and Blood Β-endorphin Level in Chronic Obstructive Pulmonary Disease.

Background Pharmacotherapy is the mainstay of dyspnea management in patients with chronic obstructive pulmonary disease (COPD). Undesirable side effects have led to the application of alternative treatment strategies such as acupuncture. Our previous study showed that transcutaneous electrical nerve stimulation over acupuncture points (Acu-TENS), a noninvasive modality, can reduce dyspnea symptoms in patients with COPD, but the underlying mechanism is unknown. Primary Study Objective This study investigated the effect of acu-TENS on forced expiratory volume in one second (FEV1), dyspnea, and Β-endorphin levels in patients with COPD. Design A double-blinded randomized controlled trial Setting: Hospital outpatient clinic Participants Forty-four subjects diagnosed with COPD Intervention Participants were randomly assigned to receive either acu-TENS or placebo-TENS on Dingchuan (EX-B1) for 45 minutes. Outcome Measures FEV1, forced vital capacity (FVC), dyspnea visual analogue score (DVAS), respiratory rate (RR), and blood Β-endorphin levels were measured before and after therapeutic intervention. Results Our findings showed that the increase in FEV1 was 24.2% greater in the acu-TENS group than the placebo group (P < .0001). The decrease in RR and DVAS was also more in the acu-TENS group by 14.2% (P < .0001) and 20.7% (P = .006), respectively. The postintervention increase in Β-endorphin was significantly higher in the acu-TENS than the placebo group (18.3%) (P = .027). Furthermore, the percentage reduction in RR correlated with the increase in Β-endorphin (R = -0.477, P = .033). Conclusion An improvement in FEV1 and dyspnea score at the end of Acu-TENS treatment was associated with a concurrent increase in b-endorphin level in patients with COPD.

Single-shot soft x-ray laser-induced ablative microstructuring of organic polymer with demagnifying projection.

We report on a single-shot micropatterning of an organic polymer achieved by ablation with demagnifying projection using a Ne-like Zn 21.2 nm soft x-ray laser. A nickel mesh with a period of 100 microm was approximately 10x demagnified and imprinted on poly(methyl methacrylate) via direct ablation. The quality of the ablated microstructure was found to be mainly dependent on the quality of the projected mask. This first demonstration (to our knowledge) of single-shot projection, single-step lithography illustrates the potential of soft x-ray lasers for the direct patterning of materials with a resolution scalable down to submicrometer domain.

Laser-ablation rates measured using x-ray laser transmission.

The rate of laser ablation at irradiances of approximately 2 x 10{14} W cm{-2} of solid iron has been measured using the transmission of a neonlike zinc x-ray laser at 21.2 nm through thin iron targets. Ablated iron becomes transparent to the x-ray laser flux, enabling the thickness of unablated material and hence the rate of ablation to be measured from time resolved x-ray laser transmission.

Hugoniot data of plastic foams obtained from laser-driven shocks.

In this paper we present Hugoniot data for plastic foams obtained with laser-driven shocks. Relative equation-of-state data for foams were obtained using Al as a reference material. The diagnostics consisted in the detection of shock breakout from double layer Al/foam targets. The foams [poly(4-methyl-1-pentene) with density 130 > rho > 60 mg/cm3] were produced at the Institute of Laser Engineering of Osaka University. The experiment was performed using the Prague PALS iodine laser working at 0.44 microm wavelength and irradiances up to a few 10(14) W/cm2. Pressures as high as 3.6 Mbar (previously unreached for such low-density materials) where generated in the foams. Samples with four different values of initial density were used, in order to explore a wider region of the phase diagram. Shock acceleration when the shock crosses the Al/foam interface was also measured.

Teaching palliative care principles to UK nursing home care assistants.

This paper describes the initiatives that led to a study day for Health Care Assistants in the UK, focusing on the principles and practice of palliative care for practitioners. Topics covered were 'What is palliative care?', 'How can you help patients with pain', 'Needs of the dying patient', 'I don't know what to say', 'Answering awkward questions', and 'Ways of relieving distressing symptoms'. Participants valued the study day and feedback showed that the Health Care Assistants, essentially assistants to qualified nursing staff with minimal or no training themselves, had many vocational and emotional needs that were not being met.

Buffered versus plain lidocaine for digital nerve blocks.

STUDY OBJECTIVES: To test whether buffered lidocaine is less painful to administer as a digital nerve block than plain lidocaine. DESIGN: Randomized, double-blind, prospective clinical trial. SETTING: University hospital emergency department. PARTICIPANTS: Adults not allergic to lidocaine requiring a digital nerve block. INTERVENTIONS: Subjects received digital nerve blocks by injection of buffered lidocaine on one side and plain lidocaine on the other in a predetermined, randomized order. Pain of infiltration was assessed. Scores were compared using a two-tailed t-test. Standard 1% lidocaine was used if additional anesthetic was required. MEASUREMENTS AND MAIN RESULTS: Thirty-one patients were enrolled. Buffered lidocaine was significantly less painful to administer than plain lidocaine (P < .001; t = 4.21). Supplemental anesthesia was required less often for buffered lidocaine (two times) compared with plain lidocaine (six times), although this difference was not statistically significant. CONCLUSION: Because it causes less pain and is equally efficacious, buffered lidocaine is preferable to plain lidocaine for digital nerve blocks in adults.

Buffered lidocaine as a local anesthetic: an investigation of shelf life.

STUDY OBJECTIVE: To determine whether buffered lidocaine must be prepared just before use. DESIGN: Randomized, double-blind, prospective trial. SETTING: University hospital. PARTICIPANTS: Twenty-four adult volunteers. INTERVENTIONS: Three buffered lidocaine solutions prepared seven days, one day, and just before use were compared with a control solution. Subjects received 0.5 mL intradermal injections of each solution. Pain of infiltration and extent and duration of anesthesia were measured. MEASUREMENTS AND MAIN RESULTS: Pain of infiltration was less with all buffered solutions than control (P less than .0001). Mean maximum diameter of anesthesia ranged from 29 to 33 mm for the buffered solutions compared with 31 mm for control. Mean duration of anesthesia was 33 minutes for control and 30 minutes for all of the buffered solutions. There was no statistically significant difference in extent or duration of anesthesia for any of the solutions (P greater than .5, beta = .15 for delta = 10%). CONCLUSION: Buffered lidocaine stays effective for up to one week after preparation. It is therefore convenient to use in emergency settings.

Automated vitrectomy in eyes with vitreocorneal touch associated with corneal dysfunction.

Of the results evaluated in 17 patients who had vitrectomy for aphakic vitreocorneal touch associated with corneal edema, nine patients had satisfactory results. Factors associated with a favorable outcome were as follows: (1) early vitrectomy; (2) previtrectomy visual acuity better than 6/120 (20/400); (3) uncomplicated cataract operation and postoperative course, and (4) broken rather than intact hyaloid face. Postoperative cystoid macular edema contributed to decreased visual acuity in eight of 12 patients.

Penetration of gentamicin into the aphakic eye.

The penetration of gentamicin is compared in the aphakic and phakic rabbit eye. Phakic and aphakic rabbits were treated with gentamicin by topical, subconjunctival, and intramuscular routes separately and in combination. These routes of therapy also were evaluated in aphakic eyes with experimentally induced endophthalmitis. The levels of gentamicin were, for the most part, higher in the aphakic, as opposed to the phakic eyes. Combination therapy produced higher levels in the noninfected than in the infected eyes. Aqueous levels were generally bactericidal by topical and subconjunctival routes. Levels in the vitreous by the routes of therapy employed in this study were at best inhibitory for the more virulent organisms.

Penetration of amikacin into the aphakic eye.

An experiment was designed to see if an aminoglycoside antibiotic, amikacin, would penetrate the vitreous of rabbits in greater concentrations in the postoperative aphakic eye than in the normal eye. Phakic and aphakic eyes were treated with amikacin by topical, subconjunctival, and intramuscular methods separately and combined. Bioassays of aqueous, anterior vitreous, and posterior vitreous revealed that concentrations of amikacin in ocular fluids after intramuscular administration were greater in the aphakic eye as compared to the normal eye; however, concentrations in the vitreous did not reach reliably bactericidal concentrations even when all three methods of administration were combined.

Full-thickness eye wall biopsy. II. In primates.

We devised a technique to perform an intact full-thickness eye wall biopsy in primates. An eye basket is sutured to the eye wall for stabilization. Trephines demarcate and incise a 4 to 7 mm. circumferential area of sclera; diathermy deepens the incision until perforation is achieved. The biopsy specimen is removed and immediately fixed for histologic evaluation, and the eye wall defect is covered by a 7 mm. scleral homograft. Our results showed that histologically excellent biopsies can be obtained with minimal damage to the eye.

The vitrophage in ocular trauma. Report of 15 cases.

Fifteen patients underwent a pars plana approach vitrectomy and membranectomy after acute and chronic injury. In all cases the lens fragments, hemorrhage, and secondary membranes were removed restoring clarity to the ocular media. In two cases the final visual acuity was limited by preexisting retinal injury. The advantages of pars plana approach are the small incision and minimal ocular manipulation during surgery. In the presence of retinal injury, diathermy during the procedure or photocoagulation within 24 hours is also indicated.

Intravitreal injection of vancomycin in experimental staphylococcal endophthalmitis.

Toxicity, clearance, and therapeutic effectiveness of intravitreal vancomycin hydrochloride injection in experimentally induced staphylococcal endophthalmitis were evaluated. Vancomycin was found to be nontoxic in a single, 1 mg/0.1 ml intravitreal dose. Therapeutic levels of vancomycin were present in the vitreous for over 72 hours and in the aqueous during a period from 6 to 48 hours after injection. Injection of a methicillin-resistant Staphylococcus aureus produced a panophthalmitis in our systemically treated controls, whereas in the rabbits treated by intraocular injection, the course of the infection was significantly altered.