Target Prescription Research Articles

Dose Coverage Beyond the Gross Tumor Volume for Various Stereotactic Body Radiotherapy Planning Techniques Reporting Similar Control Rates for Stage I Non–Small-Cell Lung Cancer

To investigate the dose falloff region for various stereotactic body radiotherapy (SBRT) planning techniques used in the treatment of Stage I non-small-cell lung cancer reporting similar control rates. The SBRT plans were constructed on five patient data sets using seven different planning regimens. These regimens varied in the number of beams, number of fractions, prescription target, and prescribed dose used. For each case all regimens were planned using a common gross tumor volume (GTV). To compare dose falloff for the various regimens, resulting physical dose grids were converted into normalized total dose (NTD) grids. Furthermore, to determine the potential coverage of microscopic extension of the various regimens minimal peripheral NTD (NTD-MP(100)) were calculated and plotted as a function of incremental volume expansions of the GTV. Average values for NTD-MP(100) varied over a range of 174 Gy at the GTV periphery, but this range fell to 10 Gy at a distance of 14 mm from the GTV. Of 35 plans, 23 resulted in potential microscopic extension coverage of 78% to 95%. Averages for five of seven regimens fell within the range of 80% to 85%. Results were negligibly affected when intrafraction motion effects were accounted for. Although average NTD-MP(100) varied dramatically at the GTV, periphery values became similar at a distance of 14 mm from the GTV. With the exception of two, potential coverage of microscopic extension was similar for all planning techniques, with averages falling within a 5% range.

A comparison of manufacturer-specific prescriptive procedures for infants

Early hearing detection and communication development (EHDCD) programs enable us to identify hearing loss in early infancy, making intervention by 6 months of age a reasonable goal. For infants and children fitted with hearing instruments, it is critical that the devices be adjusted appropriately so that the pre-lingual listener has full and consistent access to sound, without discomfort for loud sounds. Several published pediatric amplification guidelines are available to assist clinicians with the hearing aid fitting process for infants and children.1-5 While the guidelines were developed in different jurisdictions, similar recommendations are made for all stages of the hearing instrument fitting process. For example, the use of a systematic, evidence-based approach to hearing aid fitting that accounts for an infant’s external ear acoustics at the assessment, selection, and verification stages and that includes the measurement of hearing aid output limiting is a requirement of every current pediatric amplification protocol. While it is encouraging to see consensus in pediatric hearing aid fitting guidelines, there continue to be substantial differences among clinical practice behaviors. Surveys have indicated that the majority of pediatric audiologists use sound field-aided threshold measures to verify the electroacoustic performance of hearing instruments for young infants.6 Probe-microphone measures were used by roughly 20% of the audiologists fitting hearing aids to infants.6 It has been well-documented that behavioral measures (i.e., aided threshold measures) do not provide accurate estimates of the aided audibility of soft, average, and loud speech or the real-ear saturation response of the hearing aid and that infants 6 months of age and younger are not developmentally capable of performing this task.7,8 Failure to appropriately verify the electroacoustic performance of the hearing aid in terms of predicted speech audibility and maximum hearing instrument output can result in obstructing the language benefits an infant would have otherwise received from being identified at an early age and optimally fitted. It is also important to consider the prescriptive targets used to determine the recommended levels for amplified speech and target limits for hearing instrument output as a function of frequency. Prescriptive algorithms provide the foundation on which the hearing instrument performance characteristics are selected for the infant or child to be fitted. Recent survey data indicate that most audiologists fitting hearing aids to infants and young children use a published hearing aid prescriptive procedure.6,9 At present, prescriptive procedures can be divided into two classifications: (1) evidence-based generic prescriptive algorithms and (2) manufacturer-specific proprietary algorithms. Evidence-based generic prescriptive algorithms for children include the DSL m[i/o]10 and the NAL-NL1,11 both of which are intended for use with any hearing aid. Proprietary prescriptive methods incorporate prescriptive algorithms developed by manufacturers for use with their specific hearing instruments. The lack of published information regarding the development of pediatric manufacturer-specific proprietary algorithms makes it difficult for the audiologist to make an informed choice about which procedure will be best for their young patient.12 Some manufacturers have decided to forego the development of a proprietary pediatric algorithm and use either the NAL or DSL prescriptive algorithms for fitting children and have implemented these formulas in their fitting software. These generic prescriptive algorithms may have been adapted by the manufacturer to account for the unique characteristics (e.g., compression kneepoint) of their hearing aids. Several investigators have compared proprietary prescriptive algorithms for use with adults. Keidser and colleagues found a 10-dB variation in the amount of gain prescribed by NAL-NL1, DSL[i/o], and four proprietary algorithms for the same audiogram.12 A study by Hawkins and Cook compared simulated 2-cc versus actual 2-cc gain as well as simulated insertion versus actual insertion gain measures from the fitting software for 28 hearing aids of various styles from four major manufacturers.13 Results indicated a clear trend for the simulated values to overestimate what was actually provided by the hearing aids for both the 2-cc coupler and insertion gain comparisons.13 Differences of as much as 10 to 20 dB were noted for the various hearing aids and prescriptive algorithms in the study. “...an infant can end up with

Using Trainable Hearing Aids to Examine Real-World Preferred Gain

While there have been many studies of real-world preferred hearing aid gain, few data are available from participants using hearing aids with today's special features activated. Moreover, only limited data have been collected regarding preferred gain for individuals using trainable hearing aids. To determine whether real-world preferred hearing aid gain with trainable modern hearing aids is in agreement with previous work in this area, and to determine whether the starting programmed gain setting influences preferred gain outcome. An experimental crossover study. Participants were randomly assigned to one of two treatment groups. Following initial treatment, each subject crossed to the opposite group and experienced that treatment. Twenty-two adults with downward sloping sensorineural hearing loss served as participants (mean age 64.5; 16 males, 6 females). All were experienced users of bilateral amplification. Using a crossover design, participants were fitted to two different prescriptive gain conditions: VC (volume control) start-up 6 dB above NAL-NL1 (National Acoustic Laboratories-Non-linear 1) target or VC start-up 6 dB below NAL-NL1 target. The hearing aids were used in a 10 to 14 day field trial for each condition, and using the VC, the participants could "train" the overall hearing aid gain to their preferred level. During the field trial, daily hearing aid use was logged, as well as the listening situations experienced by the listeners based on the hearing instrument's acoustic scene analysis. The participants completed a questionnaire at the start and end of each field trial in which they rated loudness perceptions and their satisfaction with aided loudness levels. Because several participants potentially experienced floor or ceiling effects for the range of trainable gain, the majority of the statistical analysis was conducted using 12 of the 22 participants. For both VC-start conditions, the trained preferred gain differed significantly from the NAL-NL1 prescriptive targets. More importantly, the initial start-up gain significantly influenced the trained gain; the mean preferred gain for the +6 dB start condition was approximately 9 dB higher than the preferred gain for the -6 dB start condition, and this difference was statistically significant (p < .001). Partial eta squared (n2) = 0.919, which is a large effect size. Deviation from the NAL-NL1 target was not significantly influenced by the time spent in different listening environments, amount of hearing aid use during the trial period, or amount of hearing loss. Questionnaire data showed more appropriate ratings for loudness and higher satisfaction with loudness for the 6 dB below target VC-start condition. When trainable hearing aids are used, the initial programmed gain of hearing instruments can influence preferred gain in the real world.

Multichannel Compression Hearing Aids: Perceptual Considerations

Multichannel Compression Hearing Aids: Perceptual Considerations

User Preference and Reliability of Bilateral Hearing Aid Gain Adjustments

The purpose of the current study was to evaluate the consistency and reliability of user adjustments to hearing aid gain and the resulting effects on speech understanding. Sixteen bilaterally aided individuals with hearing loss adjusted their hearing aid gain to optimize listening comfort and speech clarity while listening to speech in quiet and noisy backgrounds. Following these adjustments, participants readjusted their aids to optimize clarity and comfort while listening to speech in quiet. These final gain settings were recorded and compared to those provided by NAL-NL1 prescriptive targets. In addition, speech understanding was tested with the hearing aids set at target and user gain settings. Performance differences between the gain settings were then assessed. Study results revealed that although some listeners preferred more or less gain than prescribed, on average, user and prescribed gain settings were similar in both ears. Some individuals, however, made gain adjustments between ears resulting in "gain mismatches." These "mismatches" were often inconsistent across trials suggesting that these adjustments were unreliable. Speech testing results, however, showed no significant difference across the different gain settings suggesting that the gain deviations introduced in this study were not large enough to significantly affect speech understanding.

Hearing Aid Maximum Output and Loudness Discomfort: Are Unaided Loudness Measures Needed?

The purpose of this study was to evaluate a clinical protocol for setting hearing aid maximum output (MPO) in adult users. The protocol consisted of matching prescriptive targets for MPO followed by aided loudness validation and adjustment. Twenty-eight adults fit with multichannel hearing aids during the previous two years were recalled for unaided loudness measures. During the recall visit, unaided frequency-specific loudness discomfort levels were measured for frequencies between 250 and 3000 Hz. These values were converted to real-ear levels by adding individually measured real-ear dial differences. Real-ear saturation responses (RESR) were measured using a 90 dB pure-tone sweep and compared to the real-ear loudness discomfort levels. All participants completed the APHAB Aversiveness scale and Munro-Patel loudness questionnaire. A subset of participants (n = 20) completed the Profile of Aided Loudness. The average RESR-UCL difference was -5.7 dB, and the maximum difference was 15 dB. For all but one participant, the average RESR values (.5-3 kHz) were either less than or no more than 5 dB above the LDLs, and the aided APHAB Aversiveness scores were below the 80th percentile. There were no significant correlations between the scores on the loudness questionnaires and the differences between RESR and LDL values. Results suggest that unaided LDL measures may be redundant if aided loudness validation measures are completed.

Risk Criteria for the Shipping Industry

AbstractThis paper proposes dual risk criteria for the shipping industry based on a goal‐setting approach to safety requiring risk in the tolerability region to be as low as reasonably practicable (ALARP) within which there is a prescriptive target risk level which should not be reached. The prescriptive target risk level is intended for smaller companies satisfying the current safety and classification rules, while it is expected that leading companies would embrace the dynamic ALARP approach as a means for improving the current practice in a search for a better and more economical solution. Furthermore, it is shown that it is possible to formulate the societal risk criteria fully consistent with often legally imposed individual risk criteria. Copyright © 2006 John Wiley &amp; Sons, Ltd.

Amplification for Infants

Amplification for Infants

Probe microphone measurements: 20 years of progress.

Probe microphone measurements: 20 years of progress.

A replicable, non-programmed, instrument-free method for the control of stuttering with prolonged speech

Abstract Recent research has challenged some assumptions upon which many prolonged speech programmes are based. This paper presents preliminary data from a new programme designed to redress this situation. The new programme operates without any of the following procedures: (1) a multiday, intensive treatment format; (2) formal transfer procedures; (3) programmed instruction; (4) standardized, prescriptive prolonged speech target behaviours, and (5) instrumentation for the on-line counting of stuttering rate and speech rate. The latter procedures have been replaced by the use of a severity rating scale. Data are presented for the first three clients to reach the maintenance phase of the programme. All clients reduced stuttering to very low levels both within and beyond the clinic.

Preferred Listening Levels of Children Who Use Hearing Aids: Comparison to Prescriptive Targets

The preferred listening levels (PLLs) of children with sensorineural hearing loss were elicited using conversation-level speech, heard through the children's own hearing aids. All hearing aids were fitted using the desired sensation level (DSL) method. Comparisons were made between the PLL and targets from the following prescriptive formulae: DSL version 4.1 and two versions of the National Acoustic Laboratories (NAL) procedure, including NAL revised for severe-profound losses (NAL)-RP and NAL nonlinear NAL/NL1. Results for this sample of children indicated that the PLL was similar to the DSL targets, and that, on average, NAL-RP/NL1 targets recommended less gain than that preferred by the majority of children in this study. The implications of factors such as acclimatization, test levels, and clinical procedures on these results are discussed.

Accuracy of predicted ear canal speech levels using the VIOLA input/output-based fitting strategy.

The Visual Input/Output Locator Algorithm (VIOLA) is a software-assisted method for prescribing amplification targets and selecting a hearing aid to match the targets. Although the procedure calls for selection and fitting of hearing aids in terms of their pure-tone input/output functions in a coupler, it is assumed that a hearing aid that matches the coupler prescription targets will produce specific amplified speech levels in the patient's ear canal. This investigation evaluated the validity of that assumption. Six hearing aids were evaluated. They were representative of linear and compression processing as well as single- and 2-channel designs. The "subject" was a KEMAR manikin with realistic assumed hearing loss and loudness perception characteristics. Each hearing aid was configured to match the subject's VIOLA prescription as closely as possible. Predicted ear canal speech levels were determined using the prescription rules and modified by the differences between coupler prescription targets and coupler performance of the actual hearing aids. With the subject wearing each hearing aid coupled to an unvented earmold, continuous speech was presented in the sound field and measured, after amplification, in the ear canal. The match between observed and predicted levels of amplified speech indicated the validity of the VIOLA assumptions under examination. The match between predicted and observed levels was good for soft speech input levels. As speech input levels increased, the differences between observed and predicted levels also increased, with the largest differences seen for loud speech inputs. When differences were seen between observed and predicted levels, they were always in the direction of lower than predicted ear canal levels. The differences between observed and predicted levels were attributed to the effects of limiting, effects of compression ratio in wide range compression, the individual subject's field-to-microphone transfer function, and the subject's individual real-ear-to-coupler level difference. Ear canal speech levels were reasonably close to predicted values, and the deviations from predicted levels were plausibly accounted for by consideration of hearing aid performance. Thus, the approach used by the VIOLA procedure holds considerable promise for extending clinical control over the complex and interactive parameters of nonlinear hearing aids. The results of this study indicate that selection and fitting of hearing aids using the current VIOLA procedure usually will result in the generation of lower than predicted ear canal speech levels, especially for loud speech inputs. However, the accuracy of the procedure could be improved substantially by modification of the software to account for the effects of limiting and those of the compression ratio in systems with compression thresholds lower than the level of unamplified loud speech.

Programmable Telecoil Responses: Potential Advantages for Assistive Listening Device Fittings.

Ten experienced hearing aid users were tested to evaluate an assistive listening device inductively coupled to three different hearing aids-their own BTE hearing aid and associated telecoil, a programmable hearing aid with the telecoil programmed using the manufacturer's algorithm, and the same programmable hearing aid with the telecoil programmed so that the real-ear gain obtained with the hearing aid-assistive listening device combination matched a prescriptive target. Results indicated that modifying the telecoil response to match a prescriptive target can result in enhanced speech understanding and higher preference rankings.

Fitting Strategies for Multiple-Memory Programmable Hearing Instruments.

Fitting a multiple-memory programmable hearing instrument presents a new set of challenges to the dispenser, compared to conventional fittings. Rather than having to compromise on a single frequency-gain response (the prescriptive target), it is now possible to create a family of hearing aid responses from which the user can select an appropriate response for a given situation. This philosophy is also applicable in the prescription of compression characteristics. The flexibility designed into the 3M two-channel compression system allows the dispenser to program very different types of signal processing strategies (low frequency compression, high frequency compression, full spectrum compression, or linear processing) into a single instrument to match the requirements of different listening environments and to meet the needs of different users. Utilizing this approach, comfort, speech intelligibility, and sound quality can be optimized in a variety of situations by considering the listener's acoustic environment and the input signals to which the hearing aid must respond.