Calibration and measurement issues for therapeutic ultrasound

This review paper examines some of the issues relating to calibration and measurement of therapeutic medical ultrasonic equipment (MUE). This is not intended to be an all-encompassing review of all aspects of characterising therapeutic ultrasound. Instead it concentrates on issues related to the acoustic output of two applications: physiotherapy and high intensity focused ultrasound surgery (HIFUS or HIFU; also referred to as high intensity therapeutic ultrasound, HITU). Physiotherapy has a well-established standards infrastructure for calibration: the requirements are small in number and well-defined. The issue for physiotherapy is not so much 'How to calibrate?' but rather, 'How to ensure that equipment IS calibrated?' The situation in the much newer area of HIFU is very different: the first steps towards writing standards are just starting and even the very basic questions of what to measure and with what type of sensor are open for debate. Readers whose main interest is in other ultrasound therapies will find ideas of relevance to their own specialty.

A buoyancy method for the measurement of total ultrasound power generated by HIFU transducers

Total acoustic output power is a key parameter for most ultrasonic medical equipment and especially for high intensity focused ultrasound (HIFU) systems, which treat certain cancers and other conditions by the noninvasive thermal ablation of the affected tissue. In planar unfocused fields, the use of a radiation force balance has been considered the most accurate method of measuring ultrasound power. However, radiation force is not strictly dependent on the ultrasound power but, rather, on the wave momentum resolved in one direction. Consequently, measurements based on radiation force become progressively less accurate as the ultrasound wave deviates further from a true plane-wave. HIFU transducers can be very strongly focused with F-numbers less than one: under these conditions, the uncertainty associated with use of the radiation force method becomes very significant. In this article, a new method for determining power is described in detail. Instead of radiation force, the new method relies on measuring the change in buoyancy caused by thermal expansion of castor oil inside a target suspended in a water bath. The change in volume is proportional to the incident energy and is independent of focusing or the angle of incidence of the ultrasound. The principles and theory behind the new method are laid out and the characteristics and construction of an appropriate target are examined and the results of validation tests are presented. The uncertainties of the method are calculated to be approximately +/-3.4% in the current implementation, with the potential to reduce these further. The new technique has several important advantages over the radiation force method and offers the potential to be an alternative primary standard method.

Validation of a health literacy screening tool (REALM) in a UK population with coronary heart disease

BACKGROUND

Health literacy (HL) has been recognized as an important public health issue in other developed countries such as the US. There is currently no HL screening tool valid for use in the UK. This study aimed to validate a US-developed HL screening tool (the Rapid Estimate for Adult Literacy in Medicine; REALM) for use in the UK against the UK's general literacy screening tool (the Basic Skills Agency Initial Assessment Test, BSAIT).

METHODS

A cross-sectional survey involving 300 adult patients admitted to hospital for investigation of coronary heart disease were given the REALM and BSAIT tools to complete as well as specific questions considered likely to predict HL. These questions relate to the difficulty in understanding medical information, medical forms or instructions on tablets, frequency of reading books and whether the participant's job involves reading.

RESULTS

The REALM was significantly correlated with the BSAIT (r = 0.70; P < 0.001), and significantly related to seven of the eight questions likely to be predictive of HL.

CONCLUSIONS

This study has shown that the REALM has face, criterion and construct validity for use as an HL screening tool in the UK, in research and in everyday clinical practice. Further studies are needed to assess the prevalence of low HL in a wider population and to explore the links that may exist between low HL and poor health in the UK.

Pharmacologic approaches for volume excess in acute kidney injury (AKI)

Volume management is an integral component of the care of patients with acute kidney injury (AKI). Considerable controversy exists regarding the use of pharmacological agents for volume management. Although overt fluid overload is often seen in AKI and may prompt attention for the use of diuretics, often these agents are used in the absence of fluid retention. Over the last decade several new agents have become available for volume removal. We reviewed the literature on this topic and addressed four key questions for the appropriate utilization of these agents. These include the drug targets and mechanism of action of available agents; clinical goals and criteria for timing of intervention; adaptation of therapy for specific clinical settings and measures required for monitoring effectiveness and patient safety. This report details our current knowledge in this area, provides evidence-based clinical practice recommendations where appropriate, and formulates a research agenda to address unanswered questions.

Large bowel obstruction and perforation secondary to endometriosis complicated by a ventriculoperitoneal shunt

A 36-year-old lady, with a past medical history of hydrocephalus requiring a ventriculoperitoneal (VP) shunt, was admitted with symptoms and signs of large bowel obstruction. Her condition worsened and she underwent laparotomy, where she had faecal peritonitis secondary to a perforated sigmoid colon. The shunt was contaminated with faeces leading to postoperative shunt infection and meningitis. Histology of the resected sigmoid colon revealed endometriosis at the site of perforation. Endometriosis is a rare cause of large bowel obstruction and literature review has found only two other cases of perforation because of endometriosis not associated with pregnancy. No case has been reported involving the concurrent surgical management of a contaminated VP shunt. We discuss the rarity of large bowel perforation and obstruction because of endometriosis, and the complications and management of VP shunts.

Capturing the value of complementary and alternative medicine: including patient preferences in economic evaluation

Complementary and alternative medicine (CAM) is growing in popularity among patients, for an increasing range of conditions. However, current provision of CAM in the National Health Service in the UK is limited, patchy and disparate, which results in considerable inequity and patient unease. This has led to an escalation in the debate about the role of CAM within the NHS. Lack of evidence about the cost effectiveness of CAM therapies compared with other forms of care is often cited as the main reason for the reluctance of funders to integrate CAM into mainstream service provision. Cost-effectiveness relies on evidence about costs and benefits. Cost data are relatively straightforward to collect but it has proved difficult to value the complete package of benefits offered by CAM, likely to be both process and outcome based, in a way that can be compared with alternatives. Stated preference discrete choice modelling (SPDCM), a method of healthcare evaluation growing in popularity, uses information about patient preferences to identify the important characteristics of an intervention or method of delivering care and how patients value these. SPDCM is a method that could be used to evaluate the 'added value' provided by CAM and thus supply evidence on cost-effectiveness that policy makers could use in configuring service provision.

GPs' experiences of primary care mental health research: a qualitative study of the barriers to recruitment

OBJECTIVE

To investigate the perceived barriers among GPs towards introducing participation in randomized controlled trials (RCTs) to patients presenting with depression during consultations.

METHODS

Qualitative study using semi-structured interviews. Interviews were recorded using a digital voice recorder, transcribed verbatim and analysed using the Framework Approach. The participants were 41 GPs from five primary care trusts in the South West who were collaborating with the University of Bristol on an RCT recruiting patients with depression.

RESULTS

Three themes were identified: (i) concern about protecting the vulnerable patient and the impact on the doctor-patient relationship; (ii) the perceived lack of skill and confidence of GPs to introduce a request for research participation within a potentially sensitive consultation; and (iii) the priority given to clinical and administrative issues over research participation. These themes were underpinned by GPs' observations that consultations with people about depression differed in content, style and perceived difficulty compared to other types of consultations.

CONCLUSION

Depressed patients were often viewed as vulnerable and in need of protection and it was seen as difficult and intrusive to introduce research. Patients were not always given the choice to participate in research in the same way that they are encouraged to participate in treatment decision making. A lack of skills in introducing research could be addressed with training through the new Primary Care Research Network. A more radical change in clinician attitudes and policy may be needed in order to give research a higher priority within primary care.

A randomized, controlled trial of routine early abdominal computed tomography in patients presenting with non-specific acute abdominal pain

AIM

To compare the effect of an initial early computed tomography (CT) examination versus standard practice (SP) on the length of hospital stay, diagnostic accuracy, and mortality of adults presenting with acute abdominal pain.

MATERIALS AND METHODS

Two hundred and five adults presenting with acute abdominal pain were randomized to undergo an early CT examination or current SP, which comprised supine abdominal and erect chest radiography. One hundred and ninety-eight patients (99 in each arm) were included in the analysis. The primary endpoint was the duration of inpatient stay; secondary endpoints were diagnostic certainty and mortality.

RESULTS

There was no significant difference in the length of hospital stay between the two arms (p=0.20). At randomization 36% (35 of 96) of CT patients and 49% (48 of 98) of SP patients were correctly diagnosed; 24h after randomization the correct diagnosis had been established in 84% of CT patients and 73% of SP patients. This refinement in diagnostic certainty was significantly better in the CT group (p<0.001). There was no difference in mortality between the two trial arms (p=0.31).

CONCLUSION

Early abdominal CT in patients with acute abdominal pain improves diagnostic certainty, but does not reduce the length of hospital stay and 6 month mortality.

Treatment monitoring and thermometry for therapeutic focused ultrasound

Therapeutic ultrasound is currently enjoying increasingly widespread clinical use especially for the treatment of cancer of the prostate, liver, kidney, breast, pancreas and bone, as well as for the treatment of uterine fibroids. The optimum method of treatment delivery varies between anatomical sites, but in all cases monitoring of the treatment is crucial if extensive clinical acceptance is to be achieved. Monitoring not only provides the operating clinician with information relating to the effectiveness of treatment, but can also provide an early alert to the onset of adverse effects in normal tissue. This paper reviews invasive and non-invasive monitoring methods that have been applied to assess the extent of treatment during the delivery of therapeutic ultrasound in the laboratory and clinic (follow-up after treatment is not reviewed in detail). The monitoring of temperature and, importantly, the way in which this measurement can be used to estimate the delivered thermal dose, is dealt with as a separate special case. Already therapeutic ultrasound has reached a stage of development where it is possible to attempt real-time feedback during exposure in order to optimize each and every delivery of ultrasound energy. To date, data from MR imaging have shown better agreement with the size of regions of damage than those from diagnostic ultrasound, but novel ultrasonic techniques may redress this balance. Whilst MR currently offers the best method for non-invasive temperature measurement, the ultrasound techniques under development, which could potentially offer more rapid visualisation of results, are discussed.

Structure determination and analysis of a bacterial chymotrypsin from Cellulomonas bogoriensis

The crystal structure of a secreted chymotrypsin from the alkaliphile Cellulomonas bogoriensis has been determined using data to 1.78 A resolution and refined to a crystallographic R factor of 0.167. The crystal structure reveals a large P1 substrate-specificity pocket, as expected for chymotrypsins. The structure is compared with close structural homologues. This comparison does not reveal clear reasons for the alkali tolerance of the enzyme, but the greater compactness of the structure and lowered hydrogen bonding may play a role.

Neonatal teeth in X-linked Opitz (G/BBB) syndrome

Two male siblings are described with a clinical and molecular diagnosis of X-linked Opitz (G/BBB) syndrome and the previously unreported feature of neonatal mandibular incisors.

Patient perspectives on multiple medications versus combined pills: a qualitative study

BACKGROUND

A growing number of patients are taking multiple medications. Unfortunately, adherence may fall as drug numbers and procedural complexity increase. While there are plausible theoretical reasons why combining pills might improve non-adherence, patients' attitudes are unknown.

AIM

To explore attitudes and practices to medication regimens among patients already in receipt of multiple medications, and to assess whether a combined tablet would be perceived as advantageous.

DESIGN

Qualitative study.

METHODS

Ninety-two men and women aged >40 years currently receiving both antihypertensive and cholesterol-lowering medications took part in 14 focus groups.

RESULTS

Drugs were seen as unwelcome but necessary. Some took drugs flexibly by changing dose timing, thereby increasing the complexity of their regimen. A routine was seen as the key to coping with multiple medications, although it was sometimes threatened by changes in prescriptions and life circumstances. While some participants welcomed a combined pill, there was uncertainty about whether a combination that mirrored their current doses would be available. There were also concerns about tablet size, allergies, the attribution of side-effects, timing of tablets throughout the day, and the ability to alter dose levels.

CONCLUSION

While some patients would be willing to try a combined pill and would appreciate the associated convenience, they are likely to have a number of concerns that prescribers should address. Willingness to move to combined therapy may be hindered if drug combinations that mirror personalized and trusted regimens are not available.

Discriminating power of localized three-dimensional facial morphology

Many genetic syndromes involve a facial gestalt that suggests a preliminary diagnosis to an experienced clinical geneticist even before a clinical examination and genotyping are undertaken. Previously, using visualization and pattern recognition, we showed that dense surface models (DSMs) of full face shape characterize facial dysmorphology in Noonan and in 22q11 deletion syndromes. In this much larger study of 696 individuals, we extend the use of DSMs of the full face to establish accurate discrimination between controls and individuals with Williams, Smith-Magenis, 22q11 deletion, or Noonan syndromes and between individuals with different syndromes in these groups. However, the full power of the DSM approach is demonstrated by the comparable discriminating abilities of localized facial features, such as periorbital, perinasal, and perioral patches, and the correlation of DSM-based predictions and molecular findings. This study demonstrates the potential of face shape models to assist clinical training through visualization, to support clinical diagnosis of affected individuals through pattern recognition, and to enable the objective comparison of individuals sharing other phenotypic or genotypic properties.