Assessment of carotid compliance using real time vascular ultrasound image analysis in Marfan syndrome.

BACKGROUND: Fibrillin-1 deficiency, dysregulated cytokine transforming growth factor-beta, and increased collagen deposition related to fibrillin-1 gene mutations could predispose to impaired carotid compliance (CC) in Marfan syndrome (MFS). We sought to detect any alterations in CC using the vascular image analysis system (VIA). METHODS AND RESULTS: Thirty-two MFS patients, 20 men and 12 women (mean age 34.2 +/- 12.05 years), and 29 controls matched for age, sex, and body surface area (BSA) were recruited. The entire length of each carotid system was initially scanned longitudinally using a 14 MHz linear transducer. Then, a stereotactic clamp held the transducer in contact with the carotid artery. Arterial diameter changes during the cardiac cycle were recorded for 1 minute from both right (RCCA) and left common carotid arteries (LCCA) separately using the VIA system. RCCA and LCCA compliance and distensibility measurements were significantly reduced in MFS patients when compared to controls, P < 0.05. RCCA and LCCA intima-media thickness did not differ between patients and controls, P > 0.05. MFS diagnosis and age were associated with reduced CC in both carotid arteries after adjusting for variables such as, sex, BSA, heart rate, beta-blockade, intima-media thickness, and aortic root size. CONCLUSIONS: Our findings showed a reduction in CC in adult patients with MFS. This could be attributed to fibrillin-1 deficiency resulting in structural abnormalities in the carotid arterial wall.

A computerized gamma probe simulator to train surgeons in the localization of sentinel nodes.

BACKGROUND: The technique of sentinel node biopsy (SNB) may be used as a staging technique for cancer patients. SNB involves the localization of lymph nodes that have accumulated a radioactive tracer, and this requires surgeons to gain and demonstrate skills in the use of hand-held radiation detectors (gamma probes). METHODS: A computerized gamma probe simulator (GAPS) has been developed as a training tool to provide realistic simulations of the clinical distribution of radioactivity, without the use of radioactive materials, and a realistic simulation of the count rate response from a gamma probe. Electromagnetic spatial tracking of the surgeon's movement of the probe allows objective assessment of the user's accuracy in localizing a virtual sentinel node. The physical accuracy of the simulation has been validated, with a spatial accuracy of (0.06 mm), and a count rate error of 0.28%. RESULTS: The GAPS has been used in the training of 94 breast surgeons, with a mean error node localization of 3.8 mm (range, 0.1-16 mm) and a mean search time of 131 s (range 36-314 s), showing that objective feedback on performance can be given by the system. Modification to train for other sentinel node applications is simple, and the system has been used for training in the application of penile sentinel node surgery. CONCLUSION: A computerized gamma probe simulator has been developed which provides realistic training tasks for surgeons in sentinel node biopsy, with a wide range of simulated clinical cases, allowing the objective assessment of a trainee's performance in the use of a hand-held gamma probe without the use of radioactive sources.

The automated assessment of ultrasound scanner lateral and slice thickness resolution: use of the step response.

The imaging performance assessment of ultrasound scanners based on traditional phantoms is limited by repeatability, subjectivity and systematic errors giving low confidence in results. A new approach to the automated measurement of scanner resolution is described. The method utilises a step change in backscatter to derive resolution from the imaging system line spread function and has been used to calculate resolution in two dimensions as a continuous function of depth. Resolution data was used to calculate resolution integrals for both lateral and slice thickness independently. For resolution integral repeatability, analysis of variance showed no significant difference between operators (p=0.05) with intra and inter-operator repeatability (+/-1 standard deviation) of 1.5% and 1.5% for lateral resolution, respectively, and 2.6% and 3.3% for slice thickness, respectively. Low contrast penetration was also calculated automatically and the worst case operator repeatability was 1.3%. The acoustic properties of the phantom were validated. The possibility of extending the technique to axial resolution is discussed.

Development of a thermal test object for the measurement of ultrasound intracavity transducer self-heating.

The elevated surface temperature of diagnostic ultrasound transducers imposes an important limitation to their safe use in clinical situations. Moreover, particular care should be taken if transvaginal transducers are to be used during routine scans in the first few weeks of pregnancy as the transducer surface can be very close to embryonic/fetal tissues. Published results have shown that the heating of tissue due to transducer self-heating can equal and often exceed the acoustic heating contribution. In this article, we report the development of a portable self contained thermal test object (TTO) capable of assessing the self-heating of intracavity diagnostic ultrasound transducers. The thermal conductivity and volumetric heat capacity of the tissue mimicking material (TMM) used in the TTO were measured, yielding values of (0.56 +/- 0.01) W m(-1) K(-1) and (3.5 +/- 0.8) MJ m(-3) K(-1). The speed of sound of the TMM was measured as 1540 m s(-1) and the attenuation over a frequency range of 2 to 10 MHz was found to be (0.50 +/- 0.01) dB cm(-1) MHz(-1). These results are in excellent agreement with the International Electrotechnical Commission (IEC 60601-2-37) requirements and the previously published properties of biological soft tissue. The temperature stability and uniformity, and suitability of the TTO for the measurement of transducer self-heating were tested and found to be satisfactory. The TTO reached a stable temperature of 37 degrees C in 3 h and the spatial variation in temperature was less than +/- 0.2 degrees C. Lastly, transducer self-heating measurements from a transvaginal transducer exceeded the IEC temperature limit of 43 degrees C in less than 5 min and the temperature reached after 30 min was 47.3 degrees C.

Chronic inflammation and increased arterial stiffness in patients with cardiac syndrome X.

AIMS: Endothelial dysfunction and subangiographic atheroma have been reported in patients with cardiac syndrome X (CSX) but little is known regarding chronic inflammation and reduced arterial distensibility as pathogenic mechanisms. We assessed whether markers of inflammation and arterial distensibility differ in CSX patients compared to control subjects. METHODS AND RESULTS: We studied 30 consecutive CSX patients (mean age 57+/-6 years, 25 women) and 30 healthy controls (mean age 54+/-8 years, 25 women). High sensitivity C-reactive protein (hs-CRP) levels were significantly higher in patients with CSX compared to controls (2.6 [1.7-4.5] vs 1.5[0.7-2.7] mg/l, P=0.02). Hs-CRP levels correlated with carotid intima-media thickness (IMT) (Spearman's rho=0.51; P=0.013). CSX patients also had significantly increased mean IMT values than controls (P<0.0001). Arterial stiffness and elastic modulus were also significantly increased in CSX patients compared to control subjects (P=0.04 and P=0.04, respectively). Distensibility tended to be lower in CSX patients than controls although this difference did not reach statistical significance. CONCLUSIONS: This study showed for the first time that compared to control subjects, patients with CSX have higher hs-CRP serum levels, increased mean common carotid artery IMT and increased arterial stiffness. The role of these abnormalities in the pathogenesis of CSX deserves investigation.