Mikko Hakulinen

Assessment of body composition by dual-energy X-ray absorptiometry, bioimpedance analysis and anthropometrics in children: the Physical Activity and Nutrition in Children study.

We compared InBody720 segmental multifrequency bioimpedance analysis (SMF‐BIA) with Lunar Prodigy Advance dual‐energy X‐ray absorptiometry (DXA) in assessment of body composition among 178 predominantly prepubertal children. Segmental agreement analysis of body compartments was carried out, and inter‐relationships of anthropometric and other measures of body composition were defined. Moreover, the relations of different reference criteria for excess body fat were evaluated.

In-line ultrasound measurement system for detecting tablet integrity.

An ultrasound measurement system for tablet defect detection is introduced. The measurement system was implemented in an eccentric single station tabletting apparatus, where ultrasound transducers were placed inside the upper and lower punches. These instrumented punches were then used to measure the speed of sound and ultrasound attenuation values in both intact and defective tablets made from dibasic calcium phosphate, microcrystalline cellulose and lactose monohydrate. Ultrasound attenuation was found to be a very sensitive method to discriminate defective tablets from intact ones. In addition, it was found that the determined ultrasound attenuation was different between all three materials used in this study, which indicates that different materials could be distinguished from one another by this detection method.

An integrated bioimpedance—ECG gating technique for respiratory and cardiac motion compensation in cardiac PET

Respiratory motion may degrade image quality in cardiac PET imaging. Since cardiac PET studies often involve cardiac gating by ECG, a separate respiratory monitoring system is required increasing the logistic complexity of the examination, in case respiratory gating is also needed. Thus, we investigated the simultaneous acquisition of both respiratory and cardiac gating signals using II limb lead mimicking electrode configuration during cardiac PET scans of 11 patients. In addition to conventional static and ECG-gated images, bioimpedance technique was utilized to generate respiratory- and dual-gated images. The ability of the bioimpedance technique to monitor intrathoracic respiratory motion was assessed estimating cardiac displacement between end-inspiration and -expiration. The relevance of dual gating was evaluated in left ventricular volume and myocardial wall thickness measurements. An average 7.6  ±  3.3 mm respiratory motion was observed in the study population. Dual gating showed a small but significant increase (4 ml, p = 0.042) in left ventricular myocardial volume compared to plain cardiac gating. In addition, a thinner myocardial wall was observed in dual-gated images (9.3  ±  1.3 mm) compared to cardiac-gated images (11.3  ±  1.3 mm, p = 0.003). This study shows the feasibility of bioimpedance measurements for dual gating in a clinical setting. The method enables simultaneous acquisition of respiratory and cardiac gating signals using a single device with standard ECG electrodes.

Real-time tablet formation monitoring with ultrasound measurements in eccentric single station tablet press.

A real-time ultrasound measurement system for tablet compression monitoring is introduced. The measurement system was tested in actual manufacturing environment and found to be capable of measuring the ultrasound response of the tabletting process from bulk to tablet. The tablet sets were compressed and the ultrasound measurements were conducted as implemented in eccentric single station tabletting apparatus in through transmission geometry. The speed of sound and ultrasound spectrum was measured during dynamic compression for microcrystalline cellulose/paracetamol tablets. The ultrasound system introduced in this study was found to be suitable for tabletting process monitoring as the mechanical properties of compressed tablets can be estimated during compression using the ultrasound system. In addition, it was found that the ultrasound was sensitive to the mixing time of magnesium stearate and the concentration of paracetamol. Thus, ultrasound measurements made during the compression can be used to monitor the tablet formation process.

Optimizing bioimpedance measurement configuration for dual-gated nuclear medicine imaging: a sensitivity study.

Motion artefacts due to respiration and cardiac contractions may deteriorate the quality of nuclear medicine imaging leading to incorrect diagnosis and inadequate treatment. Motion artefacts can be minimized by simultaneous respiratory and cardiac gating, dual-gating. Currently, only cardiac gating is often performed. In this study, an optimized bioimpedance measurement configuration was determined for simultaneous respiratory and cardiac gating signal acquisition. The optimized configuration was located on anterolateral upper thorax based on sensitivity simulations utilizing a simplified thorax model. The validity of the optimized configuration was studied with six healthy volunteers. In the peak-to-peak and frequency content analyses the optimized configuration showed consistently higher peak-to-peak values and frequency content than other studied measurement configurations. This study indicates that the bioimpedance method has potential for the dual-gating in nuclear medicine imaging. The method would minimize the need of additional equipment, is easy for the technologists to use and comfortable for the patients.

BMI influence on the reproducibility of ECG-gated myocardial perfusion imaging phase analysis in comparison with novel echocardiographic dyssynchrony estimation methods.

AimCardiac resynchronization therapy (CRT) is a treatment for patients with end-stage heart failure. However, two-thirds of the patients are nonresponders. Evaluation of left ventricular mechanical dyssynchrony may help in finding patients who will benefit from CRT. Dyssynchrony can be evaluated by the phase analysis method in myocardial perfusion imaging (MPI) or with cardiac ultrasound. The aim of this study was to investigate the reproducibility of phase analysis parameters in MPI and echocardiographic parameters in the evaluation of left ventricular mechanical dyssynchrony. In particular, the influence of BMI on reproducibility was studied. Methods and resultsTwenty-one patients underwent an ECG-gated MPI scan. Acquisition was repeated after the rest image. The patients were also studied twice with transthoracic echocardiography. Of MPI phase analysis parameters bandwidth, histogram SD and entropy% were highly reproducible in the pooled population: Cronbach’s &agr; 0.927–0.967 and intraclass correlation (ICC) 0.868–0.967, (P<0.001 for all). However, the reproducibility of bandwidth and SD was poorer in patients with BMI≥29 kg/m2 group (&agr; 0.203 and −0.055; ICC 0.106 and −0.027, NS for both) than in those with BMI<29 kg/m2 (&agr; 0.984 and 0.980; ICC 0.968 and 0.961, P<0.001 for both). In contrast, BMI had no obvious influence on the reproducibility of global longitudinal strain in echocardiography. ConclusionParameters reflecting mechanical dyssynchrony were found to be well reproducible. However, this study indicates that phase analysis results may be less reproducible in patients with high BMI, whereas global longitudinal strain in echocardiography seems to be less critical for a patient’s BMI.

Dual frequency ultrasound‐ A pulse‐echo technique for analysis of layered material

Ultrasound (US) thickness gauges typically analyse layered materials by utilizing ultrasound reflections between different layers and prior knowledge for the material order within the layered structure. In this study, a dual frequency ultrasound (DFUS) technique is applied to eliminate the effect of overlying layered structure on the measurements of the object of interest without prior knowledge of the order of materials within the multilayered structure. DFUS technique utilizes prior knowledge on US attenuation coefficient and speed at two frequencies in multilayered materials, consisting of two different material types. Then, US reflection from the front (first) and the back (last) surfaces of the multilayered structure is measured using two different US frequencies. No reflections from the internal interfaces are needed. The technique was validated using several elastomer samples and their combinations, measured at 2.25 MHz and 5.0 MHz. DFUS reduced the mean error, induced by the overlying elastomers, ...

The role of bone marrow on acoustic properties of cancellous bone ‐ finite difference time domain modelling study

Quantitative ultrasound (US) parameters are related to structure and properties of cancellous bone. The effect of bone marrow on US propagation, i.e. absorption and scattering, is still poorly understood. However, substitution of fatty marrow with water is known to significantly affect the US parameters. The present study investigates the role of marrow on US parameters, using microtomography based 3D‐finite difference time domain (FDTD) modelling. Eleven human cancellous bone samples were analysed with a micro‐CT system (SkyScan 1072) to determine microstructure and morphology. Wave 3000 Pro software (Cyberlogic Inc.) was used for simulations. Models were created to simulate experimental US measurement geometry with focused 1MHz transducers. Simulations were repeated before and after replacing the marrow with water. The voxel size of the simulation mesh significantly affected sample structure and simulations. US attenuation and speed decreased and increased, respectively, when marrow was replaced with wa...

Dual frequency ultrasound measurement of bone ‐ a technique for elimination of soft tissue effects on pulse‐echo measurements

Quantitative ultrasound (US) measurements have been suggested for screening of osteoporosis. However, soft tissues overlying bones affect reliability of the measurements. In this in vitro study, a novel dual frequency ultrasound (DFUS) technique is introduced for elimination of the errors induced by soft tissues on bone pulse‐echo US measurements. In DFUS, US reflection from soft tissue‐bone interface is measured with two different US frequencies. By knowing the frequency specific US attenuation and speed in adipose and lean tissues, the effect of soft tissue can be determined. DFUS, conducted at frequencies of 2.25 MHz and 5.0 MHz, was validated using human trabecular bone samples (n = 25) covered with heterogeneous soft tissues. DFUS, reduced (p < 0.01) the mean error induced by soft tissues from 58.6% to ‐4.9% and from 127.4% to 23.8% in broadband ultrasound backscattering and integrated reflection coefficients (at 5.0 MHz), respectively. Our results suggest that DFUS is a technique capable to minimize...