Hanna Pohjonen

Activation of multiple cortical areas in response to somatosensory stimulation: combined magnetoencephalographic and functional magnetic resonance imaging.

We combined information from functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) to assess which cortical areas and in which temporal order show macroscopic activation after right median nerve stimulation. Five healthy subjects were studied with the two imaging modalities, which both revealed significant activation in the contra‐ and ipsilateral primary somatosensory cortex (SI), the contra‐ and ipsilateral opercular areas, the walls of the contralateral postcentral sulcus (PoCS), and the contralateral supplementary motor area (SMA). In fMRI, two separate foci of activation in the opercular cortex were discerned, one posteriorly in the parietal operculum (PO), and one anteriorly near the insula or frontal operculum (anterior operculum, AO). The activation sites from fMRI were used to constrain the solution of the inverse problem of MEG, which allowed us to construct a model of the temporal sequence of activation of the different sites. According to this model, the mean onset latency for significant activation at the contralateral SI was 20 msec (range, 17–22 msec), followed by activation of PoCS at 23 msec (range, 21–25 msec). The contralateral PO was activated at 26 msec (range, 19–32 msec) and AO at 33 msec (range, 22–51 msec). The contralateral SMA became active at 36 msec (range, 24–48 msec). The ipsilateral SI, PO, and AO became activated at 54–67 msec. We conclude that fMRI provides a useful means to constrain the inverse problem of MEG, allowing the construction of spatiotemporal models of cortical activation, which may have significant implications for the understanding of cortical network functioning. Hum. Brain Mapping 8:13–27, 1999.

Pervasive Access to Images and Data—The Use of Computing Grids and Mobile/Wireless Devices Across Healthcare Enterprises

Emerging technologies are transforming the workflows in healthcare enterprises. Computing grids and handheld mobile/wireless devices are providing clinicians with enterprise-wide access to all patient data and analysis tools on a pervasive basis. In this paper, emerging technologies are presented that provide computing grids and streaming-based access to image and data management functions, and system architectures that enable pervasive computing on a cost-effective basis. Finally, the implications of such technologies are investigated regarding the positive impacts on clinical workflows

Registration and display of brain SPECT and MRI using external markers

Accurate anatomical localisation of abnormalities observed in brain perfusion single-photon emission computed tomography (SPECT) is difficult, but can be improved by correlating data from SPECT and other tomographic imaging modalities. For this purpose we have developed software to register, analyse and display99mTc-hexamethylpropyleneamine oxime SPECT and 1.0 T MRI of the brain. For registration of SPECT and MRI data external skin markers containing99mTc (220 kBq) in 50 μl of coconut butter were used. The software is coded in the C programming language, and the X Window system and the OSF/Motif standards are used for graphics and definition of the user interface. The registration algorithm follows a noniterative least-squares method using singular value decomposition of a 3×3 covariance matrix. After registration, the image slices of both data sets are shown at identical tomographic levels. The registration error in phantom studies was on average 4 mm. In the two-dimensional display mode the orthogonal cross-sections of the data sets are displayed side by side. In the three-dimensional mode MRI data are displayed as a surface-shaded 3 D reconstruction and SPECT data as cut planes. The usefulness of this method is demonstrated in patients with cerebral infarcts, brain tumour, herpes simplex encephalitis and epilepsy.

Abdominal SPECT/MRI fusion applied to the study of splenic and hepatic uptake of radiolabeled thrombocytes and colloids

The importance of applying MRI (CT)/SPECT fusion in the abdominal and thoracic areas has been recognized in recent studies aiming at radionuclide therapy of cancer. According to our earlier results spleen and liver volume determination with different segmentation methods is inaccurate with SPECT alone. We therefore applied a SPECT/MRI registration procedure to the estimation of spleen and liver volumes and spleen/liver activity ratios in three male volunteers administered111In-labeled thrombocytes and99mTc-labeled colloids. The objectives of the study were to investigate if the uptake of thrombocytes in the spleen and liver can be measured more accurately when the anatomical borders of these organs are transferred from MRI to SPECT, and to test a SPECT/MRI registration method for improving three-dimensional dosimetry for radiotherapy treatment planning. A good correlation was found between spleen/liver activity ratios calculated from volumetric average activity per pixel values and from total volumetric counts derived from registered data but not from projection data. The average registration residual with this SPECT/MRI fusion method is approximately 1–2 cm in the abdominal area. Combining anatomical images with SPECT is therefore important for improving quantitative SPECT also in the abdomen.

Images crossing borders: image and workflow sharing on multiple levels

Digitalisation of medical data makes it possible to share images and workflows between related parties. In addition to linear data flow where healthcare professionals or patients are the information carriers, a new type of matrix of many-to-many connections is emerging. Implementation of shared workflow brings challenges of interoperability and legal clarity. Sharing images or workflows can be implemented on different levels with different challenges: inside the organisation, between organisations, across country borders, or between healthcare institutions and citizens. Interoperability issues vary according to the level of sharing and are either technical or semantic, including language. Legal uncertainty increases when crossing national borders. Teleradiology is regulated by multiple European Union (EU) directives and legal documents, which makes interpretation of the legal system complex. To achieve wider use of eHealth and teleradiology several strategic documents were published recently by the EU. Despite EU activities, responsibility for organising, providing and funding healthcare systems remains with the Member States. Therefore, the implementation of new solutions requires strong co-operation between radiologists, societies of radiology, healthcare administrators, politicians and relevant EU authorities. The aim of this article is to describe different dimensions of image and workflow sharing and to analyse legal acts concerning teleradiology in the EU.

ASP archiving solution of regional HUSpacs

The application service provider (ASP) model is not novel, but widely used in several non-health care-related business areas. In this article, ASP is described as a potential solution for long-term and back-up archiving of the picture archiving and communication system (PACS) of the Hospital District of Helsinki and Uusimaa (HUS). HUSpacs is a regional PACS for 21 HUS hospitals serving altogether 1.4 million citizens. The ultimate goal of this study was to define the specifications for the ASP archiving service and to compare different commercial options for archiving solutions (costs derived by unofficial requests for proposal): in-house PACS components, the regional ASP concept and the hospital-based ASP concept. In conclusion, the large scale of the HUS installation enables a cost-effective regional ASP archiving, resulting in a four to five times more economical solution than hospital-based ASP.

Transmission imaging for registration of ictal and interictal single-photon emission tomography, magnetic resonance imaging and electroencephalography.

Abstract.A method developed for registration of ictal and interictal single-photon emission tomography (SPET), magnetic resonance imaging (MRI) and electroencephalography (EEG) is described. For SPET studies, technetium-99m ethyl cysteinate dimer (ECD) was injected intravenously while the patient was monitored on video-EEG to document the ictal or interictal state. Imaging was performed using a triple-head gamma camera equipped with a transmission imaging device using a gadolinium-153 source. The images (128×128 pixels, voxel size 3.7×3.7×3.6 mm3) were reconstructed using an iterative algorithm and postfiltered with a Wiener filter. The gold-plated silver electrodes on the patient’s scalp were utilized as markers for registration of the ictal and interictal SPET images, as these metallic markers were clearly seen on the transmission images. Fitting of the marker sets was based on a non-iterative least squares method. The interictal SPET image was subtracted from the ictal image after scaling. The T1-weighted MPRAGE MR images with voxel size of 1.0×1.0×1.0 mm3 were obtained with a 1.5-T scanner. For registration of MR and subtraction SPET images, the external marker set of the ictal SPET study was fitted to the surface of the head segmented from MR images. The SPET registration was tested with a phantom experiment. Registration of ictal and interictal SPET in five patient studies resulted in a 2-mm RMS residual of the marker sets. The estimated RMS error of registration in the final result combining locations of the electrodes, subtraction SPET and MR images was 3–5 mm. In conclusion, transmission imaging can be utilized for an accurate and easily implemented registration procedure for ictal and interictal SPET, MRI and EEG.

Calculating internal dose by convolution from SPECT/MR fusion images

A new computer program was developed to calculate the absorbed dose. The program is based on the use of the convolution method and abdominal SPECT/MR fusion images. The applicability of the method was demonstrated by using data from111In-labeled thrombocyte and99mTc-labeled colloid studies of three healthy volunteers. Dose distributions in the volunteers and the average absorbed doses in liver and spleen were calculated. The average doses for99mTc-labeled colloid study were 0.07 ± 0.02 (liver) and 0.046 ± 0.005 mGy/MBq (spleen). The results are in good agreement with a Monte Carlo (MC) based method (0.074 for liver and 0.077 mGy/MBq for spleen) used by the International Commission on Radiological Protection (ICRP). For111In-labeled thrombocyte study the doses were 0.33 ± 0.05 (liver) and 8.9 ± 1.2 mGy/MBq (spleen) versus 0.730 and 7.50, respectively. The differences in dose estimates in the111In-labeled thrombocyte study are mainly due to the approximation used in activity quantitation. Convolution of the activity distribution with a point dose kernel is an effective method for calculating absorbed dose distribution in a homogeneous media. Activity distribution must be aligned to anatomical data in order to utilize the calculated dose distribution. The program developed is applicable to and practical for clinical use provided that the input data needed are available.

Registration of anatomical and functional 3D-data sets

Multimodality imaging creates the need for combining different data from the same location of a patient. This paper describes a software package developed for the registration and visualization of functional and anatomical data. The procedure can be applied e.g. to the MR and SPET images of neurology patients.

Eesti terviseinfosüsteemi majandusmõju/puhastulu hindamine. TOF-DIGIMÕJU projekti lõpparuanne

Aruandes antakse ulevaade TOF-DIGIMOJU projekti tulemustest. Projekti pohieesmark oli tootada valja kohane metoodika riigi terviseinfosusteemi rakendamise moju hindamiseks. Riikliku terviseinfosusteemi elluviimise voimalike kulude ja tulude analuusil tugineti PENGi mudelile, mis on kavandatud spetsiaalselt infotehnoloogia investeeringute hindamiseks. PENGi meetod valiti valja eeskatt selle tervikliku kasituse tottu, mis voimaldab holmata nii arvulisi kui ka mittearvulisi andmeid. Naidishaigusena kasutati II tuupi suhkurtobe, et arvutada valja kasutegurid patsientide, tervishoiuteenuste osutajate ning kodanike/uhiskonna jaoks. Aruande VII peatukis on esitatud projekti viimases etapis koostatud soovitused selle kohta, kuidas kasutada riiklikku terviseinfosusteemitohusama tervishoiupoliitika elluviimiseks. Eesti Arst 2010; 89(10):659−696