Erkki Svedström

The Effect of Expertise on Eye Movement Behaviour in Medical Image Perception

The present eye-movement study assessed the effect of expertise on eye-movement behaviour during image perception in the medical domain. To this end, radiologists, computed-tomography radiographers and psychology students were exposed to nine volumes of multi-slice, stack-view, axial computed-tomography images from the upper to the lower part of the abdomen with or without abnormality. The images were presented in succession at low, medium or high speed, while the participants had to detect enlarged lymph nodes or other visually more salient abnormalities. The radiologists outperformed both other groups in the detection of enlarged lymph nodes and their eye-movement behaviour also differed from the other groups. Their general strategy was to use saccades of shorter amplitude than the two other participant groups. In the presence of enlarged lymph nodes, they increased the number of fixations on the relevant areas and reverted to even shorter saccades. In volumes containing enlarged lymph nodes, radiologists’ fixation durations were longer in comparison to their fixation durations in volumes without enlarged lymph nodes. More salient abnormalities were detected equally well by radiologists and radiographers, with both groups outperforming psychology students. However, to accomplish this, radiologists actually needed fewer fixations on the relevant areas than the radiographers. On the basis of these results, we argue that expert behaviour is manifested in distinct eye-movement patterns of proactivity, reactivity and suppression, depending on the nature of the task and the presence of abnormalities at any given moment.

Acute bronchial obstruction: an experimental rabbit model study

An animal model of bronchial obstruction was developed to radiologically follow up the development of postobstructive pulmonary changes. The study material consisted of 21 healthy rabbits (New Zealand White) of which 5 animals served as controls. A piece of Surgicel (Ethicon) shaped as a 3 x 3 x 10 mm cylinder was placed endobronchially through a 3-mm bronchoscope. The animals were followed up radiologically and endoscopically during the first 30 min after which the bronchoscope was extracted. Sixteen animals were followed up for at least 4 h and, in 4 animals, the foreign body (FB) was removed after 24 h. During follow-up, total collapse of the lung was observed after 1-4 h in all but 2 animals with obstruction of the main brochus. After extraction of the FB, atelectasis of the respective lung had resolved within 24 h. The animal model developed in the present study seems to be rather physiological resembling the development of pulmonary atelectasis in pediatric patients.

Pentoxifylline Reduces Regional Inflammatory and Ventilatory Disturbances in Meconium-Exposed Piglet Lungs

Neonatal meconium aspiration frequently produces severe respiratory distress, which is associated with patchy pulmonary neutrophil influx and inflammatory injury. To examine the effects of pentoxifylline (PTX), a potent anti-inflammatory agent, on regional pulmonary inflammation and ventilation after meconium aspiration, we studied 17 anesthetized and ventilated neonatal piglets (age <2 d) for 12 h. After unilateral intrapulmonary instillation of meconium, PTX treatment was started in nine animals, and eight untreated animals served as controls. Bronchoalveolar lavage (BAL) fluid and lung tissue were studied for inflammatory variables at the end of the study, and changes in regional ventilation were serially analyzed with a dynamic pulmonary x-ray imaging method. Meconium insufflation increased BAL fluid total cell, neutrophil, and macrophage counts and tumor necrosis factor-α (TNF-α) and protein concentrations as well as lung tissue myeloperoxidase activity in the instilled lungs, compared with the noninstilled side. PTX treatment prevented the increase of BAL fluid alveolar macrophage count and TNF-α and protein concentrations in the meconium-instilled lungs but had no significant effect on the pulmonary neutrophil accumulation. Ventilation of the meconium-insulted lung was initially disturbed similarly in both study groups, but PTX administration prevented the sustained local ventilatory perturbation at 4, 6, and 12 h after meconium instillation. The results thus indicate that PTX treatment may attenuate meconium-induced regional ventilation derangements, mainly through its effects on local alveolar macrophages and TNF-α production as well as alveolocapillary permeability rather than via significant prevention of accumulation of active neutrophils in the insulted lungs.

Disc degeneration and lumbar instability. Magnetic resonance examination of 16 patients.

Flexion and extension radiographs of 75 young males with low back pain disclosed abnormal segmental motion of the lumbar spine in 16 patients with translational movements in 20 intervertebral segments. These 16 patients were further investigated by magnetic resonance imaging to assess disc degeneration in the unstable segments. On T2-weighted images of the 20 segments, the disc was normal in 13 and degenerated in only 7 patients. Thus, the initial factor in lumbar instability in young patients with low back pain is not always degeneration of the disc.

Skeletal manifestations of lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is an autosomal recessive disease caused by defective transport of the cationic amino acids lysine, arginine, and ornithine at the cell membrane. About 80 patients with LPI have been described worldwide, almost half of them in Finland. The symptoms appear in early childhood as a failure to thrive, growth retardation, muscular hypotonia, and episodes of stupor after protein-rich meals. Twenty-nine Finnish patients (current median age 24.8 years, range 3.7–47.9 years) over a mean follow-up time of 18.1 years (range 1.2–27.2 years) had 57 fractures after minor trauma, mostly in childhood. Their 440 skeletal radiographs showed severe osteoporosis (13/29), controversially abnormal thickening of cortex of the metacarpals (7/29), or thin cortices of the long bones (5/29), endplate impression of vertebrae (8/29), rickets-like metaphyses (2/29), or early destruction of cartilage (3/29). Skeletal maturation was delayed by 1–5 years in 23 of 24 patients. There was no correlation between fracture incidence, radiological bone structure, and delayed skeletal maturation.

Osteoclasts derived from patients with neurofibromatosis 1 (NF1) display insensitivity to bisphosphonates in vitro

A total of 20 patients with neurofibromatosis 1 (NF1) were screened for NF1-related osteoporosis, and blood samples were collected for isolation of peripheral blood osteoclast progenitors. Patients with NF1 had higher levels of serum bone turnover markers (CTX and PINP) compared to controls. In addition, persons with high bone resorption in vitro on average had high levels of serum CTX. Of the 20 patients with NF1, 15 had low bone mineral density (osteopenia/osteoporosis), but these 15 patients did not have marked risk factors for low bone mineral density. Thus, we recommend screening for osteoporosis to all adult patients with NF1. Our aim was also to characterize the effects of bisphosphonates on NF1 osteoclasts in vitro. NF1 osteoclasts and osteoclasts from healthy controls in vitro were treated with zoledronic acid, alendronate and clodronate. These bisphosphonates caused a marked reduction in the number of normal control osteoclasts in vitro, while only a slight change was observed in the number of NF1 osteoclasts. Ras-inhibitor FTS counteracted this NF1-related insensitivity to zoledronic acid, suggesting that Ras may play a role in this phenomenon.

Radio-opaque bioactive glass markers for radiostereometric analysis

The objective of the study was to test the hypothesis that resorbable radio-opaque bioactive glass markers can be used in radiostereometric analysis (RSA). Cones made from (1) bioactive glass 1-06 with 2.5 wt.% BaSO(4), (2) glass 1-06 with 10 wt.% BaSO(4), (3) glass 1-06 without any additives and (4) nearly inert glass were created. The in vitro surface reactivity, as a surrogate of bioactivity, was analyzed using a simulated body fluid (SBF) immersion test. The in vivo performance was evaluated in the rat femur using biomechanical testing as well as histological and microcomputed tomography analysis of marker incorporation into bone. A phantom model RSA study using a porcine radius with a soft tissue envelope was carried out to determine the accuracy and precision of spherical markers for the measurement of fracture micromotion. SBF immersion studies and bone implantation studies showed that the addition of BaSO(4) slightly reduced surface reactivity in vitro and the bone-bonding properties of the bioactive glass in vivo. In the simulated RSA study with the selected resorbable marker composition (bioactive glass with 10 wt.% BaSO(4)), the accuracy of translation and rotation measurements in the longitudinal axis was +/-51 microm and +/-0.87 degrees , respectively. The precision of translation and rotation measurements in the longitudinal axis were 9 microm and 0.18 degrees , respectively. Bioactive glass markers with BaSO(4) additive appear to have adequate bone-bonding properties for marker stability and sufficient radio-opacity for RSA, but further preclinical comparison studies with tantalum markers are necessary.

Dynamic imaging of pulmonary ventilation. Description of a novel digital fluoroscopic system.

A new fluoroscopic imaging device consisting of an AT-micro-computer and a digital image memory unit has been used in experimental and clinical ventilation studies during a 2-year period. Digital images with 256 shades of gray were collected during one to 3 ventilation cycles at the rate of 6 to 25 images/s and stored on an optical laser disc. Both subtracted time interval difference (TID-) images and images relative, for example, to the mean image of the cycle (REL-images) were produced. The series of images could also be evaluated dynamically using animation sequences or analyzed using region of interest calculations. The method gave dynamic information with adequate spatial resolution and was easy to use in clinical practice. The radiation dose was kept low due to the high kilovoltage and heavy beam filtration technique. In experimental studies the software enabled flexible measurements of physiological pulmonary parameters.

Pancreatic Glucose Uptake in Vivo in Men with Newly Diagnosed Type 1 Diabetes

CONTEXT Due to the restricted accessibility of pancreatic tissue in living man, direct analysis of the events preceding development of autoimmune changes in the pancreas has been problematic. In vivo imaging of insulitis might markedly increase understanding of the events and timing of the events that are necessary for the progression toward overt type 1 diabetes. DESIGN To evaluate possibilities to visualize insulitis in man in vivo with positron emission tomography, we studied 12 male patients (age 26 +/- 7 yr) with newly diagnosed type 1 diabetes (duration range 0-7 months) and nine age- and sex-matched healthy controls after an overnight fast using 2-[(18)F]fluoro-2-deoxy-D-glucose and [(11)C]methionine. For definition of the regions of interest, pancreas was localized with magnetic resonance imaging or computed tomography-positron emission tomography. RESULTS Glucose uptake to the pancreas was markedly higher in the patients with type 1 diabetes than in the healthy controls (22.9 +/- 6.4 vs. 17.8 +/- 6.0 micromol/kg.min, P = 0.039). Glucose uptake to the pancreas of the patients was inversely associated with the duration of diabetes (r = -0.58; P = 0.024), so that in patients with newly diagnosed type 1 diabetes, glucose uptake was higher than in the healthy controls or patients with long duration of diabetes. Methionine uptake to the pancreas of the patients was similar as in the controls (3.7 +/- 1.9 vs. 4.6 +/- 2.4 micromol/kg.min, P = 0.21). CONCLUSIONS In patients with type 1 diabetes, glucose uptake to the pancreas is enhanced at or soon after the time of diagnosis.

High resolution CT of the lungs: Proper mA s settings for clinical use

Fifty-five patients undergoing routine chest CT were examined with four additional high resolution computed tomography (HRCT) slices to determine the proper milliampere-second settings for clinical HRCT of the lungs. The following technical factors were used: 1-mm collimation, 2-s scan time, 120 kVp and different milliampere settings (160 mA, 100 mA, 60 mA, 30 mA). On 47 out of 54 patients all the four HRCT cuts were at exactly the same level. These images were independently reviewed and assessed by three radiologists. The body mass index was calculated in order to determine the effect of the size of the patient on the milliamperage setting needed. The standard deviation of CT values of 1 mm and 10 mm slice was measured in a Plexiglas phantom with different mA settings. The slice thickness was measured with thermoluminescence dosimeter. In the phantom study the change of milliamperage from 160 mA to 30 mA at 120 kVp and 2 s increased standard deviation in CT units from about 4.6 to 8.9 in 1 mm slice and from about 2.9 to 4.3 in 10 mm slice. The Computed Tomography Dose Index (CTDI) values of both 1 mm and 10 mm slices at 160 mA-30 mA were approximately from 9 to 2 cGy (rad). In the patient study 1 mm HRCT scans with 120 kVp/100 mA/2 s showed the same diagnostic information as 120 kVp/160 mA/2 s scans for all patients regardless of size. If only the normal weight patients are considered, all the details were also well seen with 120 kVp/60 mA/2 s settings. In our study contrary to earlier reports 30 mA/2s was inadequate for diagnosis. We conclude that at 120 kVp medium-dose settings 60-100 mA/2 s or 120-200 mA s are in clinical practice appropriate for HRCT studies of the lungs in most patients.