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Stig A Larsson

Publications and source records attributed to Stig A Larsson.

At least 19 recordsLinked to original sources
PubMed2007

Reduction of FDG uptake in brown adipose tissue in clinical patients by a single dose of propranolol.

PURPOSE: Uptake in brown adipose tissue (hibernating fat) is sometimes seen at FDG-PET examinations. Despite a characteristic appearance, this may hide clinically relevant uptake. Stimulation of the sympathetic nervous system increases glucose uptake of brown fat. We now re-examine patients with brown fat activity that could disguise tumour uptake after pre-treatment with propranolol (a non-selective beta-blocker) in order to reduce the uptake. Our first examinations of this kind are reported. METHODS: Eleven patients with strong brown fat uptake were studied. There was a mean of 5 days (range 2-8) between the examinations. At the second examination, 80 mg of propranolol was given orally 2 h before FDG administration. In addition to visual evaluation of the brown fat uptake, SUV assessments of the uptake in brown fat, lung, heart, liver, spleen and bone marrow were made. RESULTS: All patients showed complete or almost complete disappearance of the brown fat activity at the second examination (p < 0.001) both upon visual evaluation and when comparing SUVs. In seven patients there was also uptake in a known or strongly suspected malignancy, which remained unchanged between the examinations. Beyond an insignificant decrease in the myocardial uptake, there was no redistribution to the various examined organs at the second examination. CONCLUSION: Pre-treatment with a single dose of propranolol blocks the FDG uptake in brown adipose tissue, thereby increasing the specificity of the examination. The tumour uptake seems not to be impaired.

Adipose Tissue, Brown↗
PubMed2007

Different concentrations of I-123 MIBG and In-111 pentetreotide in the two main liver lobes in children: persisting regional functional differences after birth?

PURPOSE: At examinations in children with I-123 metaiodobenzylguanidine or with In-111 pentetreotide using SPECT, we have observed a different distribution of the radiopharmaceuticals between the left and right main liver lobes. This phenomenon was studied in retrospect from clinical examinations. PATIENTS AND METHODS: Seventeen children (mean age, 51 months; range, 11-150 months) with neuroblastoma or ganglioneuroma examined with both radiopharmaceuticals within 1 week using SPECT were assessed. There was no history of liver disease and all liver lobes showed uniform activity distribution. Simultaneous radiologic examinations were all normal with regard to the liver. No child with a pathologic liver chemistry test was included. The activity ratios between the left and right main liver lobes were calculated from transverse tomographic sections. RESULTS: The mean left:right lobar activity ratio for I-123 metaiodobenzylguanidine was 1.26+/-0.12 (null hypothesis=1.00; P<0.001) and for In-111 pentetreotide 0.88+/-0.06 (null hypothesis=1.00; P<0.001). There was no age-dependent distribution of the tracers. The correlation between the tracer uptake of the different liver lobes was very weak. CONCLUSION: A functional difference between the 2 main liver lobes in utero is believed to reflect differences of the vascular supply. The current findings indicate a persisting functional heterogeneity of the liver after birth not caused by perfusion differences. A relatively higher uptake of I-123 MIBG and a lower uptake of In-111 pentetreotide of the left liver lobe are normal findings.

3-Iodobenzylguanidine↗
PubMed2006

Posture primarily affects lung tissue distribution with minor effect on blood flow and ventilation.

We used quantitative single photon emission computed tomography to estimate the proportion of the observed redistribution of blood flow and ventilation that is due to lung tissue shift with a change in posture. Seven healthy volunteers were studied awake, breathing spontaneously. Regional blood flow and ventilation were marked using radiotracers that remain fixed in the lung after administration. The radiotracers were administered in prone or supine at separate occasions, at both occasions followed by imaging in both postures. Images showed greater blood flow and ventilation to regions dependent at the time of imaging, regardless of posture at radiotracer administration. The results suggest that a shift in lung parenchyma has a major influence on the imaged distributions. We conclude that a change from the supine to the prone posture primarily causes a change in the vertical distribution of lung tissue. The effect on the vertical distribution of blood flow and ventilation within the lung parenchyma is much less.

Adult↗
PubMed2006

Physiological imaging of the lung: single-photon-emission computed tomography (SPECT).

Emission tomography provides three-dimensional, quantitative images of the distribution of radiotracers used to mark physiological, metabolic, or pathological processes. Quantitative single photon emission computed tomography (SPECT) requires correction for the image-degrading effects due to photon attenuation and scatter. Phantom experiments have shown that radioactive concentrations can be assessed within some percentage of the true value when relevant corrections are applied. SPECT is widely spread, and radiotracers are available that are easy to use and comparably inexpensive. Compared with other methods, SPECT suffers from a lower spatial resolution, and the time required for image acquisition is longer than for some alternative methods. In contrast to some other methods, SPECT allows simultaneous imaging of more than one process, e.g., both regional blood flow and ventilation, for the whole lung. SPECT has been used to explore the influence of posture and clinical interventions on the spatial distribution of lung blood flow and ventilation. Lung blood flow is typically imaged using macroaggregates of albumin. Both radioactive gases and particulate aerosols labeled with radioactivity have been used for imaging of regional ventilation. However, all radiotracers are not equally suited for quantitative measurements; all have specific advantages and limitations. With SPECT, both blood flow and ventilation can be marked with radiotracers that remain fixed in the lung tissue, which allows tracer administration during conditions different from those at image registration. All SPECT methods have specific features that result from the used radiotracer, the manner in which it is administered, and how images are registered and analyzed.

Animals↗
PubMed2006

Imaging the neurobiological substrate of atypical depression by SPECT.

PURPOSE: Neurobiological abnormalities underlying atypical depression have previously been suggested. The purpose of this study was to explore differences at functional brain imaging between depressed patients with and without atypical features and healthy controls. METHODS: Twenty-three out-patients with chronic depressive disorder recruited from a service for patients with audiological symptoms were investigated. Eleven fulfilled the DSM-IV criteria for atypical depression (mood reactivity and at least two of the following: weight gain, hypersomnia, leaden paralysis and interpersonal rejection sensitivity). Twenty-three healthy subjects served as controls. Voxel-based analysis was applied to explore differences in (99m)Tc-HMPAO uptake between groups. RESULTS: Patients in the atypical group had a higher prevalence of bilateral hearing impairment and higher depression and somatic distress ratings at the time of SPECT. Significantly higher tracer uptake was found bilaterally in the atypical group as compared with the non-atypicals in the sensorimotor (Brodmann areas, BA1-3) and premotor cortex in the superior frontal gyri (BA6), in the middle frontal cortex (BA8), in the parietal associative cortex (BA5, BA7) and in the inferior parietal lobule (BA40). Significantly lower tracer distribution was found in the right hemisphere in the non-atypicals compared with the controls in BA6, BA8, BA44, BA45 and BA46 in the frontal cortex, in the orbito-frontal cortex (BA11, BA47), in the postcentral parietal cortex (BA2) and in the multimodal association parietal cortex (BA40). CONCLUSION: The differences found between atypical and non-atypical depressed patients suggest different neurobiological substrates in these patient groups. The putative links with the clinical features of atypical depression are discussed. These findings encourage the use of functional neuroimaging in psychiatric disorders.

Adult↗
PubMed2006

The influence of photon depth of interaction and non-collinear spread of annihilation photons on PET image spatial resolution.

PURPOSE: The quality of PET imaging is impaired by parallax errors. These errors produce misalignment between the projected location of the true origin of the annihilation event and the line of response determined by the coincidence detection system. Parallax errors are due to the varying depths of photon interaction (DOI) within the scintillator and the non-collinear (NC) emission of the annihilation photons. The aim of this work was to address the problems associated with the DOI and the NC spread of annihilation photons and to develop a quantitative model to assess their impact on image spatial resolution losses for various commonly used scintillators and PET geometries. METHODS: A theoretical model based on Monte Carlo simulations was developed to assess the relative influence of DOI and the NC spread of annihilation photons on PET spatial resolution for various scintillator materials (BGO, LSO, LuAP, GSO, NaI) and PET geometries. RESULTS: The results demonstrate good agreement between simulated, experimental and published overall spatial resolution for some commercial systems, with maximum differences around 1 mm in both 2D and 3D mode. The DOI introduces an impairment of non-stationary spatial resolution along the radial direction, which can be very severe at peripheral positions. As an example, the radial spatial resolution loss due to DOI increased from 1.3 mm at the centre to 6.7 mm at 20 cm from the centre of a BGO camera with a 412-mm radius in 2D mode. Including the NC, the corresponding losses were 3.0 mm at the centre and 7.3 mm 20 cm from the centre. CONCLUSION: Without a DOI detection technique, it seems difficult to improve PET spatial resolution and increase sensitivity by reducing the detector ring radius or by extending the detector in the axial direction. Much effort is expended on the design and configuration of smaller detector elements but more effort should be devoted to the DOI complexity.

Artifacts↗
PubMed2006

Different methods for the detection of small changes in uptake between single-photon emission computed tomography (SPECT) examinations: 99mTc-sestamibi in chemotherapy for breast tumours.

AIM: This study was undertaken to evaluate different methods for the detection of small changes in uptake between single-photon emission computed tomography (SPECT) examinations in the same individual. No standard exists for making digital evaluations at single-photon examinations. For this purpose, we employed a patient cohort from a previous study assessing the response to neoadjuvant chemotherapy for breast cancer using Tc-hexakis-2-methoxyisobutylisonitrile (Tc-sestamibi). METHODS: The tumour uptake in 29 women with locally advanced breast cancer was examined using Tc-sestamibi and SPECT before neoadjuvant chemotherapy and, on average, 19 days after one chemotherapy cycle. The histology of the finally resected tumour confirmed a therapeutic response. Different assessments of the uptake, various levels of background activity subtraction and different reference tissues for relative activity calculations were used. The tumour uptake and activity of the reference tissues were also related to the administered activity. RESULTS: Different definitions of tumour activity had little influence. Relating the tumour uptake to a large portion of the abdomen, as well as visual evaluation, showed a therapeutic response. Comparison with the administered activity showed that the apparent responses were due to an increased activity of the reference tissues. Referring the tumour uptake to the administered activity truly depicted a therapeutic response. CONCLUSIONS: A critical attitude is necessary when making digital evaluations at SPECT. Digital data may seem more relevant than they really are. Relative comparisons may be unreliable. It may be necessary to develop standardized methods for this purpose.

Adult↗
PubMed2005

Paradoxical redistribution of pulmonary blood flow in prone and supine humans exposed to hypergravity.

We hypothesized that exposure to hypergravity in the supine and prone postures causes a redistribution of pulmonary blood flow to dependent lung regions. Four normal subjects were exposed to hypergravity by use of a human centrifuge. Regional lung perfusion was estimated by single-photon-emission computed tomography (SPECT) after administration of (99m)Tc-labeled albumin macroaggregates during normal and three times normal gravity conditions in the supine and prone postures. All images were obtained during normal gravity. Exposure to hypergravity caused a redistribution of blood flow from dependent to nondependent lung regions in all subjects in both postures. We speculate that this unexpected and paradoxical redistribution is a consequence of airway closure in dependent lung regions causing alveolar hypoxia and hypoxic vasoconstriction. Alternatively, increased vascular resistance in dependent lung regions is caused by distortion of lung parenchyma. The redistribution of blood flow is likely to attenuate rather than contribute to the arterial desaturation caused by hypergravity.

Adaptation, Physiological↗
PubMed2005

Regional cerebral blood flow during auditory recall in 47 subjects exposed to assaultive and non-assaultive trauma and developing or not posttraumatic stress disorder.

OBJECTIVE: Psychological trauma leads to posttraumatic stress disorder (PTSD) in susceptible subjects. The aim of this study was to investigate the differences in regional cerebral blood flow (rCBF) between two groups of subjects exposed to different types of traumatic stressor either developing or not developing PTSD. METHODS: Twenty subjects developing (S) and 27 not developing (NS) PTSD after being exposed to either earlier person-under-the-train accident (NA) or being assaulted in the underground environment (A) were included in the study. 99mTc-HMPAO SPECT was performed and the uptake in 29 regions of the brain (VOIs), bilaterally, was assessed. rCBF distribution was compared, using analysis of variance (ANOVA), between groups (S/NS) and type (A/NA) during a situation involving an auditory evoked re-experiencing of the traumatic event. Discriminant analysis was applied to test the concordance between clinical diagnosis and SPECT findings. RESULTS: In the general analyses significant differences were found between groups and types and there was a significant hemisphere x type interaction. S showed higher CBF than NS and so did A as compared to NA, particularly in the right hemisphere. Discriminant analysis correctly classified 66% of cases (p < 0001) in testing S/NS and 72% (p < 0001) in testing NA/A. CONCLUSIONS: Under recall of their traumatic experience we found higher relative CBF distribution values in S as compared to NS. CBF was higher in the right hemisphere and particularly in assaulted subjects. These findings underscore the role upon trauma recall of both the right hemisphere and the nature of the stressing event.

Acoustic Stimulation↗
PubMed2005

Different concentrations of various radiopharmaceuticals in the two main liver lobes: a preliminary study in clinical patients.

BACKGROUND: At clinical scintigraphic examinations of the abdomen using single photon emission computed tomography (SPECT), we have observed a different distribution between the left and right main liver lobes of various radiopharmaceuticals. This was studied retrospectively in clinical patients. METHODS: Examinations with [123I]-metaiodobenzylguanidine MIBG; (n=19), a 99mTc-labelled monoclonal antibody against granulocytes (n=18), and 111In-pentetreotide (n=26) were assessed. There was no known history of, or risk factor for liver disease, and all lobes showed a uniform activity distribution. Twenty healthy volunteers underwent consecutive examinations with 99mTc-dimethyliminodiacetic acid (HIDA). The activity ratios between the left and right main liver lobes were calculated from the transverse tomographic (SPECT) sections. RESULTS: The left: right lobar activity ratio for [123I]-MIBG was (mean+/-SD) 1.25+/-0.21 (null hypothesis=1.00; P<0.001); for the antibody, acquisition after 3-5 h was 0.98+/-0.06 (NS) and after 20-24 h, 0.99+/-0.11 (NS); for 111In-pentetreotide, 0.90+/-0.09 (P<0.001); for 99mTc-HIDA, immediate acquisition, 0.68+/-0.12 (P<0.001) and acquisition at 7 min, 0.66+/-0.12 (P<0.001). CONCLUSIONS: The differences in tracer uptake between the liver lobes cannot be caused only by differences in blood flow. One explanation of the higher uptake of [123I]-MIBG by the left lobe may be a greater presence of catecholamines and a higher sympathetic nerve density in this liver portion. Consequently, there may be a functional difference between the two main liver lobes.

3-Iodobenzylguanidine↗
PubMed2004

Regulation of regional lung perfusion by nitric oxide.

Improved oxygenation has previously been shown in patients with acute lung injury when ventilated in prone position. We hypothesized that this was due to higher regional production of nitric oxide in dorsocaudal lung regions. We measured nitric oxide synthase mRNA expression and nitric oxide production by citrulline assay in ventral and dorsal lung tissue from patients. In volunteers, regional lung perfusion in prone and supine postures was assessed by single photon emission computed tomography using (99m)Tc macroaggregated albumin before and after inhibition of nitric oxide synthase by N(G)-monomethyl-L-arginine infusion. Nitric oxide synthase mRNA expression and nitric oxide production were significantly higher in dorsal compared with ventral lung regions. In supine posture, lung perfusion was shifted to ventral parts during nitric oxide synthase inhibition, whereas in the prone posture lung perfusion remained unchanged. Our results suggest a role for endogenous nitric oxide in regulation of regional pulmonary perfusion.

Acid-Base Equilibrium↗
PubMed2004

Principal component and volume of interest analyses in depressed patients imaged by 99mTc-HMPAO SPET: a methodological comparison.

Previous regional cerebral blood flow (rCBF) studies on patients with unipolar major depressive disorder (MDD) have analysed clusters of voxels or single regions and yielded conflicting results, showing either higher or lower rCBF in MDD as compared to normal controls (CTR). The aim of this study was to assess rCBF distribution changes in 68 MDD patients, investigating the data set with both volume of interest (VOI) analysis and principal component analysis (PCA). The rCBF distribution in 68 MDD and 66 CTR, at rest, was compared. Technetium-99m d, l-hexamethylpropylene amine oxime single-photon emission tomography was performed and the uptake in 27 VOIs, bilaterally, was assessed using a standardising brain atlas. Data were then grouped into factors by means of PCA performed on rCBF of all 134 subjects and based on all 54 VOIs. VOI analysis showed a significant group x VOI x hemisphere interaction ( P<0.001). rCBF in eight VOIs (in the prefrontal, temporal, occipital and central structures) differed significantly between groups at the P<0.05 level. PCA identified 11 anatomo-functional regions that interacted with groups ( P<0.001). As compared to CTR, MDD rCBF was relatively higher in right associative temporo-parietal-occipital cortex ( P<0.01) and bilaterally in prefrontal ( P<0.005) and frontal cortex ( P<0.025), anterior temporal cortex and central structures ( P<0.05 and P<0.001 respectively). Higher rCBF in a selected group of MDD as compared to CTR at rest was found using PCA in five clusters of regions sharing close anatomical and functional relationships. At the single VOI level, all eight regions showing group differences were included in such clusters. PCA is a data-driven method for recasting VOIs to be used for group evaluation and comparison. The appearance of significant differences absent at the VOI level emphasises the value of analysing the relationships among brain regions for the investigation of psychiatric disease.

Algorithms↗
PubMed2004

99mTc-HMPAO distribution at SPECT is associated with succinate-cytochrome c reductase (SCR) activity in subjects with psychiatric disorders.

The origin of altered (99m)Tc-HMPAO distribution at SPECT in psychiatric disorders is unknown. Correlations between brain (99m)Tc-HMPAO distribution and muscle succinate-cytochrome c reductase (SCR, complex II + III) were assessed in 20 unmedicated psychiatric patients. Significant negative correlations were found between (99m)Tc-HMPAO distribution in associative sensory regions and SCR activity. Sensory cortices are normally enriched in complex II activity. The production of electrons and reactive oxygen species affecting the redox state is considered to be highest from complex III, but complex II may also contribute. The negative relationship between (99m)Tc-HMPAO uptake and SCR activity may be due to redox state alterations influencing fixation of the radiopharmaceutical.

Adult↗
PubMed2004

Sentinel node scintigraphy in breast cancer using a dual tracer technique.

AIM: In order to depict the anatomy and improve the localization, sentinel node scintigraphy in breast cancer was combined with intravenous administration of pertechnetate. As this may reduce the detectability of weak 'hot spots', the number of lymph nodes detected at scintigraphy and at surgery in one group of patients was compared with that obtained in another group that had not received pertechnetate. PATIENTS AND METHODS: The number of 'hot spots' at frontal and lateral views in 47 female patients at scintigraphy performed 2-3 h after subcutaneous injection of radiocolloid together with 25 MBq pertechnetate i.v. was compared in retrospect with that of 41 female patients who had not received pertechnetate. The number of lymph nodes detected at surgery using a hand-held gamma probe together with blue dye in the two groups was also compared. The washout kinetics of pertechnetate was studied in 10 patients. RESULTS: There was no difference in the number of detected lymph nodes at any comparison. The kinetics study revealed a decreasing activity with time after correction for physical decay. CONCLUSION: Administration of a 25 MBq pertechnetate i.v. in order to improve the anatomical localization at sentinel node scintigraphy in breast cancer does not reduce the detectability of radioactive lymph nodes.

Adult↗
PubMed2004

99mTc-exametazime as a breast tumor-seeking agent: comparison with 99mTc-sestamibi.

UNLABELLED: (99m)Tc-sestamibi is commonly used for mammoscintigraphy. Occasional uptake of (99m)Tc-exametazime in various tumors has been described. In this study, an intraindividual comparison of these 2 radiopharmaceuticals for mammoscintigraphy was made. METHODS: A kinetic study (30 min) in the lateral prone view of 20 breast tumors (> or =1 cm) in 20 women was conducted with (99m)Tc-exametazime. Thereafter, 21 breast tumors (> or =1 cm) in 21 women were examined with both agents (2 patients were included in both groups) under identical conditions (interval, 2-7 d). In the latter group, the tumor-to-background breast activity ratio and the tumor uptake normalized to the administered activity (cps/MBq) at 10 min after injection were calculated and compared for both agents. RESULTS: All tumors (43 tumors in 39 patients) were visualized with (99m)Tc-exametazime. There was also one instance of false-positive uptake using this agent. The uptake phase lasted approximately 10 min. Thereafter, the activity was practically stable. (99m)Tc-Sestamibi failed to depict 4 tumors. On the group level, the tracers did not differ in tumor-to-background activity ratio or normalized tumor uptake. Intraindividual agreement in tumor-to-background ratios between the tracers was moderate (intraclass correlation coefficient = 0.49). CONCLUSION: Uptake of (99m)Tc-exametazime in breast tumors > or = 1 cm seems to be comparable with that of (99m)Tc-sestamibi at a group level. The specificity is unknown. There is a restricted intraindividual agreement between the tracers, confirming different uptake mechanisms. This may open up possibilities for assessing different tumor characteristics in vivo, especially since the uptake of both agents is based on mechanisms believed to be involved in resistance to antineoplastic drugs.

Breast Neoplasms↗
PubMed2003

Physiological evaluation of a new quantitative SPECT method measuring regional ventilation and perfusion.

We have developed a new quantitative single-photon-emission computed tomography (SPECT) method that uses (113m)In-labeled albumin macroaggregates and Technegas ((99m)Tc) to estimate the distributions of regional ventilation and perfusion for the whole lung. The multiple inert-gas elimination technique (MIGET) and whole lung respiratory gas exchange were used as physiological evaluations of the SPECT method. Regional ventilation and perfusion were estimated by SPECT in nine healthy volunteers during awake, spontaneous breathing. Radiotracers were administered with subjects sitting upright, and SPECT images were acquired with subjects supine. Whole lung gas exchange of MIGET gases and arterial Po(2) and Pco(2) gases was predicted from estimates of regional ventilation and perfusion. We found a good agreement between measured and SPECT-predicted exchange of MIGET and respiratory gases. Correlations (r(2)) between SPECT-predicted and measured inert-gas excretions and retentions were 0.99. The method offers a new tool for measuring regional ventilation and perfusion in humans.

Adult↗