| 1. |
- Bajc, Marika, et al.
(författare)
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Lung ventilation/perfusion SPECT in the artificially embolized pig.
- 2002
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Ingår i: Journal of Nuclear Medicine. - 0161-5505. ; 43:5, s. 640-647
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Tidskriftsartikel (refereegranskat)abstract
- Planar lung scintigraphy is a standard method used for the diagnosis of lung embolism, but it is hampered by the high incidence of nondiagnostic tests. Ventilation/perfusion SPECT may possibly improve this situation. The objective of this study was to compare planar lung scintigraphy with ventilation/perfusion SPECT using pigs with artificially engendered lung emboli labeled with (201)Tl. METHODS: Sixteen anesthetized pigs were each injected with zero to 4 latex emboli. Cylindric emboli were used in the first 7 pigs and flat 3-tailed emboli were used in the remaining 9 pigs. The pigs spontaneously inhaled 30 MBq (99m)Tc-diethylenetriaminepentaacetic acid aerosol for ventilation scintigraphy. Planar scintigraphy and SPECT were performed using a double-head gamma camera in (99m)Tc and (201)Tl windows. Immediately thereafter, 100 MBq (99m)Tc-labeled macroaggregated albumin were injected intravenously followed by SPECT and, finally, planar scintigraphy. The ventilation background was subtracted from the perfusion tomograms for calculation of a normalized ventilation/perfusion (V/P) quotient image set. RESULTS: The cylindric emboli caused artifacts in the ventilation images; therefore, these were excluded from the final analysis. However, for the planar perfusion images of these pigs, sensitivity and specificity were 71% and 91%, respectively, whereas SPECT yielded 100% for both. For the 3-tailed emboli and ventilation/perfusion images, the sensitivity and specificity were 64% and 79%, respectively, for the planar modality, whereas SPECT yielded values of 91% and 87%, respectively. CONCLUSION: V/P SPECT may improve the diagnostic power of lung scintigraphy.
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| 2. |
- Bitzén, Ulrika, et al.
(författare)
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Dynamic elastic pressure-volume loops in healthy pigs recorded with inspiratory and expiratory sinusoidal flow modulationRelationship to static pressure-volume loops.
- 2004
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Ingår i: Intensive Care Medicine. - : Springer Science and Business Media LLC. - 0342-4642 .- 1432-1238. ; 30:3, s. 481-488
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Tidskriftsartikel (refereegranskat)abstract
- Objective: The objective was to analyse relationships between inspiratory and expiratory static and dynamic elastic pressure-volume (P-el/V) curves in healthy pigs. Design: The modulated low flow method was developed to allow studies also of the expiratory P-el/V curves. Static P-el/V (P-el,P-st/V) and dynamic P-el/V (P-el,P-dyn/V) loops were studied in healthy pigs. Setting: Animal research laboratory in a university hospital. Material: Ten healthy anaesthetised and paralysed pigs. Interventions and measurements: A computer controlled a Servo Ventilator 900C with respect to respiratory rate, inspiratory flow and expiratory pressure to achieve a sinusoidal modulation of inspiration and expiration for determination of P-el,P-dyn/V loops from zero end-expiratory pressure (ZEEP) and from a positive end-expiratory pressure (PEEP) of 6 cmH(2)O to 20, 35 and 50 cmH(2)O. The same system was used for studies of P-el,P-st/V loops with the flow-interruption method from ZEEP and PEEP to 35 cmH(2)O. Recordings were analysed with an iterative technique. Results: The feasibility of automated determination of P-el,P-dyn/V loops was demonstrated. Differences between P-el,P-dyn/V and P-el,P-st/V loops were explained by viscoelastic behaviour. P-el,P-st/V loops recorded from PEEP to 35 cmH(2)O showed no significant hysteresis, indicating a non-significant surface tension hysteresis. P-el,P-dyn/V loops from PEEP and both P-el,P-st/V and P-el,P-dyn/V loops from ZEEP to 35 cmH(2)O showed hysteresis. This indicates that lung collapse/re-expansion caused P-el/V loop hysteresis which, in P-el,P-dyn/V loops, was augmented by viscoelastic behaviour. Conclusions: Viscoelasticity influences P-el,P-dyn/V curves. Hysteresis caused by surface tension merits re-evaluation. Lung collapse and re-expansion may be indicated by hysteresis of P-el/V loops.
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| 3. |
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| 4. |
- Bitzén, Ulrika
(författare)
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Lung mechanics in the aging lung and in acute lung injury. Studies based on sinusoidal flow modulation.
- 2006
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Knowledge about lung mechanics is of interest in intensive care to adjust mechanical ventilation and in the lung laboratory for diagnostics and evaluation of patients with various kinds of respiratory diseases. In mechanical ventilation a single inspiratory elastic pressure-volume (Pel/V) curve is difficult to interpret due to continuing re-expansion of collapsed lung units over a large pressure interval. However, the volume shifts between multiple inspiratory Pel/V curves recorded at different levels of positive end-expiratory pressure (PEEP) give information about lung collapse and re-expansion. Methods based on flow interruption for measurement of Pel/V curves have limitations due to continuing gas exchange, the need for disconnection from the ventilator or the fact that they are time consuming. Recordings during constant or sinusoidal flow can be obtained using a computer-controlled ventilator. Sinusoidal flow modulation provides the possibility to separate the elastic and resistive pressure components of measured pressure, thereby providing more accurate inspiratory Pel/V curves and simultaneous data of resistance (R) in short time. The sinusoidal flow modulation method was further developed to allow recording and analysis of both inspiratory and expiratory limbs of Pel/V loops and to allow automatic recording of Pel/V loops from multiple PEEP levels. Pel/V loops obtained by the sinusoidal flow modulation method and by the flow-interruption method were compared in healthy pigs and in pigs with acute lung injury/acute respiratory distress syndrome (ALI/ARDS). Viscoelastic phenomena caused differences in Pel/V loops and influenced hysteresis. Lung collapse and re-expansion at decreasing PEEP levels could, however, be estimated by hysteresis of the Pel/V loops recorded from zero end-expiratory pressure as well as by the volume shifts between multiple inspiratory Pel/V curves recorded at different levels of PEEP. In ALI/ARDS pigs, expiratory R increased during expiration warranting determination of its volume dependence to obtain as accurate dynamic expiratory Pel/V curves as possible. In the lung laboratory lung parenchyma properties and intrinsic bronchial properties are uniquely reflected in the Pel/V and elastic pressure-resistance (Pel/R) diagrams, respectively, measured at regulated flow rate. The flow-regulation method, previously based on square wave flow modulation (V'square method), was further developed applying sinusoidal flow rate adapted to body size (V'sine method) and iterative parameter estimation for mathematical characterization of Pel/V, Pel/C and Pel/R curves. The quality of results obtained with the V'sine method was equal to that of the more time consuming V'square method. In healthy subjects no effect of heart artefact correction was found. For the V'sine method representative reference values, based on 60 healthy 20 65 year old never-smokers, are presented for Pel/V, Pel/C and Pel/R curves. After normalization to lung size women and men had similar lung mechanics. By relating the Pel/V, Pel/C and Pel/R curves to age and lung size normal ranges were importantly narrowed. Elastic recoil pressure (Pel) decreased with age to an extent in agreement with the higher rates observed in previous studies. The width of the normal range for the Pel/V curve increased with age indicating individual rate of aging as in the skin. At Pel 5 cmH2O, roughly corresponding to functional residual capacity, compliance (C) increased with age as previously observed. At Pel values ? 10 cmH2O C decreased with age. The findings may suggest that the lower part of the Pel/V curve in old subjects is influenced by collapsing alveoli, while in younger subjects airway closure dominates. Expiratory R in relation to Pel decreased with age. When C and R were related to volume rather than to Pel no age dependence was observed. Accordingly, dimension of the lung rather than the distending pressure Pel seems to be a determinant of C and R.
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| 5. |
- Bitzén, Ulrika, et al.
(författare)
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Measurement and mathematical modelling of elastic and resistive lung mechanical properties studied at sinusoidal expiratory flow.
- 2010
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 30, s. 439-446
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Tidskriftsartikel (refereegranskat)abstract
- Summary Elastic pressure/volume (P(el)/V) and elastic pressure/resistance (P(el)/R) diagrams reflect parenchymal and bronchial properties, respectively. The objective was to develop a method for determination and mathematical characterization of P(el)/V and P(el)/R relationships, simultaneously studied at sinusoidal flow-modulated vital capacity expirations in a body plethysmograph. Analysis was carried out by iterative parameter estimation based on a composite mathematical model describing a three-segment P(el)/V curve and a hyperbolic P(el)/R curve. The hypothesis was tested that the sigmoid P(el)/V curve is non-symmetric. Thirty healthy subjects were studied. The hypothesis of a non-symmetric P(el)/V curve was verified. Its upper volume asymptote was nearly equal to total lung capacity (TLC), indicating lung stiffness increasing at high lung volume as the main factor limiting TLC at health. The asymptotic minimal resistance of the hyperbolic P(el)/R relationship reflected lung size. A detailed description of both P(el)/V and P(el)/R relationships was simultaneously derived from sinusoidal flow-modulated vital capacity expirations. The nature of the P(el)/V curve merits the use of a non-symmetric P(el)/V model.
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| 6. |
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| 7. |
- Bitzén, Ulrika, et al.
(författare)
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Retinyl palmitate is a reproducible marker for chylomicron elimination from blood
- 1994
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Ingår i: Scandinavian Journal of Clinical & Laboratory Investigation. - : Informa UK Limited. - 1502-7686 .- 0036-5513. ; 54:8, s. 611-613
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Tidskriftsartikel (refereegranskat)abstract
- To study the individual variation in chylomicron clearance rate, young healthy volunteers were given a p.o. dose of 50,000 IU retinyl palmitate in the morning to label their chylomicrons. Serial blood samples were then obtained in the time interval 4-8 h after retinyl palmitate intake, to closely monitor the clearance of retinyl ester from the blood. The procedure was repeated in an identical way two days later. The calculated individual halflives for retinyl palmitate clearance ranged from 1.54 to 9.90 h, i.e. a more than five-fold variation. The intraindividual variation was much less (relative SD 11%). Retinyl palmitate clearance (and probably chylomicron clearance) is, thus, relatively constant within the same individual on different occasions but varies considerably between individuals.
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| 8. |
- Burman, Pia, et al.
(författare)
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11C-metomidate PET/CT detected multiple ectopic adrenal rest tumors in a woman with congenital adrenal hyperplasia
- 2021
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Ingår i: Journal of Clinical Endocrinology and Metabolism. - : Oxford University Press. - 0021-972X .- 1945-7197. ; 106:2, s. e675-e679
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Tidskriftsartikel (refereegranskat)abstract
- ContextWomen with congenital adrenal hyperplasia (CAH) may present with androgen excess that is difficult to control with conventional suppressive doses of glucocorticoids. Clinical management is challenging, and the woman is at great risk of developing steroid-induced complications.Patients and MethodsA 32-year-old woman with salt-wasting CAH due to 21-hydroxylase deficiency underwent right-sided adrenalectomy because of a large myelolipoma. Over the years, androgens became increasingly difficult to suppress on prednisolone 5 + 0 + 2.5 mg daily, and at age 39 years the left adrenal with an enlarging myelolipoma was removed. A month later serum testosterone levels had increased from 4.1 preoperatively to 18.3 nmol/L (reference 0.2-1.8 nmol/L), and adrenocorticotropin levels from 32 to 283 pmol/L (reference < 14 pmol/L). No adrenal parenchyma was visualized on computed tomography (CT). In the further search for the source of the markedly elevated testosterone, positron emission tomography (PET) was performed with 2 different tracers, 18fluorodeoxyglucose (18FDG) reflecting glucose metabolism and 11C-metomidate, an inhibitor of 11-β-hydroxylase targeting adrenocortical tissue.Results18FDG-PET/CT with cosyntropin stimulation showed ovarian/paraovarian hypermetabolism, suggestive of adrenal rest tumors. Further characterization with 11C-metomidate PET/CT showed uptakes localized to the ovaries/adnexa, behind the spleen, and between the right crus diaphragmaticus and inferior vena cava.ConclusionAdrenal rest tumors can give rise to high androgen levels in spite of suppressive supraphysiological glucocorticoid doses. This case illustrates, for the first time, the value of 11C-metomidate PET as a sensitive method in documenting adrenal rest tumors, currently considered rare in women with CAH.
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| 9. |
- Economou Lundeberg, Johan, et al.
(författare)
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Comparison between silicon photomultiplier-based and conventional PET/CT in patients with suspected lung cancer—a pilot study
- 2019
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Ingår i: EJNMMI Research. - : Springer Science and Business Media LLC. - 2191-219X. ; 9:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Lung cancer is one of the most common cancers in the world. Early detection and correct staging are fundamental for treatment and prognosis. Positron emission tomography with computed tomography (PET/CT) is recommended clinically. Silicon (Si) photomultiplier (PM)-based PET technology and new reconstruction algorithms are hoped to increase the detection of small lesions and enable earlier detection of pathologies including metastatic spread. The aim of this study was to compare the diagnostic performance of a SiPM-based PET/CT (including a new block-sequential regularization expectation maximization (BSREM) reconstruction algorithm) with a conventional PM-based PET/CT including a conventional ordered subset expectation maximization (OSEM) reconstruction algorithm. The focus was patients admitted for 18F-fluorodeoxyglucose (FDG) PET/CT for initial diagnosis and staging of suspected lung cancer. Patients were scanned on both a SiPM-based PET/CT (Discovery MI; GE Healthcare, Milwaukee, MI, USA) and a PM-based PET/CT (Discovery 690; GE Healthcare, Milwaukee, MI, USA). Standardized uptake values (SUV) and image interpretation were compared between the two systems. Image interpretations were further compared with histopathology when available. Results: Seventeen patients referred for suspected lung cancer were included in our single injection, dual imaging study. No statically significant differences in SUVmax of suspected malignant primary tumours were found between the two PET/CT systems. SUVmax in suspected malignant intrathoracic lymph nodes was 10% higher on the SiPM-based system (p = 0.026). Good consistency (14/17 cases) between the PET/CT systems were found when comparing simplified TNM staging. The available histology results did not find any obvious differences between the systems. Conclusion: In a clinical setting, the new SiPM-based PET/CT system with a new BSREM reconstruction algorithm provided a higher SUVmax for suspected lymph node metastases compared to the PM-based system. However, no improvement in lung cancer detection was seen.
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| 10. |
- Gunnlaugsson, Adalsteinn, et al.
(författare)
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A prospective phase II study of prostate-specific antigen-guided salvage radiotherapy and Ga-68-PSMA-PET for biochemical relapse after radical prostatectomy-The PROPER 1 trial
- 2022
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Ingår i: Clinical and Translational Radiation Oncology. - : Elsevier BV. - 2405-6308. ; 36, s. 77-82
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: The treatment of biochemical recurrence (BCR) after prostatectomy is challenging as the site of the recurrence is often undetectable. Our aim was to test a personalised treatment concept for BCR based on PSA kinetics during salvage radiotherapy (SRT) combined with prostate-specific membrane antigen positron emission tomography (PSMA-PET). Materials and methods: This phase II trial included 100 patients with BCR. PSMA-PET was performed at baseline. PSA was measured weekly during SRT. Initially, 70 Gy in 35 fractions was prescribed to the prostate bed. Radiotherapy was adapted after 50 Gy. Non-responders (PSA still >= 0.15 ng/mL) received sequential lymph node irradiation with a boost to PSMA-PET positive lesions, while responders (PSA < 0.15 ng/mL) continued SRT as planned. PET-findings were only taken into consideration for treatment planning in case of PSA non-response after 50 Gy. Results: Data from 97 patients were eligible for analysis. Thirty-four patients were classified as responders and 63 as non-responders. PSMA-PET was positive in 3 patients (9%) in the responder group and in 22 (35%) in the non-responder group (p = 0.007). The three-year failure-free survival was 94% for responders and 68% for non-responders (median follow-up 38 months). There were no significant differences in physician-reported urinary and bowel toxicity. Patient-reported diarrhoea at end of SRT was more common among non-responders. Conclusion: This new personalised treatment concept with intensified SRT based on PSA response demonstrated a high tumour control rate in both responders and non-responders. These results suggest a clinically significant effect with moderate side effects in a patient group with otherwise poor prognosis. PSMA-PET added limited value. The treatment approach is now being evaluated in a phase III trial.
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