1
|
Puig O, Vestergaard MB, Lindberg U, Hansen AE, Ulrich A, Andersen FL, Johannesen HH, Rostrup E, Law I, Larsson HBW, Henriksen OM. Phase contrast mapping MRI measurements of global cerebral blood flow across different perfusion states - A direct comparison with 15O-H 2O positron emission tomography using a hybrid PET/MR system. J Cereb Blood Flow Metab 2019; 39:2368-2378. [PMID: 30200799 PMCID: PMC6890999 DOI: 10.1177/0271678x18798762] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/25/2018] [Accepted: 07/29/2018] [Indexed: 11/29/2022]
Abstract
Phase-contrast mapping (PCM) magnetic resonance imaging (MRI) provides easy-access non-invasive quantification of global cerebral blood flow (gCBF) but its accuracy in altered perfusion states is not established. We aimed to compare paired PCM MRI and 15O-H2O positron emission tomography (PET) measurements of gCBF in different perfusion states in a single scanning session. Duplicate combined gCBF PCM-MRI and 15O-H2O PET measurements were performed in the resting condition, during hyperventilation and after acetazolamide administration (post-ACZ) using a 3T hybrid PET/MR system. A total of 62 paired gCBF measurements were acquired in 14 healthy young male volunteers. Average gCBF in resting state measured by PCM-MRI and 15O-H2O PET were 58.5 ± 10.7 and 38.6 ± 5.7 mL/100 g/min, respectively, during hyperventilation 33 ± 8.6 and 24.7 ± 5.8 mL/100 g/min, respectively, and post-ACZ 89.6 ± 27.1 and 57.3 ± 9.6 mL/100 g/min, respectively. On average, gCBF measured by PCM-MRI was 49% higher compared to 15O-H2O PET. A strong correlation between the two methods across all states was observed (R2 = 0.72, p < 0.001). Bland-Altman analysis suggested a perfusion dependent relative bias resulting in higher relative difference at higher CBF values. In conclusion, measurements of gCBF by PCM-MRI in healthy volunteers show a strong correlation with 15O-H2O PET, but are associated with a large and non-linear perfusion-dependent difference.
Collapse
Affiliation(s)
- Oriol Puig
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Mark B Vestergaard
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Ulrich Lindberg
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Adam E Hansen
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Annette Ulrich
- Department of Cardiothoracic Anesthesiology, Copenhagen University Hospital Rigshospitalet Blegdamsvej, Copenhagen, Denmark
| | - Flemming L Andersen
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Helle H Johannesen
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Egill Rostrup
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Ian Law
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Henrik BW Larsson
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Otto M Henriksen
- Department of Clinical Physiology, Nuclear Medicine and PET, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| |
Collapse
|
2
|
Seawright JW, Sridharan V, Landes RD, Cao M, Singh P, Koturbash I, Mao XW, Miousse IR, Singh SP, Nelson GA, Hauer-Jensen M, Boerma M. Effects of low-dose oxygen ions and protons on cardiac function and structure in male C57BL/6J mice. Life Sci Space Res (Amst) 2019; 20:72-84. [PMID: 30797436 PMCID: PMC6391741 DOI: 10.1016/j.lssr.2019.01.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/31/2018] [Revised: 01/11/2019] [Accepted: 01/12/2019] [Indexed: 05/07/2023]
Abstract
PURPOSE Astronauts traveling beyond low-Earth orbit will be exposed to high linear-energy transfer charged particles. Because there is concern about the adverse effects of space radiation on the cardiovascular system, this study assessed cardiac function and structure and immune cell infiltration in a mouse model of charged-particle irradiation. MATERIALS AND METHODS Male C57BL/6 J mice were exposed to oxygen ions (16O, 600 MeV/n at 0.25-0.26 Gy/min to a total dose of 0, 0.05, 0.1, 0.25, or 1 Gy), protons (150 MeV, 0.35-0.55 Gy/min to 0, 0.5, or 1 Gy), or protons (150 MeV, 0.5 Gy) followed by 16O (600 MeV/n, 0.1 Gy). Separate groups of mice received 137Cs γ-rays (1 Gy/min to 0, 0.5, 1, or 3 Gy) as a reference. Cardiac function and blood velocity were measured with ultrasonography at 3, 5, 7, and 9 months after irradiation. At 2 weeks, 3 months, and 9 months, cardiac tissue was collected to assess apoptosis, tissue remodeling, and markers of immune cells. RESULTS Ejection fraction and fractional shortening decreased at 3 and 7 months after 16O. These parameters did not change in mice exposed to γ-rays, protons, or protons followed by 16O. Each of the radiation exposures caused only small increases in cleaved caspase-3 and numbers of apoptotic nuclei. Changes in the levels of α-smooth muscle cell actin and a 75-kDa peptide of collagen type III in the left ventricle suggested tissue remodeling, but there was no significant change in total collagen deposition at 2 weeks, 3 months, and 9 months. Increases in protein amounts of cluster of differentiation (CD)2, CD68, and CD45 as measured with immunoblots at 2 weeks, 3 months, and 9 months after exposure to protons or 16O alone suggested immune cell infiltration. For type III collagen, CD2 and CD68, the efficacy in inducing protein abundance of CD2, CD68, and CD45 was 16O > protons > γ-rays > protons followed by 16O. CONCLUSIONS Low-dose, high-energy charged-particle irradiation caused mild changes in cardiac function and tissue remodeling in the mouse.
Collapse
Affiliation(s)
- John W Seawright
- Division of Radiation Health, University of Arkansas for Medical Sciences, 4301 West Markham Slot 522-10, Little Rock, AR 72205, USA
| | - Vijayalakshmi Sridharan
- Division of Radiation Health, University of Arkansas for Medical Sciences, 4301 West Markham Slot 522-10, Little Rock, AR 72205, USA
| | - Reid D Landes
- Department of Biostatistics, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Maohua Cao
- Division of Radiation Health, University of Arkansas for Medical Sciences, 4301 West Markham Slot 522-10, Little Rock, AR 72205, USA
| | - Preeti Singh
- Division of Radiation Health, University of Arkansas for Medical Sciences, 4301 West Markham Slot 522-10, Little Rock, AR 72205, USA
| | - Igor Koturbash
- Department of Environmental and Occupational Health, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Xiao-Wen Mao
- Department of Basic Sciences and Radiation Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Isabelle R Miousse
- Department of Environmental and Occupational Health, University of Arkansas for Medical Sciences, Little Rock, AR, USA; Department of Biochemistry and Molecular Biology, University of Arkansas for Medical Sciences, Little Rock, AR, USA
| | - Sharda P Singh
- Department of Internal Medicine, Texas Tech Health Sciences Center, Lubbock, TX, USA
| | - Gregory A Nelson
- Department of Basic Sciences and Radiation Medicine, Loma Linda University, Loma Linda, CA, USA
| | - Martin Hauer-Jensen
- Division of Radiation Health, University of Arkansas for Medical Sciences, 4301 West Markham Slot 522-10, Little Rock, AR 72205, USA
| | - Marjan Boerma
- Division of Radiation Health, University of Arkansas for Medical Sciences, 4301 West Markham Slot 522-10, Little Rock, AR 72205, USA.
| |
Collapse
|
3
|
Yee SH, Lee K, Jerabek PA, Fox PT. Quantitative measurement of oxygen metabolic rate in the rat brain using microPET imaging of briefly inhaled 15O-labelled oxygen gas. Nucl Med Commun 2006; 27:573-81. [PMID: 16794518 DOI: 10.1097/01.mnm.0000220586.02591.fd] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE The quantitative measurement of cerebral metabolic rate of oxygen (CMRO(2)) for rats using positron emission tomography (PET) has been technically difficult. The present study was performed to provide a technique to measure CMRO(2) for rats using a dedicated animal PET technique. METHODS CMRO(2) in the rat brain was quantitatively measured under alpha-chloralose anaesthesia (30 mg . kg(-1) . h(-1), intravenous infusion) using a PET imaging technique. In our experiment, the (15)O-labelled gas tracer (O(15)O) was administered by a bolus insufflation into the lung through a surgically placed cannula in the trachea. The tracer distribution was then dynamically imaged using the microPET. Unlike other conventional PET methods in which a series of arterial blood samples need to be withdrawn for the measurement of an arterial input function, no arterial blood sampling was employed. Instead, the heart was scanned in dynamic mode at the same time of imaging the brain, and the region of interest drawn over the heart was analysed to obtain an arterial input function. RESULTS The CMRO(2) value (micromol . 100 g(-1) . min(-1)) from 10 rats was 208 +/- 15 (mean +/- SD). CONCLUSIONS Our results suggest that the microPET-based CMRO(2) measurement in the rat brain combined with a non-invasive measurement of arterial input function is promising, especially for many applications involving small animals in which repeated measurements of absolute CMRO(2) need to be performed.
Collapse
Affiliation(s)
- Seong-Hwan Yee
- Research Imaging Center, University of Texas Health Science Center, San Antonio, 78229, USA.
| | | | | | | |
Collapse
|
4
|
Mizoguchi S, Suzuki Y, Kiyosawa M, Mochizuki M, Ishii K. Differential activation of cerebral blood flow by stimulating amblyopic and fellow eye. Graefes Arch Clin Exp Ophthalmol 2005; 243:576-82. [PMID: 15650860 DOI: 10.1007/s00417-004-1009-5] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2004] [Accepted: 07/16/2004] [Indexed: 10/25/2022] Open
Abstract
PURPOSE Positron emission tomography (PET), the blood flow response in the primary visual cortex (V1) to two visual stimuli, low temporal frequency (6 Hz) to activate the parvocellular system, and high temporal frequency (25 Hz) to activate the magnocellular system were used to investigate pathophysiologic mechanism of amblyopia. METHODS Five women and one man who were aged between 26 and 60 years, who were ophthalmologically normal except for amblyopia, and who had corrected visual acuity in the amblyopic eye of 0.6 or worse were examined. An intravenous injection of the H(2)(15)O was given, and the regional cerebral blood flow was measured by PET during full-field stimulation with either 6 Hz or 25 Hz flicker to the amblyopic or the sound eye. RESULT The activation of blood flow in the contra-lateral area V1 by the 6-Hz stimulation of the sound eye was greater than that during the stimulation of the amblyopic eye (P<0.05, small volume correction, n=6). With 25-Hz stimulation of the sound and amblyopic eyes, the blood flow in the contra-lateral and ipsi-lateral areas V1 was not significantly different. CONCLUSION The decreased activation of blood flow in the contra-lateral V1 by low temporal frequency stimuli supports the hypothesis that the parvocellular pathway in amblyopic eyes is depressed.
Collapse
Affiliation(s)
- Shoichi Mizoguchi
- Department of Ophthalmology and Visual Science, Tokyo Medical and Dental University Graduate School, Tokyo, Japan
| | | | | | | | | |
Collapse
|
5
|
Weber B, Westera G, Treyer V, Burger C, Khan N, Buck A. Constant-infusion H(2)15O PET and acetazolamide challenge in the assessment of cerebral perfusion status. J Nucl Med 2004; 45:1344-50. [PMID: 15299060] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/30/2023] Open
Abstract
UNLABELLED Assessing the baseline perfusion and perfusion reserve after acetazolamide (ACZ) challenge is a common method for the evaluation of patients with cerebrovascular disease. Most previous studies using H(2)(15)O PET applied the bolus injection technique. There is considerable discrepancy regarding the optimal time point of imaging after ACZ injection. The purpose of this study was to continuously monitor cerebral blood flow (CBF) after ACZ using constant-infusion H(2)(15)O PET. METHODS Four patients with stenoses of an internal carotid artery and 6 with moyamoya disease were studied. H(2)(15)O was continuously infused, and data were recorded in 1-min frames. After equilibration of H(2)(15)O, 5 min of baseline data were acquired, and then 1 g of ACZ was administered intravenously and data collection continued for 10-22 min. Arterial blood was continuously drawn for absolute quantification of CBF. RESULTS The arterial (15)O concentration remained generally stable during scanning, and the cerebellar blood flow fluctuations of the 5 baseline scans were small. The scan-to-scan difference was 6% (difference of 2 successive scans/mean). In the nonpathologic areas, the increase in CBF started 1-2 min after administration of ACZ. The largest fraction of the increase occurred from 0 to 10 min. The ratio of CBF in pathologic areas to CBF in cerebellum showed an initial decrease that stabilized after 5 min. CONCLUSION A continuous-infusion protocol is a viable alternative to single bolus injections for the assessment of cerebral perfusion status. Such a protocol is advantageous when the time course of CBF after an intervention is not known. With continuous monitoring, the optimal time point for evaluation of a certain parameter can be chosen post hoc. Furthermore, the time course of CBF itself may allow the definition of new parameters for evaluating perfusion status in cerebrovascular patients, both for assessment before a revascularization procedure and for follow-up. A limitation of the present study is the relatively small number of patients with each type of cerebrovascular disease and the lack of healthy subjects.
Collapse
Affiliation(s)
- Bruno Weber
- Division of Nuclear Medicine, University Hospital Zurich, Zurich, Switzerland.
| | | | | | | | | | | |
Collapse
|
6
|
Seki C, Kershaw J, Toussaint PJ, Kashikura K, Matsuura T, Fujita H, Kanno I. 15O Radioactivity clearance is faster after intracarotid bolus injection of 15O-labeled oxyhemoglobin than after 15O-water injection. J Cereb Blood Flow Metab 2003; 23:838-44. [PMID: 12843787 DOI: 10.1097/01.wcb.0000071889.63724.1f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The authors tested the hypothesis that the oxygen content of brain tissue is negligible by injecting an intracarotid bolus of 15O-labeled tracer into rats. Under the hypothesis, the clearance rates of 15O radioactivity from the brain after injections of both 15O-labeled water (H(2)15O) and 15O-labeled oxyhemoglobin (HbO15O) should be identical. However, the logarithmic slope of the 15O radioactivity curve after HbO15O injection (0.494 +/- 0.071 min-1) was steeper than that after H(2)15O injection (0.406 +/- 0.038 min-1) (P<0.001, n = 13), where the time range used in the comparison was between 60 and 120 seconds after the injection. A possible interpretation of this result is that nonmetabolized O15O may dwell in the brain tissue for a finite period of time before it is eventually metabolized or returned to the blood stream unaltered. These findings contradict assumptions made by models currently used to measure cerebral oxygen metabolism.
Collapse
Affiliation(s)
- Chie Seki
- Akita Laboratory, Japan Science and Technology Corporation, Akita, Japan
| | | | | | | | | | | | | |
Collapse
|
7
|
Abstract
[14O]water was produced by the 14N(p,n)14O reaction in quantities greater than 80mCi (EOB). The carbon-11 impurity in the final product was approximately 0.003 +/- 0.002% of 14O activity at EOB. A factor of 0.5 +/- 0.02 was obtained to correct the dose calibrator for the additional 2.313 MeV gamma-ray. The effective dose equivalent was calculated for 14O and 15O using MIRDOSE, and the 14O dose was found to be approximately 70% of that for 15O. For scanner performance based on noise equivalent count measurements, the peak activity concentration for 14O was 30% lower than that for 15O. At their peak activity concentrations the noise equivalent count rate for 14O was found to be about 13% less than that for 15O.
Collapse
Affiliation(s)
- Munawwar Sajjad
- PET Imaging Service, Veterans Affairs Medical Center, Minneapolis, MN 55417, USA.
| | | | | | | | | |
Collapse
|
8
|
Stoll HP, Hutchins GD, Winkle WL, Nguyen AT, Appledorn CR, Janzen I, Seifert H, Rübe C, Schieffer H, March KL. Advantages of short-lived positron-emitting radioisotopes for intracoronary radiation therapy with liquid-filled balloons to prevent restenosis. J Nucl Med 2001; 42:1375-83. [PMID: 11535728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/21/2023] Open
Abstract
UNLABELLED Balloon catheters filled with liquid radioisotopes provide excellent dose homogeneity for intracoronary radiation therapy but are associated with risk for rupture or leakage. We hypothesized that the safety of liquid-filled balloons may be improved once positron emitters with half-lives below 2 h are used instead of the high-energy beta-emitters 166Ho, 186Re, or 188Re, all of which have a longer half-life of at least 17 h. METHODS To support this concept, the suitability of 18F (half-life, 109.8 min), 68Ga (half-life, 67.6 min), 11C (half-life, 20.4 min), 13N (half-life, 9.97 min), and 15O (half-life, 2.04 min) for intracoronary radiation therapy was evaluated. Potential tissue penetration of positron radiation was assessed in a series of phantom experiments using Gafchromic film. Antiproliferative efficacy of positrons emitted by 68Ga was investigated in vitro using cultured bovine aortic smooth muscle cells (BASMCs), and was compared with gamma-radiation emitted by 137Cs. To characterize the remaining risk, we estimated radiotoxicity after accidental intravascular balloon rupture on the basis of tabulated isotope-specific doses (ICRP 53) and compared these values with 188Re. RESULTS Half-dose depth of tissue penetration measured in phantom experiments was 0.29 mm for 18F, 0.42 mm for 11C, 0.54 mm for 13N, 0.79 mm for 15O, and 0.9 mm for 68Ga. Irradiation of cultured BASMCs with positron radiation (68Ga) induced dose-dependent inhibition of proliferation with complete proliferative arrest at doses exceeding 6 Gy. ED(50) and ED(80) were 2.5 +/- 0.4 Gy (mean +/- SD) and 4.4 +/- 0.8 Gy, respectively. Antiproliferative efficacy was equal to that of the 662-keV gamma-radiation emitted by 137Cs (ED(50), 3.8 +/- 0.2 Gy; ED(80), 8.0 +/- 0.3 Gy). Estimates made for patient whole-body and organ doses were generally below 50 mSv/1.85 GBq for all investigated positron emitters. The same dose estimates for 188Re were 6-20 fold higher. CONCLUSION Among the studied radioisotopes, 68Ga is the most attractive source for liquid-filled balloons because of its convenient half-life, sufficient positron energy (2.92 MeV), documented antiproliferative efficacy, and uncomplicated availability from a radioisotope generator. The safety profile for 68Ga is significantly better than that of 188Re, which suggests this radioisotope should be evaluated further in preclinical studies.
Collapse
Affiliation(s)
- H P Stoll
- Medical Clinic III, Cardiology, Department of Radiation Oncology, University Hospital Homburg/Saar, Germany
| | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Agostini D, Iida H, Takahashi A, Tamura Y, Henry Amar M, Ono Y. Regional myocardial metabolic rate of oxygen measured by O2-15 inhalation and positron emission tomography in patients with cardiomyopathy. Clin Nucl Med 2001; 26:41-9. [PMID: 11139052 DOI: 10.1097/00003072-200101000-00010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
BACKGROUND Positron emission tomography (PET) metabolic studies have investigated the pathways involved in fatty acid, glucose, and oxidative metabolism in cardiomyopathy and the impairments that occur in the damaged myocardium, but none have provided absolute quantitative variables. Recently, quantitative measurements of the metabolic rate of oxygen (MMRO2) and oxygen extraction fraction (OEF) using O2-15-labeled oxygen gas have been validated in animals and healthy volunteers. The purposes of the current study were to measure MMRO2 and OEF in cardiomyopathy with left ventricular (LV) dysfunction. METHODS The authors selected 25 study participants: 16 patients (10 with ischemic and 6 with dilated) cardiomyopathy with LV dysfunction, and 9 healthy volunteers. As evaluated by echocardiography, LV ejection fraction (LVEF) was decreased in patients (35%+/-9% vs. 65%+/-5%, P<0.01). The PET protocol consisted of transmission, C O2-15 static, H2 O-15 dynamic, and O2-15 gas inhalation steady state scans. An entire myocardial region of interest was drawn to encompass the entire LV myocardium on three midventricular slices in each participant. RESULTS Data showed in patients with dilated cardiomyopathy significant reductions of MMRO2 (0.051+/-0.02 ml x min(-1) x g(-1) vs. 0.108+/-0.02 ml x min(-1) x g(-1), p = 0.01) and OEF (0.55+/-0.15 vs. 0.71+/-0.08, P = 0.01) when compared with healthy volunteers. Furthermore, OEF decreased significantly in lateral and inferior walls. Significant correlations were observed among OEF and the rate-pressure product (RPP) (P = 0.02), LVEF (P<0.001), MMRO2 and RPP (P = 0.04), and LVEF (P = 0.05). In patients with ischemic cardiomyopathy, MMRO2 was significantly reduced (0.039+/-0.02 ml x min(-1) x g(-1) vs. 0.108+/-0.02 ml x min(-1) x g(-1); p = 0.005) but not OEF (0.63+/-0.2 vs. 0.71+/-0.08; P = NS), when compared with healthy volunteers. Significant correlations were observed among OEF and RPP (P = 0.03), LVEF (P = 0.002), MMRO2 and RPP (P<0.01), and LVEF (P = 0.03). CONCLUSIONS These data show that O2-15 gas inhalation and PET allow myocardial MMRO2 and OEF to be measured in patients with cardiomyopathy.
Collapse
Affiliation(s)
- D Agostini
- Service de Médecine Nucléaire, CHU C te de Nacre, Caen, France.
| | | | | | | | | | | |
Collapse
|
10
|
Wu TH, Liu RS, Chong NS, Tsai CS, Lee JS. Evaluation of equivalent dose to working staff with oxygen-15-water in positron emission tomographic studies. Appl Radiat Isot 2000; 53:463-8. [PMID: 10972154 DOI: 10.1016/s0969-8043(99)00281-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
With its short physical half-life and allowing for higher dosage injections, oxygen-15 labeled water has become increasingly important in many clinical applications. However, the use of oxygen-15 labeled water could potentially result in radiation exposures to working staff exceeding regulatory limits. In this study, thermoluminescent dosimeters (LiF-100H) were attached at various parts of the body to measure the accumulated equivalent doses of a physician and to evaluate the radiation risk to the sensitive organs which could receive as many as 10 intravenous injections of (15)O-water for each subject studied. The results showed that during the injections, the hands of a physician received the highest dose, which was about 25.8 times that of the routine chest X-ray dose. If protective shieldings were provided during injection, about 83% of the dose could be effectively reduced. Even without any protective shielding, the estimated maximum dose to the physician was still within the regulatory limit, 50 mSv/year, suggested by ICRP 60. In conclusion, reducing excess radiation exposure to workers, by minimizing the time spent in close contact with patients, increasing the distance from the source and providing suitable protective shielding would be the most effective approach.
Collapse
Affiliation(s)
- T H Wu
- lnstitute of Radiological Sciences, National Yang-Ming University, Taipei, Taiwan
| | | | | | | | | |
Collapse
|
11
|
Moreno-Cantú JJ, Thompson CJ, Meyer E, Fiset P, Zatorre RJ, Klein D, Reutens DC. Enhancement of the signal-to-noise ratio in H2(15)O bolus PET activation images: a combined cold-bolus, switched protocol. J Nucl Med 2000; 41:926-33. [PMID: 10809210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/16/2023] Open
Abstract
UNLABELLED To increase the signal-to-noise ratio (S/N) of H2(15)O bolus PET activation images, we designed and tested a data acquisition protocol that alters the relative distribution of tracer in the uptake and washout phases of the input function. This protocol enhances the S/N gains obtained with conventional switched protocols by combining task switching and the use of a large bolus of blood free of tracer (cold bolus). The cold bolus is formed by sequestering blood in the lower limbs with a double cuff before tracer injection. METHODS The effect of a combined cold-bolus, switched protocol on the signal from activation images was first simulated using a compartmental model of the uptake of H2(15)O into the brain. Then, the effectiveness of the protocol was investigated in 4 healthy volunteers performing a language task. Each volunteer underwent scanning 12 times: 3 activation/ baseline and 3 baseline/activation scans using the conventional switched protocol and 3 activation/baseline and 3 baseline/activation scans using the combined cold-bolus, switched protocol. The S/N changes introduced when using the cold bolus were analyzed by comparing, across protocols, the magnitude and statistical significance of the activation foci associated with the execution of the language task identified in the averaged subtracted images, and by comparing image noise levels. RESULTS In the simulated datasets, the combined protocol yielded a substantial increase in the activation signals for scan durations greater than 60 s, in comparison with equivalent signals yielded by the switched protocol alone. In the PET experiments, activation foci obtained using the combined protocol had significantly higher t statistic values than did equivalent foci detected using the conventional switched protocol (mean improvement, 36%). Analysis of the S/N in the averaged subtracted images revealed that the improvements in statistical significance of the activation foci were caused by increases in the signal magnitudes and not by decreases in overall image noise. CONCLUSION We designed a data acquisition protocol for H2(15)O bolus PET activation studies that combines the use of a tracer-free bolus with a switched protocol. Simulated and experimental data suggest that this combined protocol enhances the S/N gains obtained with a conventional switched protocol. Implementation of the combined protocol in H2(15)O bolus activation studies was easy.
Collapse
Affiliation(s)
- J J Moreno-Cantú
- Department of Neurology and Neurosurgery, McConnell Brain Imaging Center, Montreal Neurological Institute, Quebec, Canada
| | | | | | | | | | | | | |
Collapse
|
12
|
Abstract
In positron emission tomography studies using bolus injection of [15O]water, activation responses reflect underlying CBF changes during a short time (15 to 20 seconds) after arrival of the bolus in the brain. This CBF sensitivity window may be too short for complex activation paradigms, however, particularly those of longer duration. To perform such paradigms, we used a slow infusion method of tracer administration to lengthen the CBF sensitivity window. The present study was designed to determine if this slow infusion technique yields similar results to a bolus injection with a short activation task involving memory for faces. When analyzed using statistical parametric mapping, scanning durations of either 90 or 120 seconds and a 90-second slow infusion schedule produced very similar results to a standard 60-second scan collected after bolus injection, indicating that statistically similar brain activation maps can be produced with the two infusion techniques. This slow infusion approach allows for increased flexibility in designing future studies in which a short CBF sensitivity window is a limiting factor.
Collapse
Affiliation(s)
- L L Beason-Held
- National Institute on Aging, National Institutes of Health, Bethesda, Maryland, USA
| | | | | | | |
Collapse
|
13
|
Vafaee MS, Meyer E, Marrett S, Paus T, Evans AC, Gjedde A. Frequency-dependent changes in cerebral metabolic rate of oxygen during activation of human visual cortex. J Cereb Blood Flow Metab 1999; 19:272-7. [PMID: 10078879 DOI: 10.1097/00004647-199903000-00005] [Citation(s) in RCA: 89] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
To test the hypothesis that brain oxidative metabolism is significantly increased upon adequate stimulation, we varied the presentation of a visual stimulus to determine the frequency at which the metabolic response would be at maximum. The authors measured regional CMR(O2) in 12 healthy normal volunteers with the ECAT EXACT HR+ (CTI/Siemens, Knoxville, TN, U.S.A.) three-dimensional whole-body positron emission tomograph (PET). In seven successive activating conditions, subjects viewed a yellow-blue annular checkerboard reversing its contrast at frequencies of 0, 1, 4, 8, 16, 32, and 50 Hz. Stimulation began 4 minutes before and continued throughout the 3-minute dynamic scan. In the baseline condition, the subjects began fixating a cross hair 30 seconds before the scan and continued to do so for the duration of the 3-minute scan. At the start of each scan, the subjects inhaled 20 mCi of (15)O-O2 in a single breath. The CMR(O2) value was calculated using a two-compartment, weighted integration method. Normalized PET images were averaged across subjects and coregistered with the subjects' magnetic resonance imaging in stereotaxic space. Mean subtracted image volumes (activation minus baseline) of CMR(O2) then were obtained and converted to z statistic volumes. The authors found a statistically significant focal change of CMR(O2) in the striate cortex (x = 9; y = -89; z = -1) that reached a maximum at 4 Hz and dropped off sharply at higher stimulus frequencies.
Collapse
Affiliation(s)
- M S Vafaee
- McConnell Brain Imaging Centre, Positron Emission Tomography Laboratories, Montreal Neurological Institute, McGill University, Quebec, Canada
| | | | | | | | | | | |
Collapse
|
14
|
Moreno-Cantú JJ, Thompson CJ, Zatorre RJ. Evaluation of the ECAT EXACT HR+ 3-D PET scanner in H2(15)O brain activation studies: dose fractionation strategies for rCBF and signal enhancing protocols. IEEE Trans Med Imaging 1998; 17:979-985. [PMID: 10048854 DOI: 10.1109/42.746630] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We evaluated the performance of the ECAT EXACT HR+ 3-D whole-body positron emission tomography (PET) scanner when employed to measure brain function using H2(15)O bolus activation protocols that are completed in single same-day data acquisition sessions. Using vibrotactile and auditory stimuli as independent activation tasks, we studied the scanner performance under different imaging conditions in five healthy volunteers. Cerebral blood flow images were acquired from each volunteer using H2(15)O bolus injections of activity varying from 5-20 mCi. One-session dose-fractionation strategies were analyzed for rCBF, standard activity-concentration, switched, and cold-bolus/switched protocols. Performance characteristics. The scanner dead time grew linearly with injected dose from 10% to 25%. Random events varied from 30% to 50% of the detected events. Random and scattered events were corrected adequately at all doses. Estimated noise-effective-count curves plateau at about 10 mCi. One-session 12-injection bolus PET activation protocols. Using an acquisition protocol that accounts for the scanner performance and the practical aspects of imaging volunteers and neurological patients in a single same-day session, we assessed the correlation between the significance of activation foci and the dose/injection used. The one-session protocol employs 12 bolus injections/subject. We present evidence suggesting that when an rCBF protocol is used, image noise is reduced significantly when the activity injected increases from 5 to 10 mCi. Increasing the dose from 10 to 15 or 20 mCi yielded further but smaller reductions. Our observations also suggest that image noise will be strongly reduced if a 20-mCi dose/injection is used when data are collected using protocols that employ long acquisition times such as a switched or a cold-bolus/switched protocol.
Collapse
Affiliation(s)
- J J Moreno-Cantú
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, Canada
| | | | | |
Collapse
|
15
|
Deloar HM, Watabe H, Nakamura T, Narita Y, Yamadera A, Fujiwara T, Itoh M. Internal dose estimation including the nasal cavity and major airway for continuous inhalation of C15O2, 15O2 and C15O using the thermoluminescent dosimeter method. J Nucl Med 1997; 38:1603-13. [PMID: 9379201] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
UNLABELLED In the steady state method, 15O-labeled gases (C15O2, 15O2 and C15O) are administered to the body by continuous inhalation in various clinical PET studies. During inhalation, the nasal cavity and major airway may obtain a substantial amount of dose, being the source organs as well as the target organs. The internal absorbed dose to those organs and their contribution to the other target organs have not been calculated by the MIRD method. To calculate the internal dose in the MIRD method, the S values, the absorbed doses per unit of cumulated activities from nasal cavity and major airway to the other organs and vice versa, are needed, and these values are not available. METHODS In this study, we introduced a mathematical model of the nasal cavity and major airway to calculate their S values to 23 target organs and from 11 source organs to them. Individual experiments were performed to measure the total uptake percentage and body surface doses of 15O-labeled gases from continuous inhalation. RESULTS Using the body surface doses measured by thermoluminescent dosimeters, the cumulated activities of 11 source organs were estimated with the mathematical transformation method, and then the internal absorbed doses in 23 target organs were calculated by the MIRD method. Our experimental results were compared with the other results, and good agreements were observed. CONCLUSION Among the target organs, the critical organ is the airway, and the absorbed dose is 2.57 x 10(-2) mGy.MBq-1.
Collapse
Affiliation(s)
- H M Deloar
- Cyclotron and Radioisotope Center, Tohoku University, Aramaki, Japan
| | | | | | | | | | | | | |
Collapse
|
16
|
Itoh M, Iwata R, Miyake M, Fujiwara T, Ido T, Nakamura T. [Development of simple on-line [oxygen-15]water infuser]. Kaku Igaku 1996; 33:663-7. [PMID: 8741512] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
A [15O]water production and infusion system was newly developed for blood flow study with positron emission tomography. The system utilizes a electrostatic cooling unit to liquify [15O]vapor in a coiled plastic tube. Labeled [15O]water is collected into an infusion syringe by a wash of the trapping tube with saline. The system is simple and efficient; the recovery rate of [15O]water is over 90% at 10 degrees C of cooling temperature.
Collapse
Affiliation(s)
- M Itoh
- Division of Nuclear Medicine, Tohoku University
| | | | | | | | | | | |
Collapse
|
17
|
Taniguchi H, Oguro A, Koyama H, Masuyama M, Takahashi T. Analysis of models for quantification of arterial and portal blood flow in the human liver using PET. J Comput Assist Tomogr 1996; 20:135-44. [PMID: 8576464 DOI: 10.1097/00004728-199601000-00025] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
OBJECTIVE The purpose of our study was to quantify arterial and portal hepatic arterial blood flows. MATERIALS AND METHODS Four models were developed using PET. The first model consisted of the components of the liver and the portal system. The second applied "curve analysis" to this model. The third model introduced a portosystemic shunt factor, whereas the last model introduced a coefficient for circulation time within the portal organs. In 51 patients (34 men and 17 women), PET scans of the liver were performed using the H2 15O dynamic method. RESULTS Under all four models, the arterial and portal hepatic arterial blood flows of 504 regions of interest were calculated using the nonlinear least-squares method, and results were compared by the sum of the squares of errors. Additionally, results from the H2 15O dynamic method were compared by results from the C15O2 steady-state method. CONCLUSION Of the four models, the last model produced curves with the best fit. When hepatic blood flow was quantified using PET and the H2 15O dynamic method, a model applying "curve analysis" and components related to portosystemic shunting and circulation time was found to be most accurate.
Collapse
Affiliation(s)
- H Taniguchi
- First Department of Surgery, Kyoto Prefectural University of Medicine, Japan
| | | | | | | | | |
Collapse
|
18
|
Abstract
Earlier dosimetry estimates for [15O]water assumed its instantaneous equilibrium with total body water. This assumption leads to an underestimation of the absorbed doses to organs with high blood flows, since the biodistribution of this short-lived radiopharmaceutical is dependent upon blood flow to organs. We have developed a physiologically based whole body blood flow model (WBBFM) using a commercially available icon-driven mathematical simulation software package and applied it to the reevaluation of [15O]water dosimetry in humans. The WBBFM uses multiple parallel compartments to represent organs, heart chambers, the injection site for [15O]water, and blood sampling sites (arterial and venous). Input values to the WBBFM include organ blood flows, organ masses, organ water volumes, organ:blood partition coefficients, injected activity and S-values of [15O]. The WBBFM is based on the same assumptions that are used in calculating regional blood flow using [15O]water and simulates the human body closely in its physiologic response. The activity in each organ is derived from the simulation and is used to calculate absorbed doses. The WBBFM calculated absorbed doses in microGy/MBq (mrad/mCi) to various organs are as follows: heart--2.66 (9.84), kidneys--2.20 (8.15), thyroid--1.83 (6.78), brain--1.66 (6.13), ovaries--1.25 (4.61), breast--1.24 (4.59), and small intestine--1.03 (3.83). These values are approximately two- to threefold higher than the earlier estimates of Kearfott [J. Nucl. Med. 23, 1031-1037 (1982)] and similar to the recent findings of Herscovitch et al. [J. Nucl. Med. 34, 155P (1983)]. We believe this approach yields more realistic dosimetry estimates for [15O]water. Accordingly, we have revised the amount of [15O]water administered during regional blood flow studies at our institution. The relative ease and accuracy of this approach suggests its usefulness in dosimetry estimation for other freely diffusible radiopharmaceuticals.
Collapse
Affiliation(s)
- S Narayana
- Department of Radiology, University of Iowa, Iowa City 52242, USA
| | | | | | | | | |
Collapse
|
19
|
Brihaye C, Depresseux JC, Comar D. Radiation dosimetry for bolus administration of oxygen-15-water. J Nucl Med 1995; 36:651-6. [PMID: 7699461] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
UNLABELLED We describe the development of a biokinetic model which permits an estimation of organ activities and the dosimetry of a bolus of 15O-water. The aim of this study was to estimate time-activity functions and deduce the cumulated activities in different organs so that the radiation absorbed dose values can be estimated. METHODS The model we used includes the right heart chambers, lungs, left heart chamber, brain, liver, kidneys, muscles, gastrointestinal tract and the remainder of the body. Activity in an organ will decay by physical decay with the decay constant, lambda, and can diffuse in the organ. An exception is the heart, where blood is ejected from the heart chambers. Depending on the location of the organ in relation to the blood sampling point, organ activities can be calculated by convolution or deconvolution. RESULTS The radiation absorbed dose values were estimated and an effective dose equivalent HE of 1.16 microSv/MBq (4.32 mrem/mCi) as well as an effective dose E of 1.15 microSv/MBq (4.25 mrem/mCi) were calculated. The cumulated activities in select organs measured by PET gave good agreement with the values calculated by this model. CONCLUSION The values of effective dose equivalent and effective dose for bolus administration of 15O-water calculated from the absorbed doses estimated by the proposed kinetic model are almost three times higher than those previously published. A total of 8700 MBq (235 mCi) of 15O-water can be administered if an effective dose of 10 mSv (1 rem) is accepted.
Collapse
Affiliation(s)
- C Brihaye
- Centre de Recherches du Cyclotron, Université de Liège, Belgium
| | | | | |
Collapse
|
20
|
Iida H, Takahashi A, Tamura Y, Ono Y, Lammertsma AA. Myocardial blood flow: comparison of oxygen-15-water bolus injection, slow infusion and oxygen-15-carbon dioxide slow inhalation. J Nucl Med 1995; 36:78-85. [PMID: 7799088] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
UNLABELLED This study investigates the most appropriate protocol for measuring regional myocardial blood flow (MBF) using 15O-water in clinical applications. METHODS Regional MBF, perfusable tissue fraction (PTF) and arterial blood volume (Va) were measured using 15O-water and dynamic PET on five healthy volunteers based on previously published models. Calculated values were compared for the following three tracer administration protocols: 15O-water bolus injection, 15O-water slow (2 min) infusion and 15O-carbon dioxide slow (2 min) inhalation. For the two slow administration protocols, the three parameters MBF, PTF and Va were computed by fitting the model equations to the myocardial regional time-activity curve. For the bolus injection of 15O-water, only two parameters, MBF and PTF, were fitted by using a fixed Va value obtained by a carbon dioxide blood volume scan. RESULTS All protocols provided consistent MBF values, and the calculated values were homogeneous throughout the whole myocardial segments for all subjects. PTF values were also homogeneous and consistent in the anterior and lateral wall regions, but were significantly greater in the septum (approximately 20%) when the slow 15O-carbon dioxide inhalation protocol was used. MBF and PTF values obtained from the bolus injection protocol showed the smallest intersubject and interregional variations. The simulation study also showed that the magnitude of error was smallest when the bolus injection protocol was employed. CONCLUSION The data suggest that the 15O-water bolus injection protocol together with the two-parameter fitting procedure provides the most accurate results for MBF and PTF. However, it requires arterial cannulation and a separate carbon monoxide scan. For clinical studies, however, the 15O-water infusion protocol would be a good alternative, providing MBF and PTF results with an acceptable degree of accuracy and without the need for arterial cannulation.
Collapse
Affiliation(s)
- H Iida
- Research Institute for Brain and Blood Vessels, Akita, Japan
| | | | | | | | | |
Collapse
|
21
|
Smith T, Tong C, Lammertsma AA, Butler KR, Schnorr L, Watson JD, Ramsay S, Clark JC, Jones T. Dosimetry of intravenously administered oxygen-15 labelled water in man: a model based on experimental human data from 21 subjects. Eur J Nucl Med 1994; 21:1126-34. [PMID: 7828623 DOI: 10.1007/bf00181069] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Models based on uniform distribution of tracer in total body water underestimate the absorbed dose from H2(15)O because of the short half-life (2.04 min) of 15O, which leads to non-uniform distribution of absorbed dose and also complicates the direct measurement of organ retention curves. However, organ absorbed doses can be predicted by the present kinetic model based on the convolution technique. The measured time course of arterial H2(15)O concentration following intravenous administration represents the input function to organs. The impulse response of a given organ is its transit time function determined by blood flow and the partition of water between tissue and blood. Values of these two parameters were taken from the literature. Integrals of the arterial input function and organ transit time functions were used to derive integrals of organ retention functions (organ residence times). The latter were used with absorbed dose calculation software (MIRDOSE-2) to obtain estimates for 24 organs. From the mean values of organ absorbed doses, the effective dose equivalent (EDE) and effective dose (ED) were calculated. From measurements on 21 subjects, the average value for both EDE and ED was calculated to be 1.2 microSv.MBq-1 compared with a value of about 0.5 microSv.MBq-1 predicted by uniform water distribution models. Based on the human data, a method of approximating H2(15)O absorbed dose values from body surface area is described.
Collapse
Affiliation(s)
- T Smith
- Section of Medical Physics, Clinical Research Centre, Harrow, UK
| | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Löttgen J, Wagner R, Richerzhagen N, Wienhard K. Automatic control device for the continuous administration of (15)O labeled gaseous tracers for PET measurements. Appl Radiat Isot 1994; 45:923-8. [PMID: 7951180 DOI: 10.1016/0969-8043(94)90229-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
An automatic control device for the administration of (15)O labelled gaseous PET tracers with constant dose per time (continuous inhalation) is presented. The system controls the flow through the target, the flow to the patient and the dose to the patient simultaneously. The desired values for the dose and the flow to the patient are variable. The dose to the patient is kept constant with +/- 4% even if the beam current raises or if the beam is off for some seconds.
Collapse
Affiliation(s)
- J Löttgen
- Max Planck Institut für neurologische Forschung, Köln, Germany
| | | | | | | |
Collapse
|
23
|
Sadato N, Yonekura Y, Senda M, Iwasaki Y, Matoba N, Tamaki N, Sasayama S, Magata Y, Konishi J. PET and the autoradiographic method with continuous inhalation of oxygen-15-gas: theoretical analysis and comparison with conventional steady-state methods. J Nucl Med 1993; 34:1672-80. [PMID: 8410280] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The steady-state method using 15O gas inhalation and positron emission tomography (PET) is a simple and practical way of imaging cerebral blood flow (CBF) and oxygen metabolism. Several disadvantages do exist, however, including prolonged examination time, requirement of steady-state and a large tissue heterogeneity effect. To avoid the drawbacks of the steady-state method but to preserve its simplicity, we applied the PET/autoradiographic method to the build-up phase during the continuous inhalation of 15O-gas with intermittent arterial sampling. A simulation study was performed to determine the optimal scanning period, evaluate the delay and dispersion effect of the input function and estimate the tissue heterogeneity effect. To assess the clinical feasibility of the proposed technique for the study of oxygen metabolism, sequential measurements with this method and the conventional steady-state method were performed in eight patients. The simulation study showed that a 5-min scan started 3 min after the commencement of 15O-gas inhalation was optimal. With this method, the delay and dispersion effect on CBF was the same as that of the conventional steady-state method, but the tissue heterogeneity effect was reduced. In eight patients, CBF values calculated by this method showed time dependency and were slightly higher than those obtained by the steady-state method. The oxygen extraction fraction showed no significant time dependency and was well correlated with that obtained by the steady-state method. We conclude that the proposed method is a simple and acceptable alternative to the conventional steady-state method.
Collapse
Affiliation(s)
- N Sadato
- Department of Nuclear Medicine, Kyoto University Faculty of Medicine, Japan
| | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Iida H, Jones T, Miura S. Modeling approach to eliminate the need to separate arterial plasma in oxygen-15 inhalation positron emission tomography. J Nucl Med 1993; 34:1333-40. [PMID: 8326395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
A mathematical model has been developed to predict the arterial metabolite concentration curve using the whole blood radioactivity curve in positron emission tomography (PET) during 15O2 inhalation. Production of arterial H2 15O due to aerobic metabolism in the body was modeled as a single rate constant, which was determined from 200 steady-state values of plasma and whole blood concentrations recorded during continuous inhalation of 15O2 and C15O2. Comparison of this method in eight 15O2 inhalation studies (four at rest and four during motor stimulation) performed on four subjects resulted in: (1) arterial H2 15O curves that were well matched in shape to those measured by the frequent plasma separation and (2) cerebral metabolic rate of oxygen (CMRO2) and cerebral blood flow (CBF) were consistent with those obtained by the frequent plasma separation procedure (maximum difference was 3%). An error sensitivity analysis was also performed and demonstrated that errors expected in this modeling approach caused only negligible errors in CMRO2 and CBF estimates. Thus, the arterial H2 15O concentration curve can be accurately predicted using the whole blood time-activity curve; hence, plasma separation can be avoided in 15O2 inhalation PET.
Collapse
Affiliation(s)
- H Iida
- Research Institute for Brain and Blood Vessels, Akita, Japan
| | | | | |
Collapse
|
25
|
Lammertsma AA, Martin AJ, Friston KJ, Jones T. In vivo measurement of the volume of distribution of water in cerebral grey matter: effects on the calculation of regional cerebral blood flow. J Cereb Blood Flow Metab 1992; 12:291-5. [PMID: 1548301 DOI: 10.1038/jcbfm.1992.39] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
The present study was undertaken to determine the apparent value for the volume of distribution of water to be used in the dynamic/integral technique for generating functional CBF images. A value of 0.86 resulted in only a minor loss of accuracy compared to the more accurate (but time-consuming) dynamic only analysis, which incorporated the regionally fitted estimates of the volume of distribution of water. In contrast to the traditionally used in vitro value of 0.95, the value of 0.86 allows for the inclusion of a significant part of the washout phase in the integral analysis, thereby producing statistically improved CBF images.
Collapse
|
26
|
Abstract
We measured the rate of washout of 15O-labeled water generated from labeled oxygen accumulated in brain after bolus [15O]O2 inhalation, and compared the washout with that of labeled water measured with H215O. Contrary to the original expectation, the radioactive water generated from labeled oxygen failed to leave the brain tissue at the rate predicted by exogenous water. Therefore, the use of a separately measured value for exogenous water clearance led to an error in the calculation of oxygen consumption. A new method presented in this paper eliminated the error by yielding oxygen consumption in a single oxygen study. We used time-weighted integration to estimate three parameters, including the unidirectional clearance from blood to brain (KO2(1)), the fractional clearance of the distribution volume in brain (kO2(2)), and the vascular volume correction (VO). We showed that the clearance of oxygen from blood to brain can be estimated with acceptable precision by this new approach, and that the new method yields a reliable measure of oxygen consumption.
Collapse
Affiliation(s)
- S Ohta
- Positron Imaging Laboratories, McConnell Brain Imaging Center, Montreal Neurological Institute, Quebec, Canada
| | | | | | | |
Collapse
|
27
|
Herholz K, Pietrzyk U, Wienhard K, Hebold I, Pawlik G, Wagner R, Holthoff V, Klinkhammer P, Heiss WD. Regional cerebral blood flow measurement with intravenous [15O]water bolus and [18F]fluoromethane inhalation. Stroke 1989; 20:1174-81. [PMID: 2772978 DOI: 10.1161/01.str.20.9.1174] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
In 20 patients with ischemic cerebrovascular disease, classic migraine, or angiomas, we compared paired dynamic positron emission tomographic measurements of regional cerebral blood flow using both [15O]water and [18F]fluoromethane as tracers. Cerebral blood flow was also determined according to the autoradiographic technique with a bolus injection of [15O]water. There were reasonable overall correlations between dynamic [15O]water and [18F]fluoromethane values for cerebral blood flow (r = 0.82) and between dynamic and autoradiographic [15O]water values for cerebral blood flow (r = 0.83). We found a close correspondence between abnormal pathologic findings and visually evaluated cerebral blood flow tomograms obtained with the two tracers. On average, dynamic [15O]water cerebral blood flow was 6% lower than that measured with [18F]fluoromethane. There also was a general trend toward a greater underestimation with [15O]water in high-flow areas, particularly in hyperemic areas, probably due to incomplete first-pass extraction of [15O]water. Underestimation was not detected in low-flow areas or in the cerebellum. Absolute cerebral blood flow values were less closely correlated between tracers and techniques than cerebral blood flow patterns. The variability of the relation between absolute flow values was probably caused by confounding effects of the variation in the circulatory delay time. The autoradiographic technique was most sensitive to this type error.
Collapse
Affiliation(s)
- K Herholz
- Max-Planck-Institut für neurologische Forschung, Köln, Federal Republic of Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
28
|
Powers WJ, Stabin M, Howse D, Eichling JO, Herscovitch P. Radiation absorbed dose estimates for oxygen-15 radiopharmaceuticals (H2(15)O, C15O, O15O) in newborn infants. J Nucl Med 1988; 29:1961-70. [PMID: 3193210] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In preparation for measurement of regional cerebral oxygen metabolism by positron emission tomography, radiation absorbed dose estimates for 19 internal organs, blood, and total body were calculated for newborn infants following bolus intravenous administration of H2(15)O and brief inhalation of C15O and O15O. Cumulated activity for each radiopharmaceutical was calculated from a compartmental model based on the known biologic behavior of the compound. Values for mean absorbed dose/unit cumulated activity (S) for internal organs and total body were based on a newborn phantom. S was separately calculated for blood. Total radiopharmaceutical absorbed dose estimates necessary to measure cerebral oxygen metabolism in a 3.51-kg infant based on 0.7 mCi/kg H2(15)O and 1 mCi/kg C15O and O15O were determined to be 1.6 rad to the lung (maximum organ dose), 0.28 rad to the marrow, 0.46 rad to the gonads, and 0.22 rad to total body. These values are similar to those for current clinical nuclear medicine procedures employing 99mTc in newborn infants.
Collapse
Affiliation(s)
- W J Powers
- Div. of Radiation Sciences, Mallinckrodt Institute of Radiology, St. Louis, MO 63110
| | | | | | | | | |
Collapse
|
29
|
Meyer E, Yamamoto LY, Evans AC, Tyler JL, Diksic M, Feindel W. Radiation dose to upper airways from inhaled oxygen-15 carbon dioxide. J Nucl Med 1987; 28:234-9. [PMID: 3100734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
According to Powell et al., significant retention of 15O in the tracheal mucosa results in a radiation absorbed dose of 75 to 200 rad upon breathing of 15O-CO2 for one hour at 1 mCi/liter. Such a high dose would seriously compromise the 15O-CO2 inhalation method for positron emission tomographic (PET) measurement of cerebral blood flow (CBF). In order to verify these results, we have assayed 15O activity in the tracheal region of three volunteers by PET during inhalation of 15O-CO2 and 15O-O2. Using methods similar to those of the above authors for estimating absorbed dose in the tracheal mucosa, we have obtained a value of 14-38 rad, which is more in keeping with 3-5 rad found by Bigler et al. from direct assay of mucus and saliva. We conclude that the 15O-CO2 inhalation method is a safe and practical means of measuring CBF by PET.
Collapse
|
30
|
Jones SC, Greenberg JH, Reivich M. Error analysis for the determination of cerebral blood flow with the continuous inhalation of 15O-labeled carbon dioxide and positron emission tomography. J Comput Assist Tomogr 1982; 6:116-24. [PMID: 6802887 DOI: 10.1097/00004728-198202000-00020] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The inhalation of C15O2 can be used for determining local cerebral blood flow (LCBF) using a quantitative model. The determination of LCBF in three dimensions using positron emission tomography (PET) involves errors due to counting statistics, data manipulation, and the estimation of parameters in the mathematical model. This work examines error propagation and its relation to the radiation dose to the subject's lungs. An expression has been derived for the root mean square uncertainty in LCBF as a function of LCBF, the spatial resolution and the sensitivity of PET instrument, the normal variability in the brain-blood partition coefficient for water, and absorbed radiation dose to the subject's lungs. The error in LCBF increases as CBF increases. At a normal cortical LCBF of 80 ml/100 g-m and a PET instrument with a 1.65 cm FWHM resolution, and a 46,000 cps per microCi/g sensitivity per slice, an error (coefficient of variation) of 5% results from an inhaled activity of 250 mCi, resulting in a lung dose of 5 rads, the maximum permissible dose allowed. For a more acceptable dose of 1.2 rads, the error is 7%. At a higher resolution (0.8 cm FWHM) and lower sensitivity (15,000 cps per microCi/g per slice), errors become on the order of 28% for a lung dose of 1.2 rads. Errors due to other factors such as blood sample counting, and instrument cross calibration can be virtually eliminated by proper technical strategies. This consideration of error and its relation to radiation dose is important for the application of this inhalation technique for the quantification of LCBF.
Collapse
|
31
|
Abstract
This investigation tests the hypothesis that the normal cerebral image obtained non-invasively during continuous inhalation of C15O2 is related to cerebral blood flow. Trace amounts of CO2 labeled with the positron-emitting radionuclide 15O were administered to 4 normal subjects at normo- and hypocapnia and to 2 of these subjects at hypercapnia. Hypocapnia typically caused a marked decrease in cerebral 15O activity, and hypercapnia a small increase in activity. The relative difference in the change in count rate in response to hypo- and hypercapnia is what one would expect if the activity represented bloow flow, according to a mathematical model which assumes the 15O label enters the brain as water of perfusion. The findings in this study suggest that the normal cerebral image obtained during continuous inhalation of C15O2 is related to cerebral blood flow, but in a non-linear fashion, and that the technique would be more sensitive to ischemic events than to hyperemic phenomena.
Collapse
|
32
|
Nichols AB, Cochavi S, Moore RH, Beller GA. Detection of experimental pulmonary emboli in dogs by sequential positron imaging after inhalation of 15O-carbon dioxide. Circ Res 1978; 42:53-63. [PMID: 618603 DOI: 10.1161/01.res.42.1.53] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
After inhalation, C15O2 (T1/2 = 2 minutes) rapidly diffuses into pulmonary blood and is cleared from the lungs within 10 seconds. The purpose of this study was to determine whether impaired clearance of inhaled C15O2 from oligemic zones, distal to areas of obstructed pulmonary blood flow, could be detected by serial pulmonary imaging with a positron camera. Experimental obstruction of branches of the pulmonary artery was induced in 19 anesthetized dogs by inflation of balloon-tipped catheters (8-12 mm in diameter), injection of radiopaque silicone spheres (0.5-4.0 mm), and embolization with barium-impregnated autologous blood clots (1-5 mm) via the right external jugular vein. After a single bolus injection of 2 mCi of C15O2 into the endotracheal tube, serial lung images of 15O activity were obtained over 60-180 seconds. Obstruction of pulmonary arterial branches resulted in visualization of discrete zones of impaired 15O clearance which varied in area with catheter diameter. Location and size of these zones were confirmed by repeat imaging after direct injection of 15O-labeled blood through the distal catheter lumen. In dogs receiving autologous clots (n = 8), similar zones of impaired 15O clearance were consistently imaged, and single emboli as small as 2 mm in diameter produced regions of retained 15O activity. Zones of retained 15O activity corresponded to the location of radiopaque emboli on chest radiographs. This study introduces a new technique of radionuclide imaging for detection of pulmonary emboli that is noninvasive, safe, sensitive, and repeatable at short intervals.
Collapse
|
33
|
Lenzi GL, Jones T, McKenzie CG, Buckingham PD, Clark JC, Moss S. Study of regional cerebral metabolism and blood flow relationships in man using the method of continuously inhaling oxygen-15 and oxygen-15 labelled carbon dioxide. J Neurol Neurosurg Psychiatry 1978; 41:1-10. [PMID: 621525 PMCID: PMC492955 DOI: 10.1136/jnnp.41.1.1] [Citation(s) in RCA: 47] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
A new technique for assessing regional oxygen use and blood flow has been applied to a wide range of neurological patients. The method couples the brain's high metabolic demand for oxygen with a shortlived radioactive form of this metabolite, namely oxygen-15 (half life: 2.1 min). This combination produces during the continuous inhalation of either molecular oxygen-15 or labelled carbon dioxide, steady state functional images of the brain which are relatively free of contribution from extracerebral tissues. These are complementary images in that they relate to regional oxygen uptake and blood flow and hence offer a direct insight to the regional demand-to-supply relationships within the brain in physiological and pathological conditions. In the clinical groups studied, metabolic and circulatory defects were observed and instances of cerebrovascular insufficiency and relative luxury perfusion were defined which hitherto have been deduced from indirect methods. The clinical acceptability of this non-invasive approach allowed us to study those categories of patients which normally do not warrant invasive examination.
Collapse
|
34
|
Taplin GV, Chopra SK, Elam D. Imaging experimental pulmonary ischemic lesions after inhalation of a diffusible radioaerosol: concise communication. J Nucl Med 1977; 18:250-4. [PMID: 839271] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Regional lung ischemia was imaged with a rapidly diffusible radioaerosol of pertechnetate. The method is compared with similar techniques using 11C and 15O. The principles involved include (A) the rapid alveolar-capillary diffusion of inhaled radioactive gases (11CO, C15O, and C15O2) and the radioaerosol of 99mTcO4-; (B) the patency of the airways to the ischemic regions; and, most importantly; (C) the much slower tracer removal from lung tissue with a stagnant circulation as opposed to the surrounding normal lung. The 11CO and C15O label the hemoglobin in red blood cells, and the C15O2 labels water in the circulation and in the stagnant ischemic region. The TcO4- probably labels the albumin of the plasma in the embolized regions and in the circulating blood. Experiments involving pulmonary embolism in dogs, proved by pre- and post-mortem angiography and gross post-mortem examination, show that positive ischemic lesions (hot spots) are observed, after TcO4- aerosol and C15O2 gas inhalation, in the embolized region on the same day. Clinical trials with aerosol-inhalation method in suspected pulmonary embolism and now under way.
Collapse
|