| 1. |
- Akil, Shahnaz, et al.
(författare)
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Appropriate coronary revascularization can be accomplished if myocardial perfusion is quantified by positron emission tomography prior to treatment decision
- 2021
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 28:4, s. 1664-1672
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Tidskriftsartikel (refereegranskat)abstract
- Background: Many patients undergo percutaneous coronary intervention (PCI) without the use of non-invasive stress testing prior to treatment. The aim of this study was to determine the potential added value of guiding revascularization by quantitative assessment of myocardial perfusion prior to intervention. Methods and Results: Thirty-three patients (10 females) with suspected or established CAD who had been referred for a clinical coronary angiography (CA) with possibility for PCI were included. Adenosine stress and rest 13N-NH3 PET, cardiac magnetic resonance (CMR), and cardiopulmonary exercise test were performed 4 ± 3 weeks before and 5 ± 1 months after CA. The angiographer was blinded to the PET and CMR results. Myocardial flow reserve (MFR) < 2.0 by PET was considered abnormal. A PCI was performed in 19/33 patients. In 41% (11/27) of the revascularized vessel territories, a normal regional MFR was found prior to the PCI and no improvement in MFR was found at follow-up (P = 0.9). However, vessel territories with regional MFR < 2.0 at baseline improved significantly after PCI (P = 0.003). Of the 14 patients not undergoing PCI, four had MFR < 2.0 in one or more coronary territories. Conclusion: Assessment of quantitative myocardial perfusion prior to revascularization could lead to more appropriate use of CA when managing patients with stable CAD.
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| 2. |
- Akil, Shahnaz, et al.
(författare)
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Influence of different time framings, reconstruction algorithms and post-processing methods on the quantification of myocardial blood flow from 13N-NH3 PET images
- 2024
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Ingår i: Clinical Physiology and Functional Imaging. - 1475-0961. ; 44:2, s. 154-163
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Tidskriftsartikel (refereegranskat)abstract
- Background: The aim was to investigate to what extent the quantification of myocardial blood flow (MBF) from dynamic 13N-NH3 positron emission tomography (PET) images is affected by time frame schemes, time-of-flight (ToF), reconstruction algorithms, blood pool volume of interest (VOI) locations and compartment models in patients with suspected chronic coronary syndrome. Methods: A standard MBF value was determined from 25 patients' rest/stress 13N-NH3 PET/CT images reconstructed with ordered subset expectation maximization (OSEM), 5 s time frame for the first frames without ToF, subsequently analyzed using a basal VOI and the deGrado compartment model. MBFs calculated using 2 or 10 s for the first frames, ToF, block-sequential regularized expectation maximization (BSREM), apical or large VOI, Hutchins or Krivokapich compartment models were compared to MBFstandard in Bland–Altman plots (bias ± SD). Results: Good agreement in global rest/stress MBF (mL/min/g) was found when changing the time frame scheme or reconstruction algorithm (MBFstandard vs. MBF2s: −0.02 ± 0.06; MBF10s: 0.01 ± 0.07; MBFBSREM: 0.01 ± 0.07), while a lower level of agreement was found when altering the other factors (MBFstandard vs. MBFToF: −0.07 ± 0.10; MBFapical VOI: −0.27 ± 0.25; MBFlarge VOI: −0.11 ± 0.10; MBFHutchins: −0.08 ± 0.10; MBFKrivokapich: −0.47 ± 0.50). Conclusions: Quantification of MBF from 13N-NH3 PET images is more affected by choice of compartment models, ToF and blood pool VOIs than by different time frame schemes and reconstruction algorithms.
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| 3. |
- Akil, Shahnaz, et al.
(författare)
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Qualitative assessments of myocardial ischemia by cardiac MRI and coronary stenosis by invasive coronary angiography in relation to quantitative perfusion by positron emission tomography in patients with known or suspected stable coronary artery disease
- 2020
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 27:6, s. 2351-2359
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Tidskriftsartikel (refereegranskat)abstract
- Background: To relate findings of qualitative evaluation of first-pass perfusion-CMR and anatomical evaluation on coronary angiography (CA) to the reference standard of quantitative perfusion, cardiac PET, in patients with suspected or known stable coronary artery disease (CAD). Methods and Results: Forty-one patients referred for CA due to suspected stable CAD, prospectively performed adenosine stress/rest first-pass perfusion-CMR as well as 13N-NH3 PET on the same day, 4 ± 3 weeks before CA. Angiographers were blinded to PET and CMR results. Regional myocardial flow reserve (MFR) < 2.0 on PET was considered pathological. Vessel territories with stress-induced ischemia by CMR or vessels with stenosis needing revascularization had a significantly lower MFR compared to those with no regional stress-induced ischemia or vessels not needing revascularization (P < 0.001). In 4 of 123 vessel territories with stress-induced ischemia by CMR, PET showed a normal MFR. In addition, 12 of 123 vessels that underwent intervention showed normal MFR assessed by PET. Conclusion: The limited performance of qualitative assessment of presence of stable CAD with CMR and CA, when related to quantitative 13N-NH3 cardiac PET, shows the need for fully quantitative assessment of myocardial perfusion and the use of invasive flow reserve measurements for CA, to confirm the need of elective revascularization.
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| 4. |
- Bajc, Marika, et al.
(författare)
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V/P SPECT as a diagnostic tool for pregnant women with suspected pulmonary embolism.
- 2015
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Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 42:8, s. 1325-1330
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the study was to assess the prevalence of pulmonary embolism (PE) and other lung diseases among pregnant women with suspected PE and to calculate the radiation exposure to patient and fetus in this population. As a secondary aim, we evaluated the negative predictive value of a normal ventilation/perfusion single photon emission computed tomography (V/P SPECT) examination in pregnancy.
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| 5. |
- Chittenden, Sarah J., et al.
(författare)
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A Phase 1, Open-Label Study of the Biodistribution, Pharmacokinetics, and Dosimetry of Ra-223-Dichloride in Patients with Hormone-Refractory Prostate Cancer and Skeletal Metastases
- 2015
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Ingår i: Journal of Nuclear Medicine. - : Society of Nuclear Medicine. - 0161-5505 .- 2159-662X. ; 56:9, s. 1304-1309
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this single-site, open-label clinical trial was to determine the biodistribution, pharmacokinetics, absorbed doses, and safety from 2 sequential weight-based administrations of Ra-223-dichloride in patients with bone metastases due to castration-refractory prostate cancer. Methods: Six patients received 2 intravenous injections of Ra-223-dichloride, 6 wk apart, at 100 kBq/kg of whole-body weight. The pharmacokinetics and biodistribution as a function of time were determined, and dosimetry was performed for a range of organs including bone surfaces, red marrow, kidneys, gut, and whole body using scintigraphic imaging; external counting; and blood, fecal, and urine collection. Safety was assessed from adverse events. Results: The injected activity cleared rapidly from blood, with 1.1% remaining at 24 h. The main route of excretion was via the gut, although no significant toxicity was reported. Most of the administered activity was taken up rapidly into bone (61% at 4 h). The range of absorbed doses delivered to the bone surfaces from a emissions was 2,331-13,118 mGy/MBq. The ranges of absorbed doses delivered to the red marrow were 177-994 and 1-5 mGy/MBq from activity on the bone surfaces and from activity in the blood, respectively. No activity-limiting toxicity was observed at these levels of administration. The absorbed doses from the second treatment were correlated significantly with the first for a combination of the whole body, bone surfaces, kidneys, and liver. Conclusion: A wide range of interpatient absorbed doses was delivered to normal organs. Intrapatient absorbed doses were significantly correlated between the 2 administrations for any given patient. The lack of gastrointestinal toxicity is likely due to the low absorbed doses delivered to the gut wall from the gut contents. The lack of adverse myelotoxicity implies that the absorbed dose delivered from the circulating activity may be a more relevant guide to the potential for marrow toxicity than that due to activity on the bone surfaces.
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| 6. |
- Engblom, Henrik, et al.
(författare)
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Fully quantitative cardiovascular magnetic resonance myocardial perfusion ready for clinical use : A comparison between cardiovascular magnetic resonance imaging and positron emission tomography
- 2017
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Ingår i: Journal of Cardiovascular Magnetic Resonance. - : Springer Science and Business Media LLC. - 1097-6647 .- 1532-429X. ; 19:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Recent studies have shown that quantification of myocardial perfusion (MP) at stress and myocardial perfusion reserve (MPR) offer additional diagnostic and prognostic information compared to qualitative and semi-quantitative assessment of myocardial perfusion distribution in patients with coronary artery disease (CAD). Technical advancements have enabled fully automatic quantification of MP using cardiovascular magnetic resonance (CMR) to be performed in-line in a clinical workflow. The aim of this study was to validate the use of the automated CMR perfusion mapping technique for quantification of MP using 13N-NH3 cardiac positron emission tomography (PET) as the reference method. Methods: Twenty-one patients with stable CAD were included in the study. All patients underwent adenosine stress and rest perfusion imaging with 13N-NH3 PET and a dual sequence, single contrast bolus CMR on the same day. Global and regional MP were quantified both at stress and rest using PET and CMR. Results: There was good agreement between global MP quantified by PET and CMR both at stress (-0.1 ± 0.5 ml/min/g) and at rest (0 ± 0.2 ml/min/g) with a strong correlation (r = 0.92, p < 0.001; y = 0.94× + 0.14). Furthermore, there was strong correlation between CMR and PET with regards to regional MP (r = 0.83, p < 0.001; y = 0.87× + 0.26) with a good agreement (-0.1 ± 0.6 ml/min/g). There was also a significant correlation between CMR and PET with regard to global and regional MPR (r = 0.69, p = 0.001 and r = 0.57, p < 0.001, respectively). Conclusions: There is good agreement between MP quantified by 13N-NH3 PET and dual sequence, single contrast bolus CMR in patients with stable CAD. Thus, CMR is viable in clinical practice for quantification of MP.
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| 7. |
- Eriksson, Mats, et al.
(författare)
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Plutonium hot particle separation techniques using real-time digital image systems
- 2002
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section A: Accelerators, Spectrometers, Detectors, and Associated Equipment. - 0167-5087. ; 488:1-2, s. 375-380
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Tidskriftsartikel (refereegranskat)abstract
- Two real-time digital imaging systems, able to replace conventional autoradiography for radioactive hot particle separation and identification, are presented in this paper. The hot plutonium particles used for the study originate from the Thule nuclear weapon accident, Both of the real-time imaging techniques are initiated with sample splitting and measurements with a HPGe detector. in order to detect the gamma-emitting Pu-241 daughter Am-241, which is an indicator of plutonium hot particle in the sample. The time required for the whole process of separation and identification of one single particle from a bulk sediment sample (150 g dry weight) is of the order of 1-2 days, and is highly dependent on its activity. The real-time digital imaging systems presented in this paper are preferable, compared to conventional autoradiography and the CR-39 technique, when separation and identification of hot particles are needed as they are much faster and in addition give a real-time image of the particle. (C) 2002 Elsevier Science B.V. All rights reserved.
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| 8. |
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| 9. |
- Hedeer, Fredrik, et al.
(författare)
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Diagnostic accuracy for CZT gamma camera compared to conventional gamma camera technique with myocardial perfusion single-photon emission computed tomography : Assessment of myocardial infarction and function
- 2023
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1071-3581 .- 1532-6551. ; 30:5, s. 1935-1946
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Tidskriftsartikel (refereegranskat)abstract
- Background: The solid-state cadmium-zinc-telluride (CZT) gamma camera for myocardial perfusion single-photon emission computed tomography (MPS) has theoretical advantages compared to the conventional gamma camera technique. This includes more sensitive detectors and better energy resolution. We aimed to explore the diagnostic performance of gated MPS with a CZT gamma camera compared to a conventional gamma camera for detection of myocardial infarct (MI) and assessment of left ventricular (LV) volumes and ejection fraction (LVEF), using cardiac magnetic resonance (CMR) as the reference method. Methods: Seventy-three patients (26% female) with known or suspected chronic coronary syndrome were examined with gated MPS using both a CZT gamma camera and a conventional gamma camera as well as with CMR. Presence and extent of MI on MPS and late gadolinium enhancement (LGE) CMR was evaluated. For LV volumes, LVEF and LV mass, gated MPS images and cine CMR images were evaluated. Results: MI was found in 42 patients on CMR. The overall sensitivity, specificity, positive and negative predictive values for the CZT and the conventional gamma camera were the same (67%, 100%, 100% and 69%). For infarct size > 3% on CMR, the sensitivity was 82% for the CZT and 73% for the conventional gamma camera, respectively. LV volumes were significantly underestimated by MPS compared to CMR (P ≤.002 for all measures). The underestimation was slightly less pronounced for the CZT compared to the conventional gamma camera (2-10 mL, P ≤.03 for all measures). For LVEF, however, accuracy was high for both gamma cameras. Conclusion: Differences between a CZT and a conventional gamma camera for detection of MI and assessment of LV volumes and LVEF are small and do not appear to be clinically significant.
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| 10. |
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| 11. |
- Hindorf, Cecilia, et al.
(författare)
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Clinical dosimetry in the treatment of bone tumors: old and new agents
- 2011
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Ingår i: Quarterly Journal of Nuclear Medicine and Molecular Imaging. - 1824-4785. ; 55:2, s. 198-204
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Tidskriftsartikel (refereegranskat)abstract
- Treatment of multisite, sclerotic bone metastases is successfully performed by radionuclide therapy. Pain palliation is the most common aim for the treatment. Two radiopharmaceuticals are currently approved by the European Medicines Agency (Sm-153-EDTMP and Sr-89-Cl-2) whilst other radiopharmaceuticals are at different stages of development, or are approved in some European countries (Re-186-HEDP, Sn-117(m)-DTPA and Ra-223-Cl-2). The tissues at risk for the treatment are bone marrow and normal bone. A review of the methods applied for dosimetry for these tissues and for tumours is performed, including the calculation of S values (the absorbed dose per decay) and optimal procedures on how to obtain biodistribution data for each radiopharmaceutical. The dosimetry data can be used to individualise and further improve the treatment for each patient. Dosimetry for radionuclide therapy of bone metastases is feasible and can be performed in a routine clinical practice.
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| 12. |
- Hindorf, Cecilia, et al.
(författare)
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EANM Dosimetry Committee guidelines for bone marrow and whole-body dosimetry
- 2010
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Ingår i: European Journal of Nuclear Medicine and Molecular Imaging. - : Springer Science and Business Media LLC. - 1619-7070 .- 1619-7089. ; 37:6, s. 1238-1250
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Tidskriftsartikel (refereegranskat)abstract
- The level of administered activity in radionuclide therapy is often limited by haematological toxicity resulting from the absorbed dose delivered to the bone marrow. The purpose of these EANM guidelines is to provide advice to scientists and clinicians on data acquisition and data analysis related to bone-marrow and whole-body dosimetry. The guidelines are divided into sections "Data acquisition" and "Data analysis". The Data acquisition section provides advice on the measurements required for accurate dosimetry including blood samples, quantitative imaging and/or whole-body measurements with a single probe. Issues specific to given radiopharmaceuticals are considered. The Data analysis section provides advice on the calculation of absorbed doses to the whole body and the bone marrow. The total absorbed dose to the bone marrow consists of contributions from activity in the bone marrow itself (self-absorbed dose) and the cross-absorbed dose to the bone marrow from activity in bone, larger organs and the remainder of the body. As radionuclide therapy enters an era where patient-specific dosimetry is used to guide treatments, accurate bone-marrow and whole-body dosimetry will become an essential element of treatment planning. We hope that these guidelines will provide a basis for the optimization and standardization of the treatment of cancer with radiopharmaceuticals, which will facilitate single- and multi-centre radionuclide therapy studies.
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| 13. |
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| 14. |
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| 15. |
- Hindorf, Cecilia, et al.
(författare)
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Importance of correct patient positioning in myocardial perfusion SPECT when using a CZT camera.
- 2014
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Ingår i: Journal of Nuclear Cardiology. - : Springer Science and Business Media LLC. - 1532-6551 .- 1071-3581. ; 21:4, s. 695-702
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Tidskriftsartikel (refereegranskat)abstract
- Myocardial perfusion single photon emission computed tomography (MPS) is one of the most widely used diagnostic methods in patients with suspected ischemic heart disease (IHD). Recently, a novel technique based on cadmium-zinc-telluride (CZT) detectors, pinhole collimators, and a stationary gantry was introduced for MPS. The aim of this work was to investigate how patient positioning affects the reconstructed MPS images using this novel technique.
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| 16. |
- Hindorf, Cecilia
(författare)
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Internal dosimetry. Macroscopic, small-scale and microscopic perspectives
- 2004
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Internal dosimetry deals with the assessment of absorbed dose for radionuclides distributed inside the body. The absorbed dose is in its turn used for correlation with the biological effect caused by the irradiation. In radioimmunotherapy is however the correlation not easily found and factors influencing this are evaluated and discussed in this work. The internal dosimetry could be subdivided into three levels; macroscopic, small-scale, and microscopic dosimetry. Macroscopic dosimetry: The MIRD S formalism is used to assess the mean absorbed dose to normal organs and tissues. The activity distribution is assumed to be uniform and the calculated mean absorbed dose serves as a good representation of the absorbed dose since the volumes are large compared to the range of emitted particles. The mean absorbed dose to normal organs and tumours was determined for B-cell lymphoma patients undergoing radioimmunotherapy with 90Y-hLL2 (Paper I). The absorbed dose to bone marrow, which is the most radiation sensitive tissue in the body, could be calculated via a method based on the activity in blood samples. The ratio of the activity concentration in bone marrow to the activity concentration in blood was, however, found not to be constant over time. A method for taking this into account in the calculations was proposed (Paper II). Lymphomas are in general radiation sensitive, fast-responding tumours. A decrease in the mass of a tumour during the course of radioimmunotherapy could have a strong influence on the calculated absorbed dose and a method for correction due to this effect was developed (Paper III). Small-scale dosimetry: The MIRD formalism is used, but as the volume is smaller, the mean absorbed dose serves as a poorer representation of the absorbed dose. A model of the anatomy of a mouse was developed and the influence on the S values (absorbed dose per decay) for the choice of organ mass, shape of the organs and distances between the organs was investigated (Paper IV). The average number of atoms per tumour cell was determined from blood samples from a patient having a B cell lymphoma. The MIRD cellular S values were used for calculation of the mean absorbed dose to a cell (Paper V). Internal microdosimetry: The absorbed dose is the expectation value of the specific energy, which is a quantity that takes stochastic effects of the energy depositions into account. The smaller a volume, the larger stochastic effects are seen. Lymphoma patients could have a leukaemic spread of their disease and as 90Y often is used for therapy, the treatment to the single tumour cells is not optimized. Theoretical calculations were performed based on experimental data for an evaluation (Paper VI).
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| 17. |
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| 18. |
- Hindorf, Cecilia, et al.
(författare)
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Quantitative imaging of 223Ra-chloride (Alpharadin) for targeted alpha-emitting radionuclide therapy of bone metastases.
- 2012
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Ingår i: Nuclear Medicine Communications. - 1473-5628. ; 33:7, s. 726-732
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Ra is an alpha particle emitter that targets areas of increased bone turnover in bone metastases. Alpha particles account for 95% of the 27.8 MeV emitted per decay. Less than 2% of the emissions are from photons. This means that a high absorbed dose will be delivered locally, although the number of photons for imaging will be low. The purpose of this study was to investigate the possibility of quantitative imaging of Ra to enable biodistribution studies. METHODS: A Philips Forte gamma camera, equipped with a medium-energy collimator, was used. Basic imaging parameters were determined from phantom studies, and the accuracy of activity quantification was tested in a phantom study and within a patient study. RESULTS: Imaging parameters were determined for the three most suitable photon peaks from the acquired energy spectrum (82, 154 and 270 keV). Camera sensitivity is constant for circular sources with areas greater than 10 cm. The spatial resolution (full-width at half-maximum) was 1.1 cm for each of the three energy windows. The possibility for quantitative imaging was further investigated for the 82 keV energy window, which showed the highest sensitivity and spatial resolution. A phantom study showed that activity could be quantified to within 10% for a 200 ml volume placed within water containing background activity and to within 50% for a 0.5 ml phantom. Quantification of activity in bone after administrations of 100 kBq/kg of Ra-chloride proved the feasibility of quantitative imaging of patients who have received radionuclide therapy. CONCLUSION: Because of the high-energy deposition of Ra, only a low injected activity is required for therapy, which results in a low count rate for the gamma camera. Nevertheless, this study has demonstrated that it is possible to quantify uptake with a sufficient degree of accuracy to obtain clinically relevant information.
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| 19. |
- Hindorf, Cecilia, et al.
(författare)
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Radiation protection in nuclear medicine
- 2016
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Ingår i: Radiation Protection in Medical Imaging and Radiation Oncology. - 9781482245370 - 9781482245387 ; , s. 111-135
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Bokkapitel (refereegranskat)
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| 20. |
- Hindorf, Cecilia, et al.
(författare)
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Single-cell dosimetry for radioimmunotherapy of B-cell lymphoma patients with special reference to leukemic spread
- 2007
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Ingår i: Cancer Biotherapy & Radiopharmaceuticals. - : Mary Ann Liebert Inc. - 1557-8852 .- 1084-9785. ; 22:3, s. 357-366
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Tidskriftsartikel (refereegranskat)abstract
- Aims: Many lymphoma patients have both macroscopic tumors and single-cell manifestations of their disease. Treatment efficacy could, therefore, depend on the radionuclide used. The aim of this study was to investigate dosimetry at a cellular level for three isotopes of radioiodine. Methods: Cells were assumed to be spherical with radii of 6.35, 7.7, and 9.05 mu m corresponding to the dimensions of the Raji cells. The radius of the nucleus was assumed to be 75% of the cellular radius. The electron energies were 18, 28, and 190 keV, corresponding to the mean electron energy per decay for I-125, I-123, and I-131, respectively. S-values for different activity distributions were simulated using Monte Carlo and dose-volume histograms as well as absorbed doses, and absorbed dose rates were calculated. Results: I-125 gives the highest absorbed dose (similar to 4-40 times that of I-131), whereas I-123 Will give the highest absorbed dose rate (similar to 100 times that of I-131). Under the given assumptions, the absorbed dose at this level is more dependent on the Size of the cells than on whether the radioimmunoconjugate is internalized. Conclusions: This enquiry showed that both I-123 and I-125 have greater potential than I-131 for the treatment of leukemic spread in patients With lymphoma.
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| 21. |
- Hindorf, Cecilia, et al.
(författare)
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Time dependence of the activity concentration ratio of red marrow to blood and implications for red marrow dosimetry.
- 2002
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Ingår i: Cancer. - : Wiley. - 1097-0142 .- 0008-543X. ; 94:4 Suppl, s. 1235-1239
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: The method for red marrow dosimetry in radioimmunotherapy, in the absence of specific activity uptake in red marrow, is based on the activity measured in the blood or plasma. The activity concentration ratio of red marrow to blood is then assumed to be constant. The aim of the current study was to determine whether this ratio varies with time after injection. METHODS: Measurements were carried out with both animals and patients.Tumor-bearing rats were intravenously injected with iodine-131-, iodine-125-, indium-111-, or rhenium-188-labeled BR96, a chimeric immunoglobulin G1 monoclonal antibody. (All were chelate-labeled, except for iodine-131, which was iodogen-labeled.) Measurements were made of the activity concentration in blood and bone marrow at different points in time after injection, and the ratio of activity concentration in red marrow and blood as a function of time postinjection (RMBLR[t)]) was calculated. For patients treated with iodine-131-labeled monoclonal antibody (LL2, Immunomedics Inc., Morris Plains, NJ; anti-CD22; immunoglobulin G2 isotype of mouse origin), blood samples were drawn and scintillation camera images taken at different times after injection. The red marrow activity concentration in the sacrum was determined by activity quantification from regions of interest. The activity concentration in blood was also measured. The RMBLR(t) was calculated based on these data. RESULTS: For both patients and rats, the RMBLR(t) was increased 72 hours after injection. Furthermore, it was found that the use of a constant RMBLR can lead to an over- or underestimation of the absorbed dose in bone marrow. CONCLUSIONS: These data demonstrate the difficulty in using fixed values of the activity concentration ratio of red marrow to blood for dosimetry.
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| 22. |
- Hindorf, Cecilia, et al.
(författare)
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Traceable calibration with 177Lu and comparison of activity meters at hospitals in Norway and Sweden
- 2023
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Ingår i: Physica medica (Testo stampato). - : Elsevier. - 1120-1797 .- 1724-191X. ; 116
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: The activity meter is used to determine the activity of delivered radiopharmaceuticals, administered activity to patients and reference activity when gamma-cameras are calibrated prior to imaged-based dosimetry. The aim is to describe a procedure for cross-calibration of activity meters at different clinical sites, and report on 177Lu activity results when using factory-set calibration factors compared to when calibration is performed with traceability to a primary standard.Methods: Thirty activity meters placed at seven hospitals in Norway and Sweden from four manufacturers: Capintec, Commecer, NuviaTech and Veenstra were included. A stock solution with 177Lu was prepared at the local sites and measured in each activity meter with factory settings. The solution was shipped to the reference site at Lund University for measurements in a secondary standard activity meter. Deviations between local and reference activity measurements were determined for three geometries: 25-mL vial, 10-mL syringe and 1-mL syringe.Results: The median of the deviations was 6.4 % for the 25 mL vial, 5.9 % for the 10 mL syringe and 6.8 % for the 1 mL syringe. The median of the deviations for the 25 mL vial, was 1.5 % for activity meters from Capintec, 7.0 % for Comecer, 11.0 % for NuviaTech and 2.4 % for Veenstra. The majority of the deviations were positive and the maximum deviation was 14.5 %.Conclusion: The activity of 177Lu measured in an activity meter with factory-set dial settings may yield deviations up to 14.5%, compared to activities measured with traceability to a primary standard. This would imply an undertreatment of patients.
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| 23. |
- Holstensson, Maria, et al.
(författare)
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Optimization of energy-window settings for scatter correction in quantitative In-111 imaging: Comparison of measurements and Monte Carlo simulations
- 2007
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Ingår i: Cancer Biotherapy & Radiopharmaceuticals. - : Mary Ann Liebert Inc. - 1557-8852 .- 1084-9785. ; 22:1, s. 136-142
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Tidskriftsartikel (refereegranskat)abstract
- Activity quantification in nuclear medicine imaging is highly desirable, particularly for dosimetry and biodistribution studies of radiopharmaceuticals. Quantitative In-111 imaging is increasingly important with the current interest in therapy using Y-90 radiolabeled antibodies. One of the major problems in quantification is scatter in the images, which leads to degradation of image quality. The aim of this study was to optimize the energy-window settings for quantitative In-111 imaging with a camera that enabled acquisition in three energy windows. Experimental measurements and Monte Carlo simulations, using the SI-MIND code, were conducted to investigate parameters such as sensitivity, image contrast, and image resolution. Estimated scatter-to-total ratios and distributions, as obtained by the different window settings, were compared with corresponding simulations. Results showed positive agreement between experimental measurements and results from simulations, both quantitatively and qualitatively. We conclude that of the investigated methods, the optimal energy-window setting was two windows centered at 171 and 245 keV, together with a broad scatter window located between the photopeaks.
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| 24. |
- Kalaitzidis, Philip, et al.
(författare)
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Monte Carlo investigation of PET [68Ga]Ga-DOTA-TOC activity-administration protocols for consistent image quality
- 2023
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Ingår i: Heliyon. - 2405-8440. ; 9:9
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Tidskriftsartikel (refereegranskat)abstract
- One example of a PET exam that suffers from noise problems is [68Ga]Ga-DOTA-TOC, where patients are generally administered between 100 and 200 MBq [68Ga]Ga-DOTA-TOC, irrespective of size. However, a fixed activity can result in low signal-to-noise ratios (SNRs) in larger patients. This study aimed to evaluate the impact on image quality with respect to injected activity and patient habitus through Monte Carlo (MC) simulation. Eight anthropomorphic computer phantoms with body mass indices (BMIs) between 19 kg/m2 and 38 kg/m2 and tumours distributed in the liver were simulated using the MC software Gate v8.2 with an activity distribution defined according to [68Ga]Ga-DOTA-TOC standardised uptake values. Three activity-administration protocols were simulated: (i) with a fixed activity of 100 MBq, (ii) with the activity scaled by 2 MBq/kg, and (iii) with the activity scaled by a body size-dependent power-function based on the SNR obtained with (ii). BMI, weight, body surface area, and abdominal circumference were evaluated body size parameters. Images were reconstructed with the CASToR software and evaluated for background SNR and lesion contrast-to-noise ratio (CNR). Large SNR variabilities were obtained with protocols (i) and (ii), while (iii) generated good consistency. Several tumours failed to reach a CNR of 5 for large phantoms with protocol (i), but the CNR was generally improved by (ii) and (iii). An activity scaled by patient habitus generate better image quality consistency, which increases the likelihood that patients receive a similar standard of care.
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| 25. |
- Kalaitzidis, Philip, et al.
(författare)
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Validation of a computational chain from PET Monte Carlo simulations to reconstructed images
- 2022
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Ingår i: Heliyon. - : Elsevier BV. - 2405-8440. ; 8:4
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Tidskriftsartikel (refereegranskat)abstract
- The study aimed to create a pipeline from Monte Carlo simulated projections of a Gate PET system to reconstructed images. The PET system was modelled after the GE Discovery MI (DMI) PET/CT, and the simulated projections were reconstructed with the stand-alone reconstruction software CASToR. Attenuation correction, normalisation calibration, random estimation, and scatter estimation for the simulations were computed with in-house programs. The pipeline was compared in both projection and image space with data acquired on a clinical DMI and reconstructed with GE's off-line PET reconstruction software (PET Toolbox) and CASToR. The simulated and measured data were compared for the number of prompt coincidences, scatter fraction, contrast recovery coefficient (CRC), signal-to-noise ratio (SNR), background variability, residual lung error, and image profiles. A slight discrepancy was noted in the projection space, but good agreements were generally achieved in image space between simulated and measured data. The CRC was found to be 81 % for Gate – CASToR, 84 % for GE – CASToR, and 84 % for GE - PET Toolbox for the largest sphere of the NEMA image quality (IQ) phantom, and the SNR was found to be 98 for Gate – CASToR, 91 for GE – CASToR, and 93 for GE – PET Toolbox. Profiles drawn over the spheres for the NEMA IQ phantom and the Data Spectrum (DS) phantom show a good match between measurement and simulation. The results indicate feasibility to utilise the pipeline as a tool for off-line simulation-based studies. A complete pipeline introduces possibilities to study the impact of single parameters in the whole chain from simulation to reconstructed images.
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