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Yu Z, Rahman MA, Schindler T, Laforest R, Jha AK. A physics and learning-based transmission-less attenuation compensation method for SPECT. PROCEEDINGS OF SPIE--THE INTERNATIONAL SOCIETY FOR OPTICAL ENGINEERING 2021; 11595. [PMID: 34658480 DOI: 10.1117/12.2582350] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Attenuation compensation (AC) is a pre-requisite for reliable quantification and beneficial for visual interpretation tasks in single-photon emission computed tomography (SPECT). Typical AC methods require the availability of an attenuation map, which is obtained using a transmission scan, such as a CT scan. This has several disadvantages such as increased radiation dose, higher costs, and possible misalignment between SPECT and CT scans. Also, often a CT scan is unavailable. In this context, we and others are showing that scattered photons in SPECT contain information to estimate the attenuation distribution. To exploit this observation, we propose a physics and learning-based method that uses the SPECT emission data in the photopeak and scatter windows to perform transmission-less AC in SPECT. The proposed method uses data acquired in the scatter window to reconstruct an initial estimate of the attenuation map using a physics-based approach. A convolutional neural network is then trained to segment this initial estimate into different regions. Pre-defined attenuation coefficients are assigned to these regions, yielding the reconstructed attenuation map, which is then used to reconstruct the activity distribution using an ordered subsets expectation maximization (OSEM)-based reconstruction approach. We objectively evaluated the performance of this method using highly realistic simulation studies conducted on the clinically relevant task of detecting perfusion defects in myocardial perfusion SPECT. Our results showed no statistically significant differences between the performance achieved using the proposed method and that with the true attenuation maps. Visually, the images reconstructed using the proposed method looked similar to those with the true attenuation map. Overall, these results provide evidence of the capability of the proposed method to perform transmission-less AC and motivate further evaluation.
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Affiliation(s)
- Zitong Yu
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA, 63130
| | - Md Ashequr Rahman
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA, 63130
| | - Thomas Schindler
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, MO, USA, 63110
| | - Richard Laforest
- Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, MO, USA, 63110
| | - Abhinav K Jha
- Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO, USA, 63130.,Mallinckrodt Institute of Radiology, Washington University in St. Louis, St. Louis, MO, USA, 63110
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Li Y, Chen J, Brown JL, Treves ST, Cao X, Fahey FH, Sgouros G, Bolch WE, Frey EC. DeepAMO: a multi-slice, multi-view anthropomorphic model observer for visual detection tasks performed on volume images. J Med Imaging (Bellingham) 2021; 8:041204. [PMID: 33521164 DOI: 10.1117/1.jmi.8.4.041204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2020] [Accepted: 12/31/2020] [Indexed: 11/14/2022] Open
Abstract
Purpose: We propose a deep learning-based anthropomorphic model observer (DeepAMO) for image quality evaluation of multi-orientation, multi-slice image sets with respect to a clinically realistic 3D defect detection task. Approach: The DeepAMO is developed based on a hypothetical model of the decision process of a human reader performing a detection task using a 3D volume. The DeepAMO is comprised of three sequential stages: defect segmentation, defect confirmation (DC), and rating value inference. The input to the DeepAMO is a composite image, typical of that used to view 3D volumes in clinical practice. The output is a rating value designed to reproduce a human observer's defect detection performance. In stages 2 and 3, we propose: (1) a projection-based DC block that confirms defect presence in two 2D orthogonal orientations and (2) a calibration method that "learns" the mapping from the features of stage 2 to the distribution of observer ratings from the human observer rating data (thus modeling inter- or intraobserver variability) using a mixture density network. We implemented and evaluated the DeepAMO in the context of Tc 99 m -DMSA SPECT imaging. A human observer study was conducted, with two medical imaging physics graduate students serving as observers. A 5 × 2 -fold cross-validation experiment was conducted to test the statistical equivalence in defect detection performance between the DeepAMO and the human observer. We also compared the performance of the DeepAMO to an unoptimized implementation of a scanning linear discriminant observer (SLDO). Results: The results show that the DeepAMO's and human observer's performances on unseen images were statistically equivalent with a margin of difference ( Δ AUC ) of 0.0426 at p < 0.05 , using 288 training images. A limited implementation of an SLDO had a substantially higher AUC (0.99) compared to the DeepAMO and human observer. Conclusion: The results show that the DeepAMO has the potential to reproduce the absolute performance, and not just the relative ranking of human observers on a clinically realistic defect detection task, and that building conceptual components of the human reading process into deep learning-based models can allow training of these models in settings where limited training images are available.
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Affiliation(s)
- Ye Li
- Johns Hopkins University, Whiting School of Engineering, Department of Electrical and Computer Engineering, Baltimore, Maryland, United States.,Johns Hopkins University, School of Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, Maryland, United States
| | - Junyu Chen
- Johns Hopkins University, Whiting School of Engineering, Department of Electrical and Computer Engineering, Baltimore, Maryland, United States.,Johns Hopkins University, School of Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, Maryland, United States
| | - Justin L Brown
- University of Florida, J. Crayton Pruitt Family Department of Biomedical Engineering, Gainesville, Florida, United States
| | - S Ted Treves
- Brigham and Women's Hospital, Department of Radiology, Boston, Massachusetts, United States.,Harvard Medical School, Department of Radiology, Boston, Massachusetts, United States
| | - Xinhua Cao
- Harvard Medical School, Department of Radiology, Boston, Massachusetts, United States.,Boston Children's Hospital, Department of Radiology, Boston, Massachusetts, United States
| | - Frederic H Fahey
- Harvard Medical School, Department of Radiology, Boston, Massachusetts, United States.,Boston Children's Hospital, Department of Radiology, Boston, Massachusetts, United States
| | - George Sgouros
- Johns Hopkins University, School of Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, Maryland, United States
| | - Wesley E Bolch
- University of Florida, J. Crayton Pruitt Family Department of Biomedical Engineering, Gainesville, Florida, United States
| | - Eric C Frey
- Johns Hopkins University, Whiting School of Engineering, Department of Electrical and Computer Engineering, Baltimore, Maryland, United States.,Johns Hopkins University, School of Medicine, Russell H. Morgan Department of Radiology and Radiological Science, Baltimore, Maryland, United States
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Yamada Y, Nakano S, Gatate Y, Okano N, Muramatsu T, Nishimura S, Kuji I, Fukushima K, Matsunari I. Feasibility of simultaneous 99mTc-tetrofosmin and 123I-BMIPP dual-tracer imaging with cadmium-zinc-telluride detectors in patients undergoing primary coronary intervention for acute myocardial infarction. J Nucl Cardiol 2021; 28:187-195. [PMID: 30603890 DOI: 10.1007/s12350-018-01585-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2018] [Accepted: 12/17/2018] [Indexed: 11/25/2022]
Abstract
BACKGROUND Simultaneous dual-tracer imaging using isotopes with close photo-peaks may benefit from improved properties of cadmium-zinc-telluride (CZT)-based scanners. METHODS Thirty patients having undergone primary percutaneous coronary intervention for acute myocardial infarction underwent single-(99mTc-tetrofosmin (TF) or 123I-BMIPP first) followed by simultaneous 99mTc-TF /123I-BMIPP dual-tracer imaging using a Discovery NM/CT 670 CZT. The values for the quantitative gated-SPECT (QGS) and the quantitative perfusion SPECT (QPS) were assessed. RESULTS The intra-class correlation (ICC) coefficients between the single- and dual-tracer imaging were high in all the QGS and QPS data (Summed motion score: 0.95, summed thickening score: 0.94, ejection fraction: 0.98, SRS for 99mTc-TF: 0.97/ for 123I-BMIPP: 0.95). Wall motion, wall thickening and rest scores per coronary-territory-based regions were also comparable between the single- and dual imaging (ICC coefficient > 0.91). The interrater concordance in the visual analysis for the infarction and perfusion-metabolism mismatch was significant for the global and regional left ventricle (P < 0.001). CONCLUSION The quantitative/semi-quantitative values for global and regional left-ventricular function, perfusion, and fatty acid metabolism were closely comparable between the dual-tracer imaging and the single-tracer mode. These data suggests the feasibility of the novel CZT-based scanner for the simultaneous 99mTc-TF /123I-BMIPP dual-tracer acquisitions in clinical settings.
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Affiliation(s)
- Yoshihiro Yamada
- Department of Cardiology International Medical Center, Saitama Medical University, 1397-1 Yamane Hidaka, Saitama, 350-1298, Japan
| | - Shintaro Nakano
- Department of Cardiology International Medical Center, Saitama Medical University, 1397-1 Yamane Hidaka, Saitama, 350-1298, Japan.
| | - Youdou Gatate
- Department of Cardiology International Medical Center, Saitama Medical University, 1397-1 Yamane Hidaka, Saitama, 350-1298, Japan
| | - Nanami Okano
- Division of Nuclear Medicine, Department of Radiology, Saitama Medical University, Saitama, Japan
| | - Toshihiro Muramatsu
- Department of Cardiology International Medical Center, Saitama Medical University, 1397-1 Yamane Hidaka, Saitama, 350-1298, Japan
| | - Shigeyuki Nishimura
- Department of Cardiology International Medical Center, Saitama Medical University, 1397-1 Yamane Hidaka, Saitama, 350-1298, Japan
| | - Ichiei Kuji
- Department of Nuclear Medicine International Medical Center, Saitama Medical University, Saitama, Japan
| | - Kenji Fukushima
- Department of Nuclear Medicine International Medical Center, Saitama Medical University, Saitama, Japan
| | - Ichiro Matsunari
- Division of Nuclear Medicine, Department of Radiology, Saitama Medical University, Saitama, Japan
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Li Y, O'Reilly S, Plyku D, Treves ST, Fahey F, Du Y, Cao X, Sexton-Stallone B, Brown J, Sgouros G, Bolch WE, Frey EC. Current pediatric administered activity guidelines for 99m Tc-DMSA SPECT based on patient weight do not provide the same task-based image quality. Med Phys 2019; 46:4847-4856. [PMID: 31448427 DOI: 10.1002/mp.13787] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2019] [Revised: 08/16/2019] [Accepted: 08/16/2019] [Indexed: 11/11/2022] Open
Abstract
PURPOSE In the current clinical practice, administered activity (AA) for pediatric molecular imaging is often based on the North American expert consensus guidelines or the European Association of Nuclear Medicine dosage card, both of which were developed based on the best clinical practice. These guidelines were not formulated using a rigorous evaluation of diagnostic image quality (IQ) relative to AA. In the guidelines, AA is determined by a weight-based scaling of the adult AA, along with minimum and maximum AA constraints. In this study, we use task-based IQ assessment methods to rigorously evaluate the efficacy of weight-based scaling in equalizing IQ using a population of pediatric patients of different ages and body weights. METHODS A previously developed projection image database was used. We measured task-based IQ, with respect to the detection of a renal functional defect at six different AA levels (AA relative to the AA obtained from the guidelines). IQ was assessed using an anthropomorphic model observer. Receiver-operating characteristics (ROC) analysis was applied; the area under the ROC curve (AUC) served as a figure-of-merit for task performance. In addition, we investigated patient girth (circumference) as a potential improved predictor of the IQ. RESULTS The data demonstrate a monotonic and modestly saturating increase in AUC with increasing AA, indicating that defect detectability was limited by quantum noise and the effects of object variability were modest over the range of AA levels studied. The AA for a given value of the AUC increased with increasing age. The AUC vs AA plots for all the patient ages indicate that, for the current guidelines, the newborn and 10- and 15-yr phantoms had similar IQ for the same AA suggested by the North American expert consensus guidelines, but the 5- and 1-yr phantoms had lower IQ. The results also showed that girth has a stronger correlation with the needed AA to provide a constant AUC for 99m Tc-DMSA renal SPECT. CONCLUSIONS The results suggest that (a) weight-based scaling is not sufficient to equalize task-based IQ for patients of different weights in pediatric 99m Tc-DMSA renal SPECT; and (b) patient girth should be considered instead of weight in developing new administration guidelines for pediatric patients.
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Affiliation(s)
- Ye Li
- Department of Electrical and Computer Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA.,The Russell H Morgan Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, Baltimore, MD, 21287, USA
| | - Shannon O'Reilly
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, 19104, USA
| | - Donika Plyku
- The Russell H Morgan Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, Baltimore, MD, 21287, USA
| | - S Ted Treves
- Department of Radiology, Brigham and Women's Hospital, Boston, MA, 02115, USA.,Department of Radiology, Harvard Medical School, Boston, MA, 02115, USA
| | - Frederic Fahey
- Department of Radiology, Harvard Medical School, Boston, MA, 02115, USA.,Department of Radiology, Boston Children's Hospital, Boston, MA, 02115, USA
| | - Yong Du
- The Russell H Morgan Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, Baltimore, MD, 21287, USA
| | - Xinhua Cao
- Department of Radiology, Harvard Medical School, Boston, MA, 02115, USA.,Department of Radiology, Boston Children's Hospital, Boston, MA, 02115, USA
| | | | - Justin Brown
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611, USA
| | - George Sgouros
- The Russell H Morgan Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, Baltimore, MD, 21287, USA.,School of Medicine, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, 21287, USA
| | - Wesley E Bolch
- J. Crayton Pruitt Family Department of Biomedical Engineering, University of Florida, Gainesville, FL, 32611, USA
| | - Eric C Frey
- Department of Electrical and Computer Engineering, Whiting School of Engineering, Johns Hopkins University, Baltimore, MD, 21218, USA.,The Russell H Morgan Department of Radiology and Radiological Science, School of Medicine, Johns Hopkins University, Baltimore, MD, 21287, USA.,School of Medicine, Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University, Baltimore, MD, 21287, USA
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Biggans TJ. Same day cerebral perfusion and dopamine transporter imaging for differential diagnosis of cerebral impairment. Med Eng Phys 2019; 64:56-64. [PMID: 30630721 DOI: 10.1016/j.medengphy.2018.12.016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 12/17/2018] [Accepted: 12/31/2018] [Indexed: 10/27/2022]
Abstract
When cognitive impairment is first evident it can be difficult to distinguish between different conditions such as idiopathic Parkinson's disease and Lewy body dementia. Imaging both cerebral perfusion and dopamine transporter function has been shown to provide accurate differentiation between the most common conditions. At present cerebral perfusion and dopamine transporter imaging is conducted on separate days. Carrying out both scans on the same day has the potential to benefit the patient through the social convenience of one visit to hospital and the earlier availability of results. This work considered whether it was possible to obtain diagnostic quality images from Ioflupane (123I) single positron emission tomography (SPECT) acquired at the same time as or four hours after a Exametazime (99mTc) SPECT on the same day. Possible changes to the Ioflupane (123I) SPECT acquisition and processing protocols such as a new energy window and use of a resolution recovery algorithm were explored using phantom studies. Initial phantom results show that when a four hour delay between acquisitions is used comparable contrast to noise ratios can be achieved (4.23 vs. 4.63) with an insignificant loss in resolution (11.51 mm vs. 11.35 mm full width at half maximum (FWHM)). An offset energy window (159 keV -5.5% & +15.5%) was found to provide the highest contrast to noise ratio. This work provides a proof of concept for same day imaging.
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Affiliation(s)
- Thomas J Biggans
- Nuclear Medicine, Ninewells Hospital, Dundee, DD1 9SY, United Kingdom.
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Esquinas PL, Rodríguez-Rodríguez C, Esposito TVF, Harboe J, Bergamo M, Celler A, Saatchi K, Sossi V, Häfeli UO. Dual SPECT imaging of 111In and 67Ga to simultaneously determine in vivo the pharmacokinetics of different radiopharmaceuticals: a quantitative tool in pre-clinical research. ACTA ACUST UNITED AC 2018; 63:235029. [DOI: 10.1088/1361-6560/aaef63] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Jones KM, Solnes LB, Rowe SP, Gorin MA, Sheikhbahaei S, Fung G, Frey EC, Allaf ME, Du Y, Javadi MS. Use of quantitative SPECT/CT reconstruction in 99mTc-sestamibi imaging of patients with renal masses. Ann Nucl Med 2017; 32:87-93. [PMID: 29214562 DOI: 10.1007/s12149-017-1222-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 11/26/2017] [Indexed: 01/05/2023]
Abstract
OBJECTIVE Technetium-99m (99mTc)-sestamibi single-photon emission computed tomography/computed tomography (SPECT/CT) has previously been shown to allow for the accurate differentiation of benign renal oncocytomas and hybrid oncocytic/chromophobe tumors (HOCTs) apart from other malignant renal tumor histologies, with oncocytomas/HOCTs showing high uptake and renal cell carcinoma (RCC) showing low uptake based on uptake ratios from non-quantitative single-photon emission computed tomography (SPECT) reconstructions. However, in this study, several tumors fell close to the uptake ratio cutoff, likely due to limitations in conventional SPECT/CT reconstruction methods. We hypothesized that application of quantitative SPECT/CT (QSPECT) reconstruction methods developed by our group would provide more robust separation of hot and cold lesions, serving as an imaging framework on which quantitative biomarkers can be validated for evaluation of renal masses with 99mTc-sestamibi. METHODS Single-photon emission computed tomography data were reconstructed using the clinical Flash 3D reconstruction and QSPECT methods. Two blinded readers then characterized each tumor as hot or cold. Semi-quantitative uptake ratios were calculated by dividing lesion activity by background renal activity for both Flash 3D and QSPECT reconstructions. RESULTS The difference between median (mean) hot and cold tumor uptake ratios measured 0.655 (0.73) with the QSPECT method and 0.624 (0.67) with the conventional method, resulting in increased separation between hot and cold tumors. Sub-analysis of 7 lesions near the separation point showed a higher absolute difference (0.16) between QPSECT and Flash 3D mean uptake ratios compared to the remaining lesions. CONCLUSIONS Our finding of improved separation between uptake ratios of hot and cold lesions using QSPECT reconstruction lays the foundation for additional quantitative SPECT techniques such as SPECT-UV in the setting of renal 99mTc-sestamibi and other SPECT/CT exams. With robust quantitative image reconstruction and biomarker analysis, there may be an expanded role for SPECT/CT imaging in renal masses and other pathologic conditions.
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Affiliation(s)
- Krystyna M Jones
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
| | - Lilja B Solnes
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
| | - Steven P Rowe
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA.,The James Buchanan Brady Urological Institute and Department of Urology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Baltimore, MD, 21287, USA
| | - Michael A Gorin
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA.,The James Buchanan Brady Urological Institute and Department of Urology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Baltimore, MD, 21287, USA
| | - Sara Sheikhbahaei
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
| | - George Fung
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
| | - Eric C Frey
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
| | - Mohamad E Allaf
- The James Buchanan Brady Urological Institute and Department of Urology, Johns Hopkins University School of Medicine, 600 N. Wolfe St., Baltimore, MD, 21287, USA
| | - Yong Du
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
| | - Mehrbod S Javadi
- The Russell H. Morgan Department of Radiology and Radiological Science, Johns Hopkins University School of Medicine, 601 N. Caroline St., Baltimore, MD, 21287, USA
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Simultaneous Tc-99m and I-123 dual-radionuclide imaging with a solid-state detector-based brain-SPECT system and energy-based scatter correction. EJNMMI Phys 2016; 3:10. [PMID: 27357946 PMCID: PMC4927533 DOI: 10.1186/s40658-016-0147-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 06/09/2016] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND A brain single-photon emission computed tomography (SPECT) system using cadmium telluride (CdTe) solid-state detectors was previously developed. This CdTe-SPECT system is suitable for simultaneous dual-radionuclide imaging due to its fine energy resolution (6.6 %). However, the problems of down-scatter and low-energy tail due to the spectral characteristics of a pixelated solid-state detector should be addressed. The objective of this work was to develop a system for simultaneous Tc-99m and I-123 brain studies and evaluate its accuracy. METHODS A scatter correction method using five energy windows (FiveEWs) was developed. The windows are Tc-lower, Tc-main, shared sub-window of Tc-upper and I-lower, I-main, and I-upper. This FiveEW method uses pre-measured responses for primary gamma rays from each radionuclide to compensate for the overestimation of scatter by the triple-energy window method that is used. Two phantom experiments and a healthy volunteer experiment were conducted using the CdTe-SPECT system. A cylindrical phantom and a six-compartment phantom with five different mixtures of Tc-99m and I-123 and a cold one were scanned. The quantitative accuracy was evaluated using 18 regions of interest for each phantom. In the volunteer study, five healthy volunteers were injected with Tc-99m human serum albumin diethylene triamine pentaacetic acid (HSA-D) and scanned (single acquisition). They were then injected with I-123 N-isopropyl-4-iodoamphetamine hydrochloride (IMP) and scanned again (dual acquisition). The counts of the Tc-99m images for the single and dual acquisitions were compared. RESULTS In the cylindrical phantom experiments, the percentage difference (PD) between the single and dual acquisitions was 5.7 ± 4.0 % (mean ± standard deviation). In the six-compartment phantom experiment, the PDs between measured and injected activity for Tc-99m and I-123 were 14.4 ± 11.0 and 2.3 ± 1.8 %, respectively. In the volunteer study, the PD between the single and dual acquisitions was 4.5 ± 3.4 %. CONCLUSIONS This CdTe-SPECT system using the FiveEW method can provide accurate simultaneous dual-radionuclide imaging. A solid-state detector SPECT system using the FiveEW method will permit quantitative simultaneous Tc-99m and I-123 study to become clinically applicable.
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Kobayashi M, Matsunari I, Nishi K, Mizutani A, Miyazaki Y, Ogai K, Sugama J, Shiba K, Kawai K, Kinuya S. Simultaneous acquisition of (99m)Tc- and (123)I-labeled radiotracers using a preclinical SPECT scanner with CZT detectors. Ann Nucl Med 2016; 30:263-71. [PMID: 26747655 DOI: 10.1007/s12149-015-1055-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Accepted: 12/23/2015] [Indexed: 11/26/2022]
Abstract
OBJECTIVE Simultaneous acquisition of (99m)Tc and (123)I was evaluated using a preclinical SPECT scanner with cadmium zinc telluride (CZT)-based detectors. METHODS 10-ml cylindrical syringes contained about 37 MBq (99m)Tc-tetrofosmin ((99m)Tc-TF) or 37 MBq (123)I-15-(p-iodophenyl)-3R,S-methyl pentadecanoic acid ((123)I-BMIPP) were used to assess the relationship between these SPECT radioactive counts and radioactivity. Two 10-ml syringes contained 100 or 300 MBq (99m)Tc-TF and 100 MBq (123)I-BMIPP to assess the influence of (99m)Tc upscatter and (123)I downscatter, respectively. A rat-sized cylindrical phantom also contained both 100 or 300 MBq (99m)Tc-TF and 100 MBq (123)I-BMIPP. The two 10-ml syringes and phantom were scanned using a pinhole collimator for rats. Myocardial infarction model rats were examined using 300 MBq (99m)Tc-TF and 100 MBq (123)I-BMIPP. Two 1-ml syringes contained 105 MBq (99m)Tc-labeled hexamethylpropyleneamine oxime ((99m)Tc-HMPAO) and 35 MBq (123)I-labeled N-ω-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl) nortropane ((123)I-FP-CIT). The two 1-ml syringes were scanned using a pinhole collimator for mice. Normal mice were examined using 105 MBq (99m)Tc-HMPAO and 35 MBq (123)I-FP-CIT. RESULTS The relationship between SPECT radioactive counts and radioactivity was excellent. Downscatter contamination of (123)I-BMIPP exhibited fewer radioactive counts for 300 MBq (99m)Tc-TF without scatter correction (SC) in 125-150 keV. There was no upscatter contamination of (99m)Tc-TF in 150-175 keV. In the rat-sized phantom, the radioactive count ratio decreased to 4.0 % for 300 MBq (99m)Tc-TF without SC in 125-150 keV. In the rats, myocardial images and radioactive counts of (99m)Tc-TF with the dual tracer were identical to those of the (99m)Tc-TF single injection. Downscatter contamination of (123)I-FP-CIT was 4.2 % without SC in 125-150 keV. In the first injection of (99m)Tc-HMPAO and second injection of (123)I-FP-CIT, brain images and radioactive counts of (99m)Tc-HMPAO with the dual tracer in normal mice also were the similar to those of the (99m)Tc-HMPAO single injection. In the first injection of (123)I-FP-CIT and second injection of (99m)Tc-HMPAO, the brain images and radioactive counts with the dual tracer were not much different from those of the (123)I-FP-CIT single injection. CONCLUSIONS Dual-tracer imaging of (99m)Tc- and (123)I-labeled radiotracers is feasible in a preclinical SPECT scanner with CZT detector. When higher radioactivity of (99m)Tc-labeled radiotracers relative to (123)I-labeled radiotracers is applied, correction methods are not necessarily required for the quantification of (99m)Tc- and (123)I-labeled radiotracers when using a preclinical SPECT scanner with CZT detector.
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Affiliation(s)
- Masato Kobayashi
- Wellness Promotion Science Center, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan.
| | - Ichiro Matsunari
- Clinical Research Department, The Medical and Pharmacological Research Center Foundation, Hakui, Japan
- Division of Nuclear Medicine, Department of Radiology, Saitama Medical University Hospital, Saitama, Japan
| | - Kodai Nishi
- Department of Radioisotope Medicine, Atomic Bomb Disease Institute, Nagasaki University, Nagasaki, Japan
| | - Asuka Mizutani
- Graduate School of Medicine, Division of Health Sciences, Osaka University, Osaka, Japan
| | - Yoshiharu Miyazaki
- Clinical Research Department, The Medical and Pharmacological Research Center Foundation, Hakui, Japan
| | - Kazuhiro Ogai
- Wellness Promotion Science Center, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan
| | - Jyunko Sugama
- Wellness Promotion Science Center, Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, 5-11-80 Kodatsuno, Kanazawa, 920-0942, Japan
| | - Kazuhiro Shiba
- Division of Tracer Kinetics, Advanced Science Research Center, Kanazawa University, Kanazawa, Japan
| | - Keiichi Kawai
- School of Health Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
| | - Seigo Kinuya
- School of Medical Sciences, College of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kanazawa, Japan
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Du Y, Bhattacharya M, Frey EC. Simultaneous Tc-99m/I-123 dual-radionuclide myocardial perfusion/innervation imaging using Siemens IQ-SPECT with SMARTZOOM collimator. Phys Med Biol 2014; 59:2813-28. [PMID: 24819280 PMCID: PMC4142679 DOI: 10.1088/0031-9155/59/11/2813] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Simultaneous dual-radionuclide myocardial perfusion/innervation SPECT imaging can provide important information about the mismatch between scar tissue and denervated regions. The Siemens IQ-SPECT system developed for cardiac imaging uses a multifocal SMARTZOOM collimator to achieve a four-fold sensitivity for the cardiac region, compared to a typical parallel-hole low-energy high-resolution collimator, but without the data truncation that can result with conventional converging-beam collimators. The increased sensitivity allows shorter image acquisition times or reduced patient dose, making IQ-SPECT ideal for simultaneous dual-radionuclide SPECT, where reduced administrated activity is desirable in order to reduce patient radiation exposure. However, crosstalk is a major factor affecting the image quality in dual-radionuclide imaging. In this work we developed a model-based method that can estimate and compensate for the crosstalk in IQ-SPECT data. The crosstalk model takes into account interactions in the object and collimator-detector system. Scatter in the object was modeled using the effective source scatter estimation technique (ESSE), previously developed to model scatter with parallel-hole collimators. The geometric collimator-detector response was analytically modeled in the IQ-SPECT projector. The estimated crosstalk was then compensated for in an iterative reconstruction process. The new method was validated with data from both Monte Carlo simulations and physical phantom experiments. The results showed that the estimated crosstalk was in good agreement with simulated and measured results. After model-based compensation the images from simultaneous dual-radionuclide acquisitions were similar in quality to those from single-radionuclide acquisitions that did not have crosstalk contamination. The proposed model-based method can be used to improve simultaneous dual-radionuclide images acquired using IQ-SPECT. This work also demonstrates that ESSE scatter modeling can be applied to non-parallel-beam projection geometries.
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Affiliation(s)
- Yong Du
- Department of Radiology, Johns Hopkins University, 601 N Caroline Street, JOHC 4263, Baltimore, MD 21287, USA
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Rakvongthai Y, El Fakhri G, Lim R, Bonab AA, Ouyang J. Simultaneous 99mTc-MDP/123I-MIBG tumor imaging using SPECT-CT: phantom and constructed patient studies. Med Phys 2013; 40:102506. [PMID: 24089927 PMCID: PMC3785531 DOI: 10.1118/1.4820977] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2013] [Revised: 08/26/2013] [Accepted: 08/27/2013] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Authors' goal is to evaluate the performance of simultaneous (99m)Tc-MDP/(123)I-MIBG tumor imaging with fast Monte-Carlo (MC) based joint iterative reconstruction as compared to sequential (99m)Tc-MDP and (123)I-MIBG tumor imaging. METHODS Noise-free (99m)Tc and (123)I SPECT projections were acquired separately using an anthropomorphic torso phantom modified to include a fillable tube around the lungs to mimic ribs. Additionally, (99m)Tc and (123)I projections were acquired separately using a 1-cm spherical "tumor" placed at various distances from one detector. Tumor-present data were generated by adding tumor projections to the torso phantom data, which were scaled to the total counts in typical clinical studies. Twenty-five noise realizations were generated by adding Poisson noise to the projection data for each radionuclide. Dual-radionuclide data were synthesized by summing the (99m)Tc and (123)I projections. Image reconstruction was performed using: (1) SR-OSEM, ordered subset expectation maximization (OSEM) without scatter correction (SC) using single-radionuclide (SR) data; (2) SR-MC-OSEM, OSEM with a fast MC-based SC using SR data; (3) DR-OSEM, OSEM without SC using dual-radionuclide (DR) data; and (4) DR-MC-JOSEM, joint OSEM with a fast MC-based SC using DR data. Ten (99m)Tc-MDP and ten (123)I-MIBG data sets, which had tumors mathematically inserted, were also used to evaluate the performance of authors' approach. For the phantom study, relative bias and relative standard deviation of tumor uptake were computed for each tumor using the tumor uptake in the noise-free single-radionuclide images, which were reconstructed by SR-MC-OSEM, as the gold standard. For both the phantom and constructed patient studies, mean contrast and standard deviation of contrast were computed for each tumor for both the single- and dual-radionuclide images. Additionally, contrast recovery was computed as the ratio between mean contrast and the mean contrast for SR-MC-OSEM. RESULTS For the phantom study, DR-MC-JOSEM yielded 2.7% on average relative bias of tumor uptake using the images, which were reconstructed from the noise-free SR data with SR-MC-OSEM, as the gold-standard. For both the phantom and constructed patient studies, DR-MC-JOSEM yielded 94.7% and 95.2% tumor contrast recovery on average using SR-MC-OSEM as the reference, in the phantom and constructed patient studies, respectively. DR-MC-JOSEM yielded comparable relative standard deviation of bias and standard deviation of contrast to SR-MC-OSEM. CONCLUSIONS Simultaneous (99m)Tc-MDP/(123)I-MIBG tumor imaging using authors' dual-radionuclide reconstruction approach yielded comparable image quality to sequential (99m)Tc-MDP and (123)I-MIBG imaging. For patients who need to undergo both scans, authors' approach offers perfectly registered dual-tracer images under identical conditions without compromising image quality, and reduces the imaging cost while increasing patient throughput.
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Affiliation(s)
- Yothin Rakvongthai
- Center for Advanced Medical Imaging Sciences, Division of Nuclear Medicine and Molecular Imaging, Massachusetts General Hospital, 55 Fruit Street, Boston, Massachusetts 02114 and Department of Radiology, Harvard Medical School, 25 Shattuck Street, Boston, Massachusetts 02115
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Cao YJ, Caffo BS, Fuchs EJ, Lee LA, Du Y, Li L, Bakshi RP, Macura K, Khan WA, Wahl RL, Grohskopf LA, Hendrix CW. Quantification of the spatial distribution of rectally applied surrogates for microbicide and semen in colon with SPECT and magnetic resonance imaging. Br J Clin Pharmacol 2012; 74:1013-22. [PMID: 22404308 PMCID: PMC3522815 DOI: 10.1111/j.1365-2125.2012.04267.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2011] [Accepted: 02/23/2012] [Indexed: 11/29/2022] Open
Abstract
AIMS We sought to describe quantitatively the distribution of rectally administered gels and seminal fluid surrogates using novel concentration-distance parameters that could be repeated over time. These methods are needed to develop rationally rectal microbicides to target and prevent HIV infection. METHODS Eight subjects were dosed rectally with radiolabelled and gadolinium-labelled gels to simulate microbicide gel and seminal fluid. Rectal doses were given with and without simulated receptive anal intercourse. Twenty-four hour distribution was assessed with indirect single photon emission computed tomography (SPECT)/computed tomography (CT) and magnetic resonance imaging (MRI), and direct assessment via sigmoidoscopic brushes. Concentration-distance curves were generated using an algorithm for fitting SPECT data in three dimensions. Three novel concentration-distance parameters were defined to describe quantitatively the distribution of radiolabels: maximal distance (D(max) ), distance at maximal concentration (D(Cmax) ) and mean residence distance (D(ave) ). RESULTS The SPECT/CT distribution of microbicide and semen surrogates was similar. Between 1 h and 24 h post dose, the surrogates migrated retrograde in all three parameters (relative to coccygeal level; geometric mean [95% confidence interval]): maximal distance (D(max) ), 10 cm (8.6-12) to 18 cm (13-26), distance at maximal concentration (D(Cmax) ), 3.8 cm (2.7-5.3) to 4.2 cm (2.8-6.3) and mean residence distance (D(ave) ), 4.3 cm (3.5-5.1) to 7.6 cm (5.3-11). Sigmoidoscopy and MRI correlated only roughly with SPECT/CT. CONCLUSIONS Rectal microbicide surrogates migrated retrograde during the 24 h following dosing. Spatial kinetic parameters estimated using three dimensional curve fitting of distribution data should prove useful for evaluating rectal formulations of drugs for HIV prevention and other indications.
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Affiliation(s)
- Ying J Cao
- Department of Medicine, Division of Clinical Pharmacology, The Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA
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Shcherbinin S, Chamoiseau S, Celler A. Quantitative image reconstruction for dual-isotope parathyroid SPECT/CT: phantom experiments and sample patient studies. Phys Med Biol 2012; 57:4755-69. [PMID: 22772024 DOI: 10.1088/0031-9155/57/15/4755] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
We investigated the quantitative accuracy of the model-based dual-isotope single-photon emission computed tomography (DI-SPECT) reconstructions that use Klein-Nishina expressions to estimate the scattered photon contributions to the projection data. Our objective was to examine the ability of the method to recover the absolute activities pertaining to both radiotracers: Tc-99m and I-123. We validated our method through a series of phantom experiments performed using a clinical hybrid SPECT/CT camera (Infinia Hawkeye, GE Healthcare). Different activity ratios and different attenuating media were used in these experiments to create cross-talk effects of varying severity, which can occur in clinical studies. Accurate model-based corrections for scatter and cross-talk with CT attenuation maps allowed for the recovery of the absolute activities from DI-SPECT/CT scans with errors that ranged 0-10% for both radiotracers. The unfavorable activity ratios increased the computational burden but practically did not affect the resulting accuracy. The visual analysis of parathyroid patient data demonstrated that our model-based processing improved adenoma/background contrast and enhanced localization of small or faint adenomas.
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Affiliation(s)
- S Shcherbinin
- Department of Radiology, University of British Columbia, 366-828 West 10th Avenue, Vancouver BC, V5Z 1M9, Canada.
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15
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Distribution of cell-free and cell-associated HIV surrogates in the colon after simulated receptive anal intercourse in men who have sex with men. J Acquir Immune Defic Syndr 2012; 59:10-7. [PMID: 21937920 DOI: 10.1097/qai.0b013e3182373b5e] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
OBJECTIVES Describing the distribution and clearance of HIV surrogates within the gastrointestinal tract to inform rectal microbicide development. DESIGN Radiolabeled simulated HIV-infected semen was administered, imaged, and biopsied to simulate and measure colonic HIV distribution after anal intercourse. METHODS Healthy male subjects with a history of receptive anal intercourse and experience with the use of anal sex toys were recruited to this study. Apheresis isolated leukocytes were collected before simulated intercourse. These autologous leukocytes, radiolabeled with 9.25 MBq (111)Indium-oxine (cell-associated HIV surrogate), and sulfur colloid particles, labeled with 37 MBq (99m)Technectium (cell-free HIV surrogate), were mixed in 3 mL autologous seminal plasma. This simulated HIV-infected semen was administered to subjects via an artificial phallus with urethra after 5 minutes of simulated intercourse. Postdosing dual isotope Single photon emission computed tomography coupled with traditional computed tomography (SPECT/CT) images were acquired at 1, 4, 8, and 24 hours. At 5 hours postdosing, colon biopsies were collected, CD4 cells were extracted, and samples analyzed for radioactivity. RESULTS SPECT/CT images showed similar luminal distribution for both surrogates, with migration limited to the rectosigmoid colon in all subjects. SPECT showed at least 75% overlap in distribution of both surrogates up to 4 hours after dosing. Biopsies indicate that 2.4% of CD4 cells extracted from rectosigmoid colon tissue were exogenously administered. CONCLUSIONS Our HIV surrogates stayed within the rectosigmoid colon for 24 hours. Exogenously dosed autologous lymphocytes and HIV-sized particles migrate to similar locations and associate with the colonic tissue in the lumen.
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Louissaint NA, Fuchs EJ, Bakshi RP, Nimmagadda S, Du Y, Macura KJ, King KE, Wahl R, Goldsmith AJ, Caffo B, Cao YJ, Anderson J, Hendrix CW. Distribution of cell-free and cell-associated HIV surrogates in the female genital tract after simulated vaginal intercourse. J Infect Dis 2012; 205:725-32. [PMID: 22279121 DOI: 10.1093/infdis/jir841] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Rational development of drugs to prevent human immunodeficiency virus (HIV) transmission benefits from an understanding HIV distribution in the female genital tract after intercourse. This study describes HIV distribution using surrogates of cell-free and cell-associated HIV and semen. METHODS Apheresis-derived, autologous, lymphocyte-rich cells radiolabeled with 3.7-MBq (100-μCi) indium 111 ((111)In)-oxine (cell-associated HIV surrogate) and 18.5-MBq (500-μCi) technetium 99m ((99m)Tc)-sulfur colloid (HIV-sized 100-nm particle, cell-free HIV surrogate) were resuspended in 3 mL of hydroxyethylcellulose gel (semen simulant) with gadoteridol and dosed via artificial phallus after simulated intercourse. Postdosing dual-isotope single photon emission computed tomography with computed tomography (SPECT/CT) and magnetic resonance (MR) images were acquired to determine the surrogates' distribution. Seven hours after dosing, vaginal biopsy and luminal samples were collected at discrete locations in 8 subjects. RESULTS SPECT/CT and MR analysis showed HIV and semen surrogate distribution with highest signal intensity in the vaginal pericervical area, without detectable signal in the uterus. One-third of the administered dose was retained in the female genital tract after 4 hours. Cell-free and cell-associated surrogate distribution coincided. CONCLUSIONS We demonstrate the feasibility of dual-isotope SPECT/CT and MR imaging to determine the distribution of HIV and semen surrogates after simulated intercourse without disrupting vaginal contents. Surrogate distribution suggests topical microbicides do not need to reach the uterus for efficacy.
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Fung GSK, Higuchi T, Park MJ, Segars WP, Tsui BMW. Development of a 4D Digital Phantom for Tracer Kinetic Modeling and Analysis of Dynamic Perfusion PET and SPECT Simulation Studies. IEEE NUCLEAR SCIENCE SYMPOSIUM CONFERENCE RECORD. NUCLEAR SCIENCE SYMPOSIUM 2011; 2011:4192-4195. [PMID: 26536594 PMCID: PMC4603825 DOI: 10.1109/nssmic.2011.6153803] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The goal is to develop a 4D digital perfusion cardiac-torso (PCAT) phantom, a tracer kinetic extension of the XCAT phantom, by modeling the time activity curves (TACs) of individual organ regions in the phantom for dynamic perfusion PET and SPECT simulation studies. The PCAT phantom is based on a generalized compartmental model, which accepts the blood input function, multiple series or parallel compartments, the bidirectional rate constants between the compartments, the blood volume in the tissue, the extraction curves, and other properties of a specific tracer. Based on the kinetic differential equations of the compartmental model, the TACs of the targeted organ regions were determined. For a specific time point, a voxelized anatomical realistic phantom, which with or without the cardiac and respiratory motions, was generated and the activity concentrations in the organ regions were assigned according to the corresponding TACs. According to the dynamic scanning protocol, multiple phantoms at different acquisition time points, which could have uniform or non-uniform time intervals, were generated. When combining the dynamic phantoms with realistic projection simulator, realistic dynamic projection data could be generated by easily adopting to various scanning protocols and imaging systems. With the availability of the "known truth", the activity map of the targeted organ regions, the TACs, the estimated rate constants and other kinetic parameters, from the projection data and the reconstructed images could be quantitatively evaluated. We demonstrate the usefulness of the 4D PCAT phantom in initial simulation studies in dynamic myocardial perfusion PET imaging with different tracers. The PCAT phantom was found to be an important bridge between the creation of TACs and the generation of simulated projection data. It is a useful simulation tool to study different kinetic analysis methods, acquisition protocols, reconstruction methods, and imaging parameter settings.
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Affiliation(s)
- George S. K. Fung
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - Takahiro Higuchi
- Nuklearmedizinische Klinik und Poliklinik, Comprehensive Heart Failure Center, Universitätsklinikum Würzburg, Würzburg, Germany
| | - Min Jae Park
- Department of Radiology, Johns Hopkins University, Baltimore, MD, USA
| | - W. Paul Segars
- Department of Radiology, Duke University, Durham, NC, USA
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Hutton BF, Buvat I, Beekman FJ. Review and current status of SPECT scatter correction. Phys Med Biol 2011; 56:R85-112. [PMID: 21701055 DOI: 10.1088/0031-9155/56/14/r01] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Song N, Du Y, He B, Frey EC. Development and evaluation of a model-based downscatter compensation method for quantitative I-131 SPECT. Med Phys 2011; 38:3193-204. [PMID: 21815394 PMCID: PMC3125085 DOI: 10.1118/1.3590382] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2010] [Revised: 04/08/2011] [Accepted: 04/22/2011] [Indexed: 11/07/2022] Open
Abstract
PURPOSE The radionuclide 131I has found widespread use in targeted radionuclide therapy (TRT), partly due to the fact that it emits photons that can be imaged to perform treatment planning or posttherapy dose verification as well as beta rays that are suitable for therapy. In both the treatment planning and dose verification applications, it is necessary to estimate the activity distribution in organs or tumors at several time points. In vivo estimates of the 131I activity distribution at each time point can be obtained from quantitative single-photon emission computed tomography (QSPECT) images and organ activity estimates can be obtained either from QSPECT images or quantification of planar projection data. However, in addition to the photon used for imaging, 131I decay results in emission of a number of other higher-energy photons with significant abundances. These higher-energy photons can scatter in the body, collimator, or detector and be counted in the 364 keV photopeak energy window, resulting in reduced image contrast and degraded quantitative accuracy; these photons are referred to as downscatter. The goal of this study was to develop and evaluate a model-based downscatter compensation method specifically designed for the compensation of high-energy photons emitted by 131I and detected in the imaging energy window. METHODS In the evaluation study, we used a Monte Carlo simulation (MCS) code that had previously been validated for other radionuclides. Thus, in preparation for the evaluation study, we first validated the code for 131I imaging simulation by comparison with experimental data. Next, we assessed the accuracy of the downscatter model by comparing downscatter estimates with MCS results. Finally, we combined the downscatter model with iterative reconstruction-based compensation for attenuation (A) and scatter (S) and the full (D) collimator-detector response of the 364 keV photons to form a comprehensive compensation method. We evaluated this combined method in terms of quantitative accuracy using the realistic 3D NCAT phantom and an activity distribution obtained from patient studies. We compared the accuracy of organ activity estimates in images reconstructed with and without addition of downscatter compensation from projections with and without downscatter contamination. RESULTS We observed that the proposed method provided substantial improvements in accuracy compared to no downscatter compensation and had accuracies comparable to reconstructions from projections without downscatter contamination. CONCLUSIONS The results demonstrate that the proposed model-based downscatter compensation method is effective and may have a role in quantitative 131I imaging.
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Affiliation(s)
- Na Song
- Division of Medical Imaging Physics, Department of Radiology, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
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El Fakhri G, Ouyang J. Dual-radionuclide brain SPECT for the differential diagnosis of parkinsonism. Methods Mol Biol 2011; 680:237-246. [PMID: 21153385 DOI: 10.1007/978-1-60761-901-7_16] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Parkinsonism is a neurological syndrome characterized by tremor, bradykinesia, rigidity, and postural instability. The underlying causes of parkinsonism are numerous. It is of paramount importance to make clean distinction among these diseases. However, the differential diagnosis of parkinsonism is challenging. Simultaneous dual-radionuclide brain SPECT allows us to assess both blood perfusion and dopamine transporter function under the identical physiological conditions. This approach has been proven to improve the differential diagnosis of parkinsonism. The simultaneous (99m)Tc-ECD/(123)I-FP-CIT brain SPECT protocols, which are used for the differential diagnosis of idiopathic Parkinson's disease and multiple system atrophy as well as corticobasal degeneration and progressive supranuclear palsy, are presented.
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Affiliation(s)
- Georges El Fakhri
- Division of Nuclear Medicine and Molecular Imaging, Department of Radiology, Harvard Medical School, Massachusetts General Hospital, Boston, MA 02114, USA.
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Goorden MC, Beekman FJ. High-resolution tomography of positron emitters with clustered pinhole SPECT. Phys Med Biol 2010; 55:1265-77. [DOI: 10.1088/0031-9155/55/5/001] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Du Y, Frey EC. Quantitative evaluation of simultaneous reconstruction with model-based crosstalk compensation for 99mTc/123I dual-isotope simultaneous acquisition brain SPECT. Med Phys 2009; 36:2021-33. [PMID: 19610291 PMCID: PMC2736700 DOI: 10.1118/1.3120411] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/07/2008] [Revised: 01/31/2009] [Accepted: 03/24/2009] [Indexed: 11/07/2022] Open
Abstract
A model-based method has been previously developed to estimate and compensate for the crosstalk and downscatter contamination in simultaneous 123I/99mTc dual-isotope SPECT imaging. In this method, photon scatter in the object is modeled using the effective source scatter estimate technique. Photon interactions with the collimator-detector are estimated using precalculated Monte Carlo simulated point response functions. Two different approaches, simultaneous and alternating model-based compensations, have been proposed for iterative reconstruction-based crosstalk and downscatter contamination compensation. In this work, both model-based approaches were evaluated in the context of quantitative accuracy when imaging the dopaminergic system using both Monte Carlo simulated and experimentally acquired data. Results indicate that mddel-based estimates of the crosstalk and downscatter contamination in both energy windows were in good agreement with the truth for the simulated data. The effects of the contamination reduced image contrast and overestimated absolute activity in all structures by up to 66%. Compensation using both model-based approaches improved image contrast. Errors in absolute activity quantitation were also reduced to less than +/-5% for most brain structures. The accuracy of striatal specific binding potentials, calculated as the ratio of activity in various striatal structures to the background, was also greatly improved after model-based compensation. In conclusion, model-based compensation of simultaneously acquired images of 99mTc and 123I labeled brain imaging agents provided image quality and quantitative accuracy that were comparable to the image without crosstalk. Both proposed compensation approaches can potentially be applied clinically, but when reconstruction time is a limiting factor, the alternating model-based compensation may be preferable.
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Affiliation(s)
- Yong Du
- Department of Radiology, Division of Medical Imaging Physics, Johns Hopkins Medical Institutions, Baltimore, Maryland 21287, USA.
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