Single Photon Emission Computed Tomography Method Research Articles

Development of Solutions Based on Computer Simulation for Quantitative SPECT/CT

Purpose: In modern nuclear medicine, an ordered subset expectation maximization (OSEM) iterative algorithm is used to obtain images by single photon emission computed tomography (SPECT) method. At the same time, the problem of choosing the stopping iteration number at which the solution will be as close as possible to the exact value has not been solved. The purpose of this work is to study the problem of stopping the OSEM algorithm. Material and methods: The studies were carried out using the method of mathematical modeling based on the software package “Virtual Platform for Simulation Testing of the SPECT/CT Method”. Computer experiments simulated SPECT/CT with 99mTc phosphotech of a patient with metastatic lesion of the posterior segment of the third rib. The stopping criterion of the iterative OSEM algorithm was studied to obtain a solution that is quantitatively closest to the exact value of the accumulated activity at the tumor. Results: In computer modeling experiments, the tumor dependent Pearson chi-square test was shown to provide a solution that should give correct values for the SUVmean score. However, further research is needed on this important problem to determine how strongly the number of iterations depends on the size of the tumor and the amount of activity accumulated in it. Conclusion: Based on the results obtained, we can conclude that in the SPECT method, in order to move to accurate quantitative estimates of the accumulated activity in the tumor, it is necessary to develop a tumor-oriented stopping criterion for iterative algorithm. If there are several tumors, the stopping iteration numbers for them may differ. Further research on this important issue is planned.

EEG Driven Autonomous Injection System For An Epileptic Neuroimaging Application.

Seizure episodes are frequently observed for adults and children suffering from medically refractory epilepsy and the events remain debilitating unless treated with a more comprehensive approach. Ictal perfusion studies with single-photon emission computed tomography (SPECT) is one of the non invasive imaging modality that has been extensively used to adequately localize the seizure focus. Current practices include the tracer injection within a short time interval at the onset of seizure to generate desirable SPECT scan quality with accurate information on foci region. However, the onset of a seizure is a highly unpredictable event and also with added subclinical events, the overall procedure makes it difficult to administer the tracer manually within the ideal time frame.Hence a complete autonomous injection of radioactive tracer element without manual intervention is expected to offer a highly accurate epileptical focus region and aids in further management of the patient. Electroencephalogram (EEG) physiological signals in the preictal phase contain sufficient indicators to predict the seizure event. The proposed injection system works on the seizure prediction model from the EEG signals to release the dosage, making the system completely autonomous in action. The accuracy of the prediction model based on the publicly available seizure embedded EEG datasets was designed to achieve 94% accuracy, and the model was deployed on an edge system. The syringe based injection system was characterized to emulate dosage release action with minimum volumetric error, and low injection time, on predicting seizure Ictal event from the EEG signal. The proposed system is a step towards developing an autonomous injection system for epileptic neuroimaging applications in hospital settings.Clinical relevance- Autonomous injection of tracer dosage for obtaining accurate and high quality Ictal SPECT scan results is preferred over the manual operation in clinical and hospital residential settings as a part of pre-surgical evaluations. The EEG signal based early prediction of seizure ensures adequate time for radioactive tracer element to reach the brain cells and eventually helps to accurately localize the onset region of seizure in the brain. The EEG driven automated injection system for the noninvasive Ictal SPECT method is clinically important as a pre-surgical evaluation in MRI negative or discordant cases for further surgical actions.

Investigation of the new non-invasive semi-quantitative method of 123I-IMP pediatric cerebral perfusion SPECT.

In pediatric cases requiring quantification of cerebral blood flow (CBF) using 123I-N-isopropyl-p-iodoamphetamine (123I-IMP) single-photon emission computed tomography (SPECT), arterial blood sampling is sometimes impossible due to issues such as movement, crying, or body motion. If arterial blood sampling fails, quantitative diagnostic assessment becomes impossible despite radiation exposure. We devised a new easy non-invasive microsphere (e-NIMS) method using whole-body scan data. This method can be used in conjunction with autoradiography (ARG) and can provide supportive data for invasive CBF quantification. In this study, we examined the usefulness of e-NIMS for pediatric cerebral perfusion semi-quantitative SPECT and compared it with the invasive ARG. The e-NIMS estimates cardiac output (CO) using whole-body acquisition data after 123I-IMP injection and the body surface area from calculation formula. A whole-body scan was performed 5 minutes after the 123I-IMP injection and CO was estimated by region of interest (ROI) counts measured for the whole body, lungs, and brain using the whole-body anterior image. The mean CBF (mCBF) was compared with that acquired via ARG in 115 pediatric patients with suspected cerebrovascular disorders (age 0–15 years). Although the mCBF estimated by the e-NIMS indicated a slight deviation in the extremely low- or high-mCBF cases when compared with the values acquired using the invasive ARG, there was a good correlation between the two methods (r = 0.799; p < 0.001). There were no significant differences in the mCBF values based on physical features, such as patients’ height, weight, and age. Our findings suggest that 123I-IMP brain perfusion SPECT with e-NIMS is the simplest semi-quantitative method that can provide supportive data for invasive CBF quantification. This method may be useful, especially in pediatric brain perfusion SPECT, when blood sampling or identifying pulmonary arteries for CO estimation using the graph plot method is difficult.

Cost-impact of cardiac magnetic resonance imaging with Fast-SENC compared to SPECT in the diagnosis of coronary artery disease in the U.S

Aims: The purpose of this study is to assess the economic cost differences and the associated treatment resource changes between the developing coronary artery disease (CAD) diagnostic tool fast strain-encoded cardiac imaging (Fast-SENC) and the current commonly used stress test single-photon emission computed tomography (SPECT).Materials and methods: A “payer perspective” model was created first, consisting of long-term and short-term components that used a hypothetical cohort of patients of average age (60.8 years) presenting with chest pain and suspected CAD to assess cost-impact. A cost impact model was then built that assessed likely savings from a “hospital perspective” from substituting Fast-SENC for a portion of SPECTs assuming an average number of annual SPECT tests performed in US hospitals.Results: In the payer model, using Fast-SENC followed by coronary angiography (CA) and percutaneous coronary intervention (PCI) treatment when necessary is less costly than the SPECT method when considering both direct and indirect costs of testing. Expected costs of the Fast-SENC were between $2,510 and $2,632 per correct diagnosis, while expected costs for the SPECT were between $3,157 and $4,078. Fast-SENC reduced false positives by 50% and false negatives by 86%, generating additional cost savings. The hospital model showed total costs per CAD patient visit of $825 for SPECT and $376 for Fast-SENC.Limitations: Limitations of this study are that clinical data are sourced from other published clinical trials on how CAD diagnostic strategies impact clinical outcome, and that necessary assumptions were made which impact health outcomes.Conclusion: The lower cost, higher sensitivity and specificity rates, and faster, less burdensome process for detecting CAD patients make Fast-SENC a more capable and economically beneficial stress test than SPECT. The payer model and hospital model demonstrate an alignment between payer and provider economics as Fast-SENC provides monetary savings for patients and resource benefits for hospitals.

Is Single-Photon Emission Computed Tomography/Computed Tomography Superior to Single-Photon Emission Computed Tomography in Assessing Unilateral Condylar Hyperplasia?

Single-photon emission computed tomography (SPECT) with technetium-99m diphosphates plays an important role in assessing unilateral condylar hyperplasia (UCH). The aim of this study was to evaluate whether quantification methods of SPECT plus CT (SPECT/CT) based on precise region-of-interest (ROI) drawings made under the guide of CT images were more accurate than conventional SPECT methods in the assessment of UCH growth. This study is a nonblinded retrospective case series. Patients with UCH who had undergone SPECT/CT were enrolled. CT images were used to guide ROI drawings around the anatomic contour of the affected and contralateral condyles on SPECT/CT images versus fixed ROIs on conventional SPECT images. Mean and maximum values within the ROIs were recorded to compute percentile ratios. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and receiver operating characteristic (ROC) curves were calculated separately for SPECT-based methods (SPECTaver, SPECTmax) and SPECT/CT methods (SPECTCTaver, SPECTCTmax). The area under the ROC curve of each method was calculated and compared pairwise. Fifty-six patients (30 patients with progressive and 26 patients with nonprogressive mandibular asymmetry) were evaluated. SPECTmax had the highest sensitivity of 83.3%, followed by SPECTCTmax, SPECTaver, and SPECTCTaver. In contrast, SPECTaver, SPECTCTmax, and SPECTmax had similar specificities, PPVs, and NPVs. Nonetheless, SPECTCTaver had the lowest specificity, PPV, and NPV among all methods. ROC analysis also showed similar diagnostic performances among SPECTaver, SPECTmax, and SPECTCTmax (P>.05) and poorer diagnostic performance of SPECTCTaver compared with the other 3 methods (P<.05). The method of using ROIs drawn around the contour of the condyle on SPECT/CT images does not show improved accuracy over conventional SPECT-fixed ROI methods in assessing UCH.

Evaluation of Timepix3 based CdTe photon counting detector for fully spectroscopic small animal SPECT imaging

The imaging method of SPECT (Single Photon Emission Computed Tomography) is used in nuclear medicine for diagnostics of various diseases or organs malfunctions. The distribution of medically injected, inhaled, or ingested radionuclides (radiotracers) in the patient body is imaged using gamma-ray sensitive camera with suitable imaging collimator. The 3D image is then calculated by combining many images taken from different observation angles. Most of SPECT systems use scintillator based cameras. These cameras do not provide good energy resolution and do not allow efficient suppression of unwanted signals such as those caused by Compton scattering. The main goal of this work is evaluation of Timepix3 detector properties for SPECT method for functional imaging of small animals during preclinical studies. Advantageous Timepix3 properties such as energy and spatial resolution are exploited for significant image quality improvement. Preliminary measurements were performed on specially prepared plastic phantom with cavities filled by radioisotopes and then repeated with in vivo mouse sample.

The influence of gravity on regional lung blood flow in humans: SPECT in the upright and head-down posture.

Previous studies in humans have shown that gravity has little influence on the distribution of lung blood flow while changing posture from supine to prone. This study aimed to evaluate the maximal influence of posture by comparison of regional lung blood flow in the upright and head-down posture in 8 healthy volunteers, using a tilt table. Regional lung blood flow was marked by intravenous injection of macroaggregates of human albumin labeled with 99mTc or 113mIn, in the upright and head-down posture, respectively, during tidal breathing. Both radiotracers remain fixed in the lung after administration. The distribution of radioactivity was mapped using quantitative single photon emission computed tomography (SPECT) corrected for attenuation and scatter. All images were obtained supine during tidal breathing. A shift from upright to the head-down posture caused a clear redistribution of blood flow from basal to apical regions. We conclude that posture plays a role for the distribution of lung blood flow in upright humans, and that the influence of posture, and thereby gravity, is much greater in the upright and head-down posture than in horizontal postures. However, the results of the study demonstrate that lung structure is the main determinant of regional blood flow and gravity is a secondary contributor to the distribution of lung blood flow in the upright and head-down positions.NEW & NOTEWORTHY Using a dual-isotope quantitative SPECT method, we demonstrated that although a shift in posture redistributes blood flow in the direction of gravity, the results are also consistent with lung structure being a greater determinant of regional blood flow than gravity. To our knowledge, this is the first study to use modern imaging methods to quantify the shift in regional lung blood flow in humans at a change between the upright and head-down postures.

A COMPARISON OF THE DIAGNOSTIC ACCURACY OF MIBG, ECD AND FP-CIT SPECT FOR DETECTING LEWY BODY DISEASE IN A MEMORY CLINIC

99mTc-ethyl cysteinate dimer (ECD) cerebral blood flow single photon emission computed tomography (SPECT), 123I-2β-Carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane (123I-FP-CIT) dopamine transporter (DAT) SPECT and 123I-metaiodobenzylguanidine (MIBG) myocardial SPECT can be used to assist in the diagnosis of patients with Lewy bodies disease (LBD). We compared the diagnostic value of these three SPECT methods in differentiating LBD from non-LBD. Patients with no-LBD (n=48) and patients with LBD (n=17) who underwent ECD SPECT, DAT SPECT and MIBG myocardial scintigraphy were enrolled. Patients with LBD consisted of dementia with Lewy bodies (n=33), Parkinson disease (n=7), Parkinson disease with dementia (n=4), and REM sleep behavior disorder (n=4). Patients with non-LBD consisted of Alzheimer disease (n=9), progressive supranuclear palsy (n=2), multiple system atrophy (n=1), corticobasal degeneration (n=1), vascular dementia (n=1), essential tremor (n=1), sleep apnea syndrome (n=1), and normal (n=1). The sensitivity, specificity, and accuracy of those methods were calculated. The sensitivity and specificity of differentiating LBD from non-LBD were 73.0 and 100 % by the MIBG heart uptake, 64.0 and 82.0 % by the striatum uptake on DAT SPECT, and 76.0 and 53.0 % by ECD SPECT, respectively. These results suggested that using these methods is a useful and practical approach to differentiate LBD from non-LBD.

Development and evaluation of an improved quantitative 90Y bremsstrahlung SPECT method

Yttrium-90 ((90)Y) is one of the most commonly used radionuclides in targeted radionuclide therapy (TRT). Since it decays with essentially no gamma photon emissions, surrogate radionuclides (e.g., (111)In) or imaging agents (e.g., (99m)Tc MAA) are typically used for treatment planning. It would, however, be useful to image (90)Y directly in order to confirm that the distributions measured with these other radionuclides or agents are the same as for the (90)Y labeled agents. As a result, there has been a great deal of interest in quantitative imaging of (90)Y bremsstrahlung photons using single photon emission computed tomography (SPECT) imaging. The continuous and broad energy distribution of bremsstrahlung photons, however, imposes substantial challenges on accurate quantification of the activity distribution. The aim of this work was to develop and evaluate an improved quantitative (90)Y bremsstrahlung SPECT reconstruction method appropriate for these imaging applications. Accurate modeling of image degrading factors such as object attenuation and scatter and the collimator-detector response is essential to obtain quantitatively accurate images. All of the image degrading factors are energy dependent. Thus, the authors separated the modeling of the bremsstrahlung photons into multiple categories and energy ranges. To improve the accuracy, the authors used a bremsstrahlung energy spectrum previously estimated from experimental measurements and incorporated a model of the distance between (90)Y decay location and bremsstrahlung emission location into the SIMIND code used to generate the response functions and kernels used in the model. This improved Monte Carlo bremsstrahlung simulation was validated by comparison to experimentally measured projection data of a (90)Y line source. The authors validated the accuracy of the forward projection model for photons in the various categories and energy ranges using the validated Monte Carlo (MC) simulation method. The forward projection model was incorporated into an iterative ordered subsets-expectation maximization (OS-EM) reconstruction code to allow for quantitative SPECT reconstruction. The resulting code was validated using both a physical phantom experiment with spherical objects in a warm background and a realistic anatomical phantom simulation. In the physical phantom study, the authors evaluated the method in terms of quantitative accuracy of activity estimates in the spheres; in the simulation study, the authors evaluated the accuracy and precision of activity estimates from various organs and compared them to results from a previously proposed method. The authors demonstrated excellent agreement between the experimental measurement and Monte Carlo simulation. In the XCAT phantom simulation, the proposed method achieved much better accuracy in the modeling (error in photon counts was -1.1 %) compared to a previously proposed method (errors were more than 20 %); the quantitative accuracy of activity estimates was excellent for all organs (errors were from -1.6 % to 11.9 %) and comparable to previously published results for (131)I using the same collimator. The proposed (90)Y bremsstrahlung SPECT reconstruction method provided very accurate estimates of organ activities, with accuracies approaching those previously observed for (131)I. The method may be useful in verifying organ doses for targeted radionuclide therapy using (90)Y.

IMAGE QUANTIFICATION FOR RADIATION DOSE CALCULATIONS—LIMITATIONS AND UNCERTAINTIES

Radiation dose calculations in nuclear medicine depend on quantification of activity via planar and/or tomographic imaging methods. However, both methods have inherent limitations, and the accuracy of activity estimates varies with object size, background levels, and other variables. The goal of this study was to evaluate the limitations of quantitative imaging with planar and single photon emission computed tomography (SPECT) approaches, with a focus on activity quantification for use in calculating absorbed dose estimates for normal organs and tumors. To do this we studied a series of phantoms of varying complexity of geometry, with three radionuclides whose decay schemes varied from simple to complex. Four aqueous concentrations of ⁹⁹mTc, ¹³¹I, and ¹¹¹In (74, 185, 370, and 740 kBq mL⁻¹) were placed in spheres of four different sizes in a water-filled phantom, with three different levels of activity in the surrounding water. Planar and SPECT images of the phantoms were obtained on a modern SPECT/computed tomography (CT) system. These radionuclides and concentration/background studies were repeated using a cardiac phantom and a modified torso phantom with liver and "tumor" regions containing the radionuclide concentrations and with the same varying background levels. Planar quantification was performed using the geometric mean approach, with attenuation correction (AC), and with and without scatter corrections (SC and NSC). SPECT images were reconstructed using attenuation maps (AM) for AC; scatter windows were used to perform SC during image reconstruction. For spherical sources with corrected data, good accuracy was observed (generally within ±10% of known values) for the largest sphere (11.5 mL) and for both planar and SPECT methods with ⁹⁹mTc and ¹³¹I, but were poorest and deviated from known values for smaller objects, most notably for ¹¹¹In. SPECT quantification was affected by the partial volume effect in smaller objects and generally showed larger errors than the planar results in these cases for all radionuclides. For the cardiac phantom, results were the most accurate of all of the experiments for all radionuclides. Background subtraction was an important factor influencing these results. The contribution of scattered photons was important in quantification with ¹³¹I; if scatter was not accounted for, activity tended to be overestimated using planar quantification methods. For the torso phantom experiments, results show a clear underestimation of activity when compared to previous experiment with spherical sources for all radionuclides. Despite some variations that were observed as the level of background increased, the SPECT results were more consistent across different activity concentrations. Planar or SPECT quantification on state-of-the-art gamma cameras with appropriate quantitative processing can provide accuracies of better than 10% for large objects and modest target-to-background concentrations; however when smaller objects are used, in the presence of higher background, and for nuclides with more complex decay schemes, SPECT quantification methods generally produce better results.

The Bnai Zion Planar Method: a simplified technique for the quantitation of the absolute renal uptake of 99mTc-DMSA in children

Radionuclide imaging of the kidneys using dimercaptosuccinic acid chelate labeled with technetium-99m (Tc-DMSA) is a well-established method for evaluating the extent of kidney parenchymal involvement in the scenario of urinary tract infection and for the estimation of the functional renal mass. We have developed a simplified technique, Bnai Zion Planar Method (BZPM), to estimate absolute DMSA uptake by the kidneys, which uses a shorter time of acquisition and does not require cumbersome calculations of attenuation correction. The aim of this study was to validate this technique by comparing it with the Quantitative DMSA single-photon emission computed tomography (SPECT) (QDMSA) measurements as the reference method. Sixty-one consecutive children (mean age 5.4+/-4.8 years) were included in the study. Absolute uptake of the radiopharmaceutical by the kidneys was measured using the QDMSA SPECT methods described earlier with data acquisition of 20 min. Kidney volumes and radioactivity concentration measurements were calculated on the reconstruction data using the threshold method. For the simplified technique (BZPM), a planar posterior view of the kidneys was acquired for 1 min at the end of the QDMSA SPECT study. In both kidneys we observed a significant strong correlation between the two methods. BZPM measurements were very similar to those obtained using the validated QDMSA method, as determined by linear regression analysis (Pearson's r=0.924, P<0.001), r(2)=0.854. The uptake according to QDMSA can be predicted by the uptake measured by the BZPM method using the following regression equation: QDMSA=0.445+1.061 BZPM. BZPM estimation in children using the newly proposed planar method was found to be nearly identical to the validated QDMSA SPECT method.

Echocardiographic validation of the layer of maximum count method in the estimation of the left ventricular EF using gated myocardial perfusion SPECT: correlation with QGS, ECTb, and LVGTF

Quantitative gated single-photon emission computed tomography (SPECT) (QGS), Emory Cardiac toolbox (ECTb), layer of maximum count (LMC), and left ventricular global thickening fraction (LVGTF) are four different methods designed to estimate the LV ejection fraction (EF). The third method (LMC) is relatively new and achieved good results in preliminary investigations. Thus, the objective of the study was to further assess the performance of the LMC versus two-dimensional echocardiography in the estimation of the LVEF in comparison with other methods. Data for 38 patients were analyzed retrospectively (27 males) with a mean age of 51+/-10 years. All patients underwent gated myocardial perfusion gated SPECT and two-dimensional echocardiography. EF estimated by the four methods and echocardiography were recorded and analyzed with paired t-test, Pearson's correlation coefficient, analysis of variance, and Bland-Altman plot. The mean EF by echocardiography was significantly higher than QGS and LMC (P<0.0001 and P = 0.003, respectively), whereas it was significantly lower than ECTb and LVGTF methods (P = 0.02 and 0.001, respectively). QGS, ECTb, and LMC correlated significantly in the measurements of the EF with echocardiography (r = 0.844, 0.825, and 0.700, respectively); however, a lower correlation was found between LVGTF and echocardiography (r = 0.595). The agreement limits were (-7.6, 16.1) and (10.5, -15.7) for QGS and ECTb, respectively, whereas it was (-11.6, 19.6) and (-27.9, 15.7) for LMC and LVGTF, respectively. Pair-wise comparison has shown that the EF calculated by QGS was significantly lower than ECTb (P = 0.009) and LVGTF (P<0.0001), whereas it was not different from LMC (P = 0.928). For ECTb, the EF was significantly higher than LMC (P = 0.011), but was not different from LVGTF method (P = 0.173). Further, the EF by LMC was significantly lower than LVGTF method (P<0.0001). The quantitative gated SPECT methods showed a significant correlation with echocardiography in the calculation of the EF. LMC method showed close results to those obtained by QGS and ECTb with similar variability versus the measurements made by echocardiography. This study has investigated the utility of using LMC method in clinical practice; however, it will be more feasible when it becomes independent and extensively validated with other accurate techniques and in different patient conditions.

Multimodal Imaging of Integrin Receptor-Positive Tumors by Bioluminescence, Fluorescence, Gamma Scintigraphy, and Single-Photon Emission Computed Tomography Using a Cyclic RGD Peptide Labeled with a Near-Infrared Fluorescent Dye and a Radionuclide

Integrins, particularly the alpha(v)beta(3) heterodimers, play important roles in tumor-induced angiogenesis and invasiveness. To image the expression pattern of the alpha(v)beta(3) integrin in tumors through a multimodality imaging paradigm, we prepared a cyclic RGDyK peptide analogue (LS308) bearing a tetraazamacrocycle 1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid (DOTA) and a lipophilic near-infrared (NIR) fluorescent dye cypate. The alpha(v)beta(3) integrin binding affinity and the internalization properties of LS308 mediated by the alpha(v)beta(3) integrin in 4t1luc cells were investigated by receptor binding assay and fluorescence microscopy, respectively. The in vivo distribution of (111)In-labeled LS308 in a 4t1luc tumor-bearing mouse model was studied by fluorescence, bioluminescence, planar gamma, and single-photon emission computed tomography (SPECT). The results show that LS308 has high affinity for alpha(v)beta(3) integrin and internalized preferentially via the alpha(v)beta(3) integrin-mediated endocytosis in 4t1luc cells. We also found that LS308 selectively accumulated in alpha(v)beta(3)-positve tumors in a receptor-specific manner and was visualized by the four imaging methods. Whereas the endogenous bioluminescence imaging identified the ensemble of the tumor tissue, the fluorescence and SPECT methods with the exogenous contrast agent LS308 reported the local expression of alpha(v)beta(3) integrin. Thus, the multimodal imaging approach could provide important complementary diagnostic information for monitoring the efficacy of new antiangiogenic drugs.

Application of technetium-99m-sestamibi in differentiation of active from inactive pulmonary tuberculosis using a single photon emission computed tomography method

We studied the usefulness of 99mTc-methoxyisobutylisonitrile (MIBI) scintigraphy for differentiation between active and inactive pulmonary tuberculosis. Thirty-six patients (aged 27-82 years, 16 males and 20 females) were included in our study. Each patient was injected with 740 MBq (20 mCi) 99mTc-MIBI and both planar and single photon emission computed tomography (SPECT) imaging were performed 15 and 60 min after injection. Twenty-four patients had active pulmonary tuberculosis (proven by sputum culture), and the remainder 12 had negative sputum culture. Semiquantitative as well as visual assessments were done on all sets of images. All of the 12 patients in the control group had negative scintigraphy on both planar and SPECT images. Twenty patients with active pulmonary tuberculosis had positive 99mTc-MIBI scintigraphy on planar images (sensitivity of 87.5%). SPECT images were positive in 23 patients with active pulmonary tuberculosis (sensitivity of 95.8%). Both semiquantitative and visual assessment of planar and SPECT images showed statistically significant differences between active and inactive pulmonary tuberculosis patients (P<0.001). Comparison of 15 and 60 min image sets did not show any statistically significant difference (P=0.956 and 0.457 for planar and SPECT images, respectively). 99mTc-MIBI has significant uptake in the active tuberculosis lesions and can be used to differentiate between active and inactive tuberculosis. The SPECT method is especially useful because of its higher sensitivity.

The Clinical Value of Tc-99m TRODAT-1 SPECT for Evaluating Disease Severity in Young Patients With Symptomatic and Asymptomatic Wilson Disease

The purpose of this study was to determine the clinical value of applying Tc-99m TRODAT-1 single photon emission computed tomography (SPECT) of the dopamine transporter to evaluate disease severity in young patients with symptomatic or asymptomatic Wilson disease (WD). The evaluation of Tc-99m TRODAT-1 SPECT was performed in 18 patients with symptomatic WD, 13 patients with asymptomatic WD, and, as controls, 12 normal volunteers matched for age and gender. The neurologic symptoms of symptomatic patients were evaluated by an experienced neurologist. The ratios of specific striatal Tc-99m TRODAT-1 binding [with the cerebellum (CB) as the reference region] were calculated as striatum (ST)/CB and compared among the 3 groups. Using correlation analysis, the ratios for the WD patients were compared with clinical data on the severity of neurologic symptoms. Significant differences of ST/CB ratios were found among the 3 groups (Sym vs. Nor, P = 0.000; Asym vs. Nor, P = 0.036; Sym vs. Asym, P = 0.011, respectively). In 23 patients (18 with symptomatic WD, 5 with asymptomatic WD), the posterior putamina showed more remarkable deformation and decreased radiotracer uptake. The ST/CB ratios correlated negatively with the severity of neurologic symptoms (r = -0.80, P < 0.01). The decreased striatal Tc-99m TRODAT-1 uptake found in young WD patients, including symptomatic WD and some asymptomatic WD, as detected with SPECT, seems to indicate presynaptic damage of the dopaminergic nerve terminals. The decrease in radiotracer uptake was more prominent in the posterior putamina than in the caudate heads. The Tc-99m TRODAT-1 SPECT method can be used effectively for evaluating disease severity in WD.

Single photon emission computed tomography for gastric volume assessment: A method with observer-defined regions of interest

Single photon emission computed tomography (SPECT) imaging allows non-invasive measurement of gastric volume. In previous studies, the processing of the SPECT data involved global threshold algorithms that do not take into account the non-uniform distribution of radioactivity in the gastric wall. The aim of this study was to develop a simple alternative method based on observer-defined regions of interest. A phantom study was performed to standardize volume calculations from SPECT derived cross-sectional areas. In 12 healthy volunteers, the principle was then used to determine gastric volume before and after a 600 ml liquid meal. Furthermore, gastric emptying of the meal was followed with planar scintigraphy. The median volume of the stomach was 86 ml (range 62-130 ml) at baseline, 642 ml (536-748 ml) immediately after the meal, and 370 ml (221-481 ml) 1 h after the meal. The coefficient of variation for the calculations was 9%, 2% and 4%, respectively. The median increase in gastric volume was 562 ml (501-628 ml) immediately after the meal and 294 ml (159-370 ml) after 1 h. Gastric retention of the meal was 68% (50-73%) after 0.5 h and 51% (39-57%) after 1 h. The present manual technique may be a reliable alternative to the automated SPECT methods for assessing gastric volume. The liquid meal that was used in our study did not seem to cause an increase in gastric volume that differed from the volume of the meal.

Brain Perfusion Single Photon Emission Computed Tomography Findings in Patients with Posttraumatic Anosmia and Comparison with Radiological Imaging

Different techniques in neuroimaging have been proposed for assessment of olfactory dysfunction but they are not without limitations. Recently, some studies showed the usefulness of single photon emission-computed tomography (SPECT) in evaluation of patients with posttraumatic anosmia. This study was designed to assess the possible diagnostic value of SPECT findings in patients with posttraumatic anosmia in comparison with magnetic resonance imaging (MRI)/CT imaging. Sixteen patients who had head trauma and consequently anosmia, which was defined according to Cain's identification test, were included in this study. Two nonanosmic groups, traumatic patients and nontraumatic healthy individuals, were selected as control groups for this study. Qualitative and semiquantitative brain perfusion SPECT was performed by measuring the uptake ratio of the orbital frontal cortex to occipital pole in the sagittal projections (uptake index). All 16 target patients had a previous CT scan and/or MRI. Semiquantitative and qualitative brain perfusion SPECT were compared with radiological imaging. Semiquantitative assessment of brain perfusion SPECT revealed remarkable orbital frontal hypoperfusion as compared with two control groups. 87.5% of anosmic patients showed orbital frontal hypoperfusion (-2 SD below the lowest level in healthy controls). In addition, the semiquantitative SPECT method detected more orbitofrontal abnormality than the qualitative method or radiological imaging (MRI and/or CT). Findings suggest that by using SPECT, posttraumatic anosmia corresponds to the hypoperfusion in the orbital frontal cortex in a great number of patients. Because of its availability, rather low cost, technical ease, and possibility to obtain objective quantitative information, brain perfusion SPECT can be complementary to other diagnostic techniques in the evaluation of olfactory function, although additional neurophysiological and imaging studies are needed.

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

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

Imaging in breast cancer – breast cancer imaging revisited

Imaging in breast cancer – breast cancer imaging revisited

Relationship of gastric emptying and volume changes after a solid meal in humans

Noninvasive imaging has been developed to measure gastric volumes. The relationship between gastric emptying and volume postprandially is unclear. The aims were to 1) develop a 3-dimensional (3D) single photon emission-computed tomography (SPECT) method to simultaneously measure gastric volume and emptying postprandially, 2) describe the course of gastric volume change during emptying of the meal, and 3) assess a 3D method measuring gastric emptying. In 30 healthy volunteers, we used (111)In-planar and (99m)Tc-SPECT imaging to estimate gastric emptying and volume after a radiolabeled meal. A customized analysis program of SPECT imaging assessed gastric emptying. A Bland-Altman plot assessed the performance of the new SPECT analysis compared with planar analysis. Gastric volume postprandially exceeds the fasting volume plus meal volume. The course of volume change and gastric emptying differ over time. Higher differences in volumes exist relative to fasting plus residual meal volumes at 15 min (median 763 vs. 568 ml, respectively, P < 0.001), 1 h (median 632 vs. 524 ml, P < 0.001), and 2 h (median 518 vs. 428 ml, P < 0.02), in contrast to similar volumes at 3 h (median 320 vs. 314 ml, P = 0.85). Analysis of SPECT imaging accurately measures gastric emptying compared with planar imaging with median differences of 1% (IQR -2.25 to 2.0) at 1 h, 1% (-3.25 to 2.25) at 2 h, and -2.5% (-4 to 0) at 3 h. Gastric volume exceeds meal volume during the first 2 postprandial hours, and simultaneous measurements of gastric volume and emptying can be achieved with a novel 3D SPECT method.