Role of CT attenuation correction gated SPECT MPI in prediction of pulmonary hypertension

OBJECTIVE

To elucidate the value of gated SPECT-MPI using CT attenuation correction (AC) for prediction of pulmonary hypertension (PHT) in coronary patients by estimation of reliability of non-contrast CT in measurement of main pulmonary artery diameter (MPAd) as well as by assessment of potential predictive role of gated parameters as beneficial accessory findings.

BACKGROUND

Contrast-enhanced CT is known as an accurate tool for assessment of MPAd to predict PHT. [1] The low-dose non-contrast CT which is used for AC in MPI study, however, has an unclear value in precise vascular diameter measurement; it is also uncertain whether gated parameters could help to predict PHT.

METHODS AND PATIENTS

A total of 207 patients, who had a transthoracic echocardiography and MPI with an interval of maximum one month, underwent this retrospective study. PHT was defined as a RVSP ≥36 mmHg by echocardiography; peak tricuspid regurgitation velocity (PTRV) was also calculated to use as a criterion for PHT. Of all subjects, 120 had RVSP ≥ 36 and 87 showed RVSP < 36; there also were 191 and 16 patients with PTRV ≤ 3.4 m/s and >3.4 m/s, respectively. Comparison was made unconnectedly between each group regarding the echocardiography results with the MPI parameters, with and without CT-AC, including MPAd derived from CT as well as RV/LV uptake ratio, shape index and septal wall motion and thickening scores to define the best indicators of PHT.

RESULTS

There was a significant association between established benchmark of PHT in echocardiography (RVSP), with MPAd derived from non-contrast CT as well as with LV shape index from gated study and RV/LV uptake ratio acquired from non-AC SPECT-MPI. Also, stress and rest RV/LV uptake ratio, MPAd, LV end-systolic and LV end-diastolic shape indexes are significantly higher in patients with RVSP ≥ 36 mmHg compare to patients with RVSP < 36 mmHg.

CONCLUSIONS

Gated-SPECT-MPI using CT-AC can predict PHT by reliable estimation of MPAd as well as by defining RV/LV uptake ratio and shape index, providing an added clinical value for this invaluable modality in cardiac patients.

Left Ventricular Myocardial Dysfunction Evaluation in Thalassemia Patients Using Echocardiographic Radiomic Features and Machine Learning Algorithms

Heart failure caused by iron deposits in the myocardium is the primary cause of mortality in beta-thalassemia major patients. Cardiac magnetic resonance imaging (CMRI) T2* is the primary screening technique used to detect myocardial iron overload, but inherently bears some limitations. In this study, we aimed to differentiate beta-thalassemia major patients with myocardial iron overload from those without myocardial iron overload (detected by T2*CMRI) based on radiomic features extracted from echocardiography images and machine learning (ML) in patients with normal left ventricular ejection fraction (LVEF > 55%) in echocardiography. Out of 91 cases, 44 patients with thalassemia major with normal LVEF (> 55%) and T2* ≤ 20 ms and 47 people with LVEF > 55% and T2* > 20 ms as the control group were included in the study. Radiomic features were extracted for each end-systolic (ES) and end-diastolic (ED) image. Then, three feature selection (FS) methods and six different classifiers were used. The models were evaluated using various metrics, including the area under the ROC curve (AUC), accuracy (ACC), sensitivity (SEN), and specificity (SPE). Maximum relevance-minimum redundancy-eXtreme gradient boosting (MRMR-XGB) (AUC = 0.73, ACC = 0.73, SPE = 0.73, SEN = 0.73), ANOVA-MLP (AUC = 0.69, ACC = 0.69, SPE = 0.56, SEN = 0.83), and recursive feature elimination-K-nearest neighbors (RFE-KNN) (AUC = 0.65, ACC = 0.65, SPE = 0.64, SEN = 0.65) were the best models in ED, ES, and ED&ES datasets. Using radiomic features extracted from echocardiographic images and ML, it is feasible to predict cardiac problems caused by iron overload.

Comparison of Average Absorbed Dose Distributions of Organs in SPECT-CT Imaging Using Monte Carlo Simulation

Purpose: The use of ionizing radiation in medical research, treatment, and diagnosis is inevitable and expanding day by day. Meanwhile, in two modes of Computed Tomography (CT) and Single Photon Emission Computed Tomography (SPECT) imaging, the dose received by the organs is featured with limitations and problems, which are often referred to as the CT Dose Index volume (CTDIvol.) and the Dose Length Product (DLP). This study aimed to estimate the average dose of organs and compare them in each of these two modalities. Materials and Methods: Using the GATE code to simulate the SPECT-CT system and the International Commission on Radiological Protection (ICRP) voxelized phantom as the patient was investigated. The mean dose distribution in three groups of children, adults, and obese people with different body thicknesses was estimated. The dose received by each of the two systems was evaluated separately and results were discussed and analyzed comparatively. Results: In the kidney, bladder, intestine, colon, liver, and gallbladder, the dose received in CT is at least 10% more than nuclear medicine. For example, the ratio of the dose received in CT to the dose received in nuclear medicine in the lung was about 1.08 and in the esophagus was about 1.24. Subsequently, the ratio increased to 0.25 in the bladder and 0.19 in the colon and intestine. Moreover, the major organs that received the maximum dose, result in CT at least 10% more than nuclear medicine. Conclusion: The dose received in organs such as the esophagus, breast, and lung during CT imaging protocol and also maximum dose were at least ten percent more than nuclear medicine.

Breathing-induced Errors in Quantification and Description of Dominant Intra-Prostatic Lesions (Dils) in PET Images: A Simulation Study by Means of The 4D NCAT Phantom

BACKGROUND

Respiratory movement and the motion range of the diaphragm can affect the quality and quantity of prostate images.

OBJECTIVE

This study aimed to investigate the magnitude of respiratory-induced errors to determine Dominant Intra- prostatic Lesions (DILs) in positron emission tomography (PET) images.

MATERIAL AND METHODS

In this simulation study, we employed the 4D NURBS-based cardiac-torso (4D-NCAT) phantom with a realistic breathing model to simulate the respiratory cycles of a patient to assess the displacement, volume, maximum standardized uptake value (SUV_max), mean standardized uptake value (SUV_mean), signal to noise ratio (SNR), and the contrast of DILs in frames within the respiratory cycle.

RESULTS

Respiration in a diaphragm motion resulted in the maximum superior-inferior displacement of 3.9 and 6.1 mm, and the diaphragm motion amplitudes of 20 and 35 mm. In a no-motion image, the volume measurement of DILs had the smallest percentage of errors. Compared with the no-motion method, the percentages of errors in the average method in 20 and 35 mm- diaphragm motion were 25% and 105%, respectively. The motion effect was significantly reduced in terms of the values of SUV_max and SUV_mean in comparison with the values of SUV_max and SUV_mean in no- motion images. The contrast values in respiratory cycle frames were at a range of 3.3-19.2 mm and 6.5-46 for diaphragm movements' amplitudes of 20 and 35 mm.

CONCLUSION

The respiratory movement errors in quantification and delineation of DILs were highly dependent on the range of motion, while the average method was not suitable to precisely delineate DILs in PET/CT in the dose-painting technique.

Evaluation of Dose-Painting in the Dominant Intraprostatic Lesions by Radiobiological Parameters using 68Ga- PSMA PET/CT

BACKGROUND

Patients diagnosed with dominant intraprostatic lesions (DIL) may need radiation doses over than 80 Gy. Dose-painting by contours (DPC) is a useful technique which helps the patients. Dose-painting approach need to be evaluated.

OBJECTIVE

To evaluate the DCP technique in the case of boosting the DILs by radiobiological parameters, tumor control probability (TCP), and normal tissue complication probability (NTCP) via PET/CT images traced by ⁶⁸Ga-PSMA.

MATERIAL AND METHODS

In this analytical study, ⁶⁸Ga-PSMA PET/CT images were obtained from patients with DILs that were delineated using the Fuzzy c-mean (FCM) algorithm and thresholding methods. The protocol of therapy included two phases; at the first phase (ph1), a total dose of 72 Gy in 36 fractions were delivered to the planning target volume (PTV1); the seconds phase consisted of the application of variable doses to the PTV2. Moreover, two concepts were also considered to calculate the TCP using the Zaider-Minerbo model.

RESULTS

The lowest volume in DILs belonged to the DIL1 extracted by the FCM method. According to dose-volume parameters of the rectum and bladder, by the increase in the PTV dose higher than 92 Gy, the amounts of rectum and bladder doses are increased. There was no difference between the TCPs of DILs at doses higher than 86 Gy and 100 Gy for ordinary and high clone density, respectively.

CONCLUSION

Consequently, our dose-painting approach for DILs, extracted by the FCM method via PET/CT images, can reduce the total dose for prostate radiation with 100% tumor control and less normal tissue complications.

Cardiac SPECT radiomic features repeatability and reproducibility: A multi-scanner phantom study

BACKGROUND

The aim of this work was to assess the robustness of cardiac SPECT radiomic features against changes in imaging settings, including acquisition, and reconstruction parameters.

METHODS

Four commercial SPECT and SPECT/CT cameras were used to acquire images of a static cardiac phantom mimicking typical myorcardial perfusion imaging using 185 MBq of 99mTc. The effects of different image acquisition and reconstruction parameters, including number of views, view matrix size, attenuation correction, as well as image reconstruction related parameters (algorithm, number of iterations, number of subsets, type of post-reconstruction filter, and its associated parameters, including filter order and cut-off frequency) were studied. In total, 5,063 transverse views were reconstructed by varying the aforementioned factors. Eighty-seven radiomic features including first-, second-, and high-order textures were extracted from these images. To assess reproducibility and repeatability, the coefficient of variation (COV), as a widely adopted metric, was measured for each of the radiomic features over the different imaging settings.

RESULTS

The Inverse Difference Moment Normalized (IDMN) and Inverse Difference Normalized (IDN) features from the Gray Level Co-occurrence Matrix (GLCM), Run Percentage (RP) from the Gray Level Co-occurrence Matrix (GLRLM), Zone Entropy (ZE) from the Gray Level Size Zone Matrix (GLSZM), and Dependence Entropy (DE) from the Gray Level Dependence Matrix (GLDM) feature sets were the only features that exhibited high reproducibility (COV ≤ 5%) against changes in all imaging settings. In addition, Large Area Low Gray Level Emphasis (LALGLE), Small Area Low Gray Level Emphasis (SALGLE) and Low Gray Level Zone Emphasis (LGLZE) from GLSZM, and Small Dependence Low Gray Level Emphasis (SDLGLE) from GLDM feature sets turned out to be less reproducible (COV > 20%) against changes in imaging settings. The GLRLM (31.88%) and GLDM feature set (54.2%) had the highest (COV < 5%) and lowest (COV > 20%) number of the reproducible features, respectively. Matrix size had the largest impact on feature variability as most of the features were not repeatable when matrix size was modified with 82.8% of them having a COV > 20%.

CONCLUSION

The repeatability and reproducibility of SPECT/CT cardiac radiomic features under different imaging settings is feature-dependent. Different image acquisition and reconstruction protocols have variable effects on radiomic features. The radiomic features exhibiting low COV are potential candidates for future clinical studies.

Advanced Noise-Optimized Dual-Energy Virtual Monochromatic Imaging vs. Conventional 120-kVp CT Imaging: Image Quality Assessment

Purpose: This study aimed at evaluating the image quality characteristics of advanced noise-optimized and traditional virtual monochromatic images compared with conventional 120-kVp images from second-generation Dual-Source CT. Materials and Methods: For spiral scans six syringes filled with diluted iodine contrast material (1, 2, 5, 10, 15, 20 mg I/ml) were inserted into the test phantom and scanned with a second-generation dual-source CT in both single-energy (120-kVp) and dual-energy modes. Images set contain conventional single-energy 120-kVp, and virtual monochromatic were reconstructed with energies ranging from 40 to 190-keV in 1-keV steps. An energy-domain noise reduction algorithm was applied and the mean CT number, image noise, and iodine CNR were calculated. Results: The iodine CT number of conventional 120-kVp images compared with monochromatic of 40-, 50-, 60- and 70-keV images showed increase. The improvement ratio of image noise on Advanced Virtual Monochromatic Images (AVMIs) compared with the Traditional Virtual Monochromatic Images (TVMIs) at energies of 40-, 50-, 60, 70-keV was 52.9%, 35.7%, 8.1%, 2.1%, respectively. At AVMIs from 75- to 190-keV, the image noise value was less than conventional 120-kVp images. CNR improvement ratio at 20 mg/ml of iodinated contrast material for TVMIs and AVMIs compared to 120-kVp CT images and AVMIs compared to TVMI was 18.3% and 56.3%, 32.1% respectively. Conclusion: Both TVMIs (in energies ranging from 54 to 71-keV) and AVMIs (in energies ranging from 40 to 74-keV) represent improvement in the iodine contrast-to-noise ratio than conventional 120-kVp CT images for the same radiation dose. Also, AVMIs compared to TVMIs have been obtained considerable noise reduction and CNR improvement for low-energy virtual monochromatic images. In the present study, we show that virtual monochromatic image and its Advanced version (AVMI) may boost the dual-energy CT advantages by providing higher CNR images in the same exposure value compared to routinely acquired single-energy CT images.

Synthesis and evaluation of 99mTc-DOTA-ARA-290 as potential SPECT tracer for targeting cardiac ischemic region

Objectives

Myocardial infarction caused by ischemia of heart tissue is the main reason for death worldwide; therefore, early detection can reduce mortality and treatment costs. Erythropoietin (EPO) has protection effects on ischemic tissue due to nonhematopoietic peptide (pHBSP; ARA-290) which is derived from the B-subunit of EPO.

Materials and Methods

We designed and synthesized a modified DOTA-(Lys-Dabcyl⁶, Phe⁷)-ARA-290 using Fmoc solid-phase peptide synthesis strategies. To improve serum stability, Fmoc-Lys-(Dabcyl)-OH as lipophilic amino acid was synthesized along with Fmoc-Phe-OH which then were substituted with Arg⁶ and Ala⁷, respectively; they were then investigated for the ability to detect ischemic cardiac imaging. DOTA-(Lys-Dabcyl⁶,Phe⁷)-ARA-290 was labeled with technetium 99m, and its radiochemical purity (RCP), stability in the presence of human serum and, specific bind to hypoxic H9c2 cells were evaluated. In vivo studies for biodistribution and SPECT scintigraphy were checked in a normal and cardiac ischemia rat model.

Results

Radiolabeling purity was obtained more than 96% by ITLC, and in vitro stability of the radiopeptide up to 6 hr was 85%. The binding of ^99mTc-ARA-290 to hypoxic cells was remarkably higher than normoxic cells (3 times higher than normoxic cells at 1 hr). Biodistribution and SPECT imaging on the cardiac ischemic model showed that radiopeptide considerably accumulated in the ischemic region (cardiac ischemic-to-lung rate = 3.65 ID/g % at 0.5 hr).

Conclusion

The results of studies, in vitro and in vivo, indicated that 99mTc-DOTA-(Lys-Dabcyl6,Phe7)-ARA-290 could be an appropriate candidate for early diagnosis of cardiac ischemia.

Myocardial strain by cardiac magnetic resonance: A valuable predictor of outcome after infarct revascularization

PURPOSE

To evaluate the prognostic value of left ventricular strains by cardiac magnetic resonance feature tracking (CMR-FT) in patients with re-perfused myocardial infarction (MI).

METHODS

The study enrolled 58 patients with re-vascularized MI who underwent CMR within a week from acute MI. An 18-month follow-up was carried out for the composite endpoint of major adverse cardiovascular events (MACE). A 3 to 6-month post-MI ejection fraction (EF) was also measured. The predictive value of global longitudinal, circumferential, and radial strains (GLS, GCS, and GRS, respectively) for MACE and the follow-up EF was evaluated.

RESULTS

All the global strains showed significant impairment in MACE positive cases (P < 0.05 for all). On univariate regression, MACE was reversely associated with early post-MI EF (OR: 0.90, 95% CI: 0.83-0.98, P: 0.01), and directly associated with GLS (OR: 1.32, 95% CI: 1.03-1.69, P: 0.02), GCS (OR: 1.23, 95% CI: 1.00-1.50, P: 0.04) and EDVI (OR:1.02, 95 %CI: 1.00-1.04, P: 0.01). On multivariate regression model, only the interaction between EF and GLS showed a significant association with MACE (OR[CI95%]: 1.1 [1.06-1.21]). EF < 30% and GLS > -8.9% had the highest sensitivity (78.9% and 89.5%, respectively) and specificity (45.2% and 54.8%, respectively) to predict MACE. The combination of EF < 30% and GLS > -8.9% increased the sensitivity to 94.7%. In addition, the cutoff values of 35.1% for early post-MI EF and -10% for GLS could identify patients with impaired follow-up EF with more than 80% sensitivity and specificity [AUC (CI95%): 0.893(0.76-1.00) for EF and AUC (CI95%):0.836(0.67-1,00) for GLS, P < 0.05 for both)].

CONCLUSIONS

GLS by CMR-FT is a powerful prognosticator of MACE and functional recovery in MI survivors, with incremental value added to early post-MI EF alone.

Novel manganese carbon quantum dots as a nano-probe: Facile synthesis, characterization and their application in naproxen delivery (Mn/CQD/SiO2@naproxen)

This study for the first time pursues two crucial aims of using Naproxen as a non-steroidal anti-inflammatory drug in a better, non-invasive setting and introducing a simple and biocompatible nano-carrier (Mn/CQD/SiO₂) which is a magneto carbon quantum dots modified with mesoporous silica probe which can be served as a drug delivery and tracer system. SiO₂modification was doneby mesoporous silica which improves biocompatibility and provideslow cytotoxicity. Naproxen was conjugated to the nano-probe to form Mn/CQD/SiO₂@naproxen and biodistribution was investigated. Physicochemical characteristics of the Mn/CQD/SiO₂@naproxen were investigated using FT-IR, SEM, TEM, UV-Vis and BET. Antiproliferation assay using MTT assay was performed on HEK-293 cells to determine the cytotoxity of Mn/CQD/SiO₂@naproxen. Relaxivity of Mn/CQD/SiO2 was examined thereafter. To investigate the imaging capability of Mn/CQD/SiO₂@naproxen and biodistribution of Naproxen, fluorescent imaging was done. To confirm the data, then the levels of COX Gene expression was determined. The specific surface area, pore volume, and pore radius were 44.4 m²/g, 10.23 cm³/g, and 25.9 nm respectively. MTT assay showed no cytotoxicity. Relaxivity of Mn/CQD/SiO₂ was higher than conventional Gd-based contrast agent. Fluorescence imaging of Mn/CQD/SiO₂@naproxen showed the biodistribution of naproxen. COX Gene expression confirmed the biodistribution data. By increasing the accumulation in liver COX production reduced. All in all, unique features of Mn/CQD/SiO₂ including biocompatibility, low toxicity, magnetic and fluorescence properties showed that it can be used in biomedical sciences.

Role of Technetium-99m-Ethylenedicysteine in the Calculation of Differential Renal Function: A Comparison Study with Dimercaptosuccinic Acid Renal Scintigraphy

Purpose of the Study:

The aim of our study was to compare the technetium-99m (Tc-99m)-ethylenedicysteine (EC) renography calculation of differential renal function (DRF) with this measurement using Tc-99m-dimercaptosuccinic acid (DMSA) scintigraphy.

Materials and Methods:

Patients referred to our department were included in our study, and both DMSA and EC scans were performed for each patient according to the standard imaging protocols. A checklist was filled for each patient. Statistical analysis was performed using correlation and regression methods.

Results:

Forty-two patients (mean age: 3.6 ± 3.4 years), including 32 boys and 10 girls, participated in our study. The results of EC scintigraphy were significantly correlated with the values of DMSA scintigraphy (P < 0.001). Performing linear regression, EC renography significantly (P < 0.001) predicted the DRF as it was calculated by DMSA scintigraphy (R² = 0.92, P < 0.001). This test was significant in both male and female subgroups (P < 0.001).

Conclusions:

Overall, our study findings were similar to the reported results in the other reviewed studies, showing that Tc-99m-EC can be considered as an alternative for DMSA scintigraphy, providing interchangeable results.

Application of radiolabeled peptides in tumor imaging and therapy

Scientists are looking for new therapies to cope with the rise in cancer worldwide. Since cancer cells overexpress peptide receptors and owing to small size, easy uptake by tumor cells, easy preparation, and with no toxicity, the use of radiolabeled peptides with high specificity and affinity for accurate imaging and therapy has attracted much attention. To develop an ideal imaging or treatment radiolabeled peptide, there are some aspects in the components of radiolabeled peptide including radionuclide, peptide, chelator, and spacer that should be considered. Some peptides, including somatostatin, RGD, neurotensin, bombesin, exendin, vasoactive intestinal peptide, and gastrin are currently under (pre)clinical investigations. Today, nanoparticles are suitable tools for targeting peptide for molecular imaging and therapy of tumors with low toxicity. This paper presents some essential aspects in developing a valuable radiolabeled peptide and some radiolabeled peptides with regard to their applications in tumor imaging and therapy in pre-clinical and clinical phases.

The impact of frame numbers on cardiac ECG-gated SPECT images with interpolated extra frames using echocardiography

Background: Cardiac echocardiography and cardiac ECG-gated single-photon emission computed tomography (SPECT) are the most common modalities for left ventricle (LV) volumes and function assessment. The temporal resolution of SPECT images is limited and an ECG provides better temporal resolution. This study investigates the impact of frame numbers on images in terms of qualitative and quantitative assessments.

Methods: In this study, 5 patients underwent echocardiography and cardiac ECG-gated SPECT imaging, and 5 standard views of the LV were recorded to determine LV walls boundaries and volumes. Also, 2 original images with 8 frames and 16 frames per cardiac cycle were recorded simultaneously in a single gantry orbit. Using the data extracted from the LV model, 8 extra new frames were created with interpolation between existing frames of the original 8-frame image. Three series of images (8 and 16 original and 16 interpolated) were reconstructed separately. LV volumes and ejection fraction (EF) were calculated using Quantitative Gated SPECT (QGS) software.

Results: Compared to the original 8-frame gating, original 16-frame gated images resulted in larger end-diastole volume (EDV) (mean ± SD: 68.6 ± 27.11 mL vs 66.2±25.41 mL, p<0.001), smaller end-systole volume (ESV) (mean ± SD: 24.6±8.7 mL vs 26±7.3 mL, p<0.001), and higher EF (64% vs 60.2%, p<0.001). The results for the interpolated series were also different from the original images (closer to the original 16-frame series rather than 8-frame).

Conclusion: Changing the frame number from 8 to 16 in cardiac ECG-gated SPECT images caused a significant change in LV volumes and EF. Frame interpolation with sophisticated algorithms can be used to improve the temporal resolution of SPECT images.

Synthesis, radiolabelling, and biological assessment of folic acid-conjugated G-3 99mTc-dendrimer as the breast cancer molecular imaging agent

Hence, in this study, the authors aimed to develop a dendrimer-based imaging agent comprised of poly(ethylene glycol) (PEG)-citrate, technetium-99 m (99mTc), and folic acid. The dendrimer-G3 was synthesised and conjugated with folic acid, which confirmed by Fourier transform infrared, proton nuclear magnetic resonance, dynamic light scattering, and transition electron microscopy. 2,3-bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-Tetrazolium-5-Carboxanilide cytotoxicity assay kit was used to measure the cellular toxicity of dendrimer. Imaging and biodistribution studies were conducted on the mice bearing tumour. The results showed that the fabricated dendrimer-G3 has a size of 90 ± 3 nm, which was increased to 100 ± 4 nm following the conjugation with folic acid. The radiostablity investigation showed that the fabricated dendrimers were stable in the human serum at various times. Toxicity assessment confirmed no cellular toxicity against HEK-293 cells at 0.25, 0.5, 1, 2, 4, and 8 mg/μl concentrations. The in vivo studies demonstrated that the synthesised dendrimers were able to provide a bright SPECT image applicable for tumour detection. In conclusion, the authors' study documented the positive aspects of PEG-citrate dendrimer conjugated with folic acid as the SPECT contrast agent for breast cancer detection.

Prediction of Response to Neoadjuvant Chemoradiotherapy by MRI-Based Machine Learning Texture Analysis in Rectal Cancer Patients

INTRODUCTION

Neoadjuvant chemoradiotherapy (nCRT) followed by surgical resection is the standard treatment for locally advanced rectal cancer (LARC). Radiomics can be used as noninvasive biomarker for prediction of response to therapy. The main aim of this study was to evaluate the association of MRI texture features of LARC with nCRT response and the effect of Laplacian of Gaussian (LoG) filter and feature selection algorithm in prediction process improvement.

METHODS

All patients underwent MRI with a 3T clinical scanner, 1 week before nCRT. For each patient, intensity, shape, and texture-based features were derived from MRI images with LoG filter using the IBEX software and without preprocessing. We identified responder from a non-responder group using 9 machine learning classifiers. Then, the effect of preprocessing LoG filters with 0.5, 1 and 1.5 value on these classification algorithms' performance was investigated. Eventually, classification algorithm's results were compared in different feature selection methods.

RESULT

Sixty-seven patients with LARC were included in the study. Patients' nCRT responses included 11 patients with Grade 0, 19 with Grade 1, 26 with Grade 2, and 11 with Grade 3 according to AJCC/CAP pathologic grading. In MR Images which were not preprocessed, the best performance was for Ada boost classifier (AUC = 74.8) with T2W MR Images. In T1W MR Images, the best performance was for aba boost classifier (AUC = 78.1) with a σ = 1 preprocessing LoG filter. In T2W MR Images, the best performance was for naive Bayesian network classifier (AUC = 85.1) with a σ = 0.5 preprocessing LoG filter. Also, performance of machine learning models with CfsSubsetEval (CF SUB E) feature selection algorithm was better than others.

CONCLUSION

Machine learning can be used as a response predictor model in LARC patients, but its performance should be improved. A preprocessing LoG filter can improve the machine learning methods performance and at the end, the effect of feature selection algorithm on model's performance is clear.

Author Correction: Prediction of Response to Neoadjuvant Chemoradiotherapy by MRI-Based Machine Learning Texture Analysis in Rectal Cancer Patients

The original version of this article unfortunately contained a mistake. In the author group section, the correct name of the fourth author is "Reza Ghalehtaki." The authors apologize for this oversight and for any confusion it may have caused.

PEG-Citrate dendrimer second generation: is this a good carrier for imaging agents In Vitro and In Vivo?

While cancer is the leading cause of human's deaths worldwide, finding an imaging agent which can detect cancer tumours is needed for cancer diagnosis. In the present study, PEG-citrate dendrimer-G2 was used as a nano-carrier of FITC dye and Iohexol to help passive targeting and uptake of both imaging agents in cancer cells/tumour in vitro and in vivo. Dendrimer was synthesisedand the product characterised using LC-MS, FT-IR, DLS, ELS, AFM, and 1HNMR. After FITC loading into dendrimer, MTT was performed to determine the cytotoxicity of formulation on HEK-293 and MCF-7 cells. In vitro imaging using dendrimer-FITC was done via fluorescent microscope thereafter. Moreover, CT imaging using Iohexol was employed to show the targeting nature and ability of the complex to use as imaging agent in vivo. Data yielded in this study corroborate the notion that the promised dendrimer was synthesised properly and had no toxicity along with FITC on normal cell. Furthermore, CT and fluorescent images showed the targeting nature and imaging ability of Iohexol/FITC loaded dendrimer in vitro and in vivo. Overall, results showed promising characteristics of the novel complexes using dendrimer-G2 both in vitro and in vivo.

Neo-adjuvant chemoradiotherapy response prediction using MRI based ensemble learning method in rectal cancer patients

OBJECTIVES

The aim of this study was to investigate and validate the performance of individual and ensemble machine learning models (EMLMs) based on magnetic resonance imaging (MRI) to predict neo-adjuvant chemoradiation therapy (nCRT) response in rectal cancer patients. We also aimed to study the effect of Laplacian of Gaussian (LOG) filter on EMLMs predictive performance.

METHODS

98 rectal cancer patients were divided into a training (n = 53) and a validation set (n = 45). All patients underwent MRI a week before nCRT. Several features from intensity, shape and texture feature sets were extracted from MR images. SVM, Bayesian network, neural network and KNN classifiers were used individually and together for response prediction. Predictive performance was evaluated using the area under the receiver operator characteristic (ROC) curve (AUC).

RESULTS

Patients' nCRT responses included 17 patients with Grade 0, 28 with Grade 1, 34 with Grade 2, and 19 with Grade 3 according to AJCC/CAP pathologic grading. In without preprocessing MR Image the best result was for Bayesian network classifier with AUC and accuracy of 75.2% and 80.9% respectively, which was confirmed in the validation set with an AUC and accuracy of 74% and 79% respectively. In EMLMs the best result was for 4 (SVM.NN.BN.KNN) classifier EMLM with AUC and accuracy of 97.8% and 92.8% in testing and 95% and 90% in validation set respectively.

CONCLUSIONS

In conclusion, we observed that machine learning methods can used to predict nCRT response in patients with rectal cancer. Preprocessing LOG filters and EL models can improve the prediction process.

Gdn 3+@CNTs-PEG versus Gadovist®: In Vitro Assay

Objectives

Carbon nanotubes (CNTs) are allotropes of carbon with a length-to-diameter ratio greater than 10⁶ with the potential uses as medical diagnostic or therapeutic agents. In vitro studies have revealed that gadolinium (Gd) nanoparticle-catalyzed single-walled carbon nanotubes (SWCNTs) possess superparamagnetic properties, which enable them to be used as contrast agents in magnetic resonance imaging (MRI). Our study synthesized Gd-CNT for use as MRI contrast agents.

Methods

To reduce the toxicity and solubility of CNTs, it was functionalized, and after loading with Gd was coated with polyethylene glycols (PEG). We then synthesized different concentrations of Gd_n³⁺@CNTs-PEG and Gadovist^® to be evaluated as MRI contrast agents.

Results

The analysis showed that the Gd concentration in Gadovist^® was 12.18% higher than synthesized Gd_n³⁺@CNTs-PEG, but the mean signal intensity of the Gd_n³⁺@CNTs-PEG was approximately 3.3% times higher than Gadovist^®.

Conclusions

Our findings indicate that synthesized Gd_n³⁺@CNTs-PEG has the potential to be used as an MRI contrast agent in vitro, but in vivo assessment is necessary to determine the bio-distribution, kinetic, and signal enhancement characteristics.

A Hybrid Multilayer Filtering Approach for Thyroid Nodule Segmentation on Ultrasound Images

OBJECTIVES

Speckle noise is the main factor that degrades ultrasound image contrast and segmentation failure. Determining an effective filter can reduce speckle noise and improve segmentation performances. The aim of this study was to define a useful filter to improve the segmentation outcome.

METHODS

Twelve filters, including median, hybrid median (Hmed), Fourier Butterworth, Fourier ideal, wavelet (Wlet), homomorphic Fourier Butterworth, homomorphic Fourier ideal, homomorphic wavelet (Hmp_Wlet), frost, anisotropic diffusion, probabilistic patch-based (PPB), and homogeneous area filters, were used to find the best filter(s) to prepare thyroid nodule segmentation. A receiver operating characteristic (ROC) analysis was used for filter evaluation in the nodule segmentation process. Accordingly, 10 morphologic parameters were measured from segmented regions to find the best parameters that predict the segmentation performance.

RESULTS

The best segmentation performance was reached by using 4 hybrid filters that mainly contain contrast-limited adaptive histogram equalization, Wlet, Hmed, Hmp_Wlet, and PPB filters. The area under the ROC curve for these filters ranged from 0.900 to 0.943 in comparison with the original image, with an area under the curve of 0.685. From 10 morphologic parameters, the area, convex area, equivalent diameter, solidity, and extent can evaluate segmentation performance.

CONCLUSIONS

Hybrid filters that contain contrast-limited adaptive histogram equalization, Wlet, Hmed, Hmp_Wlet, and PPB filters have a high potential to provide good conditions for thyroid nodule segmentation in ultrasound images. In addition to an ROC analysis, morphometry of a segmented region can be used to evaluate segmentation performances.

CAD system based on B-mode and color Doppler sonographic features may predict if a thyroid nodule is hot or cold

OBJECTIVES

The aim of this study was to evaluate if the analysis of sonographic parameters could predict if a thyroid nodule was hot or cold.

METHODS

Overall, 102 thyroid nodules, including 51 hyperfunctioning (hot) and 51 hypofunctioning (cold) nodules, were evaluated in this study. Twelve sonographic features (i.e., seven B-mode and five Doppler features) were extracted for each nodule type. The isthmus thickness, nodule volume, echogenicity, margin, internal component, microcalcification, and halo sign features were obtained in the B-mode, while the vascularity pattern, resistive index (RI), peak systolic velocity, end diastolic velocity, and peak systolic/end diastolic velocity ratio (SDR) were determined, based on Doppler ultrasounds. All significant features were incorporated in the computer-aided diagnosis (CAD) system to classify hot and cold nodules.

RESULTS

Among all sonographic features, only isthmus thickness, nodule volume, echogenicity, RI, and SDR were significantly different between hot and cold nodules. Based on these features in the training dataset, the CAD system could classify hot and cold nodules with an area under the curve (AUC) of 0.898. Also, in the test dataset, hot and cold nodules were classified with an AUC of 0.833.

CONCLUSIONS

2D sonographic features could differentiate hot and cold thyroid nodules. The CAD system showed a great potential to achieve it automatically.

KEY POINTS

• Cold nodules represent higher volume (p = 0.005), isthmus thickness (p = 0.035), RI (p = 0.020), and SDR (p = 0.044) and appear hypoechogenic (p = 0.010) in US. • Nodule volume with an AUC of 0.685 and resistive index with an AUC of 0.628 showed the highest classification potential among all B-mode and Doppler features respectively. • The proposed CAD system could distinguish hot nodules from cold ones with an AUC of 0.833 (sensitivity 90.00%, specificity 70.00%, accuracy 80.00%, PPV 87.50%, and NPV 75.00%).

Technetium-99m chelator-free radiolabeling of specific glutamine tumor imaging nanoprobe: in vitro and in vivo evaluations

Introduction

Nowadays, molecular imaging radiopharmaceuticals', nanoparticles', and/or small-molecule biomarkers' applications are increasing rapidly worldwide. Thus, researchers focus on providing the novel, safe, and cost-effective ones.

Materials and methods

In the present experiment, technetium-99m (^99mTc)-labeled PEG-citrate dendrimer-G₂ conjugated with glutamine (nanoconjugate) was designed and assessed as a novel tumor imaging probe both in vitro and in vivo. Nanoconjugate was synthesized and the synthesis was confirmed by Fourier transform infrared, proton nuclear magnetic resonance, liquid chromatography-mass spectrometry, dynamic light scattering, and static light scattering techniques. The toxicity was assessed by XTT and apoptosis and necrosis methods.

Results

Radiochemical purity indicates that the anionic dendrimer has a very high potential to complex formation with ^99mTc and is also very stable in the human serum in different times. Results from the imaging procedures showed potential ability of nanoconjugates to detect tumor site.

Conclusion

Suitable features of the anionic dendrimer show that it is a promising agent to improve nanoradiopharmaceuticals.

Radiation Protection Knowledge, Attitude, and Practice (KAP) in Interventional Radiology

Objectives

Due to increasing cardiac disease and its mortality rate, the frequency of cardiac imaging has grown and, as a result, interventional cardiologists potentially receive high radiation doses in cardiac examinations. This study aimed to assess the knowledge, attitude, and practice (KAP) level of radiation protection (RP) among interventional radiology staff in Iranian health care centers across the country.

Methods

We used a validated questionnaire survey consisting of 30 multiple-choice questions to perform a cross-sectional study. Participants were healthcare personnel working professionally with radiation at different levels (i.e., secretary, radiology technologists, nurse, and physician). The questionnaire was divided into three sections to assess KAP regarding RP.

Results

Significant differences exist in RP KAP mean scores based on educational age (p < 0.050). There was no significant difference in RP KAP mean scores when looking at sex, practice age, and hospital type (p > 0.050). We found a significant difference between RP KAP mean scores and different regions (p < 0.050).

Conclusions

Educational and practice age, sex, type of hospital, and geographical region affect he KAP of interventional radiology staff regarding RP. Since many of the subjective radiation harms for both medical team and patients, this can be easily controlled and prevented; a checkup for personnel of interventional radiology departments, considering samples from different parts of the country with different levels of education, continuous training, and practical courses may help map the status of KAP. The results of this study may also help authorized health physics officers design strategic plans to enhance the quality of such services in radiation departments.

Predictive quantitative sonographic features on classification of hot and cold thyroid nodules

PURPOSE

This study investigated the potentiality of ultrasound imaging to classify hot and cold thyroid nodules on the basis of textural and morphological analysis.

METHODS

In this research, 42 hypo (hot) and 42 hyper-function (cold) thyroid nodules were evaluated through the proposed method of computer aided diagnosis (CAD) system. To discover the difference between hot and cold nodules, 49 sonographic features (9 morphological, 40 textural) were extracted. A support vector machine classifier was utilized for the classification of LNs based on their extracted features.

RESULTS

In the training set data, a combination of morphological and textural features represented the best performance with area under the receiver operating characteristic curve (AUC) of 0.992. Upon testing the data set, the proposed model could classify the hot and cold thyroid nodules with an AUC of 0.948.

CONCLUSIONS

CAD method based on textural and morphological features is capable of distinguishing between hot from cold nodules via 2-Dimensional sonography. Therefore, it can be used as a supplementary technique in daily clinical practices to improve the radiologists' understanding of conventional ultrasound imaging for nodules characterization.

Assessment of the scatter correction procedures in single photon emission computed tomography imaging using simulation and clinical study

BACKGROUND

Compton-scattered photons transfer incorrect spatial information. These photons are detected in used photo-peak energy window. In this study, three scatter correction procedures including dual-energy window (DEW), three energy window (TEW), and new approach were evaluated, and then the best procedure based on simulation and clinical conditions introduced.

MATERIALS AND METHODS

In this study, simulation projections and three-dimensional nonuniform rational B-spline-based Cardiac-Torso phantoms were produced by GEANT4 application for emission tomography simulation code. For clinical study, 2-day stress/rest myocardial perfusion imaging (MPI) protocol was performed with 99m Tc-sestamibi for 46 patients. Image quality parameters including contrast, signal-to-noise ratio (SNR), and relative noise of the background (RNB) were evaluated.

RESULTS

The simulation results showed that contrast values for DEW, TEW, and new approach were (0.45 ± 0.07, 0.5 ± 0.08, and 0.63 ± 0.09), SNR values (4.74 ± 0.94, 5.58 ± 1.08, and 6.56 ± 1.24), and RNB values (0.33 ± 0.06, 0.33 ± 0.07, and 0.33 ± 0.05), respectively. In clinical study, the contrast values for DEW, TEW, and new approach were 0.53 ± 0.03, 0.57 ± 0.07, and 0.62 ± 0.04 in rest MPI and were 0.52 ± 0.04, 0.57 ± 0.06, and 0.6 ± 0.05 in stress MPI, respectively. Moreover, for the rest images, the SNR values were 7.65 ± 1.9, 9.08 ± 2.2, and 10.2 ± 1.75 and for stress images were 7.76 ± 1.99, 9.12 ± 2.25, and 10.17 ± 2.04, respectively. Finally, RNB values for rest and stress images were 0.12 ± 0.03, 0.13 ± 0.03, and 0.13 ± 0.03, respectively.

CONCLUSION

The simulation and the clinical studies showed that the new approach could be better performance than DEW, TEW methods, according to values of the contrast, and the SNR for scatter correction.

AS1411 Aptamer-Anionic Linear Globular Dendrimer G2-Iohexol Selective Nano-Theranostics

Molecular theranostics is of the utmost interest for diagnosis as well as treatment of different malignancies. In the present study, anionic linear globular dendrimer G2 is employed as a suitable carrier for delivery and AS1411 aptamer is exploited as the targeting agent to carry Iohexol specifically to the human breast cancer cells (MCF-7). Dendrimer G2 was prepared and conjugation of dendrimer and aptamer was carried out thereafter. Based on the data yielded by AFM, morphology of smooth and spherical non-targeted dendrimer changed to the rough aspherical shape when it conjugated. Then, conjugation was confirmed using DLS, ELS and SLS methods. Toxicity on nucleolin positive MCF-7 cells and nucleolin negative HEK-293 cells was assessed by XTT and apoptosis/necrosis assays. In vitro uptake was determined using DAPI-FITC staining and ICP-MS methods. In vivo studies including in vivo CT imaging, pathology and blood tests were done to confirm the imaging ability, bio-safety and targeted nature of the Nano-Theranostics in vivo. In a nutshell, the prepared construction showed promising effects upon decreasing the toxicity of Iohexol on normal cells and accumulation of it in the cancer tumors as well as reducing the number of cancer cells.

The impact of image reconstruction settings on 18F-FDG PET radiomic features: multi-scanner phantom and patient studies

OBJECTIVES

The purpose of this study was to investigate the robustness of different PET/CT image radiomic features over a wide range of different reconstruction settings.

METHODS

Phantom and patient studies were conducted, including two PET/CT scanners. Different reconstruction algorithms and parameters including number of sub-iterations, number of subsets, full width at half maximum (FWHM) of Gaussian filter, scan time per bed position and matrix size were studied. Lesions were delineated and one hundred radiomic features were extracted. All radiomics features were categorized based on coefficient of variation (COV).

RESULTS

Forty seven percent features showed COV ≤ 5% and 10% of which showed COV > 20%. All geometry based, 44% and 41% of intensity based and texture based features were found as robust respectively. In regard to matrix size, 56% and 6% of all features were found non-robust (COV > 20%) and robust (COV ≤ 5%) respectively.

CONCLUSIONS

Variability and robustness of PET/CT image radiomics in advanced reconstruction settings is feature-dependent, and different settings have different effects on different features. Radiomic features with low COV can be considered as good candidates for reproducible tumour quantification in multi-center studies.

KEY POINTS

• PET/CT image radiomics is a quantitative approach assessing different aspects of tumour uptake. • Radiomic features robustness is an important issue over different image reconstruction settings. • Variability and robustness of PET/CT image radiomics in advanced reconstruction settings is feature-dependent. • Robust radiomic features can be considered as good candidates for tumour quantification.

Radiation dose in cardiac SPECT/CT: An estimation of SSDE and effective dose

AIMS

The dose levels for Computed Tomography (CT) localization and attenuation correction of Single Photon Emission Computed Tomography (SPECT) are limited and reported as Volume Computed Tomography Dose Index (CTDIvol) and Dose-Length Product (DLP). This work presents CT dose estimation from Cardiac SPECT/CT based on new American Association of Physicists in Medicine (AAPM) Size Specific Dose Estimation (SSDE) parameter, effective dose, organ doses and also emission dose from nuclear issue.

MATERIAL AND METHODS

Myocardial perfusion SPECT/CT for 509 patients was included in the study. SSDE, effective dose and organ dose were calculated using AAPM guideline and Impact-Dose software. Data were analyzed using R and SPSS statistical software. Spearman-Pearson correlation test and linear regression models were used for finding correlations and relationships among parameters.

RESULTS

The mean CTDIvol was 1.34 mGy±0.19 and the mean SSDE was 1.7 mGy±0.16. The mean±SD of effective dose from emission, CT and total dose were 11.5±1.4, 0.49±0.11 and 12.67±1.73 (mSv) respectively. The mean±SD of effective dose from emission, CT and total dose were 11.5±1.4, 0.49±0.11 and 12.67±1.73 (mSv) respectively. The spearman test showed that correlation between body size and organ doses is significant except thyroid and red bone marrow. CTDIvol was strongly dependent on patient size, but SSDE was not. Emission dose was strongly dependent on patient weight, but its dependency was lower to effective diameter.

CONCLUSION

The dose parameters including CTDIvol, DLP, SSDE, effective dose values reported here are very low and below the reference level. This data suggest that appropriate CT acquisition parameters in SPECT/CT localization and attenuation correction are very beneficial for patients and lowering cancer risks.

Comparison of Gated SPECT Myocardial Perfusion Imaging with Echocardiography for the Measurement of Left Ventricular Volumes and Ejection Fraction in Patients With Severe Heart Failure

Background:

Gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) is known as a feasible tool for the measurement of left ventricular ejection fraction (EF) and volumes, which are of great importance in the management and follow-up of patients with coronary artery diseases. However, considering the technical shortcomings of SPECT in the presence of perfusion defect, the accuracy of this method in heart failure patients is still controversial.

Objectives:

The aim of the present study was to compare the results from gated SPECT MPI with those from echocardiography in heart failure patients to compare echocardiographically-derived left ventricular dimension and function data to those from gated SPECT MPI in heart failure patients.

Patients and Methods:

Forty-one patients with severely reduced left ventricular systolic function (EF ≤ 35%) who were referred for gated SPECT MPI were prospectively enrolled. Quantification of EF, end-diastolic volume (EDV), and end-systolic volume (ESV) was performed by using quantitative gated spect (QGS) (QGS, version 0.4, May 2009) and emory cardiac toolbox (ECTb) (ECTb, revision 1.0, copyright 2007) software packages. EF, EDV, and ESV were also measured with two-dimensional echocardiography within 3 days after MPI.

Results:

A good correlation was found between echocardiographically-derived EF, EDV, and ESV and the values derived using QGS (r = 0.67, r = 0.78, and r = 0.80 for EF, EDV, and ESV, respectively; P < 0.001) and ECTb (r = 0.68, 0.79, and r = 0.80 for EF, EDV, and ESV, respectively; P < 0.001). However, Bland-Altman plots indicated significantly different mean values for EF, 11.4 and 20.9 using QGS and ECTb, respectively, as compared with echocardiography. ECTb-derived EDV was also significantly higher than the EDV measured with echocardiography and QGS. The highest correlation between echocardiography and gated SPECT MPI was found for mean values of ESV different.

Conclusions:

Gated SPECT MPI has a good correlation with echocardiography for the measurement of left ventricular EF, EDV, and ESV in patients with severe heart failure. However, the absolute values of these functional parameters from echocardiography and gated SPECT MPI measured with different software packages should not be used interchangeably.

Influence of respiratory motion correction on quantification of myocardial perfusion SPECT

BACKGROUND

Respiratory-related cardiac motion could have considerable effects on myocardial perfusion imaging, leading to misinterpretation of the images. In this study, we examined the influence of respiratory correction on ECG-gated myocardial perfusion SPECT (RC-GSPECT) concerning regional myocardial perfusion and function.

MATERIALS AND METHODS

Using the NCAT phantom, a typical torso phantom was generated. SimSET, a Monte Carlo simulator, was used to image the photon emerging from the phantom. Twenty-six patients underwent a 2-day stress-rest ECG-gated myocardial perfusion SPECT (GSPECT) imaging. A separate study was also performed by simultaneous respiratory and cardiac triggering with the real-time position management (RPM) for respiratory correction (RC).

RESULTS

In simulation study, count density in the inferior and inferoseptal walls increased in the lower bin of the respiratory cycle. On the other hand, there was a higher correlation between RC-GSPECT and echocardiography for left ventricular ejection fraction (LVEF) (r = 0.95, P < .01 vs r = 0.88, P < .01 for GSPECT).

CONCLUSION

We proposed a new approach for respiratory and cardiac-gated SPECT to eliminate respiratory motion artifacts. RC-GSPECT is a feasible method in MPI studies and may play an important role to improve the quality of MPI images, particularly in the inferior wall.

The Effect of Milk, Water and Lemon Juice on Various Subdiaphragmatic Activity-Related Artifacts in Myocardial Perfusion Imaging

Background:

Subdiaphragmatic activity can produce subdiaphragmatic-related artifacts, which can degrade the quality of myocardial perfusion imaging (MPI).

Objectives:

We examined the impact of drinking milk, water, and lemon juice on different subdiaphragmatic-related artifacts by using ^99mTc-sestamibi myocardial single-photon emission computed tomography (SPECT) in order to determine a feasible method for improving the image quality.

Patients and Methods:

A total of 179 patients (age 58 ± 9.6 years) were enrolled in this study. The patients were randomly divided into five groups. Ten minutes after injection of 740 MBq 99mTc-sestamibi in both pharmacologic stress and rest phases, the individuals in group 1 were given water and milk (125 mL of each); those in group 2 were given lemon juice (250 mL); group 3 was given milk (250 mL); and group 4 was given water (250 mL), whereas no intervention was performed in group 5. The study was double-blind for both subjects and data collectors. MPI was performed for all patients and image quality was controlled by 2 experienced nuclear physicians. Interfering activity was determined visually on reconstructed images and categorized as extracardiac normalization artifact, overlapping of activity, scattering of activity, and ramp filter artifact.

Results:

There were significant differences in terms of interfering activity among the five groups; group 3 (milk) had significantly lower interfering activity than other groups had, as defined by overlapping of activity (on both stress and rest images), ramp filter artifact (stress images), and scatter artifact (rest images) (P < 0.05). Furthermore, there was a significant difference in the incidence of good-quality images, with no interfering activity in group 3 in the resting state compared with the other groups in the study (P < 0.05).

Conclusions:

Drinking 250 mL of milk in either the stress phase or the rest phase of imaging diminishes interfering subdiaphragmatic-related artifacts, particularly overlapping of activity in MPI SPECT, resulting in better-quality images.

Assessment of left ventricular mechanical dyssynchrony by phase analysis of gated-SPECT myocardial perfusion imaging and tissue Doppler imaging: comparison between QGS and ECTb software packages

BACKGROUND

Recently, the phase analysis of gated single-photon emission computed tomography (SPECT) myocardial perfusion imaging (MPI) has become feasible via several software packages for the evaluation of left ventricular mechanical dyssynchrony. We compared two quantitative software packages, quantitative gated SPECT (QGS) and Emory cardiac toolbox (ECTb), with tissue Doppler imaging (TDI) as the conventional method for the evaluation of left ventricular mechanical dyssynchrony.

METHODS AND RESULTS

Thirty-one patients with severe heart failure (ejection fraction ≤35%) and regular heart rhythm, who referred for gated-SPECT MPI, were enrolled. TDI was performed within 3 days after MPI. Dyssynchrony parameters derived from gated-SPECT MPI were analyzed by QGS and ECTb and were compared with the Yu index and septal-lateral wall delay measured by TDI. QGS and ECTb showed a good correlation for assessment of phase histogram bandwidth (PHB) and phase standard deviation (PSD) (r = 0.664 and r = 0.731, P < .001, respectively). However, the mean value of PHB and PSD by ECTb was significantly higher than that of QGS. No significant correlation was found between ECTb and QGS and the Yu index. Nevertheless, PHB, PSD, and entropy derived from QGS revealed a significant (r = 0.424, r = 0.478, r = 0.543, respectively; P < .02) correlation with septal-lateral wall delay.

CONCLUSION

Despite a good correlation between QGS and ECTb software packages, different normal cut-off values of PSD and PHB should be defined for each software package. There was only a modest correlation between phase analysis of gated-SPECT MPI and TDI data, especially in the population of heart failure patients with both narrow and wide QRS complex.

Evaluation of three scatter correction methods based on estimation of photopeak scatter spectrum in SPECT imaging: a simulation study

Three practical methods for scatter correction of Tc-99m SPECT images are evaluated. Among these, two methods, three-energy window (TEW) methods using the trapezoidal and triangular approximations, have been described previously by investigators, and a new approximation is offered in this work. The SIMIND (SIMulation of Imaging Nuclear Detectors) Monte Carlo program is used to simulate a line source placed at on-axis and 5 cm off-axis locations, a cold-sphere/hot-background phantom, a hot-sphere/cold-background phantom, and a more clinically realistic NCAT (Nonuniform Rational B-spline-based CArdiac-Torso) phantom. For evaluation of these methods, the scatter line-spread functions and scatter fractions for the on- and off-axis line source, image contrast, signal-to-noise ratio and relative noise for the cold spheres, and recovery coefficient for the hot spheres of different diameters are compared. For the NCAT phantom, a line profile through a slice of the reconstructed image is considered before and after scatter correction, and also image contrast defined by this profile is used to compare the correction methods. The results of this study indicate that for the line source simulation the scatter fractions obtained from the proposed method are a better estimation of true scatter fractions. Also, for both the sphere simulation and NCAT simulation, the proposed method improves the image contrast as compared to the two other methods.

Evaluation of six scatter correction methods based on spectral analysis in (99m)Tc SPECT imaging using SIMIND Monte Carlo simulation

Compton-scattered photons included within the photopeak pulse-height window result in the degradation of SPECT images both qualitatively and quantitatively. The purpose of this study is to evaluate and compare six scatter correction methods based on setting the energy windows in ^99mTc spectrum. SIMIND Monte Carlo simulation is used to generate the projection images from a cold-sphere hot-background phantom. For evaluation of different scatter correction methods, three assessment criteria including image contrast, signal-to-noise ratio (SNR) and relative noise of the background (RNB) are considered. Except for the dual-photopeak window (DPW) method, the image contrast of the five cold spheres is improved in the range of 2.7-26%. Among methods considered, two methods show a nonuniform correction performance. The RNB for all of the scatter correction methods is ranged from minimum 0.03 for DPW method to maximum 0.0727 for the three energy window (TEW) method using trapezoidal approximation. The TEW method using triangular approximation because of ease of implementation, good improvement of the image contrast and the SNR for the five cold spheres, and the low noise level is proposed as most appropriate correction method.

Cellular uptake, imaging and pathotoxicological studies of a novel Gd[iii]–DO3A-butrol nano-formulation

The high adaptability of dendrimer-based contrast agents (CAs) is ideal for the reliable molecular imaging of cancerous tissues.

Correlation of automatic processing method in myocardial perfusion SPET with the interactive method

Different techniques have been introduced for full automatic processing of myocardial perfusion imaging with single-photon emission tomography. We tried to evaluate the accuracy of one of these commercial automatic processing methods. The study was performed in 300 patients during 18 months. Two post-stress acquisitions in supine and prone positions and one acquisition at rest , were performed for every patient. All images were processed both automatically and interactively and the results were compared to each other. The automatic method matched the interactive method in 95.22% for left ventricle isolation, in 99.54% for excluding extra-cardiac activity and in 98.22% for reorientation of a single projected data. The automatic method was also successful in complete processing of 81.33% sets of stress (supine)-rest and 79.77% sets of stress (prone)-rest images as compared to the interactive method. In conclusion, the fully automated processing method matches the interactive method in complete processing of myocardial perfusion imaging with single-photon emission tomography more than 79.77% and is of equal accuracy to the interactive method in supine and prone-positioned acquisitions.