SPECT Research Articles

A short-term predictive model for disease progression in acute-on-chronic liver failure: integrating spectral CT extracellular liver volume and clinical characteristics

BackgroundAcute-on-chronic liver failure (ACLF) is a life-threatening hepatic syndrome. Therefore, this study aimed to develop a comprehensive model combining extracellular liver volume derived from spectral CT (ECVIC−liver) and sarcopenia, for the early prediction of short-term (90-day) disease progression in ACLF.Materials and methodsA retrospective cohort of 126 ACLF patients who underwent hepatic spectral CT scans was included. According to the Asia-Pacific Association for the Study of the Liver (APASL) criteria, patients were divided into the progression group (n = 70) and the stable group (n = 56). ECVIC−liver was measured on the equilibrium period (EP) images of spectral CT, and L3-SMI was measured on unenhanced CT images, with sarcopenia assessed. A comprehensive model was developed by combining independent predictors. Model performance was evaluated using receiver operating characteristic (ROC) curve analysis, calibration curves, and decision curve analysis (DCA).ResultsIn the univariate analysis, BMI, WBC, PLT, PTA, L3-SMI, IC-EP, Z-EP, K140-EP, NIC-EP, ECVIC−liver, and Sarcopenia demonstrated associations with disease progression status at 90 days in ACLF patients. In multivariate logistic regression, white blood cell count (WBC) (OR = 1.19, 95% CI: 1.02–1.40; P = 0.026), ECVIC−liver (OR = 1.27, 95% CI: 1.15–1.40; P < 0.001), sarcopenia (OR = 4.15, 95% CI: 1.43–12.01; P = 0.009), MELD-Na score (OR = 1.06, 95%CI: 1.01–1.13;P = 0.042), and CLIF-SOFA score (OR = 1.37, 95%CI:1.15–1.64; P<0.001) emerged as independent risk factors for ACLF progression. The combined model exhibited superior predictive performance (AUCs = 0.910, sensitivity = 80.4%, specificity = 90.0%, PPV = 0.865, NPV = 0.851) compared to CLIF-SOFA, MELD-Na, MELD and CTP scores(both P < 0.001). Calibration curves and DCA confirmed the high clinical utility of the combined model.ConclusionsPatients without sarcopenia and/or with a lower ECVIC−liver have a better prognosis, and the integration of WBC, ECVIC−liver, Sarcopenia, CLIF-SOFA and MELD-Na scores in a composite model offers a concise and effective tool for predicting disease progression in ACLF patients.Trial registrationNot Applicable.

Abstract No. 194 In Vivo Evaluation of Spectral CT Thermometry for Non-invasive, Real-Time Temperature Monitoring of Thermal Ablation

Abstract No. 194 In Vivo Evaluation of Spectral CT Thermometry for Non-invasive, Real-Time Temperature Monitoring of Thermal Ablation

Abstract No. 193 Dual-Layer Spectral CT for Hepatocellular Carcinoma Characterization and in Vivo Hypoxia Biomarker in Woodchuck

Abstract No. 193 Dual-Layer Spectral CT for Hepatocellular Carcinoma Characterization and in Vivo Hypoxia Biomarker in Woodchuck

Advancements in Computed Tomography Angiography for Pulmonary Embolism Assessment.

Pulmonary embolism (PE) is a critical condition stemming from venous thromboembolism, with potentially fatal outcomes. Computed tomography pulmonary angiography (CTPA) serves as the gold standard for diagnosing PE, offering unparalleled diagnostic accuracy, accessibility, and speed. Recent innovations, such as spectral CT systems and artificial intelligence (AI)-driven algorithms, have enhanced the diagnostic and prognostic capabilities of CTPA, enabling precise anatomical and functional assessments. This review highlights these technological advancements and their clinical implications.

Bone metastasis classification based on federated learning for spect whole body bone scanning

Bone metastasis classification based on federated learning for spect whole body bone scanning

A randomised controlled trial comparing three clinical administration strategies in spectral detector CT pulmonary angiography with low contrast medium dose.

To compare vascular attenuation (VA) with three strategies for administering a low contrast medium (CM) dose in dual-layer spectral detector CT pulmonary angiography (CTPA). Patients were prospectively randomised into control- or one of two experimental groups. Control group patients received CM (350 mgI/mL) diluted 1:1 with saline. Experimental group B received CM (350 mgI/mL) with low flow. Experimental group C received CM with low concentration (140 mgI/mL). Virtual monoenergetic images at 40 and 55 kiloelectron Volt (keV) were reconstructed. Objective examination quality (OEQ) i.e., VA, noise, and signal-to-noise ratio, was measured and subjective examination quality (SEQ) was rated at three anatomical levels: in the pulmonary trunk (PT), the interlobar arteries and the posterior basal segmental arteries. VA in PT at 40 keV. OEQ and SEQ across all anatomic levels. A total of 328 patients were randomised. 112 vs 115 and 101 were analysed in the control (A) vs experimental groups (B and C), respectively. There were no differences in VA in PT between the groups: A vs B (p = 0.96), B vs C (p = 0.14), and A vs C (p = 0.18). Group C showed higher VA across all anatomical levels. There were no differences in SEQ. There was no difference in the attenuation in the PT between the dilution-, low flow-, and low concentration groups. However, the low concentration group showed higher attenuation in the pulmonary arteries when all anatomical levels were assessed. Question Contrast medium reduction may be accomplished with dilution, low flow, or low concentration. However, the effect of the different strategies on vascular attenuation is unknown. FindingsThere was no difference in pulmonary trunk attenuation between the three strategies on spectral detector CT pulmonary angiography. Clinical relevanceLow contrast medium dose spectral detector CT pulmonary angiography may be implemented with the administration strategy of the unit's own choice.

Use of photon-counting CT and three-dimensional printing for an intra-thoracic retained ballistic fragment in a 9-year-old.

Retained ballistic fragments from gunshot wounds pose diagnostic and management challenges for radiologists and surgeons alike. Imaging and clinical decision-making regarding removal warrant comprehensive risk/benefit discussions, considering anatomic location, complexity of surgical removal, and risk of long-term complications of bullet migration and potential lead toxicity. Herein, we describe a 9-year-old with a retained intra-thoracic para-aortic ballistic fragment causing elevated lead levels. Photon-counting detector computed tomography (PCD-CT) was used to create a 3D-printed anatomic model, critical for multidisciplinary pre-operative planning and as an educational tool with the patient and family, ultimately leading to successful surgical bullet removal. Since spectral CT imaging offers superior metal artifact reduction capabilities than conventional CT, cutting-edge technologies such as PCD-CT and 3D-printing should be considered in anatomically challenging cases.

Innovative imaging for gastric cancer: Spectral CT and HRR.

Innovative imaging for gastric cancer: Spectral CT and HRR.

Spectral computed tomography in the assessment of metastatic lymph nodes in cervical cancer patients treated with definitive radiotherapy: a single-center, prospective study.

Identifying metastatic lymph nodes (LNs) in patients with cervical cancer treated with definitive radiotherapy may inform treatment strategy and determine prognosis, but available methods have limitations, especially in developing regions. Herein, we aimed to evaluate the performance of quantitative parameters in spectral computed tomography (CT) scanning in this context, focusing on its complementary role alongside conventional diagnostic approaches like 18-fluorine-fuorodeoxyglucose positron emission tomography computed tomography (18F FDG-PET/CT). Patients with cervical cancer, who underwent pretreatment spectral CT simulation scanning and planned radiotherapy, were enrolled in this prospective study. The LNs were categorized as "metastatic" and "non-metastatic", based on a procedure that included 18F FDG-PET/CT as well as CT, magnetic resonance imaging, Node Reporting and Data System and follow-up results. Iodine concentrations (IC), normalized IC (NIC), effective atom number (effZ), and spectral curve slope (λHU) in the arterial (AP) and venous (VP) phases, were compared between metastatic and non-metastatic LNs. IC were derived from iodine-based material decomposition through manual delineation and normalized to the iodine concentration in the adjacent artery (NIC). effZ and λHU were calculated based on the effective atom number image and virtual monochromatic images. Univariate and multivariate logistic regression analyses were used to determine spectral CT factors independently associated with LNs metastasis, and their diagnostic efficacies were assessed using the area under the curve (AUC) analysis. The diagnostic efficiency of 18F FDG-PET/CT and spectral CT was compared. A total of 115 metastatic and 97 non-metastatic LNs were detected, and spectral CT parameters (IC, NIC, effZ, λHU) significantly differed between the two groups. In univariate and multivariable logistic regression analysis, λHU in the AP and NIC in the VP were independent predictors for metastatic LNs and their combination improved AUC to 0.923, with a sensitivity of 84.4%, and a specificity of 85.6%. Spectral CT could achieve similar sensitivity as 18FFDG-PET/CT in total LNs, and, more importantly, a higher sensitivity (95.5% vs. 59.1%) and diagnostic accuracy (92.9% vs. 67.9%) for para-aortic LNs. Quantitative spectral CT parameters can help distinguish metastatic from non-metastatic LNs in patients with cervical cancer treated with definitive radiotherapy. Combination of λHU in AP and NIC in VP further improves diagnostic performance. Spectral CT, while promising, complements rather than replaces PET/CT, especially for diagnosing para-aortic LNs, where PET/CT may have limitations. It could be a valuable adjunct to conventional imaging, particularly in settings with limited access to advanced tools.

Analisis Perbedaan Citra SPECT Non-AC dan CTAC pada Pemeriksaan Scintigrafi Perfusi Miokard

Background: Myocardial Perfusion Scan displays SPECT images, which is a non invasive imaging method for a quantitative view of myocardial ischemia which can’t be done with CT myocardial perfusion. The principle of myocardial perfusion scan is that the myocardial absorption of radiopharmaceuticals is proportional to coronary heart blood flow to the myocardium. The main problem with SPECT myocardial perfusion scan imaging is photon attenuation caused by soft tissue around the heart which causes inaccurate information and attenuation artifacts. One method to reduce attenuation artifacts is hybrid CT Scan imaging with SPECT tools. CT Scan images are used to correct attenuation in SPECT images. The purpose of this research is to analyze the differences between non-AC and CTAC SPECT images which will have an impact on myocardium perfusion values on myocardial perfusion scans.Methods: This research is a quantitative analysis with a direct observation approach. The research was undertaken at Nuclear Medicine and Molecular Theranostics Installation of Dr. Hasan Sadikin General Hospital in Bandung, starting November 2023 using a SPECT CT GE NM/CT 860 gamma camera. A total of 28 patients were examined for myocardial perfusion scans. Data processing is conducted by comparing the perfusion values of myocardium on non-AC and CTAC SPECT images for 28 samples by conducting hypothesis testing using paired test sample T-Test.Result: Based on the research results, non-AC, and CTAC SPECT image data showed a normal distribution using the Shapiro-Wilk test, allowing the analysis of differences using the Paired-Samples T-test. In general, the analysis results indicate a significant difference between non-AC and CTAC SPECT images, as the sig value is less than 0.05 in the RCA and LCx vascular segments, as well as in the septal, inferior, lateral, and apical wall segments. However, no significant differences were found in the LAD vascular segment and the anterior wall segment, as the sig value is greater than 0.05.Conclusions: There are differences between non-AC and CTAC SPECT images in the RCA and LCx blood vessel segments, as well as in the septal, inferior, lateral, and apical wall segments. However, no differences are observed in the LAD blood vessel segment and the anterior wall segment.

Ring-artifacts removal for spectral photon counting CT

Ring-artifacts removal for spectral photon counting CT

Improved image quality and micronodule detection in thyroid spectral computed tomography using modified swimmer's position.

Spectral computed tomography (CT) can be used as a valuable complement to ultrasound (US) in the detection of thyroid nodules. This study sought to investigate the effects of various arm positions during thyroid spectral CT scans in terms of radiation exposure, image quality, and micronodule detection (≤10 mm). A total of 180 patients (mean age: 48 years; 136 females) who underwent thyroid spectral CT were assigned to the traditional position (TDN; n=60), swimmer's position (SWIM; n=60), and modified swimmer's position (M-SWIM; n=60) groups. Image quality in the plain, arterial, and venous phases was assessed using a 4-point grading scale, the signal-to-noise ratio (SNR), and the contrast-to-noise ratio (CNR). Radiation exposure was assessed using the volume computed tomography dose index (CTDIvol), dose-length product (DLP), effective dose of the neck (EDN), and effective dose of the thyroid (EDT). The micronodule detection rates for spectral CT and US were compared using the pathology detection rate as a reference. The M-SWIM group had a significantly higher proportion of 4-point grading, SNR, and CNR than the TDN and SWIM groups (all P<0.001). The CTDIvol, DLP, EDN, and EDT were similar among the three groups (all P>0.05). The micronodule detection rate was higher in the M-SWIM group than the TDN and SWIM groups (total: 90.6% vs. 70.1% vs. 46.8%; benign: 89.1% vs. 66.7% vs. 45.5%; malignant: 94.3% vs. 79.5% vs. 51.5%; all P<0.001), but comparable to that of the US group (total: 90.6% vs. 91.2%; benign: 89.1% vs. 90.6%; malignant: 94.3% vs. 92.5%; all P>0.05). The proposed M-SWIM improved the image quality of thyroid spectral CT without increasing the radiation dose, and significantly enhanced the micronodule detection rate.

Filters Effect on Image Quality of 177Lu-DOTATATE SPECT Images for Neuro-Endocrine Tumors Scanning

Purpose: The quality of the image in SPECT scans depends on the imaging parameters which are determined experimentally in the field of nuclear medicine. Designing a dedicated scanning parameter for 177Lu-DOTATATE SPECT images is required to optimize reconstruction. Therefore, this study aims to evaluate the effect of different filters on image quality for bone SPECT scanning using 177Lu-DOTATATE. Materials and Methods: The filtered back-projection reconstruction method was used in neuro-endocrine tumor scanning using 177Lu-DOTATATE. Three hours after injection of 177Lu-DOTATATE, SPECT scans from 177Lu-DOTATATE for 30 patients were acquired using a dual-head EvoExel detector system. Seven parameters were considered, including the contrast/noise ratio, injection activity, uptake duration, acquisition time per injection, frame time, measuring time, and type of filters. Results: In all cases, the application of different filters increased Contrast to Noise Ratio (CNR) (9.1%, 1.8%, 10.9%, 61.8%, 23.6%, 29.1%, and 58.2% for Wiener, Butterworth, Parzen, Metz, Ramp, Shepp-Logan, and Hamming filters, respectively). The percentage of increase in Signal-to-Noise Ratio (SNR) was 3.3%, 1.7%, -24%, 21.7%, 9.8%, 11.9%, and 20.6%. Conclusion: Based on the quantitative analysis of the results, the application of the Metz filter (power 2) and Hamming filter (with 0.27, 0.47, and 0.67 cut-off frequencies) on SPECT scans of neuro-endocrine tumors is recommended because of their capacity to provide high-quality images.

Determination of adequate bony resection margins in inflammatory jaw pathologies using SPECT-CT in primary mandibular reconstruction with virtually planned vascularized bone flaps

ObjectivesIn advanced stages of osteoradionecrosis, medication-related osteonecrosis of the jaw, and osteomyelitis, a resection of sections of the mandible may be unavoidable. The determination of adequate bony resection margins is a fundamental problem because bony resection margins cannot be secured intraoperatively. Single-photon emission computed tomography (SPECT-CT) is more accurate than conventional imaging techniques in detecting inflammatory jaw pathologies. The clinical benefit for virtual planning of mandibular resection and primary reconstruction with vascularized bone flaps has not yet been investigated. This study aimed to evaluate the determination of adequate bony resection margins using SPECT computed tomography (SPECT-CT) for primary microvascular reconstruction of the mandible in inflammatory jaw pathologies.Materials and methodsThe cases of 20 patients with inflammatory jaw pathologies who underwent primary microvascular mandibular reconstruction after the bony resection margins were determined with SPECT-CT were retrospectively analyzed. The bony resection margins determined by SPECT-CT were histologically validated. The sensitivity was calculated as the detection rate and the positive predictive value as the diagnostic precision. Radiological ossification of the vascularized bone flaps with the mandibular stumps was assessed at least 6 months after reconstruction. The clinical course was followed for 12 months.ResultsThe determination of adequate bony resection margins with SPECT-CT yielded a sensitivity of 100% and a positive predictive value of 94.7%. Of all the bony resection margins, 97.4% were radiologically sufficiently ossified with the vascularized bone flap and showed no complications in the clinical course.ConclusionsSPECT-CT could increase the probability of determining adequate bony resection margins.Clinical relevanceSPECT-CT could have a beneficial clinical impact in the context of primary microvascular bony reconstruction in inflammatory jaw pathologies.

Novel brain SPECT imaging unravels abnormal cerebral perfusion in patients with postural orthostatic tachycardia syndrome and cognitive dysfunction

Cognitive dysfunction is frequently reported in individuals with postural orthostatic tachycardia syndrome (POTS), possibly resulting from reduced cerebral blood flow (CBF). We used brain SPECT, an accessible imaging modality that has not been systematically evaluated in this patient group. Retrospective review of participants from our registry was undertaken to identify those who had a brain SPECT performed for investigation of cognitive dysfunction. Abnormal CBF was taken as z-score > 2 standard deviations of healthy control reference values. Patient reported outcome measures (PROMs) such as autonomic, gastric and quality of life symptom scores were analyzed. From a total of 56 participants (mean 34.8 ± 10.7 years, 88% females), PROMs indicate: moderate to severe autonomic dysfunction in 75%; at least mild to moderate gastroparesis in 23%; low global health rating and utility scores. Abnormal CBF was seen in 61% but did not differ by POTS triggers. The regions with the lowest mean z-scores were the lateral prefrontal and sensorimotor cortices. Hierarchal regression analyses found number of brain regions with abnormal CBF, autonomic and gastric symptoms to account for 51% of variances in health utility. Cerebral hypoperfusion is prevalent in those with POTS and cognitive dysfunction even whilst supine, contributing to reduced quality of life.

Combining Low-energy Images in Dual-energy Spectral CT With Deep Learning Image Reconstruction Algorithm to Improve Inferior Vena Cava Image Quality.

To explore the application of low-energy image in dual-energy spectral CT (DEsCT) combined with deep learning image reconstruction (DLIR) to improve inferior vena cava imaging. Thirty patients with inferior vena cava syndrome underwent contrast-enhanced upper abdominal CT with routine dose, and the 40, 50, 60, 70, and 80keV images in the delayed phase were first reconstructed with the ASiR-V40% algorithm. Image quality was evaluated both quantitatively [CT value, SD, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) for inferior vena cava] and qualitatively to select an optimal energy level with the best image quality. Then, the optimal-energy images were reconstructed again using deep learning image reconstruction medium strength (DLIR-M) and DLIR-H (high strength) algorithms and compared with that of ASiR-V40%. The objective CT value, SD, SNR, and CNR increased with the decrease in energy level, with statistically significant differences (all P<0.05). The 40keV images had the highest CT values, SNR, and CNR and good diagnostic acceptability, and 40keV was selected as the best energy level. Compared with ASiR-V40% and DLIR-M, DLIR-H had the lowest SD, highest SNR and CNR, and subjective score (all P<0.001) with good consistencies between the 2 physicians (all k ≥0.75). The 40keV images with DLIR-H had the highest overall image quality, showing sharper edges of inferior vena cava vessels and clearer lumen in patients with Budd-Chiari syndrome. Compared with the ASiR-V algorithm, DLIR-H significantly reduces image noise and provides the highest CNR and best diagnostic image quality for the 40keV DEsCT images in imaging inferior vena cava.

Spectral CT radiomics features of the tumor and perigastric adipose tissue can predict lymph node metastasis in gastric cancer.

To develop a nomogram based on the radiomics features of tumour and perigastric adipose tissue adjacent to the tumor in dual-layer spectral detector computed tomography (DLCT) for lymph node metastasis (LNM) prediction in gastric cancer (GC). A retrospective analysis was conducted on 175 patients with gastric adenocarcinoma. They were divided into training cohort (n = 125) and validation cohort (n = 50). The radiomics features from the tumour and perigastric fat based on DLCT spectral images were extracted to construct radiomics models for LNM prediction using Lasso-GLM method. Preoperative clinicopathological features, DLCT routine parameters, and the optimal radiomics models were analyzed to establish the clinical-DLCT model, clinical-DLCT-radiomics model and a nomogram. All models were internally validated using the Bootstrap method and evaluated using receiver operating characteristic (ROC) curve. The area under the ROC curve (AUC) values of optimal radiomics models based on tumour (Model 1) and perigastric fat (Model 2) were 0.923 and 0.822 in training cohort, 0.821 and 0.767 in validation cohort. The clinical-DLCT model based on Nct and ECVID demonstrated an AUC value of 0.728 in training cohort and 0.657 in validation cohort. The clinical-DLCT-radiomics model and the nomogram were established by incorporating Nct, ECVID and the linear predictive values of Models 1 and 2, exhibiting superior predictive efficacy with an AUC value of 0.935 in training cohort and 0.876 invalidation cohort. The nomogram based on Nct, ECVID, and the radiomics features of tumour and perigastric fat in DLCT demonstrates potential for predicting LNM in GC. This approach may contribute to the development of treatment strategies and improve the clinical outcomes for GC patients.

Assessing Pulmonary Embolisms on Unenhanced CT Images Using Electron Density Images Derived from Dual-Layer Spectral Detector CT: A Single-centre Prospective Study Conducted at the Emergency Department.

Aims To evaluate the utility of unenhanced spectral imaging, electron density (ED) and overlay electron density (OED) images for assessing pulmonary embolisms in patients with suspected or confirmed acute pulmonary embolism (APE). Background Multiple spectral images can be extrapolated from spectral detector CT (SDCT), ED and OED images. ED and OED images are highly sensitive to moisture-rich tissues. Potential use for detecting pulmonary artery thrombi in non-enhanced chest CT images. Objective To assess the sensitivity, specificity and accuracy of ED and OED images obtained using SDCT for the detection of pulmonary embolism on non-enhanced images. Method Seventy-nine patients who underwent unenhanced and CT pulmonary angiography using dual-layer spectral detector CT to evaluate APE between November 2021 and April 2022 were enrolled in this retrospective study. Based on unenhanced spectral and CTPA images, two radiologists identified areas of high density in the main, lobar, and segmental pulmonary arteries on ED and OED images and detected pulmonary embolism (PE) on enhanced images using a consultative approach. CTPA results were considered the gold standard. The diagnostic performance of ED and OED in detecting PE was analyzed. Results PE was detected in 40 patients (40/79), and 17, 69, and 20 PEs were detected in the main, lobar, and segmental arteries, respectively. The PE detection sensitivity on ED images was 69.7-94.7%, and the specificity was 58.5-98.2% for the individual, main, lobe, and segmental pulmonary arteries. The sensitivity and specificity for OED images were 94.1-95.2% and 80.0-98.1%, respectively. The positive predictive value (PPV) and negative predictive value (NPV) were 53.6-87.7% and 69.7-95.9% for ED images, and 48.5-88.9% and 94.1-98.9% for OED images, respectively. The accuracy was 76.0-98.9% and 87.3-96.2% when using ED and OED images, respectively. The research identified that whether main, lobar or segmental pulmonary arteries with blood clots, EDW values ranged from 108.1-108.8 %EDW, 3.9-4.2 %EDW higher than those of arteries without emboli. Pulmonary arteries with emboli standardised ED values were 103.6-104.3 %EDW. Conclusion ED and OED images using spectral CT without contrast media demonstrated high diagnostic performance and could improve the visualization of PE.

Improving Diagnostic Accuracy in Acute Pulmonary Embolism: Insights from Spectral Dual-energy CT.

This study aims to evaluate the clinical efficacy of spectral dual-energy detector computed tomography (SDCT) and its associated parameters in diagnosing acute pulmonary embolism (APE). Retrospective analysis of imaging data from 86 APE-diagnosed patients using SDCT was conducted. Virtual monoenergetic images (VMIs) at 40, 70, and 100 KeV, Iodine concentration (IC) maps, Electron Cloud Density Map (ECDM), Effective atomic number (Z-eff) maps, and Hounsfield unit attenuation plots (VMI slope) were reconstructed from pulmonary artery phase CT images. The subtraction (SUB) and ratios of VMIs were calculated, and two experienced radiologists evaluated the patients. The Mann-Whitney U test assessed the parameter ability to differentiate between normal and obstructed lung fields and detect emboli in the pulmonary artery. Receiver Operating Characteristic Curves (ROC) were generated for performance evaluation. Significant differences (p<0.001) in 40KeV, Ratio, SUB, and Z-eff were found between normal and embolized lung fields. Logistic regression demonstrated good detection performance for Z-eff (AUC=0.986), SUB (AUC=0.975), and IC (AUC=0.974). Parameters such as 40KeV (AUC=0.990), 70KeV (AUC=0.980), 100KeV (AUC=0.962), SUB (AUC=0.990), Z-eff (AUC=0.999), and IC (AUC=1.000) exhibited good detection capabilities for identifying emboli in the pulmonary artery. SDCT facilitates the identification of diseased lung fields and localization of emboli in the pulmonary artery, thereby improving diagnostic efficiency in APE.

CT material decomposition with contrast agents: Single or multiple spectral photon-counting CT scans? A simulation study.

With the widespread introduction of dual energy computed tomography (DECT), applications utilizing the spectral information to perform material decomposition became available. Among these, a popular application is to decompose contrast-enhanced CT images into virtual non-contrast (VNC) or virtual non-iodine images and into iodine maps. In 2021, photon-counting CT (PCCT) was introduced, which is another spectral CT modality. It allows for scans with more than two different detected spectra. With these systems, it becomes possible to distinguish more than two materials. It is frequently proposed to administer more than one contrast agent, perform a single PCCT scan, and then calculate the VNC images and the contrast agent maps. This may not be optimal because the patient is injected with a material, only to have it computationally extracted again immediately afterwards by spectral CT. It may be better to do an unenhanced scan followed by one or more contrast-enhanced scans. The main argument for the spectral material decomposition is patient motion, which poses a significant challenge for approaches involving two or more temporally separated scans. In this work, we assume that we can correct for patient motion and thus are free to scan the patient more than once. Our goal is then to quantify the penalty for performing a single contrast-enhanced scan rather than a clever series of unenhanced and enhanced scans. In particular, we consider the impact on patient dose and imagequality. We simulate CT scans of three differently sized phantoms containing various contrast agents. We do this for a variety of tube voltage settings, a variety of patient-specific prefilter (PSP) thicknesses and a variety of threshold settings of the photon-counting detector with up to four energy bins. The reconstructed bin images give the expectation values of soft tissue and of the contrast agents. Error propagation of projection noise into the images yields the image noise. Dose is quantified using the total CT dose index (CTDI) value of the scans. When combining multiple scans, we further consider all possible tube current (or dose) ratios between the scans. Material decomposition is done image-based in a statistical optimal way. Error propagation into the material-specific images yields the signal-to-noise ratio at unit dose (SNRD). The winning scan strategy is the one with the highest total SNRD, which is related to the SNRD of the material that has the lowest signal-to-noise ratio (SNR) among the materials to decompose into. We consider scan strategies with up to three scans and up to three materials (water W, contrast agent X and contrast agent Y). In all cases, those scan strategies yield the best performance that combine differently enhanced scans, for example, W+WX, W+WXY, WX+WXY, W+WX+WY, with W denoting an unenhanced scan and WX, WY and WXY denoting X-, Y-, and X-Y-enhanced scans, respectively. The dose efficiency of scans with a single enhancement scheme, such as WX or WXY, is far lower. The dose penalty to pay for these single enhancement strategies is about two or greater. Our findings also apply to scans with a single energy bin and thus also to CT systems with conventional, energy-integrating detectors, that is, conventional DECT. Dual source CT (DSCT) scans are preferable over single source CT scans, also because one can use a PSP on the high Kilovolt spectrum to better separate the detected spectra. For the strategies and tasks considered here, it does not make sense to simultaneously scan with two different types of contrast agents. Iodine outperforms other high Z elements in nearly allcases. Given the significant dose penalty when performing only one contrast-enhanced scan rather than a series of unenhanced and enhanced scans, one should consider avoiding the single-scan strategies. This requires to invest in the development of accurate registration algorithms that can compensate for patient and contrast agent motion between separatescans.