Added Value of SPECT/CT Fusion in Assessing Suspected Bone Metastasis: Comparison with Scintigraphy Alone and Nonfused Scintigraphy and CT

Radiomics based on multiple machine learning methods for diagnosing early bone metastases not visible on CT images

OBJECTIVES

This study utilizes [99mTc]-methylene diphosphate (MDP) single photon emission computed tomography (SPECT) images as a reference standard to evaluate whether the integration of radiomics features from computed tomography (CT) and machine learning algorithms can identify microscopic early bone metastases. Additionally, we also determine the optimal machine learning approach.

MATERIALS AND METHODS

We retrospectively studied 63 patients with early bone metastasis from July 2020 to March 2023. The ITK-SNAP software was used to delineate early bone metastases and normal bone tissue in SPECT images of each patient, which were then registered onto CT images to outline the volume of interest (VOI). The VOI includes 63 early bone metastasis volumes and 63 normal bone tissue volumes. 126 VOIs were randomly distributed in a 7:3 ratio between the training and testing groups, and 944 radiomics features were extracted from every VOI. We established 20 machine learning models using 5 feature selection algorithms and 4 classification methods. Evaluate the performance of the model using the area under the receiver operating characteristic curve (AUC).

RESULTS

Most machine learning models demonstrated outstanding discriminative capacity, with AUCs higher than 0.70. Notably, the K-Nearest Neighbors (KNN) classifier exhibited significant performance improvement compared to the other four classifiers. Specifically, the model constructed utilizing eXtreme Gradient Boosting (XGBoost) feature selection method integrated with KNN classifier achieved the maximum AUC, which is 0.989 in the training set and 0.975 in the testing set.

CONCLUSIONS

Radiomics features integrated with machine learning methods can identify early bone metastases that are not visible on CT images. In our analysis, KNN is considered the optimal classification method.

Machine learning based on SPECT/CT to differentiate bone metastasis and benign bone lesions in lung malignancy patients

BACKGROUND

Bone metastasis is a common event in lung cancer progression. Early diagnosis of lung malignant tumor with bone metastasis is crucial for selecting effective treatment strategies. However, 14.3% of patients are still difficult to diagnose after SPECT/CT examination.

PURPOSE

Machine learning analysis of [99mTc]-methylene diphosphate (99mTc-MDP) SPECT/CT scans to distinguish bone metastases from benign bone lesions in patients with lung cancer.

METHODS

One hundred forty-one patients (69 with bone metastases and 72 with benign bone lesions) were randomly assigned to the training group or testing group in a 7:3 ratio. Lesions were manually delineated using ITK-SNAP, and 944 radiomics features were extracted from SPECT and CT images. The least absolute shrinkage and selection operator (LASSO) regression was used to select the radiomics features in the training set, and the single/bimodal radiomics models were established based on support vector machine (SVM). To further optimize the model, the best bimodal radiomics features were combined with clinical features to establish an integrated Radiomics-clinical model. The diagnostic performance of models was evaluated using receiver operating characteristic (ROC) curve and confusion matrix, and performance differences between models were evaluated using the Delong test.

RESULTS

The optimal radiomics model comprised of structural modality (CT) and metabolic modality (SPECT), with an area under curve (AUC) of 0.919 and 0.907 for the training and testing set, respectively. The integrated model, which combined SPECT, CT, and two clinical features, exhibited satisfactory differentiation in the training and testing set, with AUC of 0.939 and 0.925, respectively.

CONCLUSIONS

The machine learning can effectively differentiate between bone metastases and benign bone lesions. The Radiomics-clinical integrated model demonstrated the best performance.

Radiomics‑Clinical model based on 99mTc-MDP SPECT/CT for distinguishing between bone metastasis and benign bone disease in tumor patients

BACKGROUND

To establish a radiomics-clinical model based on 99mTc-MDP SPECT/CT for distinguishing between bone metastasis and benign bone disease in tumor patients.

METHODS

We retrospectively analyzed 256 patients (122 with bone metastasis and 134 with benign bone disease) and randomized them in the ratio of 6:2:2 into training, test and validation sets. All patients underwent 99mTc-labeled methylene diphosphonate (99mTc-MDP) SPECT/CT. We manually outlined the volumes of interest (VOIs) of lesions using ITK-SNAP from SPECT and CT images. In the training set, radiomics features were extracted using PyRadiomics and selected using Least Absolute Shrinkage and Selection Operator (LASSO) regression. Then, we established three radiomics models (CT, SPECT and SPECT-CT models) using support vector machine (SVM). In addition, a radiomics-clinical model was constructed using multivariable logistic regression analysis. The four models' performance was assessed using the area under the receiver operating characteristic curve (AUC). Using DeLong test to make comparisons between the ROC (receiver operating characteristic) curves of different models. The clinical utility of the models was evaluated using decision curve analysis (DCA).

RESULTS

The radiomics-clinical displayed excellent performance, and its AUC was 0.941 and 0.879 in the training and test sets. The DCA of radiomics-clinical model showed the highest clinical utility.

CONCLUSIONS

The radiomics-clinical nomogram for identifying bone metastasis and benign bone disease in tumor patients was suitable to assist in clinical decision.

Effect of Gaussian Smoothing Filter Size for CT-Based Attenuation Correction on Quantitative Assessment of Bone SPECT/CT: A Phantom Study

This study aims to determine the effect of Gaussian filter size for CT-based attenuation correction (CTAC) on the quantitative assessment of bone SPECT. An experiment was performed using a cylindrical phantom containing six rods, of which one was filled with water and five were filled with various concentrations of K2HPO4 solution (120-960 mg/cm3) to simulate different bone densities. 99mTc-solution of 207 kBq/ml was also included within the rods. SPECT data were acquired at 120 views for 30 s/view. CT for attenuation correction were obtained at 120 kVp and 100 mA. Sixteen different CTAC maps processed with different Gaussian filter sizes (ranging from 0 to 30 mm in 2 mm increments) were generated. SPECT images were reconstructed for each of the 16 CTAC maps. Attenuation coefficients and radioactivity concentrations in the rods were compared with those in the water-filled rod without K2HPO4 solution as a reference. Gaussian filter sizes below 14-16 mm resulted in an overestimation of radioactivity concentrations for rods with high concentrations of K2HPO4 (≥ 666 mg/cm3). The overestimation of radioactivity concentration measurement was 3.8% and 5.5% for 666 mg/cm3 and 960 mg/cm3 K2HPO4 solutions, respectively. The difference in radioactivity concentration between the water rod and the K2HPO4 rods was minimal at 18-22 mm. The use of Gaussian filter sizes smaller than 14-16 mm caused an overestimation of radioactivity concentration in regions of high CT values. Setting the Gaussian filter size to 18-22 mm enables radioactivity concentration to be measured with the least influence on bone density.

The clinical effectiveness of fused image of single-photon emission CT and facial CT for the evaluation of degenerative change of mandibular condylar head

BACKGROUND

The primary objective of this study was to assess the clinical effectiveness of fused images obtained from single-photon emission computed tomography (SPECT) and facial computed tomography (CT) for evaluating degenerative changes in the mandibular condylar head. This assessment was accomplished by comparing the Technetium-99 m methylene diphosphonate (99mTc-MDP) uptake ratio with the results of clinical and radiographic findings.

METHODS

The study included 17 patients (3 males and 14 females) with suspected osteoarthritis of the mandibular condyle, totaling 34 temporomandibular joints (TMJs). Based on clinical and radiographic examinations, the TMJs were categorized into four groups: normal (group N), internal derangement (group ID), osteoarthritis (group OA), and osteoarthritis sequelae (group OAseq). For each patient, bone SPECT and facial CT scans were registered and reconstructed to create fused SPECT/CT images. The 99mTc-MDP uptake levels in the TMJs were statistically compared among the four groups.

RESULTS

The 99mTc-MDP uptake ratio showed a gradual increase in the order of the following: group N, group OAseq, group ID, and group OA. There was a significant difference observed among groups (p = 0.003), mainly driven by the disparity between group OA and both group N (p < 0.001) and group OAseq (p = 0.048).

CONCLUSION

Fused SPECT/CT image can be an effective tool for evaluating degenerative changes in the mandibular condylar head. The technique demonstrated the ability to differentiate between normal TMJs and those with internal derangement, osteoarthritis, or osteoarthritis sequelae. This approach holds promise as a valuable method in clinical assessments of TMJ degeneration.

Quantitative vs. Qualitative SPECT-CT Diagnostic Accuracy in Bone Lesion Evaluation-A Review of the Literature

(1) Background: Considering the importance that quantitative molecular imaging has gained and the need for objective and reproducible image interpretation, the aim of the present review is to emphasize the benefits of performing a quantitative interpretation of single photon emission computed tomography-computed tomography (SPECT-CT) studies compared to qualitative interpretation methods in bone lesion evaluations while suggesting new directions for research on this topic. (2) Methods: By conducting comprehensive literature research, we performed an analysis of published data regarding the use of quantitative and qualitative SPECT-CT in the evaluation of bone metastases. (3) Results: Several studies have evaluated the diagnostic accuracy of quantitative and qualitative SPECT-CT in differentiating between benign and metastatic bone lesions. We collected the sensitivity and specificity for both quantitative and qualitative SPECT-CT; their values ranged between 74-92% and 81-93% for quantitative bone SPECT-CT and between 60-100% and 41-100% for qualitative bone SPECT-CT. (4) Conclusions: Both qualitative and quantitative SPECT-CT present an increased potential for better differentiating between benign and metastatic bone lesions, with the latter offering additional objective information, thus increasing diagnostic accuracy and enabling the possibility of performing treatment response evaluation through accurate measurements.

Sub 4 minute superfast single-photon emission computed tomography/computed tomography as an add-on for problem-solving in planar bone scintigraphy: a time-saving solution for departments without whole-body single-photon emission computed tomography/computed tomography

Whole-body bone scintigraphy remains widely used in nuclear medicine as it is a relatively inexpensive and quick test in which the whole body can be imaged with good sensitivity. However, one downside of the technique is its lack of specificity. The difficulty comes when there is a single 'hot spot' which usually requires further anatomical imaging to identify the cause and differentiate malignant from benign lesions. In this situation, hybrid imaging with single-photon emission computed tomography/computed tomography (SPECT/CT) can be a useful problem solver. The addition of SPECT/CT can however, be time-consuming, adding up to 15-20 min for every bed position required, a process that can tax the compliance of the patient and reduce the scanning capacity of the department. We report the successful implementation of a new superfast SPECT/CT protocol comprising a 1 s per view over 24 views point and shoot approach, reducing the SPECT scan time to less than 2 min and the whole SPECT/CT to under 4 min while still producing images that allow diagnostic certainty in previously equivocal lesions. This is faster than previously reported ultrafast SPECT/CT protocols. The utility of the technique is demonstrated in a pictorial review of four disparate causes of solitary bone lesions: fracture, metastasis, degenerative arthropathy and Paget's disease. This technique may prove a cost-effective problem-solving adjunct in nuclear medicine departments unable to yet offer whole-body SPECT/CT to every patient, without adding much burden to the department's gamma camera usage and patient throughput.

ACR Appropriateness Criteria® Staging of Renal Cell Carcinoma: 2022 Update

Renal cell carcinoma is a complex group of highly heterogenous renal tumors demonstrating variable biological behavior. Pretreatment imaging of renal cell carcinoma involves accurate assessment of the primary tumor, presence of nodal, and distant metastases. CT and MRI are the key imaging modalities used in the staging of renal cell carcinoma. Important imaging features that impact treatment include tumor extension into renal sinus and perinephric fat, involvement of pelvicalyceal system, infiltration into adrenal gland, involvement of renal vein and inferior vena cava, as well as the presence of metastatic adenopathy and distant metastases. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision process support the systematic analysis of the medical literature from peer reviewed journals. Established methodology principles such as Grading of Recommendations Assessment, Development, and Evaluation or GRADE are adapted to evaluate the evidence. The RAND/UCLA Appropriateness Method User Manual provides the methodology to determine the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where peer reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

Quantitative assessment of 99mTc-methylene diphosphonate bone SPECT/CT for assessing bone metastatic burden and its prognostic value in patients with castration-resistant prostate cancers: initial results in a single-center retrospective study

PURPOSE

To evaluate the prognostic value of the quantitative assessment of ^99mTc-methylene diphosphonate (^99mTc-MDP) bone SPECT/CT in castration-resistant prostate cancer (CRPC) patients with bone metastases.

METHODS

A total of 103 patients who underwent ^99mTc-MDP bone SPECT/CT imaging from the neck to the proximal femur were included. First, in 65 patients without bone metastases, the normal range of standardized uptake value (SUV) of non-pathological bone was evaluated to determine an SUV threshold to reliably exclude most normal osseous activity. Then, in 38 CRPC patients with bone metastases, lesion uptake volume (LUV), which is the extracted volume of bone metastases exhibiting high accumulation above the SUV threshold, was calculated. The relation between LUV and prostate-related mortality was statistically evaluated.

RESULTS

Based on the SUV measurements of non-pathological bones, the optimal SUV threshold, which defines abnormal bone SPECT uptake, was determined to be 8. Median LUV was 39 mL (interquartile range 4.0-104.3 mL) in the CRPC subjects with bone metastases. Kaplan-Meier survival analysis showed a significant relation between prostate cancer-specific survival and LUV (cut-off value, 19.95 mL; P = 0.001). Multivariate analysis revealed LUV as an independent prognostic factor for the survival (P = 0.008, hazard ratio 23.424). Global chi-square test showed that LUV had significant incremental prognostic value in addition to prostate-specific antigen and the interval from progression to CRPC until bone SPECT/CT (P = 0.022).

CONCLUSION

Quantitative assessment of ^99mTc-MDP bone SPECT images can provide valuable prognostic information in CRPC patients with bone metastases.

More Accurate Imaging Is Not Stage Migration: Time To Move from "Hubble" to "Webb" in Hormone-sensitive Prostate Cancer

Prostate-specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) produces strikingly superior images compared to conventional imaging, raising the important question of whether conventional imaging is sufficiently accurate to guide patient management. Reducing false positive results with consequent improvement in accuracy is not stage migration and PSMA PET/CT can be a successor to conventional imaging in the staging of metastatic hormone-sensitive prostate cancer.

Detection of prostate cancer bone metastases with fast whole-body 99mTc-HMDP SPECT/CT using a general-purpose CZT system

BACKGROUND

We evaluated the effects of acquisition time, energy window width, and matrix size on the image quality, quantitation, and diagnostic performance of whole-body ^99mTc-HMDP SPECT/CT in the primary metastasis staging of prostate cancer.

METHODS

Thirty prostate cancer patients underwent ^99mTc-HMDP SPECT/CT from the top of the head to the mid-thigh using a Discovery NM/CT 670 CZT system with list-mode acquisition, 50-min acquisition time, 15% energy window width, and 128 × 128 matrix size. The acquired list-mode data were resampled to produce data sets with shorter acquisition times of 41, 38, 32, 26, 20, and 16 min, narrower energy windows of 10, 8, 6, and 4%, and a larger matrix size of 256 × 256. Images were qualitatively evaluated by three experienced nuclear medicine physicians and quantitatively evaluated by noise, lesion contrast and SUV measurements. Diagnostic performance was evaluated from the readings of two experienced nuclear medicine physicians in terms of patient-, region-, and lesion-level sensitivity and specificity.

RESULTS

The originally acquired images had the best qualitative image quality and lowest noise. However, the acquisition time could be reduced to 38 min, the energy window narrowed to 8%, and the matrix size increased to 256 × 256 with still acceptable qualitative image quality. Lesion contrast and SUVs were not affected by changes in acquisition parameters. Acquisition time reduction had no effect on the diagnostic performance, as sensitivity, specificity, accuracy, and area under the receiver-operating characteristic curve were not significantly different between the 50-min and reduced acquisition time images. The average patient-level sensitivities of the two readers were 88, 92, 100, and 96% for the 50-, 32-, 26-, and 16-min images, respectively, and the corresponding specificities were 78, 84, 84, and 78%. The average region-level sensitivities of the two readers were 55, 58, 59, and 56% for the 50-, 32-, 26-, and 16-min images, respectively, and the corresponding specificities were 95, 98, 96, and 95%. The number of equivocal lesions tended to increase as the acquisition time decreased.

CONCLUSION

Whole-body ^99mTc-HMDP SPECT/CT can be acquired using a general-purpose CZT system in less than 20 min without any loss in diagnostic performance in metastasis staging of high-risk prostate cancer patients.

British Nuclear Medicine Society Clinical Guideline for bone scintigraphy

This guideline must be read in conjunction with the British Nuclear Medicine Society (BNMS) Generic guidelines. The purpose of this guideline is to assist specialists in Nuclear Medicine and Radionuclide Radiology in recommending, performing, interpreting and reporting the results of bone scintigraphy studies. This guideline could also be used to help individual departments formulate their own local protocols. This does not aim to be prescriptive regarding technical aspects of individual camera acquisitions, which should be developed in conjunction with the local medical physics expert.

New index to assess the extent of bone disease in patients with prostate cancer using SPECT/CT

OBJECTIVE

Assessing the extent of bone metastases in patients with prostate cancer is very important to predict patient prognosis. Therefore, the bone scan index (BSI), which is easy to use, has been used; however, the accuracy is not that high. In this study, we proposed a new index for the extent of bone disease using single-photon emission computed tomography with computed tomography (SPECT/CT) images and assessed the accuracy of calculation.

METHODS

In this study, a total of 46 bone scans from 12 patients with prostate cancer treated for bone metastases with Radium-223 were included. Whole-body planar images were obtained 150-180 min after an intravenous injection of ^99mTc-methylene diphosphonate, and cervical-to-pelvic SPECT/CT was immediately obtained. The total bone volume (TBV) and regional metabolic bone volume (MBV) were defined as Hounsfield unit of > 120, standardized uptake value (SUV) of > 0.5, and SUV of > 5-8 in four levels, respectively. Bone metabolism volumetric index (BMVI) was calculated as the percentage of the total MBV divided by TBV. The variability of the TBV measurement was evaluated by the percentage coefficient of variance (%CV) of TBV within individual patients. We evaluated the correlation of TBV with age, height, weight, and body mass index and the correlation and agreement between BSI and BMVI.

RESULTS

The mean and %CV of TBV were 4661.7 cm³ and 2.8%, respectively, and TBV was strongly correlated with body weight. BMVI was significantly higher than BSI and correlated with alkaline phosphatase. For patients with progressive bone metastases, BSI was clearly underestimated, whereas BMVI was elevated.

CONCLUSIONS

Although assessed in a small number of cases, the new index for assessing the extent of bone disease using SPECT/CT imaging was highly value than BSI and was significantly correlated with alkaline phosphatase. Therefore, this study suggests that BMVI could improve the low sensitivity of BSI in patients with low extent of disease grade.

Imaging of Bone Metastases in Breast Cancer

Bone metastases are a common site of spread in advanced breast cancer and responsible for morbidity and high health care costs. Imaging contributes to staging and response assessment of the skeleton and has been instrumental in guiding patient management for several decades. Historically this has been with radiographs, computed tomography and bone scans. More recently, molecular and hybrid imaging methods have undergone significant development, including the addition of single photon emission computed tomography/computed tomography to the bone scan, positron emission tomography, with bone-specific and tumor-specific tracers, and magnetic resonance imaging with complementary functional diffusion-weighted imaging. These have allowed different aspects of the abnormal biology associated with bone metastases to be explored. There is ability to interrogate the bone microenvironment with bone-specific tracers and cancer cell characteristics with tumor-specific methods that complement morphological appearances on computed tomography or magnetic resonance imaging. Alongside the advent of novel, more effective and nuanced therapies for bone metastases in breast cancer, there is accumulating evidence that the developments in imaging allow more sensitive and specific detection of bone metastases as well as more accurate and earlier assessment of treatment response leading to improvements in patient management.

Verification of the effect of acquisition time for SwiftScan on quantitative bone single-photon emission computed tomography using an anthropomorphic phantom

Background

SwiftScan single-photon emission computed tomography (SPECT) is a recently released scanning technique with data acquired when the detector is stationary and when it moves from one view to the next. The influence of scan time for using SwiftScan on quantitative bone SPECT remains unclear. This study aimed to clarify the effect of the scan time for SwiftScan SPECT on the image quality and quantification of bone SPECT compared to step and shoot mode (SSM) using ^99mTc-filled anthropomorphic phantom (SIM² bone phantom).

Materials and methods

Phantom SPECT/computed tomography (CT) images were acquired using Discovery NM/CT 860 (GE Healthcare) with a low-energy high-resolution sensitivity collimator. We used the fixed parameters (subsets 10 and iterations 5) for reconstruction. The coefficient of variation (CV), contrast-to-noise ratio (CNR), full width at half maximum (FWHM), and quantitative value of SwiftScan SPECT and SSM were compared at various acquisition times (5, 7, 17, and 32 min).

Results

In the short-time scan (< 7 min), the CV and CNR of SwiftScan SPECT were better than those of SSM, whereas in the longtime scan (> 17 min), the CV and CNR of SwiftScan SPECT were similar to those of SSM. The FWHMs for SwiftScan SPECT (13.6–14.8 mm) and SSM (13.5–14.4 mm) were similar. The mean absolute errors of quantitative values at 5, 7, 17, and 32 min were 38.8, 38.4, 48.8, and 48.1, respectively, for SwiftScan SPECT and 41.8, 40.8%, 47.2, and 49.8, respectively, for SSM.

Conclusions

SwiftScan on quantitative bone SPECT provides improved image quality in the short-time scan with quantification similar to or better than SSM. Therefore, in clinical settings, using SwiftScan SPECT instead of the SSM scan protocol in the short-time scan might provide higher-quality diagnostic images than SSM. Our results could provide vital information on the use of SwiftScan SPECT.

Single-Photon Emission Computed Tomography/Computed Tomography Image-Based Radiomics for Discriminating Vertebral Bone Metastases From Benign Bone Lesions in Patients With Tumors

Purpose: The purpose of this study was to investigate the feasibility of Single-Photon Emission Computed Tomography/Computed Tomography (SPECT/CT) image-based radiomics in differentiating bone metastases from benign bone lesions in patients with tumors. Methods: A total of 192 lesions from 132 patients (134 in the training group, 58 in the validation group) diagnosed with vertebral bone metastases or benign bone lesions were enrolled. All images were evaluated and diagnosed independently by two physicians with more than 20 years of diagnostic experience for qualitative classification, the images were imported into MaZda software in Bitmap (BMP) format for feature extraction. All radiomics features were selected by least absolute shrinkage and selection operator (LASSO) regression and 10-fold cross-validation algorithms after the process of normalization and correlation analysis. Based on these selected features, two models were established: The CT model and SPECT model (radiomics features were derived from CT and SPECT images, respectively). In addition, a combination model (ComModel) combined CT and SPECT features was developed in order to better evaluate the predictive performance of radiomics models. Subsequently, the diagnostic performance between each model was separately evaluated by a confusion matrix. Results: There were 12, 13, and 18 features contained within the CT, SPECT, and ComModel, respectively. The constructed radiomics models based on SPECT/CT images to discriminate between bone metastases and benign bone lesions not only had high diagnostic efficacy in the training group (AUC of 0.894, 0.914, 0.951 for CT model, SPECT model, and ComModel, respectively), but also performed well in the validation group (AUC; 0.844, 0.871, 0.926). The AUC value of the human experts was 0.849 and 0.839 in the training and validation groups, respectively. Furthermore, both SPECT model and ComModel show higher classification performance than human experts in the training group (P = 0.021 and P = 0.001, respectively) and the validation group (P = 0.037 and P = 0.007, respectively). All models showed better diagnostic accuracy than human experts in the training group and the validation group. Conclusion: Radiomics derived from SPECT/CT images could effectively discriminate between bone metastases and benign bone lesions. This technique may be a new non-invasive way to help prevent unnecessary delays in diagnosis and a potential contribution in disease staging and treatment planning.

Estimation of additional dosimetry from low-dose CT scan to 99mTc-HMDP SPECT/CT

INTRODUCTION

Currently, the addition of computed tomography (CT) to a gamma-camera has revolutionized nuclear medicine. Indeed the CT, because of its good spatial resolution, of the attenuation correction of the single photon emission computed tomography (SPECT) images and of a better anatomical localization of lesions, improves the sensitivity, specificity and accuracy of the examination. Despite the fact that the hybrid camera uses a low-dose non-diagnostic scanner, increases the overall delivered dose of radiation.

METHODS

The aim of this study was to evaluate the contribution of CT to the total effective dose of ^99mTc-HMDP (hydroxymethylenediphosphonate labelled with technetium 99 metastable) SPECT/CT for an adult oncologic population. This prospective study included 103 patients (75 women and 28 men) aged 28 to 79 years.

RESULTS

The mean effective doses of SPECT, CT and SPECT/CT were respectively 3.8 mSv, 3.3 mSv and 7.1 mSv, respectively. The average contribution of CT scans to the total effective dose for SPECT/CT examination was 45 ± 9.7%, and ranged from 10 to 67.4%. The lowest value was for the thorax area.

CONCLUSION

This radiation dose is not negligible. But, taking into account the benefit of hybrid imaging, this additional radiation remains justifiable. Nevertheless, the "As Low as Reasonably Achievable (ALARA)'' principle must be respected to ensure that the patient is not subjected to unnecessarily high levels of radiation.

SPECT/CT in the Evaluation of Suspected Skeletal Pathology

Dedicated multi-slice single-photon emission computed tomography/computed tomography (SPECT/CT) cameras have become widely available and are becoming a mainstay of clinical practice. The integration of SPECT and CT allow for precise anatomic location of scintigraphic findings. Fusion imaging with SPECT/CT can improve both sensitivity and specificity by reducing equivocal interpretation in comparison to planar scintigraphy or SPECT alone. This review article addresses the technique, basic science principles, and applications of integrated SPECT/CT in the evaluation of musculoskeletal pathology.

Automatic identification of suspicious bone metastatic lesions in bone scintigraphy using convolutional neural network

Background

We aimed to construct an artificial intelligence (AI) guided identification of suspicious bone metastatic lesions from the whole-body bone scintigraphy (WBS) images by convolutional neural networks (CNNs).

Methods

We retrospectively collected the ^99mTc-MDP WBS images with confirmed bone lesions from 3352 patients with malignancy. 14,972 bone lesions were delineated manually by physicians and annotated as benign and malignant. The lesion-based differentiating performance of the proposed network was evaluated by fivefold cross validation, and compared with the other three popular CNN architectures for medical imaging. The average sensitivity, specificity, accuracy and the area under receiver operating characteristic curve (AUC) were calculated. To delve the outcomes of this study, we conducted subgroup analyses, including lesion burden number and tumor type for the classifying ability of the CNN.

Results

In the fivefold cross validation, our proposed network reached the best average accuracy (81.23%) in identifying suspicious bone lesions compared with InceptionV3 (80.61%), VGG16 (81.13%) and DenseNet169 (76.71%). Additionally, the CNN model's lesion-based average sensitivity and specificity were 81.30% and 81.14%, respectively. Based on the lesion burden numbers of each image, the area under the receiver operating characteristic curve (AUC) was 0.847 in the few group (lesion number n ≤ 3), 0.838 in the medium group (n = 4–6), and 0.862 in the extensive group (n > 6). For the three major primary tumor types, the CNN-based lesion identifying AUC value was 0.870 for lung cancer, 0.900 for prostate cancer, and 0.899 for breast cancer.

Conclusion

The CNN model suggests potential in identifying suspicious benign and malignant bone lesions from whole-body bone scintigraphic images.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12880-021-00662-9.

Automated classification of increased uptake regions in bone single-photon emission computed tomography/computed tomography images using three-dimensional deep convolutional neural network

OBJECTIVE

This study proposes an automated classification of benign and malignant in highly integrated regions in bone single-photon emission computed tomography/computed tomography (SPECT/CT) using a three-dimensional deep convolutional neural network (3D-DCNN).

METHODS

We examined 100 regions of 35 patients with bone SPECT/CT classified as benign and malignant by other examinations and follow-ups. First, SPECT and CT images were extracted at the same coordinates in a cube, with a long side two times the diameter of a high concentration in SPECT images. Next, we inputted the extracted image to DCNN and obtained the probability of benignity and malignancy. Integrating the output from DCNN of each SPECT and CT image provided the overall result. To validate the efficacy of the proposed method, the malignancy of all images was assessed using the leave-one-out cross-validation method; besides, the overall classification accuracy was evaluated. Furthermore, we compared the analysis results of SPECT/CT, SPECT alone, CT alone, and whole-body planar scintigraphy in the highly integrated region of the same site.

RESULTS

The extracted volume of interest was 50 benign and malignant regions, respectively. The overall classification accuracy of SPECT alone and CT alone was 73% and 68%, respectively, while that of the whole-body planar analysis at the same site was 74%. When SPECT/CT images were used, the overall classification accuracy was the highest (80%), while the classification accuracy of malignant and benign was 82 and 78%, respectively.

CONCLUSIONS

This study suggests that DCNN could be used for the direct classification of benign and malignant regions without extracting the features of SPECT/CT accumulation patterns.

An alternative method for radioactivity measurement in quantitative bone SPECT/CT imaging

Bone scintigraphy with combined single-photon emission computed tomography (SPECT) and computed tomography (CT) has become widely used for the detection of bone metastases. However, calculation of the semi-quantitative standardized uptake value (SUV) requires measurement of the pre- and post-injection radioactivity of the radiopharmaceutical. This study aimed to compare measured and fixed input radioactivity values for quantitative SPECT/CT bone imaging to examine whether the fixed measurement method of radiopharmaceutical radioactivity could be used as an alternative method. Four different methods were used to quantify the Tc-99m hydroxymethylene diphosphonate input radioactivity: (A) measured pre- and post-injection radioactivity values; (B) measured pre-injection and fixed post-injection radioactivity values; (C) fixed pre-injection and measured post-injection radioactivity values; (D) fixed pre- and post-injection radioactivity values. All SPECT/CT acquisitions were analyzed using bone SPECT analysis software, and the semi-quantitative parameters (SUVpeak and SUVmean) were recorded and compared for each analytical method. Two semi-quantitative parameters showed significant differences between analytical methods A and B, A and D, and C and D. However, an additional subgroup analysis performed on patients whose median post-injection measured radioactivity value was <1.5 MBq showed no significant differences in parameters between all analytical methods. Measurement of the radiopharmaceutical radioactivity can be an alternative method because it reduces the volume of radioactivity post-injection. The simplified fixed measurement method of radiopharmaceutical radioactivity can be used as an alternative method in cases when measuring the radioactivity in quantitative bone SPECT/CT imaging is missed.

Spatiotemporal Statistical Shape Model for Temporal Shape Change Analysis of Adult Brain

BACKGROUND

This study presents a novel method of constructing a spatiotemporal statistical shape model (st-SSM) for adult brain. St-SSM is an extension of statistical shape model (SSM) in the temporal domain which will represent the statistical variability of shape as well as the temporal change of statistical variance with respect to time.

AIMS

Expectation-Maximization (EM) based weighted principal component analysis (WPCA) using a temporal weight function is applied where the eigenvalues of each data are estimated by Estep using temporal eigenvectors, and M-step updates Eigenvectors in order to maximize the variance. Both E and M-step are iterated until updating vectors reaches the convergence point. A weight parameter for each subject is allocated in accordance with the subject's age to calculate the weighted variance. A Gaussian function is utilized to define the weight function. The center of the function is a time point while the variance is a predefined parameter.

METHODS

The proposed method constructs adult brain st-SSM by changing the time point between minimum to maximum age range with a small interval. Here, the eigenvectors changes with aging. The feature vector of representing adult brain shape is extracted through a level set algorithm. To validate the method, this study employed 103 adult subjects (age: 22 to 93 y.o. with Mean ± SD = 59.32±16.89) from OASIS database. st-SSM was constructed for time point 40 to 90 with a step of 2.

RESULTS

We calculated the temporal deformation change between two-time points and evaluated the corresponding difference to investigate the influence of analysis parameter. An application of the proposed model is also introduced which involves Alzheimer's disease (AD) identification utilizing support vector machine.

CONCLUSION

In this study, st-SSM based adult brain shape feature extraction and classification techniques are introduced to classify between normal and AD subject as an application.

Patient arm position during quantitative bone single-photon emission computed tomography/computed tomography acquisition can affect image quality and quantitative accuracy: a phantom study

PURPOSE

The present study used a phantom to determine the effects of various arm positions on bone SPECT/computed tomography (CT) images and the optimal arm position to acquire good-quality and quantitatively accurate images.

MATERIALS AND METHODS

We designed a phantom study of five simulated arm positions that are assumed during SPECT image acquisition. All SPECT data were acquired during a total of 120 projections of 10 and 100 s/view over 360° in a non-circular mode and reconstructed using Flash 3D (Siemens Healthineers). We evaluated contrast (QH,17 mm), image noise (NB,17 mm), contrast-to-noise ratios (QNRs), and visual scores according to the guidelines for bone SPECT acquisition protocols published by the Japanese Society of Nuclear Medicine Technology. The SUVmean, SUVmax, and SUVpeak were calculated and quantitative errors were evaluated using the recovery coefficient (RC) and the root means square error (RMSE).

RESULTS

The spatial resolution of SPECT images was better when the arms were down than raised with simulated shoulder disorders. Raised arms with shoulder disorders significantly increased the NB,17 mm and decreased the QH,17 mm, and the QNR in each image differed over a range from 2.2 to 5.2. The visual score was >1.5 with the arms down, raised normally, and raised with moderate shoulder disorders. The SUVmax and SUVpeak were overestimated compared with 100-min data for all images, whereas SUVmean was underestimated. Raised arms with a shoulder disorder decreased RCmax, and RCmean and RCpeak suppressed differences among arm positions. In addition, RMSE with the arms down and raised normally were close to that for 100-min data.

CONCLUSION

Bone SPECT images with good quality and quantitative accuracy can be acquired with patients holding their arms down by their sides. This will help patients with shoulder pain who have difficulties raising their arms.

Comparison of irregular flux viewer system with BONENAVI version for identification of Tc-99m MDP whole body bone scan metastasis images

The Tc-99m methylene diphosphonate (MDP) whole body bone scan (WBBS) has been widely accepted as a method of choice for the initial diagnosis of bone and joint changes in patients with oncologic diseases. The WBBS has shown high sensitivity but relatively low specificity due to bone variation. This study aims to use the self-developing irregular flux viewer (IFV) system to predict possible bone lesions in planar WBBS. The study uses gradient vector flow (GVF) and self-organizing map (SOM) methods to analyze the blood fluid-dynamics and evaluate hot points. The evaluation includes a selection of 368 patients with bone metastasis from prostate cancer, lung cancer and breast cancer. Finally, we compare IFV values with BONENAVI version data. BONENAVI is a computer-assisted diagnosis system that analyzes bone scintigraphy automatically. The analysis shows that the IFV system achieves sensitivities of 93% for prostate cancer, 91% for breast cancer, and 83% for lung cancer, respectively. On the other hand, our proposed approach achieves a higher sensitivity than the results of BONEVAVI version 2.0.5 for prostate cancer (88%), breast cancer (86%) and lung cancer (82%), respectively. The study results demonstrate that the high sensitivity and specificity of the IFV system can provide assistance for image interpretation and generate prediction values for WBBS.

Early detection of steroid-induced femoral head necrosis using 99mTc-Cys-Annexin V-based apoptosis imaging in a rabbit model

Background

At present, the early diagnosis of femoral head necrosis mainly relies on Magnetic resonance imaging (MRI), and most early patients are difficult to make an accurate diagnosis. Therefore, to investigate the early diagnostic value of ^99mTc-Cys-Annexin V Single-photon emission computed tomography (SPECT) imaging were compared with MRI in rabbit models of steroid-induced femoral head necrosis.

Methods

The animal model of steroid-induced femoral head necrosis (SIFHN) was established in 5-month-old healthy New Zealand white rabbits by injecting horse serum into ear vein and methylprednisolone into gluteal muscle, the purpose of modeling is to simulate the actual clinical situation of SIFNH. ^99mTc-Cys-Annexin V SPECT imaging and MRI were performed at 2nd week, 4th week, and 6th week after modeling. After that, histopathology was used to verify the success of modeling. Apoptosis was detected by transmission electron microscopy (TEM) and terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling assay (TUNEL).

Results

At 2 weeks after the injection of hormone, ^99mTc-Cys-Annexin V SPECT image showed abnormal radioactive uptake in the bilateral femoral head. And over time, the radioactivity concentration was more obvious, and the ratio of T/NT (target tissue/non-target tissues, which is the ratio of femoral head and the ipsilateral femoral shaft) was gradually increased. In the ^99mTc-Cys-Annexin V SPECT imaging at each time point, T/NT ratio of the model group was significantly higher than that of the control group (P < 0.01); at 4 weeks after the injection of hormone, MRI showed an abnormal signal of osteonecrosis. At 2, 4, and 6 weeks after hormone injection, apoptosis was observed by TUNEL and TEM.

Conclusions

^99mTc-Cys-Annexin V SPECT imaging can diagnose steroid-induced femoral head necrosis earlier than MRI, and has potential application value for non-invasively detecting early and even ultra-early stage of femoral head necrosis.

Ten Commandments for the Diagnosis of Bone Tumors

The diagnosis of tumors and tumorlike lesions of bone is a routine part of both general and specialist radiologic practices. The spectrum of disorders ranges from the small incidental lesion to the potentially life-limiting malignancies whether primary or secondary. In this review, authored by experts from several European orthopaedic oncology centers, we present a collection of pieces of advice in the form of 10 commandments. Adherence in daily practice to this guidance should help minimize adverse patient experiences and outcomes.

Phantom and clinical evaluation of bone SPECT/CT image reconstruction with xSPECT algorithm

BACKGROUND

Two novel methods of image reconstruction, xSPECT Quant (xQ) and xSPECT Bone (xB), that use an ordered subset conjugate gradient minimizer (OSCGM) for SPECT/CT reconstruction have been proposed. The present study compares the performance characteristics of xQ, xB, and conventional Flash3D (F3D) reconstruction using images derived from phantoms and patients.

METHODS

A custom-designed body phantom for bone SPECT was scanned using a Symbia Intevo (Siemens Healthineers), and reconstructed xSPECT images were evaluated. The phantom experiments proceeded twice with different activity concentrations and sphere sizes. A phantom with 28-mm spheres containing a 99mTc-background and tumor-to-normal bone ratios (TBR) of 1, 2, 4, and 10 were generated, and convergence property against various TBR was evaluated across 96 iterations. A phantom with four spheres (13-, 17-, 22-, and 28-mm diameters), containing a 99mTc-background at TBR4, was also generated. The full width at half maximum of an imaged spinous process (10 mm), coefficients of variance (CV), contrast-to-noise ratio (CNR), and recovery coefficients (RC) were evaluated after reconstructing images of a spine using Flash 3D (F3D), xQ, and xB. We retrospectively analyzed images from 20 patients with suspected bone metastases (male, n = 13) which were acquired using [99mTc]Tc-(H)MDP SPECT/CT, then CV and standardized uptake values (SUV) at the 4th vertebral body (L4) were compared after xQ and xB reconstruction in a clinical setup.

RESULTS

Mean activity concentrations with various TBR converged according to increasing numbers of iterations. The spatial resolution of xB was considerably superior to xQ and F3D, and it approached almost the actual size regardless of the iteration numbers during reconstruction. The CV and RC were better for xQ and xB than for F3D. The CNR peaked at 24 iterations for xQ and 48 iterations for F3D and xB, respectively. The RC between xQ and xB significantly differed at lower numbers of iterations but were almost equivalent at higher numbers of iterations. The reconstructed xQ and xB images of the clinical patients showed a significant difference in the SUVmax and SUVpeak.

CONCLUSIONS

The reconstructed xQ and xB images were more accurate than those reconstructed conventionally using F3D. The xB for bone SPECT imaging offered essentially unchanged spatial resolution even when the numbers of iterations did not converge. The xB reconstruction further enhanced SPECT image quality using CT data. Our findings provide important information for understanding the performance characteristics of the novel xQ and xB algorithms.

Diagnostic performance of whole-body bone scintigraphy in combination with SPECT/CT for detection of bone metastases

OBJECTIVE

This retrospective study investigated the performance of whole-body bone scintigraphy combined with SPECT/CT and established a grading diagnostic criterion for bone metastases.

METHODS

We summarized signs of whole-body bone imaging combined with SPECT in nuclear medicine and CT signs of corresponding parts. Then we established a diagnostic criterion for bone metastases by using whole-body bone scintigraphy combined with local SPECT/CT. The criterion is classified into five grades. 120 patients with a total of 141 lesions underwent whole-body bone scintigraphy and SPECT/CT. Two reviewers read the images according to the diagnostic criterion. With pathological diagnosis as the "gold standard", the diagnostic efficacy for bone metastases and the diagnostic agreement between the two reviewers were analyzed to validate the feasibility of the criterion. Diagnostic effectiveness was expressed in terms of sensitivity, specificity, positive predictive value, negative predictive value, and accuracy.

RESULTS

The diagnostic accuracy of the two reviewers was 90.1% and 92.9% respectively, sensitivity was both 100%, specificity was 41.7% and 58.3%, positive predictive value was 89.3% and 92.1%, and negative predictive value was both 100%. The kappa value of the diagnostic tests performed by the two reviewers on whole-body bone scintigraphy combined with SPECT/CT was 0.919 (P < 0.001).

CONCLUSION

The grading diagnostic criterion for bone metastases by whole-body bone scintigraphy combined with SPECT/CT has high diagnostic accuracy and good consistency between reviewers, but the specificity was still low even with SPECT/CT.

Molecular Imaging of Bone Metastases and Their Response to Therapy

Bone metastases are common, especially in more prevalent malignancies such as breast and prostate cancer. They cause significant morbidity and draw on health-care resources. Molecular and hybrid imaging techniques, including SPECT/CT, PET/CT, and whole-body MRI with diffusion-weighted imaging, have improved diagnostic accuracy in staging the skeleton compared with previous standard imaging methods, allowing earlier tailored treatment. With the introduction of several effective treatment options, it is now even more important to detect and monitor response in bone metastases accurately. Conventional imaging, including radiographs, CT, MRI, and bone scintigraphy, are recognized as being insensitive and nonspecific for response monitoring in a clinically relevant time frame. Early reports of molecular and hybrid imaging techniques, as well as whole-body MRI, promise an earlier and more accurate prediction of response versus nonresponse but have yet to be adopted routinely in clinical practice. We summarize the role of new molecular and hybrid imaging methods, including SPECT/CT, PET/CT, and whole-body MRI. These modalities are associated with improvements in diagnostic accuracy for the staging and response assessment of skeletal metastases over standard imaging methods, being able to quantify biologic processes related to the bone microenvironment as well as tumor cells. The described improvements in the imaging of bone metastases and their response to therapy have led to adoption of some of these methods into routine clinical practice in some centers. These methods also provide a better way to assess the treatment response of bone metastases in clinical trials.

99mTc-MIP-1404 SPECT/CT for Patients With Metastatic Prostate Cancer: Interobserver and Intraobserver Variability in Treatment-Related Longitudinal Tracer Uptake Assessments of Prostate-Specific Membrane Antigen-Positive Lesions

BACKGROUND

Tc-MIP-1404 is a SPECT-suitable prostate-specific membrane antigen (PSMA) ligand for detection of prostate cancer. In patients with metastatic prostate cancer, there are no data as yet on interobserver and intraobserver variability when assessing PSMA-positive lesions for longitudinal changes of tracer uptake.

METHODS

Tc-MIP-1404 SPECT/CT scans of 22 patients with metastatic prostate cancer were analyzed, and each subject was imaged at 2 separate points in time, before and after treatment. Mean interval between scans was 10 months. Three independent observers visually assessed a total of 96 PSMA-positive metastases (bone, 69; lymph node, 22; viscera, 3) or local recurrences (n = 2) for longitudinal changes in tracer uptake on planar scintigraphy and SPECT/CT. All lesions were categorized as regressive, stable, or progressive based on visual findings and on peak SUV (SUVpeak) of quantitative SPECT/CT (progressive, >30% SUVpeak increase; regressive, <30% SUVpeak decrease; or stable, all others).

RESULTS

Quantitative analysis of PSMA-positive lesions yielded significantly higher interobserver agreement (90.6%; 95% confidence interval [CI], 0.83%-0.96%) than visual assessments by either SPECT/CT (76.0%; 95% CI, 0.66%-0.84%) or planar scintigraphy (56.3%; 95% CI, 0.46%-0.66%). Intermethod comparison of aggregated results yielded significantly higher agreement between quantitative and visual SPECT/CT (85.1%; 95% CI, 0.80%-0.89%), as opposed to quantitative SPECT/CT and planar scintigraphy (53.1%; 95% CI, 0.47%-0.59%) or visual SPECT/CT and planar scintigraphy (54.9%; 95% CI, 0.49%-0.61%). In visual and quantitative analysis of 96 PSMA-positive lesions, the number of discrepancies ranged from 9 (9.4%) for quantitative SPECT/CT to 42 (43.8%) for planar scintigraphy. Overall reader confidence was higher for SPECT/CT than for planar scintigraphy (P < 0.001). Intraobserver agreement was near-perfect for all methods, whether SPECT/CT (visual, all κ = 0.94-0.97; quantitative κ = 0.94-0.98) or planar scintigraphy (all κ = 0.90-0.94).

CONCLUSIONS

Quantitative evaluation of longitudinal change in tracer uptake by PSMA-positive lesions measured via SPECT/CT is superior to visual interpretation of images by planar scintigraphy or SPECT/CT. Compared with visual evaluation, quantitative SPECT/CT is highly reproducible, showing near-perfect agreement among observers and higher reader confidence.

[Evaluation of Post-reconstruction Filtering in Resolution Recovery Reconstruction for Bone SPECT Imaging]

PURPOSE

The aim of this study was to clarify the optimal post-reconstruction filtering type in the three- dimensional ordered subset expectation maximization (3D-OSEM) method for bone single photon emission computed tomography (SPECT) from image quality and quantitative values.

METHOD

We scanned a National Electrical Manufactures Association's body phantom for bone SPECT filled with radioactive solution of ^99mTc whose radioactivity concentration was accurately measured. The SPECT images were created using the 3D-OSEM method. Post-reconstruction filtering was performed using a Butterworth filter (BW), a Gaussian filter (GA), and a Hanning filter (HA) with various parameters. The image quality was evaluated by the normalized mean-squared error (NMSE) value and % of contrast-to-noise ratio (QNR₁₇). The image quality was evaluated by the error values between the measured radioactivity concentration and the true radioactivity concentration in the BG region and insert sphere.

RESULTS

The minimum NMSE values were 0.034 (BW), 0.036 (GA), and 0.035 (HA), and there was no difference depending on the filter type. The values of QNR₁₇ were 2.5 (BW), 2.6 (GA), and 2.6 (HA), and there was no difference depending on the filter type. The BG region was greatly affected by parameter changes in GA but less by those in BW and HA. The error values of the 37 mm insert sphere were 18.0% (BW), 28.2% (GA), and 26.2% (HA), and BW showed the lowest value.

CONCLUSION

Our results suggest that the post-reconstruction filtering type used in the 3D-OSEM method was BW from the image quality and quantitative values.

Evaluation of edge-preserving and noise-reducing effects using the nonlinear diffusion method in bone single-photon emission computed tomography

OBJECTIVES

This study aims to evaluate nonlinear diffusion (NLD) processing to smoothen images while suppressing resolution degradation in single-photon emission computed tomography (SPECT) images. Phantom data were used for NLD method optimization. The resultant optimal settings were used for NLD processing of clinical images.

MATERIALS AND METHODS

Tc was used to simulate tumors and normal soft tissues. Using the data collected, images were reconstructed. Images were processed using various k values and iteration. The background region's coefficient of variation (CV) was determined, and the effects of parameters on image properties were examined. NLD-processed images with optimal parameters were compared with Butterworth (BW)-filtered and nine-point smoothing (SM)-processed images to evaluate smoothing filter properties in real and frequency space. Receiver operating characteristic curve analysis was carried out on NLD-processed and BW048-processed bone SPECT images.

RESULTS

From CVs in background, with NLD, increased k value and iteration led to a low CV, indicating enhanced smoothing effect. At k=0.9, a strong noise-reducing effect with less iteration was achieved. Contrasts and recovery coefficients of NLD were the highest. The visual score for SPECT image quality was significantly higher with NLD than with BW048, BW090, and SM. In the low-frequency and high-frequency ranges, BW048, BW090, and NLD showed similar signal strengths and NLD and BW090 showed high signal strength, respectively. SM processing reduced the signal strength at all frequency ranges. On receiver operating characteristic analysis, noise reduction using NLD processing enhanced diagnostic performance than with the use of BW processing.

CONCLUSION

NLD processing of bone SPECT images using optimized parameters enabled smoothing with less resolution degradation.

Use of Hybrid Imaging Techniques in Diagnosis of Facet Joint Arthropathy: A Narrative Review of Three Modalities

Facet joint osteoarthritis/arthropathy of the spine is a common cause of back and neck pain that frequently overlaps clinically with other diseases of the spine. Because of the possible overlap, it is crucial to have an accurate diagnostic strategy, especially when determining the management approach. Various strategies have been suggested and adopted, with several these still being used in clinics. Over the years, because of the disadvantages of single-modality imaging methods (computed tomography, magnetic resonance imaging, single-photon emission computed tomography), the interest in radiologic examination started to move toward hybrid imaging techniques. Although the data are mixed, many initial studies have shown promise. However, there are relatively few data with comparative medial branch blocks, and further investigation is needed. Given the advantages and disadvantages of these new techniques, the imaging results have to be interpreted within clinical context and with consideration of the current state of knowledge in the decision-making process.

Characterization of Solitary Lesions in the Extremities on Whole-Body Bone Scan in Patients With Known Cancer: Contribution of Single-Photon Emission Computed Tomography/Computed Tomography

Background: Solitary lesions in the extremities showing ^99mTc-methylene diphosphate (MDP) uptake are often encountered on whole-body bone scan (WBS), and proper interpretation of this diagnostic method is important for patients with known cancer. The purpose of this study was to summarize the characteristics of solitary lesions in the extremities of patients with known cancer and to evaluate the diagnostic accuracy of single-photon emission computed tomography/computed tomography (SPECT/CT) in differentiating bone metastases from benign bone lesions.

Methods: This study was a retrospective review of 86 patients (54 males and 32 females; mean age, 57.88 ± 10.97 years; range, 31–81 years) with known cancer who underwent WBS and showed solitary lesions with ^99mTc-MDP uptake in the extremities and then underwent SPECT/CT for further diagnosis. SPECT/CT images were independently interpreted by two experienced nuclear medicine physicians. The diagnostic accuracy of SPECT/CT in differentiating malignant from benign solitary lesions in the extremities was evaluated. Inter-reviewer agreement was assessed by using weighted k statistics. The standard diagnostic criterion was based on biopsy or radiologic follow-up over at least 12 months.

Results: In total, 23 bone metastases and 63 (73.26%) benign lesions were diagnosed. The majority (16/23, 69.57%) of bone metastases were found in the diaphyses. The most common benign bone disease was a benign bone tumor (31.75%, 20/63). The majority (13/20, 65%) of benign bone tumors were enchondromas. In the proximal and distal extremities, the most common disease was degeneration (27.11%, 16/59), followed by benign bone tumors and osteonecrosis of the femoral head (ONFH) (22.03%, 13/59). In the diaphyses of the extremities, bone metastasis was the most common disease, accounting for 64% (16/25) of the findings. For the SPECT/CT analysis, the accuracy was 94.19% (81/86) for reviewer 1 and 95.34% (82/86) for reviewer 2. The weighted kappa score for inter-reviewer agreement was 0.813.

Conclusion: When solitary disease of the extremities is detected by WBS in patients with known cancer, benign lesions may be more common than malignant lesions. SPECT/CT resulted in not only fewer equivocal lesions but also in higher diagnostic accuracy.

Accurate characterization of 99mTc-MDP uptake in extraosseous neoplasm mimicking bone metastasis on whole-body bone scan: contribution of SPECT/CT

Background

^99mTc-labelled methylene diphosphonate (^99mTc-MDP) uptake can occasionally be identified in extraosseous neoplasms on whole-body scans (WBSs) and may be misinterpreted as bone metastasis. The purpose of our study was to investigate the frequency of ^99mTc-MDP uptake in extraosseous neoplasms and to assess the additional value of SPECT/CT for the localization and characterization of this unusual uptake.

Methods

Data from 7308 patients (SPECT/CT was performed in 2147 patients) with known cancer who underwent WBSs for metastatic work-up between May 2015 and July 2018 were retrospectively reviewed. The locations, numbers, and intensities of extraosseous ^99mTc-MDP uptake were evaluated by WBS, and the intratumoural calcification was evaluated by SPECT/CT. The diagnostic accuracy of SPECT/CT in locating ^99mTc-MDP uptake in extraosseous neoplasms was compared to that of WBS.

Results

A total of 41 patients showed ^99mTc-MDP uptake in extraosseous neoplasms. Of these patients, 23 patients had uncertain lesions by WBS, and further SPECT/CT was performed. The incidence of ^99mTc-MDP uptake in extraosseous neoplasms was observed to be 0.6% by WBS and 1.1% (by) SPECT/CT. During imaging analysis, WBS had an accuracy of only 35% (14/40), whereas SPECT/CT correctly located and diagnosed all 40 lesion sites in the 23 patients. Twenty-three lesion sites (57.5%, 23/40) showed moderate or high intensity of extraosseous ^99mTc-MDP uptake. Of the 23 patients, 17 patients (73.9%, 18/23) with 31 lesion sites (77.5%, 31/40) presented with intratumoural calcification.

Conclusions

^99mTc-MDP uptake in extraosseous neoplasms can be observed as 0.6% on WBS and is usually localized to the breast, liver, and lung. Nuclear physicians should be familiar with such extraosseous uptake when interpreting WBSs. SPECT/CT offers better accuracy than WBS alone for locating the majority of lesions present with intratumoural calcification.

Nuclear Medicine Imaging Techniques for Detection of Skeletal Metastases in Breast Cancer

Bone is the most common site of metastases from advanced breast cancer. Whole-body bone scintigraphy has been most frequently used in the process of managing cancer patients; its advantage is that it provides rapid whole-body imaging for screening of osteoblastic or sclerotic/mixed bone metastases at reasonable cost. Recent advanced techniques, such as single-photon emission computed tomography (SPECT)/CT, quantitative analysis, and bone scan index, contribute to better understanding of the disease state. More recent advances in machines and PET drugs improve the staging of the skeleton with higher sensitivity and specificity.

Radionuclide bone SPECT/CT in the evaluation of knee pain: comparing two-phase bone scintigraphy, SPECT and SPECT/CT

OBJECTIVE:

To assess the role of single photon emission computed tomography (SPECT/CT) in the evaluation of knee pain as well as comparing bone scintigraphy (BS), SPECT and SPECT/CT, and assessing the incremental value of SPECT/CT.

METHODS:

BS, SPECT and SPECT/CT of patients with knee pain (39 patients, 65 knees, 105 lesions) were directly compared for lesion detection, localisation and characterisation using lesion-based, knee-based and patient-based analyses in this retrospective study.

RESULTS:

Lesion detection: BS (91.4%), SPECT (100%) and SPECT/CT (100%). SPECT and SPECT/CT detected significantly more lesions than BS (p < 0.05). Lesion localisation: BS (38.5-41.7%), SPECT (74.4-83.3%) and SPECT/CT (100%). SPECT localised significantly more lesions than BS; SPECT/CT localised significantly more lesions than BS and SPECT (p < 0.01). Lesion characterisation: BS (23.0-52.1%), SPECT (30.8-56.2%) and SPECT/CT (92.3-96.9%). SPECT/CT characterised significantly more lesions than BS and SPECT (p < 0.01). Characterisation of non-arthropathy lesions: BS (6.25%), SPECT (12.5%) and SPECT/CT (93.75%). SPECT/CT characterised significantly more non-arthropathy lesions than BS and SPECT (p < 0.01). BS and SPECT detected none, while SPECT/CT detected 100% of the causative/contributing/associated conditions that co-existed with osteoarthritis. Therefore SPECT/CT detected not only just osteoarthritis but also the causative/contributing/associated conditions.

CONCLUSION:

SPECT/CT added significant incremental value to BS and SPECT irrespective of whether evaluation was lesion-based, knee-based or patient-based. SPECT/CT represents a viable alternative to MRI, and addition of SPECT/CT to BS and SPECT should be considered in the evaluation of knee pain.

ADVANCES IN KNOWLEDGE:

Incremental value of bone SPECT/CT in knee pain.

SPECT-CT versus MRI in localizing active lesions in patients with osteoporotic vertebral compression fractures

OBJECTIVE

This study aimed to evaluate the difference and consistency between single-photon emission computed tomography-computed tomography (SPECT-CT) and MRI in diagnosing osteoporotic vertebral compression fractures (OVCFs) and identifying active lesions.

PATIENTS AND METHODS

All 46 patients underwent SPECT-CT and MRI examinations. The pain vertebral body and pain sites were determined using both MRI and SPECT-CT during percutaneous kyphoplasty (PKP). The differences before and after treatment were assessed using visual analog scale scores and evaluated using a paired t-test. Furthermore, the difference and conformity of SPECT-CT and MRI in diagnosing OVCFs were determined using the McNemar test and the κ-statistic, and by calculating the accuracy index of SPECT-CT diagnosis.

RESULTS

Among all 46 patients, MRI showed 79 segments that fulfilled the diagnostic criteria for fresh OVCFs, whereas SPECT-CT showed 83 segments, and a total of 77 affected vertebral bodies were treated with PKP. Paired t-test evaluation showed that PKP was effective, suggesting that the affected sites were determined accurately (P<0.05). Furthermore, the κ-statistics indicated that these two methods were highly consistent (P<0.05) and the McNemar test indicated that the efficacy of these two diagnostic methods was closely correlated (P>0.05). In different stages of fractures, especially the acute phase, the consistency of SPECT-CT and MRI in the diagnosis of fresh OVCFs was high.

CONCLUSION

SPECT-CT is the preferred method for imaging diagnosis when patients with suspected OVCFs have contraindications to MRI, particularly for patients with acute fractures.

Functional and Hybrid Imaging of Bone Metastases

Bone metastases are common, cause significant morbidity, and impact on healthcare resources. Although radiography, computed tomography (CT), magnetic resonance imaging (MRI), and bone scintigraphy have frequently been used for staging the skeleton, these methods are insensitive and nonspecific for monitoring treatment response in a clinically relevant time frame. We summarize several recent reports on new functional and hybrid imaging methods including single photon emission CT/CT, positron emission tomography/CT, and whole-body MRI with diffusion-weighted imaging. These modalities generally show improvements in diagnostic accuracy for staging and response assessment over standard imaging methods, with the ability to quantify biological processes related to the bone microenvironment as well as tumor cells. As some of these methods are now being adopted into routine clinical practice and clinical trials, further evaluation with comparative studies is required to guide optimal and cost-effective clinical management of patients with skeletal metastases. © 2018 American Society for Bone and Mineral Research.

The clinical value of xSPECT/CT Bone versus SPECT/CT. A prospective comparison of 200 scans

Purpose

To prospectively evaluate the clinical utility of xSPECT/CT Bone, a new reconstruction algorithm for single photon emission tomography (SPECT), and compare it with standard SPECT/CT reconstruction.

Methods

Sequential reporting of SPECT/CT followed by xSPECT/CT images in 200 sequential cases commencing August 2015. Differences between the initial SPECT/CT and the final report (after xSPECT/CT reconstruction) were documented and analysed. 12–18 months after the initial study follow-up, clinical data was sought from a subset of cases in which xSPECT/CT changed the primary diagnosis and imaging correlation undertaken in all patients who subsequently had MRI or CT scans of the same region.

Results

A majority of the 200 cases were related to assessment of musculoskeletal complaints. The final (scan) diagnosis was changed after reviewing the xSPECT/CT images in 40 (20%) of cases. The reporting physician (Iain Duncan) assessed that the xSPECT/CT had provided more diagnostic information in 71% of cases. A total of 470 additional lesions were found, equivalent to 2.4 lesions per case. In 33 cases of imaging follow-up there was a high degree of correlation with bone scan findings and xSPECT correlated better than SPECT in regard to detailed findings. In only 15/40 cases of diagnostic change could the outcome be verified and in 12/15 the xSPECT/CT revised diagnosis was confirmed.

Conclusions

In this observational evaluation xSPECT/CT Bone reconstruction offers identifiable imaging improvements over standard SPECT/CT reconstruction algorithms. xSPECT/CT Bone provides an improvement in diagnostic confidence and identifies a greater number of lesions.

A new SPECT/CT reconstruction algorithm: reliability and accuracy in clinical routine for non-oncologic bone diseases

Background

xSPECT Bone® (xB) is a new reconstruction algorithm developed by Siemens® in bone hybrid imaging (SPECT/CT). A CT-based tissue segmentation is incorporated into SPECT reconstruction to provide SPECT images with bone anatomy appearance. The objectives of this study were to assess xB/CT reconstruction diagnostic reliability and accuracy in comparison with Flash 3D® (F3D)/CT in clinical routine. Two hundred thirteen consecutive patients referred to the Brest Nuclear Medicine Department for non-oncological bone diseases were evaluated retrospectively. Two hundred seven SPECT/CT were included. All SPECT/CT were independently interpreted by two nuclear medicine physicians (a junior and a senior expert) with xB/CT then with F3D/CT three months later. Inter-observer agreement (IOA) and diagnostic confidence were determined using McNemar test, and unweighted Kappa coefficient. The study objectives were then re-assessed for validation through > 18 months of clinical and paraclinical follow-up.

Results

No statistically significant differences between IOA _xB and IOA F3D were found (p = 0.532). Agreement for xB after categorical classification of the diagnoses was high (κ_xB = 0.89 [95% CI 0.84 –0.93]) but without statistically significant difference F3D (κ _F3D = 0.90 [95% CI 0.86 – 0.94]). Thirty-one (14.9%) inter-reconstruction diagnostic discrepancies were observed of which 21 (10.1%) were classified as major. The follow-up confirmed the diagnosis of F3D in 10 cases, xB in 6 cases and was non-contributory in 5 cases.

Conclusions

xB reconstruction algorithm was found reliable, providing high interobserver agreement and similar diagnostic confidence to F3D reconstruction in clinical routine.

Added value of SPECT/spiral CT versus SPECT or CT alone in diagnosing solitary skeletal lesions

Aim: The aim of this study was to investigate the added value of SPECT/spiral CT versus SPECT or CT alone in the differential diagnosis of solitary skeletal lesions.Methods: This was a retrospective study on a total of 69 patients who had a solitary skeletal “hot spot” that could not be definitively diagnosed using planar scintigraphy. Thus, SPECT/ spiral CT was performed on the indeterminate lesions. SPECT, CT and SPECT/spiral CT images were independently interpreted by two experienced doctors who have both identification of CT and nuclear medicine. Each lesion was graded on a 4-point diagnostic scale (1: benign, 2: likely benign, 3: likely malignant, 4: malignant). The final diagnosis of each lesion was based on pathological confirmation after surgery within 3 weeks of the bone scan.Results: Final diagnoses based on the pathological results revealed that 43 of the 69 patients were diagnosed with malignancy, and the remaining 26 patients were diagnosed as having benign lesions. For SPECT and CT scans, both of the reviewers rated 55.1% (38/69) and 37.7 % (26/69) of lesions as equivocal, with the help of SPECT/CT, 33.3 % (23/69) of lesions were rated as equivocal. The diagnostic accuracies of SPECT, CT alone and SPECT/CT were 66.7 % (46/69),82.6 % (57/69) and 85.5 %(59/69), respectively. The kappa scores for the degree of agreement between SPECT, CT alone or SPECT/CT with pathological results were 0.185 (p = 0.054), 0.612 (p < 0.001) and 0.671 (p < 0.001), respectively.Conclusion: Compared with SPECT or imaging alone, SPECT/ spiral CT imaging was more accurate and valuable in the differential diagnosis of solitary skeletal lesions and resulted in significantly fewer equivocal findings.

[Effect of Misregistration between SPECT and CT Images on Attenuation Correction for Quantitative Bone SPECT Imaging]

PURPOSE

The aim of this study was to evaluate the effect of misregistration between single-photon emission computed tomography (SPECT) and computed tomography (CT) images on bone SPECT.

METHODS

We acquired SPECT and CT images of a body phantom filled with bone-equivalent solution and ^99mTc for evaluation of bone SPECT. SPECT images were reconstructed using attenuation correction maps obtained by shifting the attenuation coefficients from non-shifted values (reference). Activity concentrations, SPECT standardized uptake values (SPECT-SUVs), and tumor background ratios (TBRs) were evaluated.

RESULTS

Activity concentrations and SPECT-SUVs decreased with decreasing attenuation coefficient. The difference in attenuation coefficient was especially large between the shifted-to-lung (0.085 cm^-1) and reference (0.249 cm^-1) values. Non-shifted and shifted-to-lung SPECT-SUVs were 11.5±1.0 and 2.3±0.2, respectively. TBR also decreased with decreasing attenuation coefficient. The maximum percentage change in TBR was 86% in the shifted-to-lung value.

CONCLUSIONS

Our results indicate that the accuracy of activity concentration and lesion detectability was commonly affected by misalignment between SPECT and CT images. Although the impact of SPECT/CT misregistration on bone SPECT is case-specific and difficult to predict, it is important to reduce the incidence of misregistration errors for quantitative bone SPECT imaging.

Skeletal abnormalities detected by SPECT is associated with increased relapse risk in pediatric acute lymphoblastic leukemia

Objectives

Most children with acute lymphoblastic leukemia (ALL) exhibit skeletal abnormalities. This study aimed to investigate bone lesions detected by whole-body bone single-photon emission computed tomography (SPECT) and its prognostic value in children with ALL.

Methods

A retrospective analysis was performed using whole-body bone SPECT scans obtained from children with ALL in our department between June 2008 and June 2012. A total of 166 children newly diagnosed with ALL were included, and the patients were divided into two groups: patients with positive and negative SPECT scans. We compared the clinical characteristics of the two groups and analyzed the relationship between the skeletal abnormalities detected by SPECT and prognosis.

Results

Among the 166 patients, bone scintigraphic abnormalities was detected by SPECT scan in sixty-four patients (38.6%). The most common site was the limbs. There were no significant differences in age, gender, WBC count at diagnosis, risk group and minimal residual disease (MRD) level between SPECT-positive patients and their SPECT-negative counterparts. The event-free and overall survival rates were higher in SPECT-positive patients, but the difference was not statistically significant. However, patients with positive SPECT scans, especially those with multifocal abnormalities (≥3 sites), had a higher rate of relapse (P < 0.05). Multivariate analyses identified that abnormal SPECT scan (HR = 3.547, P = 0.015) was an independent relapse risk.

Conclusion

Children with ALL and multiple skeletal abnormalities will suffer from relapse. Abnormal SPECT scan was associated with increased relapse risk which might be a potential relapse marker for ALL children.

The impact of post-radioiodine therapy SPECT/CT on early risk stratification in differentiated thyroid cancer; a bi-institutional study

Objective

SPECT/CT has numerous advantages over planar and traditional SPECT images. The aim of this study was to evaluate the role of post-radioiodine therapy SPECT/CT of patients with differentiated thyroid cancer (DTC) in early risk classification and in prediction of late prognosis.

Patients and methods

323 consecutive patients were investigated after their first radioiodine treatment (1100–3700 MBq). Both whole body scan and SPECT/CT images of the head, neck, chest and abdomen regions were taken 4–6 days after radioiodine therapy. Patients were re-evaluated 9–12 months later as well as at the end of follow up (median 37 months).

Results

Post-radioiodine therapy SPECT/CT showed metastases in 22% of patients. Lymph node, lung and bone metastases were detected in 61, 13 and 5 patients, respectively, resulting in early reclassification of 115 cases (36%). No evidence of disease was found in 251 cases at 9–12 months after radioiodine treatment and 269 patients at the end of follow-up. To predict residual disease at the end of follow-up, the sensitivities, specificities and diagnostic accuracies of the current risk classification systems and SPECT/CT were: ATA: 77%, 47% and 53%; ETA: 70%, 62% and 64%; SPECT/CT: 61%, 88% and 83%, respectively. There was no difference between cohorts of the two institutions when data were analyzed separately.

Conclusions

Based on our bi-institutional experience, the accuracy of post-radioiodine SPECT/CT outweighs that of the currently used ATA and ETA risk classification systems in the prediction of long-term outcome of DTC.

Whole-Body SPECT/CT versus Planar Bone Scan with Targeted SPECT/CT for Metastatic Workup

PURPOSE

The use of SPECT/CT in bone scans has been widespread in recent years, but there are no specific guidelines concerning the optimal acquisition protocol. Two strategies have been proposed: targeted SPECT/CT for equivocal lesions detected on planar images or systematic whole-body SPECT/CT. Our aim was to compare the diagnostic accuracy of the two approaches.

METHODS

212 consecutive patients with a history of cancer were referred for bone scans to detect bone metastases. Two experienced readers randomly evaluated for each patient either planar images with one-field SPECT/CT targeted on equivocal focal uptakes (targeted SPECT/CT) or a whole-body (two-field) SPECT/CT acquisition from the base of the skull to the proximal femurs (whole-body SPECT/CT). The exams were categorized as "nonmetastatic," "equivocal," or "metastatic" on both protocols. The presence or absence of any extra-axial skeletal lesions was also assessed. The sensitivity and specificity of both strategies were measured using the results of subsequent imaging follow-up as the reference standard.

RESULTS

Whole-body SPECT/CT had a significantly higher sensitivity than targeted SPECT/CT to detect bone metastases (p = 0.0297) and to detect extra-axial metastases (p = 0.0266). There was no significant difference in specificity among the two approaches.

CONCLUSION

Whole-body SPECT/CT is the optimal modality of choice for metastatic workup, including detection of extra-axial lesions, with improved sensitivity and similar specificity compared to targeted SPECT/CT.