A Prospective Study Comparing 99mTc-Hydroxyethylene-Diphosphonate Planar Bone Scintigraphy and Whole-Body SPECT/CT with 18F-Fluoride PET/CT and 18F-Fluoride PET/MRI for Diagnosing Bone Metastases

Whole-Body SPECT/CT: Protocol Variation and Technical Consideration-A Narrative Review

Introducing a hybrid imaging approach, such as single-photon emission computerized tomography with X-ray computed tomography (SPECT)/CT, improves diagnostic accuracy and patient management. The ongoing advancement of SPECT hardware and software has resulted in the clinical application of novel approaches. For example, whole-body SPECT/CT (WB-SPECT/CT) studies cover multiple consecutive bed positions, similar to positron emission tomography-computed tomography (PET/CT). WB-SPECT/CT proves to be a helpful tool for evaluating bone metastases (BM), reducing equivocal findings, and enhancing user confidence, displaying effective performance in contrast to planar bone scintigraphy (PBS). Consequently, it is increasingly utilized and might substitute PBS, which leads to new questions and issues concerning the acquisition protocol, patient imaging time, and workflow process. Therefore, this review highlights various aspects of WB-SPECT/CT acquisition protocols that need to be considered to help understand WB-SPECT/CT workflow processes and optimize imaging protocols.

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.

Comparison of the detectability of hot lesions on bone SPECT using six state-of-the-art SPECT/CT systems: a multicenter phantom study to optimize reconstruction parameters

Single-photon emission computed tomography with X-ray computed tomography (SPECT/CT) systems have diversified due to the remarkable developments made by each manufacturer. This study aimed to optimize the reconstruction parameters of six state-of-the-art SPECT/CT systems and compare their image quality of bone SPECT. SPECT images were acquired on SPECT/CT systems, including Symbia Intevo, Discovery NM/CT 670, Discovery NM/CT 870 CZT, Brightview XCT, and VERITON-CT. SIM² bone phantom with tough lung phantoms on both sides of the spinal inserts that simulate the thorax was used for image quality assessment. SPECT images were obtained at individual workstations using an ordered subset expectation maximization method with three-dimensional resolution recovery, as well as CT attenuation and scatter correction, subset 2, iteration 12-84, and a full width at half maximum 10-mm Gaussian smooth filter. An automatic image analysis software dedicated to SIM² bone phantom was used to assess the contrast-to-noise ratio (CNR), relative recovery coefficient, percentage of coefficient of variance, contrast, and detectability. The optimal parameters for each system were defined with superior detectability of spherical lesions and noise characteristics, as well as the highest CNR. All systems exhibited better image quality indexes using the optimal parameters than using the manufacturer's recommended parameters. The detectability of all systems was in agreement while using the optimal parameters. Detectability agreement can be achieved by optimizing the reconstruction parameters for different reconstruction algorithms, which can further improve the image quality. Therefore, future research should focus on optimal reconstruction parameters for SPECT alone.

Skeletal standardized uptake values obtained using quantitative SPECT/CT for the detection of bone metastases in patients with lung adenocarcinoma

Purpose

To assess the utility of skeletal standardized uptake values (SUVs) obtained using quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) in differentiating bone metastases from benign lesions, particularly in patients with lung adenocarcinoma.

Methods

Patients with lung adenocarcinoma who had undergone whole-body Tc-99m methyl-diphosphonate (^99mTc-MDP) bone scans and received late phase SPECT/CT were retrospectively analyzed in this study. The maximum SUV (SUVmax); Hounsfield units (HUs); and volumes of osteoblastic, osteolytic, mixed, CT-negative metastatic and benign bone lesions, and normal vertebrae were compared. Receiver operating characteristic curves were used to determine the optimal cutoff SUVmax between metastatic and benign lesions as well as the cutoff SUVmax between CT-negative metastatic lesions and normal vertebrae. The linear correlation between SUVmax and HUs of metastatic lesions as well as that between SUVmax and the volume of all bone lesions were investigated.

Results

A total of 252 bone metastatic lesions, 140 benign bone lesions, and 199 normal vertebrae from 115 patients with lung adenocarcinoma were studied (48 males, 67 females, median age: 59 years). Metastatic lesions had a significantly higher SUVmax (23.85 ± 14.34) than benign lesions (9.67 ± 7.47) and normal vertebrae (6.19 ± 1.46; P < 0.0001). The SPECT/CT hotspot of patients with bone metastases could be distinguished from benign lesions using a cutoff SUVmax of 11.10, with a sensitivity of 87.70% and a specificity of 80.71%. The SUVmax of osteoblastic (29.16 ± 16.63) and mixed (26.62 ± 14.97) lesions was significantly greater than that of osteolytic (15.79 ± 5.57) and CT-negative (16.51 ± 6.93) lesions (P < 0.0001, P = 0.0003, and 0.002). SUVmax at the cutoff value of 8.135 could distinguish CT-negative bone metastases from normal vertebrae, with a sensitivity of 100.00% and a specificity of 91.96%. SUVmax showed a weak positive linear correlation with HUs in all bone metastases and the volume of all bone lesions.

Conclusion

SUVmax of quantitative SPECT/CT is a useful index for distinguishing benign bone lesions from bone metastases in patients with lung adenocarcinoma, particularly in the diagnosis of CT-negative bone metastases, but other factors that may affect SUVmax should be considered.

ACR Appropriateness Criteria® Malignant or Aggressive Primary Musculoskeletal Tumor-Staging and Surveillance: 2022 Update

Malignant or aggressive primary musculoskeletal tumors are rare and encompass a wide variety of bone and soft tissue tumors. Given the most common site for metastasis from these primary musculoskeletal tumors is to the lung, chest imaging is integral in both staging and surveillance. Extrapulmonary metastases are rarely encountered with only a few exceptions. Following primary tumor resection, surveillance of the primary tumor site is generally recommended. Local surveillance imaging recommendations differ between primary tumors of bone origin versus soft tissue origin. This document consolidates the current evidence and expert opinion for the imaging staging and surveillance of these tumors into five clinical scenarios. The ACR 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 in which peer-reviewed literature is lacking or equivocal, experts may be the primary evidentiary source available to formulate a recommendation.

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.

Head-To-Head Comparison of 68Ga-PSMA-11 PET/CT and 99mTc-MDP Bone Scintigraphy for the Detection of Bone Metastases in Patients With Prostate Cancer: A Meta-Analysis

BACKGROUND. Bone scintigraphy (BS) using 99mTc-labeled methylene diphospho-nate (99mTc-MDP) remains the recommended imaging modality for the detection of bone metastases in patients with prostate cancer (PCa). However, PET/CT using prostate-specific membrane antigen (PSMA) ligands is increasingly recognized as a means of evaluating disease extent in patients with PCa, including use as a possible stand-alone test in high-risk patients. OBJECTIVE. The purpose of this study is to compare the diagnostic performance of 68Ga-PSMA-11 PET/CT with that of 99mTc-MDP BS for the detection of bone metastases in patients with PCa. EVIDENCE ACQUISITION. The PubMed, Embase, and Cochrane Library databases were searched through October 2021 to identify studies reporting a head-to-head comparison of 68Ga-PSMA-11 PET/CT and 99mTc-MDP BS for the detection of bone metastases in patients with PCa. Only studies with a well-defined reference standard (including various combinations of imaging and/or clinical follow-up) were included. Pooled diagnostic performance was calculated using a bivariate random-effects model, and an AUC was derived for each test from hierarchic summary ROC analysis. The complementary roles of the two tests in identifying bone metastases in patients in whom one of the tests was negative were summarized. EVIDENCE SYNTHESIS. Six studies with 546 patients were included. Pooled sensitivity and specificity, respectively, were 98% (95% CI, 94-99%) and 97% (95% CI, 91-99%) for 68Ga-PSMA-11 PET/CT versus 83% (95% CI, 69-91%) and 68% (95% CI, 41-87%) for 99mTc-MDP BS. The AUC was 0.99 (95% CI, 0.96-1.00) for 68Ga-PSMA-11 PET/CT and 0.85 (95% CI, 0.81-0.87) for 99mTc-MDP BS. Among 408 patients from five included studies, 68Ga-PSMA-11 PET/CT correctly identified bone metastases in 43 of 193 patients (22.3%) with negative 99mTc-MDP BS results, whereas 99mTc-MDP BS correctly identified bone metastases in four of 210 patients (1.9%) with negative 68Ga-PSMA-11 PET/CT results. CONCLUSION. On a per-patient basis, the diagnostic performance of 68Ga-PSMA-11 PET/CT is superior to that of 99mTc-MDP BS for the detection of PCa bone metastases. Furthermore, 99mTc-MDP BS offers limited additional information in patients with negative 68Ga-PSMA-11 PET/CT results. CLINICAL IMPACT. According to current evidence, 99mTc-MDP BS is highly unlikely to be additive to 68Ga-PSMA-11 PET/CT in identifying bone metastases in patients with PCa.

Case report: Thoracic and lumbar plasma cell myeloma mimicking hemangiomas on MRI and 18F-FDG PET/CT

Plasma cell myeloma (PCM) is a malignant clonal disease of abnormal proliferation of plasma cells, which is the second most common hematological malignancy after leukemia. PCM often diffuses and involves the bones of the whole body, especially the spinal column, ribs, skull, pelvis, and other axial bones and flat bones. Herein, we present a 55-year-old man who came to the hospital seeking medical help for low-back pain and numbness in his lower limbs. Computed tomography (CT) was performed because the clinician suspected that the patient had a herniated disc, and the results showed that the 7^th thoracic vertebrae and the 3^rd lumbar vertebrae showed a low density of bone destruction with “honeycombing” changes. Magnetic resonance imaging (MRI) showed that the corresponding lesions presented long T1 and long T2 signals, and the lesions were significantly enhanced in contrast-enhanced T1WI sequences, and fluoro18-labeled deoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) showed mild radioactive uptake in the lesions. Based on these imaging findings, the patient was considered for a diagnosis of hemangiomas, and surgery was performed because the affected vertebra was pressing on the spinal cord. However, intraoperative frozen section examination showed that the patient had plasma cell myeloma. Our case study suggests that PCM involving a single thoracic and lumbar spine is rare and should be considered as one of the imaging differential diagnoses of hemangiomas. Moreover, the diagnosis of PCM is difficult when the number of lesions is small, especially when the plasma cell ratio is within the normal reference range in laboratory tests.

Observer experience and accuracy of 18F-sodium-fluoride PET/CT for the diagnosis of bone metastases in prostate cancer

OBJECTIVE

To evaluate the diagnostic accuracy of observers with different levels of experience in reading 18F-sodium fluoride (NaF) PET/CT images for the diagnosis of bone metastases in prostate cancer (PCa) patients.

METHODS

Nine observers with varying NaF PET/CT experience, ranging from no experience to 2000+ examinations, evaluated 211 NaF PET/CT scans from PCa patients participating in one of four prospective trials. Each observer evaluated each NaF PET/CT on a patient level using a trichotomous scale: M0 (no bone metastases), Me (equivocal for bone metastases) and M1 (bone metastases). Subsequently, a dichotomous evaluation was conducted (M0/M1). The final diagnosis was retrieved from the original study. For each observer, ROC curves and the diagnostic accuracy were calculated based on dichotomous and trichotomous scales; in the latter case, Me was first regarded as M1 and then M0.

RESULTS

Across all experience levels, the sensitivity, specificity and accuracy using the dichotomous scale ranged from 0.81 to 0.89, 0.93 to 1.00 and 0.91 to 0.94, respectively. Employing the trichotomous scale, novice and experienced observers chose Me in up to 20 vs. 10% of cases, respectively. Considering Me as M0, the sensitivity, specificity and accuracy ranged from 0.78 to 0.89, 0.95 to 1.00 and 0.91 to 0.95, respectively. Considering Me as M1, the sensitivity, specificity and accuracy ranged from 0.86 to 0.92, 0.71 to 0.96 and 0.77 to 0.94, respectively.

CONCLUSION

Novice observers used the equivocal option more frequently than observers with NaF PET/CT experience. However, on the dichotomous scale, all observers exhibited high and satisfactory accuracy for the detection of bone metastases, making NaF PET/CT an effective imaging modality even in unexperienced hands.

Impact of 18F-DCFPyL PET on Staging and Treatment of Unfavorable Intermediate or High-Risk Prostate Cancer

Background Data regarding 2-(3-{1-carboxy-5-[(6-[¹⁸F]fluoro-pyridine 3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (¹⁸F-DCFPyL) PET in primary staging of prostate cancer (PCa) are limited. Purpose To compare the performance of ¹⁸F-DCFPyL PET/CT or PET/MRI (PET) with bone scan and CT with or without multiparametric MRI (hereafter, referred to as conventional imaging) in the initial staging of men with unfavorable intermediate or high-risk PCa and to assess treatment change after PET. Materials and Methods This prospective study evaluated men with biopsy-proven, untreated, unfavorable intermediate or high-risk PCa with 0 to four metastases or equivocal for extensive metastases (more than four) who underwent PET between May 2018 and December 2020. The diagnostic performance of PET in detecting pelvic nodal and distant metastases was compared with conventional imaging alone. Metastatic sites at conventional imaging and PET were compared with a composite reference standard including histopathologic analysis, correlative imaging, and/or clinical and biochemical follow-up. The intended treatment before PET was compared with the treatment plan established after performing PET. Detection rate, sensitivity, and specificity of conventional imaging and PET were compared by using McNemar exact test on paired proportions. Results The study consisted of 108 men (median age, 66 years; IQR, 61-73 years) with no metastases (n = 84), with oligometastases (four or fewer metastases; 22 men), or with equivocal findings for extensive metastases (n = 2). Detection rates at PET and conventional imaging for nodal metastases were 34% (37 of 108) and 11% (12 of 108) (P < .001), respectively, and those for distant metastases were 22% (24 of 108) and 10% (11 of 108) (P = .02), respectively. PET altered stage in 43 of 108 (40%) and treatment in 24 of 108 (22%) men. The most frequent treatment change was from systemic to local-regional therapy in 10 of 108 (9%) and from local-regional to systemic therapy in nine of 108 (8%) men. Equivocal findings were encountered less frequently with PET (one of 108; 1%) than with conventional imaging (29 of 108; 27%). Conclusion Initial staging with 2-(3-{1-carboxy-5-[(6-[¹⁸F]fluoro-pyridine 3-carbonyl)-amino]-pentyl}-ureido)-pentanedioic acid (¹⁸F-DCFPyL) PET after conventional imaging (bone scan and CT with or without multiparametric MRI) helped to detect more nodal and distant metastases than conventional imaging alone and changed treatment in 22% of men. Clinical trial registration no. NCT03535831, NCT03718260 © RSNA, 2022 Online supplemental material is available for this article. See also the editorial by Jadvar in this issue.

Impact of patient body habitus on image quality and quantitative value in bone SPECT/CT

OBJECTIVE

The first edition of guidelines for standardization of bone single photon emission computed tomography (SPECT) imaging was published in 2017, and the optimization and standardization are widely promoted. To the purpose, clarification of the factors related to image quality and quantitative values and their influence are required. The present study aimed to clarify and optimize the influence of patient body habitus on image quality and quantitative values in bone SPECT/CT.

METHODS

National Electrical Manufacturers Association body phantom (S-size) and custom-made large body phantoms (M-size and L-size) that simulate the abdomens of Japanese patients weighing 60, 80, and 100 kg, were used. Each phantom was filled with ^99mTc-solutions of 108  and 18 kBq/mL for the hot spheres and background, respectively. Dynamic SPECT acquisition was performed for 6000 s (150 s /rotation × 40 rotation). The data were divided into six projection data and reconstructed each acquisition time (150, 300, 450, 600, 750, 900 s, and single projection 6000 s). Image quality was evaluated for contrast (Q_{H, 17 mm}), background noise (N_{B, 17 mm}), contrast-to-noise ratio (CNR), maximum standardized uptake value (SUV_{max, 17 mm}), and visual assessment for a 17 mm hot sphere.

RESULTS

Image quality in the 300 s acquisition showed that values of Q_{H, 17 mm}, CNR, and SUV_{max, 17 mm} decreased (-16.7%, -11.8%, and -11.3%) for M-size and (-28.2%, -30.1%, and -21.7%) for L-size compared with S-size, respectively. No significant difference was observed in N_{B, 17 mm} values. M-size and L-size required 1.2 and 2.3 times longer acquisition, to achieve same CNR as S-size. In visual assessment, 17 mm hot sphere could not be detected only in the L-size. When the Japanese bone SPECT guidelines criteria were applied in 600 s, the sphere could be detected between all phantoms.

CONCLUSIONS

Patient body habitus significantly affects image quality and decreases the quantitative value in bone SPECT/CT. For the optimization, extend acquisition time according to the patient body habitus is effective for image quality. And for the standardization, it is important to achieve imaging conditions that meet the Japanese bone SPECT guidelines criteria to ensure adequate detectability.

Whole Skeletal Mean SUV Measured on 18F-NaF PET/CT Studies as a Prognostic Indicator in Patients with Bone Metastatic Breast Cancer

In this work we assessed the association between the whole skeletal mean standardized uptake value (SUV) measured on 18F-NaF PET/CT studies and the overall survival (OS) of bone metastatic breast cancer patients. Methods: We retrospectively analyzed 176 patients with breast cancer and bone metastatic disease who performed 18F-NaF PET/CT studies. The outcomes of the patients (dead or alive) were established based on the last information available on their files. The mean and maximum SUVs were measured in a whole skeletal volume of interest (wsVOI). The wsVOI was defined based on the CT component of the PET/CT study using Hounsfield Units thresholds. The wsVOI was then applied on the 18F-NaF PET image. Univariate analyses were performed to assess the association of the SUVs with OS. We also analyzed the association of the age of the patients, the presence of visceral metastatic disease, histological subtypes, presence of hormone receptors, human epidermal growth factor receptor 2 expression and the creatinine, CA15-3 and alkaline phosphatase (ALP) levels with OS. The variables statistically significant in the univariate analyses were included in a multivariate cox regression survival analysis. Results: In the univariate analyses there were associations of the mean and maximum whole skeletal SUVs, estrogen receptor status and the CA15-3 and ALP levels with OS. In the multivariate analysis, all the variables that were statistically significant in the univariate analysis but the CA15-3 were associated with OS. Conclusion: In patients with bone metastatic breast cancer, the whole skeletal mean SUV is an independent predictor of overall survival.

Feasibility of ultra-high-speed acquisition in xSPECT bone algorithm: a phantom study with advanced bone SPECT-specific phantom

OBJECTIVE

Although xSPECT Bone (xB) provides quantitative single-photon emission computed tomography (SPECT) high-resolution images, patients' burden remains high due to long acquisition time; therefore, this study aimed to investigate the feasibility of shortening the xB acquisition time using a custom-designed phantom.

METHODS

A custom-designed xSPECT bone-specific (xSB) phantom with simulated cortical and spongious bones was developed based on the thoracic bone phantom. Both standard- and ultra-high-speed (UHS) xB acquisitions were performed in a male patient with lung cancer. In this phantom study, SPECT was acquired for 3, 6, 9, 12, and 30 min. The clinical SPECT acquisition time per rotation was 9 and 3 min for standard and UHS, respectively. SPECT images were reconstructed using ordered subset expectation maximization with three-dimensional resolution recovery (Flash3D; F3D) and xB algorithms. Quantitative SPECT value (QSV) and coefficient of variation (CV) were measured using the volume of interests (VOIs) placed at the center of the vertebral body and hot sphere. A linear profile was plotted on the spinous process at the center of the xSB phantom; then, the full width at half maximum (FWHM) was measured. The standardized uptake value (SUV) and standard deviation from the first thoracic to the fifth lumbar vertebrae in clinical standard- and UHS-xB images were measured using a 1-cm³ VOI.

RESULTS

The QSV of F3D images was underestimated even in large regions, whereas those of xB images were close to actual radioactivity concentration. The CV was similar or lower for xB images than that for F3D images but was not decreased with increasing acquisition time for both reconstruction images. The FWHM of xB images was lower than those of F3D images at all acquisition times. The mean SUV values from the first thoracic to fifth lumbar vertebrae for standard- and UHS-xB images were 6.73 ± 0.64 and 6.19 ± 0.87, respectively, showing a strong positive correlation.

CONCLUSIONS

Results of this phantom study suggest that xB imaging can be obtained in only one-third of the acquisition time without compromising the image quality. The SUV of UHS-xB images can be similar to that of standard-xB images in terms of clinical interpretation.

Prospective comparison of the diagnostic accuracy of 18F-FDG PET/MRI, MRI, CT, and bone scintigraphy for the detection of bone metastases in the initial staging of primary breast cancer patients

OBJECTIVES

To compare the diagnostic performance of [18F]FDG PET/MRI, MRI, CT, and bone scintigraphy for the detection of bone metastases in the initial staging of primary breast cancer patients.

MATERIAL AND METHODS

A cohort of 154 therapy-naive patients with newly diagnosed, histopathologically proven breast cancer was enrolled in this study prospectively. All patients underwent a whole-body [18F]FDG PET/MRI, computed tomography (CT) scan, and a bone scintigraphy prior to therapy. All datasets were evaluated regarding the presence of bone metastases. McNemar χ2 test was performed to compare sensitivity and specificity between the modalities.

RESULTS

Forty-one bone metastases were present in 7/154 patients (4.5%). Both [18F]FDG PET/MRI and MRI alone were able to detect all of the patients with histopathologically proven bone metastases (sensitivity 100%; specificity 100%) and did not miss any of the 41 malignant lesions (sensitivity 100%). CT detected 5/7 patients (sensitivity 71.4%; specificity 98.6%) and 23/41 lesions (sensitivity 56.1%). Bone scintigraphy detected only 2/7 patients (sensitivity 28.6%) and 15/41 lesions (sensitivity 36.6%). Furthermore, CT and scintigraphy led to false-positive findings of bone metastases in 2 patients and in 1 patient, respectively. The sensitivity of PET/MRI and MRI alone was significantly better compared with CT (p < 0.01, difference 43.9%) and bone scintigraphy (p < 0.01, difference 63.4%).

CONCLUSION

[18F]FDG PET/MRI and MRI are significantly better than CT or bone scintigraphy for the detection of bone metastases in patients with newly diagnosed breast cancer. Both CT and bone scintigraphy show a substantially limited sensitivity in detection of bone metastases.

KEY POINTS

• [18F]FDG PET/MRI and MRI alone are significantly superior to CT and bone scintigraphy for the detection of bone metastases in patients with newly diagnosed breast cancer. • Radiation-free whole-body MRI might serve as modality of choice in detection of bone metastases in breast cancer patients.

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.

Correlation between 18F-FDG PET/CT and diffusion-weighted MRI parameters in head and neck squamous cell carcinoma at baseline and after chemo-radiotherapy. A retrospective single institutional study

OBJECTIVES

The relationship between glucose metabolism and tumor cellularity before chemo-radiotherapy in patients with head and neck squamous cell carcinoma (SCC) has never been compared with that of patients evaluated after treatment. This retrospective study analyzed the correlation between glucose metabolism parameters expressed by standardized uptake value (SUV) derived from 18F-fluorodeoxyglucose (18F-FDG) PET/CT and cellularity tumor parameters expressed by apparent diffusion coefficients (ADC) derived from diffusion-weighted (DW) MRI in untreated and treated patients with head and neck SCC.

METHODS

In 19 patients with no previous exposure to any treatment and 17 different chemo-radiotreated patients with head and neck SCC, we correlated the semi-quantitative uptake values (SUVmax, SUVpeak, and SUVmean) with the ADC functional parameters (ADCmin, ADCmean) including the standard deviation of ADC values (ADCsd).

RESULTS

No significant correlation was found between glucose metabolism parameters and ADCmin or ADCmean in untreated and treated patient groups. However, in untreated patients, significant inverse correlations were found between ADCsd and SUVmax (P = 0.039, r = -0.476), SUVpeak (P = 0.003, r = -0.652) and SUVmean (P = 0.039, r = -0.477). Analyses after chemo-radiotherapy in 17 patients showed no significant correlation between glucose metabolism parameters and DW MRI values, excluding a persistent significant (but lower intensity) inverse correlation between SUVpeak and ADCsd (P = 0.033, r = -0.519).

CONCLUSIONS

The demonstrated relationships suggest complex interactions especially between metabolic activity and heterogeneity of tumoral tissue, which might play a complementary role in the assessment of head and neck SCC.

TRIAL DATE OF REGISTRATION AND REGISTRATION NUMBER

Our retrospective study was registered on April 9th, 2020 by the Ethics Committee of the Coordinating Center "Area Vasta Nord Ovest" (CEAVNO) with Registration Number CEAVNO09042020.

Bone Metastasis Detection in the Chest and Pelvis from a Whole-Body Bone Scan Using Deep Learning and a Small Dataset

The aim of this study was to establish an early diagnostic system for the identification of the bone metastasis of prostate cancer in whole-body bone scan images by using a deep convolutional neural network (D-CNN). The developed system exhibited satisfactory performance for a small dataset containing 205 cases, 100 of which were of bone metastasis. The sensitivity and precision for bone metastasis detection and classification in the chest were 0.82 ± 0.08 and 0.70 ± 0.11, respectively. The sensitivity and specificity for bone metastasis classification in the pelvis were 0.87 ± 0.12 and 0.81 ± 0.11, respectively. We propose the use of hard example mining for increasing the sensitivity and precision of the chest D-CNN. The developed system has the potential to provide a prediagnostic report for physicians’ final decisions.

Molecular imaging in MSK radiology: Where are we going?

Musculoskeletal (MSK) pathologies are one of the leading causes of disability worldwide. However, treatment options and understanding of pathogenetic processes are still partially unclear, mainly due to a limited ability in early disease detection and response to therapy assessment. In this scenario, thanks to a strong technological advancement, structural imaging is currently established as the gold-standard of diagnosis in many MSK disorders but each single diagnostic modality (plain films, high-resolution ultrasound, computed tomography and magnetic resonance) still suffer by a low specificity regarding the characterization of inflammatory processes, the quantification of inflammatory activity levels, and the degree of response to therapy. To overcome these limitations, molecular imaging techniques may play a promising role. Starting from the strengths and weaknesses of structural anatomical imaging, the present narrative review aims to highlight the promising role of molecular imaging in the assessment of non-neoplastic MSK diseases with a special focus on its role to monitor treatment response.

The clinical effectiveness of reconstructing 18F-sodium fluoride PET/CT bone using Bayesian penalized likelihood algorithm for evaluation of metastatic bone disease in obese patients

OBJECTIVE

A new Bayesian penalized likelihood reconstruction algorithm for positron emission tomography (PET) (Q.Clear) is now in clinical use for fludeoxyglucose (FDG) PET/CT. However, experience with non-FDG tracers and in special patient populations is limited. This pilot study aims to compare Q.Clear to standard PET reconstructions for ¹⁸F sodium fluoride (¹⁸F-NaF) PET in obese patients.

METHODS

30 whole body ¹⁸F-NaF PET/CT scans (10 patients with BMI 30-40 Kg/m² and 20 patients with BMI >40 Kg/m²) and a NEMA image quality phantom scans were analyzed using ordered subset expectation maximization (OSEM) and Q.Clear reconstructions methods with B400, 600, 800 and 1000. The images were assessed for overall image quality (IQ), noise level, background soft tissue, and lesion detectability, contrast recovery (CR), background variability (BV) and contrast-to-noise ratio (CNR) for both algorithms.

RESULTS

CNR for clinical cases was higher for Q.Clear than OSEM (p < 0.05). Mean CNR for OSEM was (21.62 ± 8.9), and for Q.Clear B400 (31.82 ± 14.6), B600 (35.54 ± 14.9), B800 (39.81 ± 16.1), and B1000 (40.9 ± 17.8). As the β value increased the CNR increased in all clinical cases. B600 was the preferred β value for reconstruction in obese patients. The phantom study showed Q.Clear reconstructions gave lower CR and lower BV than OSEM. The CNR for all spheres was significantly higher for Q.Clear (independent of β) than OSEM (p < 0.05), suggesting superiority of Q.Clear.

CONCLUSION

This pilot clinical study shows that Q.Clear reconstruction algorithm improves overall IQ of ¹⁸F-NaF PET in obese patients. Our clinical and phantom measurement results demonstrate improved CNR and reduced BV when using Q.Clear. A β value of 600 is preferred for reconstructing ¹⁸F-NaF PET/CT with Q.Clear in obese patients.

ADVANCES IN KNOWLEDGE

¹⁸F-NaF PET/CT is less susceptible to artifacts induced by body habitus. Bayesian penalized likelihood reconstruction with¹⁸F-NaF PET improves overall IQ in obese patients.

Is 67gallium dead? A retrospective review of 67gallium imaging in a single tertiary referral centre

BACKGROUND

[67Ga]Ga-citrate scanning has been used to investigate patients with known or suspected infection for over 50 years, continuing to maintain a clinical niche in many centres. The introduction of single photon emission tomography/computed tomography (SPECT/CT) in addition to planar imaging has improved the specificity of diagnosis.

AIM

To examine the experience of modern [67Ga]Ga-citrate scanning in a single tertiary referral centre, considering the diagnostic yield of the study.

METHODS

A retrospective audit was undertaken of 100 consecutive [67Ga]Ga-citrate scans at Royal North Shore Hospital, Sydney. Recorded information included patient demographics, clinical information/history, and primary and secondary diagnoses. Subgroup analyses included patients with a confirmed diagnosis of infection or a suspected diagnosis of infection.

RESULTS

The median age of patients was 68.5 years. Totally, 39/100 patients undergoing [67Ga]Ga-citrate scanning presented with a confirmed site of infection, with 2/6 patients with infective endocarditis and 5/12 patients with bacteraemia diagnosed with an additional, previously unknown, site of active infection (compared to 1/21 patients without documented bacteraemia). 61/100 patients did not have a confirmed site of infection before [67Ga]Ga-citrate scan (as per clinical history). 34/61 of these patients had a positive scan result for active infection/inflammation. Of 20 patients with a positive blood culture but no suspected site of infection, the source was identified in 9.

CONCLUSION

[67Ga]Ga-citrate has diagnostic value in the evaluation of complex patients with high-risk infection. High diagnostic yield is demonstrated in patients with bacteraemia with or without a confirmed site of infection, particularly when combined with SPECT/CT.

Burden of metastatic bone disease measured on 18F-NaF PET/computed tomography studies as a prognostic indicator in patients with medullary thyroid cancer

PURPOSE

The aim of the study was to assess the association between the burden of metastatic bone disease measured on F-NaF PET/computed tomography (CT) studies and the overall survival (OS) of patients with medullary thyroid cancer (MTC).

METHODS

We retrospectively analyzed 31 patients with MTC who performed 18F-NaF PET/CT studies to assess skeletal metastases. The outcomes of the patients (dead or alive) were established based on the last information available on their files. In the studies considered positives for skeletal metastases, the burden of metastatic bone disease was established calculating the fluoride tumor volume (FTV). The FTV was defined using isocontour thresholds based on percentages of maximal standardized uptake values (SUVmax) in the lesions. These percentages varied from lesion to lesion and were established by visual analysis. The patients were divided into three groups as follows: without skeletal metastases (n = 11), with low FTV (≤50 cm; n = 11) and with high FTV (>50cm; n = 9). The Kaplan-Meier curves were used to analyze the OS in the three groups of patients and the log-rank test was used to determine the statistical significance of the difference between the groups.

RESULTS

There were statistically significant differences in the OS between the group with high FTV and the groups of patients with low FTV (P = 0.036) and without skeletal metastases (P = 0.001). There was not a statistically significant difference between the groups of patients with low FTV and without skeletal metastases (P = 0.147).

CONCLUSION

In patients with MTC, the burden of metastatic bone disease is associated with OS.

Bone single-photon emission computed tomography/computed tomography in cancer care in the past decade: a systematic review and meta-analysis as well as recommendations for further work

Skeletal whole-body scintigraphy (WBS), although widely used as a sensitive tool for detecting metastatic bone disease in oncology cases, has relatively low specificity. Indeterminate bone lesions (IBLs) detected by WBS cause a diagnostic dilemma, which hampers further management plans. In the advent of hybrid imaging, single-photon emission computed tomography/computed tomography (SPECT/CT) has been gaining popularity as a tool to improve the characterisation of IBLs detected by WBS. As yet, there has not been a systematic review to objectively evaluate the diagnostic capabilities of SPECT/CT in this area. We conducted a systematic review of relevant electronic databases up to 30 August 2020. The outcomes of interest were the reporting of SPECT/CT to identify benign and malignant IBLs and the calculation of the sensitivity and specificity of the index test, based on histopathological examination or clinical and imaging follow-up as the reference standard. After the risk of bias and eligibility assessment, 12 articles were identified and synthesised in the meta-analysis. The pooled sensitivity and specificity of SPECT/CT for diagnosing IBLs are 93.0% [95% confidence interval (CI) 0.91-0.95] and 96.0% (95% CI 0.94-0.97), respectively. There was heterogeneity of the articles due to variable imaging protocols, duration of follow-up and scoring methods for interpreting the SPECT/CT results. The heterogeneity poses a challenge for accurate interpretation of the true diagnostic capability of SPECT/CT. In conclusion, targeted SPECT/CT improves the specificity of diagnosing bone metastases, but efforts need to be made to standardise the thresholds for SPECT/CT, methodology, as well as harmonising the reporting and interpretation criteria. We also make some recommendations for future works.

Comparison of 18F-NaF PET/CT with Other Imaging Methods in the Detection of Bone Metastases in Patients with Medullary Thyroid Cancer: a Report of a Series of 31 Cases

PURPOSE

To compare the 18F-NaF PET/CT studies (18F-NaF) with other imaging methods in the detection of skeletal metastases (SM) in patients with medullary thyroid cancer (MTC).

METHODS

We retrospectively analyzed 31 patients with MTC who performed 18F-NaF to assess SM. The results of the 18F-NaF were compared with other imaging methods performed for metastasis detection: 99Tc-MDP bone scan (BS), magnetic resonance imaging (MRI), contrast-enhanced CT (CT), and 68Ga-Dotatate and 18F-FDG PET/CT studies. A qualitative analysis comparing the 18F-NaF findings with the ones of the other methods was performed, and the results were classified as superior (>), equal (=), and inferior (<).

RESULTS

Eleven patients had no bone metastases detected on any of the imaging methods used. Twenty patients presented SM depicted on 18F-NaF. Of these 20 patients, 12 performed bone scan (in 9 18F-NaF > BS and in 3 18F-NaF = BS), 1 performed 18F-FDG (18F-NaF > 18F-FDG), 4 performed 68Ga-Dotatate (in 2 18F-NaF > 68Ga-Dotatate and in 2 18F-NaF = 68Ga-Dotatate), 20 performed CT of at least one body segment (in 15 18F-NaF = CT and in 5 18F-NaF > CT), and 16 performed MRI of at least one body segment, and in all of them, the 18F-NaF was equal to the MRI. Beside this, the 18F-NaF detected SM in body segments not routinely scanned in MRI and CT.

CONCLUSION

In patients with MTC, the 18F-NaF seems to be equal or superior to other imaging modalities in the detection of SM and allows the analysis of the whole skeletal in a single study.

Clinical value of dual-phase F-18 sodium fluoride PET/CT for diagnosing bone metastasis in cancer patients with solitary bone lesion

Background

The present study aimed to investigate whether dual-phase F-18 sodium-fluoride (NaF) positron emission tomography/computed tomography (PET/CT) could improve the diagnostic accuracy of detecting bone metastasis in cancer patients with a solitary bone lesion compared to conventional F-18 NaF PET/CT.

Methods

We retrospectively enrolled 113 cancer patients who underwent dual-phase F-18 NaF PET/CT for the differential diagnosis of a solitary bone lesion seen on bone scintigraphy. According to the dual-phase PET/CT protocol, an early-phase scan was acquired immediately after radiotracer injection and a conventional F-18 NaF PET/CT scan was performed. The diagnostic abilities of the visual analysis of conventional and dual-phase PET/CT scans and two quantitative parameters (lesion-to-blood pool uptake ratio on early-phase scan and lesion-to-bone uptake ratio on conventional scan) for detecting bone metastasis were compared. The final diagnosis of bone metastasis was made by histopathological confirmation or follow-up imaging studies.

Results

A metastatic bone lesion was diagnosed in 28 patients (24.8%). The sensitivity, specificity, and accuracy were 100.0%, 70.6%, and 77.9%, respectively, for visual analysis of conventional F-18 NaF PET/CT, 92.9%, 42.4%, 54.9%, respectively, for lesion-to-bone uptake ratio, 96.4%, 88.2%, and 90.3%, respectively, for visual analysis of dual-phase PET/CT, and 92.9%, 81.2%, and 83.2%, respectively, for lesion-to-blood pool uptake ratio. Visual analysis of dual-phase PET/CT was shown to have the highest area under the receiver operating characteristic curve value (0.923; 95% CI, 0.858-0.965) among all parameters.

Conclusions

Dual-phase F-18 NaF PET/CT showed a high diagnostic ability for detecting bone metastasis with improved specificity and accuracy compared to conventional F-18 NaF PET/CT in cancer patients. Dual-phase F-18 NaF PET/CT might help diagnose bone metastasis in patients with malignancies who were shown to have a solitary bone lesion on bone scintigraphy.

Observer agreement and accuracy of 18F-sodium fluoride PET/computed tomography in the diagnosis of skull-base bone invasion and osseous metastases in newly diagnosed nasopharyngeal carcinoma

OBJECTIVES

To evaluate the interobserver agreement and the diagnostic performance in F-sodium fluoride (F-NaF) PET/computed tomography (CT) for the detection of skull-base bone invasion (SBBI) and osseous metastases in patients with newly diagnosed nasopharyngeal carcinoma (NPC).

METHODS

One hundred seventeen patients with newly diagnosed NPC between 2017 and 2019 who underwent F-NaF PET/CT was in included. Two experienced observers independently evaluated the F-NaF PET/CT of SBBI and osseous metastases on a patient level using a two-category scale present on a dichotomous scale, respectively. On a patient level, the diagnostic performance was calculated using a sensitivity analysis.

RESULTS

The interobserver agreement on a patient level of SBBI and osseous metastases were perfect on a patient-level (κ: 0.85), (κ: 0.808), respectively. On a lesion level of detection of osseous metastases, the observers agreed on the number as well as the location of osseous metastases in 101 (86.3%) patients. The sensitivity, specificity, accuracy, positive predictive value, and negative predictive value of detection of SBBI and osseous metastases were ranged 0.911-0.962, 0.921-0.974, 0.932-0.957, 0.962-0.986, and 0.841-0.923, and ranged 0.917-0.958, 0.899-0.957, 0.906-0.949, 0.863-0.936, and 0.939-0.970, respectively.

CONCLUSION

The interobserver agreement of F-NaF PET/CT for the detection of SBBI and osseous metastases in patients with NPC were both very high among trained observers. Moreover, the diagnostic performance of NaF PET/CT was satisfactory, rendering NaF PET/CT a robust tool in the diagnostic armamentarium.

Inter- and intraobserver agreement in standard and ultra-fast single-photon emission computed tomography/computed tomography for the assessment of bone metastases

OBJECTIVE

To investigate inter- and intraobserver agreement using standard (std)-single-photon emission computed tomography/computed tomography (SPECT/CT) or ultra-fast acquisition (UF)-SPECT/CT as an add-on to planar whole-body bone scintigraphy (WB-BS) for the detection of bone metastases in patients with known cancer.

METHODS

Images from patients (n = 104) participating in a prospective trial comparing SPECT/CT as an add-on to WB-BS with two different acquisition methods (std-SPECT/CT; 20 s per view, 32 views and UF-SPECT/CT; 16 views of 10 s per view) were included. The combinations of WB-BS with the two different SPECT/CT acquisition methods were independently evaluated by two experienced observers using a three-point scale (M0: no metastases, Me: equivocal for bone metastases and M1: bone metastases). The observers re-evaluated the scans 6 months later. Inter- and intraobserver agreement was calculated using linear weighted kappa.

RESULTS

The linear weighted kappa for the interobserver agreement was 0.78 [95% confidence interval (CI) 0.61-0.94] for WB-BS with std-SPECT/CT and 0.84 (95% CI 0.67-1.00) for WB-BS with UF-SPECT/CT. Similar values were observed for the intraobserver agreement, in which the linear weighted kappa was 0.76 (95% CI 0.60-0.92) and 0.73 (95% CI 0.57-0.90) for std-SPECT/CT and UF-SPECT/CT, respectively.

CONCLUSION

Satisfactory inter- and intraobserver agreement was seen for both acquisition methods, emphasizing that the use of SPECT/CT as an add-on to WB-BS is a robust method for the detection of bone metastases even when conducted with a very short acquisition time.

The Value of 68Ga-PSMA PET/CT Following Equivocal 18F-NaF PET/CT in Prostate Cancer Patients

Background: Inconclusive bone scans are a challenge but there is no consensus about follow-up imaging. We evaluated the use of ⁶⁸gallium-labelled prostate-specific membrane antigen (⁶⁸Ga-PSMA) PET/CT if ¹⁸F-sodium fluoride (¹⁸F-NaF) PET/CT was inconclusive. Methods: This retrospective study included patients with no previously known bone metastases who had one or more equivocal bone lesions on ¹⁸F-NaF PET/CT and underwent additional ⁶⁸Ga-PSMA PET/CT. The bone lesions were deemed as true metastases or not based on follow-up by surveying supplemental imaging modalities and hospital records. A subgroup of patients with “most valid follow-up” was created, which included patients with unmeasurable PSA after prostatectomy or subsequent imaging (additional ¹⁸F-NaF PET/CT, ⁶⁸Ga-PSMA PET/CT, CT, or MRI). Results: Of the 2918 patients referred for ¹⁸F-NaF PET/CT from the department of urology in the inclusion period, 51 (1.7%) were inconclusive regarding bone metastases and underwent additional ⁶⁸Ga-PSMA PET/CT. Thirteen of these patients (25%) were ultimately diagnosed with bone metastases. Patient-based sensitivity, specificity, and accuracy of additional ⁶⁸Ga-PSMA PET/CT were 100%, 95%, and 96%, respectively. In patients with “most valid follow-up”, the same parameters were 100%, 93%, and 94%, respectively. Conclusion: ⁶⁸Ga-PSMA PET/CT is an excellent complementary modality in when ¹⁸F-NaF PET/CT is equivocal.

Prediction of Response to Tumor Necrosis Value-α Blocker Is Suggested by 18F-NaF SUVmax But Not by Quantitative Pharmacokinetic Analysis in Patients With Ankylosing Spondylitis

OBJECTIVE. We aimed to evaluate the pharmacokinetics and maximum standardized uptake value (SUV_max) of ¹⁸F-NaF PET/CT for assessment of disease activity and prediction of response in patients with ankylosing spondylitis (AS). MATERIALS AND METHODS. Twenty-seven patients (age, interquartile range, 30.25-49.75 years) with AS who were receiving a tumor necrosis factor-α (TNF-α) blocker were included. All patients underwent dynamic PET of the pelvis followed by whole-body PET/CT. Quantitative analysis of kinetic data of the sacroiliac joints (SIJs) was performed, and the SUV_max of the SIJs and SUV_max of the spine were calculated. Clinical indexes related to AS disease activity (serum C-reactive protein level, Bath ankylosing spondylitis disease activity index [ BASDAI], and Bath ankylosing spondylitis functional index) were evaluated. Clinical response was defined as an improvement from the initial BASDAI score of 50% or more (BASDAI 50) within 2 years after baseline ¹⁸F-NaF PET/CT. RESULTS. The BASDAI score at ¹⁸F-NaF PET/CT was significantly different between the responders and nonresponders: ¹⁸F-NaF uptake at the spine was significantly higher in the responders than in the nonresponders. Only SUV_max of the spine had a significant positive correlation with BASDAI score at PET/CT (r = 0.38, p = 0.048). The BASDAI score at PET/CT (odds ratio [OR], 35.32; 95% CI, 2.09-57.84; p = 0.014) and SUV_max of the spine (OR, 14.69; 95% CI, 0.79-27.27; p = 0.027) were significantly associated with BASDAI 50 response prediction. CONCLUSION. The results of our study suggest that the SUV_max of the spine on whole-body ¹⁸F-NaF PET/CT is a reliable and noninvasive biomarker for predicting therapeutic response to TNF-α blocker and shows better performance for predicting response than quantitative pharmacokinetic parameters. Fluorine-18-labeled NaF PET/CT showed axial bone lesions with bone formation and can be used as a monitoring tool in patients with AS receiving anti-TNF-α drugs. However, these results need to be validated in a larger cohort.

Added value of 68Ga-PSMA PET/CT for the detection of bone metastases in patients with newly diagnosed prostate cancer and a previous 99mTc bone scintigraphy

Purpose

To investigate the added value and diagnostic accuracy of ⁶⁸Ga-PSMA PET/CT versus bone scintigraphy (BS) for bone metastasis detection at the primary staging of prostate cancer (PCa).

Methods

Inclusion criteria involved consecutive patients with newly diagnosed intermediate- to high-risk PCa, who had undergone BS, mostly with supplementary SPECT/low-dose CT, and ⁶⁸Ga-PSMA-11 PET/CT within less than 3 months without therapy initiation between the two investigations. BS was evaluated according to clinical routine and reported as no bone metastases (M0), bone metastases (M1), or equivocal (Me). The ⁶⁸Ga-PSMA-11 PET/CT was blindly evaluated by three specialists as M0, M1, or Me at the patient level. Sensitivity analyses were conducted using a “best valuable comparator” using all available imaging and clinical follow-up as a reference.

Results

In total, 112 patients were included; ⁶⁸Ga-PSMA-11 PET/CT showed a sensitivity of 1.00, specificity of 0.93–0.96, positive predictive value of 0.74–0.81, and negative predictive value of 1.00. ⁶⁸Ga-PSMA-11 PET/CT revealed bone metastases in 8 of 81 patients with M0 disease according to BS. ⁶⁸Ga-PSMA-11 PET/CT confirmed the presence of bone metastases in all patients (n = 9) with M1 disease according to BS. In patients with Me by BS, ⁶⁸Ga-PSMA PET/CT provided a definite result in 20 of 22 patients. ⁶⁸Ga-PSMA-11 PET/CT resulted in a false-positive answer in four patients with solitary rib lesions.

Conclusion

⁶⁸Ga-PSMA-11 PET/CT revealed bone metastases in 10% of patients without bone metastases on BS and in 36% patients with indeterminate BS. However, solitary PSMA-avid lesions in the ribs should be interpreted cautiously as they may represent false-positive findings.

Non-FDG PET/CT in Diagnostic Oncology: a pictorial review

Positron emission tomography/computed tomography (PET/CT) is currently one of the main imaging modalities for cancer patients worldwide. Fluorodeoxyglucose (FDG) PET/CT has earned its global recognition in the modern management of cancer patients and is rapidly becoming an important imaging modality for patients with cardiac, neurological, and infectious/inflammatory conditions.

Despite its proven benefits, FDG has limitations in the assessment of several relevant tumours such as prostate cancer. Therefore, there has been a pressing need for the development and clinical application of different PET radiopharmaceuticals that could image these tumours more precisely. Accordingly, several non-FDG PET radiopharmaceuticals have been introduced into the clinical arena for management of cancer. This trend will undoubtedly continue to spread internationally. The use of PET/CT with different PET radiopharmaceuticals specific to tumour type and biological process being assessed is part of the personalised precision medicine approach.

The objective of this publication is to provide a case-based method of understanding normal biodistribution, variants, and pitfalls, including several examples of different imaging appearances for the main oncological indications for each of the new non-FDG PET radiopharmaceuticals. This should facilitate the interpretation and recognition of common variants and pitfalls to ensure that, in clinical practice, the official report is accurate and helpful.

Some of these radiopharmaceuticals are already commercially available in many countries (e.g. ⁶⁸Ga-DOTATATE and DOTATOC), others are in the process of becoming available (e.g. ⁶⁸Ga-PSMA), and some are still being researched. However, this list is subject to change as some radiopharmaceuticals are increasingly utilised, while others gradually decrease in use.

Observer Agreement and Accuracy of 18F-Sodium Fluoride PET/CT in the Diagnosis of Bone Metastases in Prostate Cancer

Our aim was to evaluate the interobserver agreement in ¹⁸F-sodium fluoride (NaF) PET/CT for the detection of bone metastases in patients with prostate cancer (PCa). Methods: ¹⁸F-NaF PET/CT scans were retrieved from all patients who participated in 4 recent prospective trials. Two experienced observers independently evaluated the ¹⁸F-NaF PET/CT scans on a patient level using a 3-category scale (no bone metastases [M0], equivocal for bone metastases, and bone metastases present [M1]) and on a dichotomous scale (M0/M1). In patients with no more than 10 lesions, the location and number of lesions were recorded. On a patient level, the diagnostic performance was calculated using a sensitivity analysis, in which equivocal lesions were handled as M0 as well as M1. Results: ¹⁸F-NaF PET/CT scans from 219 patients with PCa were included, of whom 129 patients were scanned for primary staging, 67 for biochemical recurrence, and 23 for metastatic castration-resistant PCa. Agreement between the observers was almost perfect on a patient level (3-category unweighted κ = 0.83 ± 0.05, linear weighted κ = 0.90 ± 0.06, and dichotomous κ = 0.91 ± 0.07). On a lesion level (dichotomous scale), the observers agreed on the number and location of bone metastases in 205 (93.6%) patients. In the remaining 14 patients, the readers disagreed on the number of lesions in 13 patients and the location of bone metastases in 1 patient. A final diagnosis of bone metastases was made for 211 of 219 patients. The sensitivity ranged from 0.86 to 0.92, specificity from 0.83 to 0.97, positive predictive value from 0.70 to 0.93, and negative predictive value from 0.94 to 0.96. Conclusion: The interobserver agreement on ¹⁸F-NaF PET/CT for the detection of bone metastases in patients with PCa was very high among trained observers, both on a patient level and on a lesion level. Moreover, the diagnostic performance of ¹⁸F-NaF PET/CT was satisfactory, rendering ¹⁸F-NaF PET/CT a robust tool in the diagnostic armamentarium.

Multimodality Imaging of Prostate Cancer

Prostate cancer is a very heterogeneous disease, and contemporary management is focused on identification and treatment of the prognostically adverse high-risk tumors while minimizing overtreatment of indolent, low-risk tumors. In recent years, imaging has gained increasing importance in the detection, staging, posttreatment assessment, and detection of recurrence of prostate cancer. Several imaging modalities including conventional and functional methods are used in different clinical scenarios with their very own advantages and limitations. This continuing medical education article provides an overview of available imaging modalities currently in use for prostate cancer followed by a more specific section on the value of these different imaging modalities in distinct clinical scenarios, ranging from initial diagnosis to advanced, metastatic castration-resistant prostate cancer. In addition to established imaging indications, we will highlight some potential future applications of contemporary imaging modalities in prostate cancer.

Molecular imaging of bone metastases using bone targeted tracers

Molecular imaging using bone targeted tracers has been used in clinical practice for almost fifty years and still plays an essential role in the diagnosis and follow-up of bone metastases. It includes both [99mTc]bisphosphonates for bone scan and [18F]NaF for positron emission tomography/computed tomography (PET/CT) which are very sensitive to detect osteoblastic activity, but it is important to consider several aspects to increase the specificity of reported findings (such as specific tracer characteristics and mechanism of action, patient's clinical history, common metastatic patterns, changes after treatment, limitations of the technique, variations and pitfalls). This will enable useful information for clinical management being provided in the report. Furthermore, iatrogenic skeletal adverse events are common and they should also be identified, as they have impact on patient's quality of life. This review makes a brief summary of the mechanism of action of bone targeted tracers, followed by a discussion of classic patterns of bone metastasis, treatment response assessment and iatrogenic skeletal complications. The value of hybrid imaging techniques with bone targeted tracers, including single photon emission computed tomography and PET/CT is also explored. The final part summarizes new bone targeted tracers with superior imaging characteristics that are being developed, and which may further enhance the applications of radionuclide bone imaging.

Consensus on molecular imaging and theranostics in prostate cancer

Rapid developments in imaging and treatment with radiopharmaceuticals targeting prostate cancer pose issues for the development of guidelines for their appropriate use. To tackle this problem, international experts representing medical oncologists, urologists, radiation oncologists, radiologists, and nuclear medicine specialists convened at the European Association of Nuclear Medicine Focus 1 meeting to deliver a balanced perspective on available data and clinical experience of imaging in prostate cancer, which had been supported by a systematic review of the literature and a modified Delphi process. Relevant conclusions included the following: diphosphonate bone scanning and contrast-enhanced CT are mentioned but rarely recommended for most patients in clinical guidelines; MRI (whole-body or multiparametric) and prostate cancer-targeted PET are frequently suggested, but the specific contexts in which these methods affect practice are not established; sodium fluoride-18 for PET-CT bone scanning is not widely advocated, whereas gallium-68 or fluorine-18 prostate-specific membrane antigen gain acceptance; and, palliative treatment with bone targeting radiopharmaceuticals (rhenium-186, samarium-153, or strontium-89) have largely been replaced by radium-223 on the basis of the survival benefit that was reported in prospective trials, and by other systemic therapies with proven survival benefits. Although the advances in MRI and PET-CT have improved the accuracy of imaging, the effects of these new methods on clinical outcomes remains to be established. Improved communication between imagers and clinicians and more multidisciplinary input in clinical trial design are essential to encourage imaging insights into clinical decision making.

Adductor Insertion Avulsion Syndrome with Stress Fracture in Morbidly Obese Patient Diagnosed on 18F-Sodium Fluoride Positron Emission Tomography-Computed Tomography

Adductor insertion avulsion syndrome, also known as “thigh splints,” is a painful condition affecting the proximal to mid-femur at the insertion of the adductor muscles of the thigh. ¹⁸F-Sodium fluoride (¹⁸F-NaF) is increasingly used in diagnosing skeletal pain which is not identified on radiographs. We report a case of a 56-year-old morbidly obese woman with left hip pain referred for ¹⁸F-NaF positron emission tomography–computed tomography (PET-CT) as magnetic resonance imaging cannot be performed due to obesity. ¹⁸F-NaF PET-CT shows an increase in tracer uptake at the posteromedial cortex of the upper shaft of left femur. Findings are likely due to adductor insertion avulsion syndrome. ¹⁸F-NaF provides important diagnostic information that might alter treatment options.

Unsuspected Metastases to Muscles in Osteosarcoma Detected on 18F-Sodium Fluoride PET-CT

Metastasis of osteosarcoma to the muscles is extremely rare. F-sodium fluoride (NaF) is a bone-seeking agent that can also localize extraosseous calcifying lesions. We report the case of a 33-year-old woman with osteosarcoma of the right fibula treated with surgery and chemotherapy 2 years back who was referred for F-NaF PET-CT to evaluate possible metastatic lesions. F-NaF PET-CT unexpectedly detected 2 foci of soft tissue increased tracer uptake in the right lateral abdominal and left paraspinal muscles, which corresponded to the focal calcification in the muscles. The pathological examination revealed metastatic osteosarcoma to the muscles.

The clinical significance of incidental soft tissue uptake on whole body 18F-sodium fluoride bone PET-CT

¹⁸F-sodium fluoride (NaF) is a PET bone imaging agent and is commonly used in imaging patients with cancer; however, similar to technetium-99m medronic acid (^99mTc-MDP), it can be useful in the evaluation of benign bone and joint conditions. NaF is an excellent bone-seeking agent with high bone uptake due to rapid single-pass extraction. It has negligible plasma protein binding, rapid blood, renal clearance, high bone uptake and almost all NaF delivered is retained by bone after a single pass of blood; however, uptake of NaF can be observed in non-osseous structures such as the arterial vasculature, gastrointestinal tract, genitourinary tract, and viscera. In this article, we present a spectrum of clinical cases with non-osseous NaF uptake in patients referred for cancer staging.

Comparison of 18F-NaF PET/CT and 18F-FDG PET/CT for Detection of Skull-Base Invasion and Osseous Metastases in Nasopharyngeal Carcinoma

Our study aimed at comparing the diagnostic value of 18F-NaF positron emission tomography-computed tomography (PET/CT) and 18F-fluorodeoxyglucose (FDG) PET/CT for detection of skull-base invasion and osseous metastases in patients with nasopharyngeal carcinoma (NPC). Our study retrospectively analyzed 45 patients with pathologically proven NPC. They all underwent both 18F-NaF PET/CT and 18F-FDG PET/CT within a 7-day interval. Bone metastases were confirmed by follow-up using PET/CT, enhance-contrast computed tomography (CT), and magnetic resonance image (MRI). These two examinations were compared using per-patient-based analysis and per-lesion-based analysis. 18F-NaF PET/CT detected 27 patients with skull-base invasion, whereas 18F-FDG PET/CT detected 17 patients. 18F-NaF PET/CT and 18F-FDG PET/CT differed significantly in diagnosing skull-base invasion (p=0.02) and sensitivity (p=0.008). The sensitivity, specificity, and agreement rate of 18F-NaF PET/CT for detecting bone metastatic lesions were 98.3%, 65.7%, and 92.9%, respectively; these values were 42.9%, 97.1%, and 51.9%, respectively, for 18F-FDG PET/CT. 18F-NaF PET/CT and 18F-FDG PET/CT differed significantly in the number of osseous metastases detected (t=2.45, p=0.18) sensitivity (p < 0.0001) and specificity (p=0.003). In patients with nasopharyngeal carcinoma, 18F-NaF PET/CT assessed invasion of the skull base better and detected more osseous metastases than 18F-FDG PET/CT.

Advantages of systematic trunk SPECT/CT to planar bone scan (PBS) in more than 300 patients with breast or prostate cancer

PROPOSE

The aim of our study was to evaluate the potential benefit of a systematic trunk SPECT/CT associated with a Planar Bone Scan (PBS) in breast cancer (BC) and prostate cancer (PCa) patients at initial staging or recurrence.

RESULTS

In 328 patients, sensitivities and specificities were between 74.4-93% and 78.8-97.5% for PBS and 97.7-100% and 96.8-98.6% for SPECT/CT respectively. PBS was considered equivocal for 67 compared to only 6 patients for trunk SPECT/CT. Regardless of "optimistic" or "pessimistic" analysis of equivocal trunk SPECT/CT lesions, the trunk SPECT/CT was almost perfect, allowing to rely on this result for excluding metastatic disease which was corroborated by ROC curve analysis. The trunk SPECT/CT allowed downstaging for 62 patients (19%) and upstaging for 11 patients.

MATERIALS AND METHODS

PBS and a trunk SPECT/CT were systematically performed in all patients. Independent review of PBS and trunk SPECT/CT was performed for each patient and an abnormality interpretative score (Sc) with 3 levels was built: Sc 1: metastatic or probably metastatic pattern, Sc 2: equivocal pattern, Sc 3: benign or probably benign pattern or no abnormality. The bone pattern status was defined by at least 1 year follow-up. The clinical impact was evaluated in terms of down and upstaging in patient analysis.

CONCLUSIONS

Trunk SPECT/CT improves the performance of PBS in BC and PCa assessments and results in improvements in both the detection performance of bone metastases as well as a better characterization of equivocal lesions.

Prospective comparative study of 18F-sodium fluoride PET/CT and planar bone scintigraphy for treatment response assessment of bone metastases in patients with prostate cancer

AIM

To compare ¹⁸F-sodium fluoride positron emission tomography/computed tomography (NaF PET/CT) and ^99mTc-labelled diphosphonate bone scan (BS) for the monitoring of bone metastases in patients with prostate cancer undergoing anti-cancer treatment.

MATERIAL AND METHODS

Data from 64 patients with prostate cancer were included. The patients received androgen-deprivation therapy (ADT), next-generation hormonal therapy (NGH) or chemotherapy. The patients had a baseline scan and 1-3 subsequent scans during six months of treatment. Images were evaluated by experienced nuclear medicine physicians and classified for progressive disease (PD) or non-PD according to the Prostate Cancer Working Group 2 (PCWG-2) criteria. The patients were also classified as having PD/non-PD according to the clinical and prostate-specific antigen (PSA) responses.

RESULTS

There was no difference between NaF PET/CT and BS in the detection of PD and non-PD during treatment (McNemar's test, p = .18). The agreement between BS and NaF PET/CT for PD/non-PD was moderate (Cohen's kappa 0.53, 95% confidence interval 0.26-0.79). Crude agreement between BS and NaF PET/CT for the assessment of PD/non-PD was 86% (89% for ADT, n = 28; 88% for NGH, n = 16, and 80% for chemotherapy, n = 20). In most discordant cases, BS found PD when NaF PET/CT did not, or BS detected PD on an earlier scan than NaF PET/CT. Biochemical progression (27%) occurred more frequently than progression on functional imaging (BS, 22% and NaF PET/CT, 14%). Clinical progression was rare (11%), and almost exclusively seen in patients receiving chemotherapy.

CONCLUSION

There was no difference between NaF PET/CT and BS in the detection of PD and non-PD; however, BS seemingly detects PD by the PCWG-2 criteria earlier than NaF-PET, which might be explained by the fact that NaF-PET is more sensitive at the baseline scan.

Technical feasibility, radiation dosimetry and clinical use of 18F-sodium fluoride (NaF) in evaluation of metastatic bone disease in pediatric population

PURPOSE

The role of ¹⁸F-fluoride (¹⁸F-NaF) PET-CT for the detection of bone metastases in adults is well established and is considered superior to conventional bone scintigraphy. However, data pertaining use of ¹⁸F-NaF PET-CT in pediatric oncology is relatively sparse. The aim of the present study is to retrospectively analyze and share a single-center experience of ¹⁸F-NaF PET-CT in pediatric population and to provide preliminary information regarding imaging technique, feasibility of this modality in young patients and radiation dosimetry measurements in pediatric oncology cases.

MATERIALS AND METHODS

Twenty-four pediatric patients (mean age 8.0 ± 3.9) were included in the study for retrospective analysis. All patients were referred for primary staging or restaging for potential osseous metastatic disease and PET-CT scan was performed by injecting 2.2 MBq/kg (0.06 mCi/kg) of ¹⁸F-NaF.

RESULTS

Nine patients were imaged for primary staging and in all cases increase osteoblastic activity was seen in the primary tumor and of these, metastatic bone disease was identified in 2/9 patients. In the restaging group comprising 15/24 patients, metastatic deposits were identified in 3/15 whilst no disease was seen in the remaining 12 patients. Patients were injected a mean dose of 90.35 ± 22.9 MBq with an estimated mean effective absorbed doses of 2.98 ± 0.75 mSv for ¹⁸F-NaF and 3.37 ± 2.4 mSv for CT alone. Mean cumulative effective dose of ¹⁸F-NaF PET-CT scan was 5.11 ± 2.7 mSv.

CONCLUSIONS

¹⁸F-NaF PET-CT may be a feasible alternative to ^99mTc MDP for radionuclide bone scintigraphy in the evaluation of pediatric bone pathology. Due to its better pharmacokinetics, there is potential that osseous staging can be achieved with relatively low doses and with a similar radiation burden as with ^99mTc-MDP imaging.