Quantitative bone SPECT/CT: high specificity for identification of prostate cancer bone metastases

Bone Metastasis in Prostate Cancer: Bone Scan Versus PET Imaging

Prostate cancer is the second most common cause of malignancy among men, with bone metastasis being a significant source of morbidity and mortality in advanced cases. Detecting and treating bone metastasis at an early stage is crucial to improve the quality of life and survival of prostate cancer patients. This objective strongly relies on imaging studies. While CT and MRI have their specific utilities, they also possess certain drawbacks. Bone scintigraphy, although cost-effective and widely available, presents high false-positive rates. The emergence of PET/CT and PET/MRI, with their ability to overcome the limitations of standard imaging methods, offers promising alternatives for the detection of bone metastasis. Various radiotracers targeting cell division activity or cancer-specific membrane proteins, as well as bone seeking agents, have been developed and tested. The use of positron-emitting isotopes such as fluorine-18 and gallium-68 for labeling allows for a reduced radiation dose and unaffected biological properties. Furthermore, the integration of artificial intelligence (AI) and radiomics techniques in medical imaging has shown significant advancements in reducing interobserver variability, improving accuracy, and saving time. This article provides an overview of the advantages and limitations of bone scan using SPECT and SPECT/CT and PET imaging methods with different radiopharmaceuticals and highlights recent developments in hybrid scanners, AI, and radiomics for the identification of prostate cancer bone metastasis using molecular imaging.

The diagnostic value of quantitative bone SPECT/CT in solitary undetermined bone lesions

Objective

To investigate the diagnostic value of the maximum standard uptake value (SUVmax) of quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) in solitary undetermined bone lesions.

Methods

In Part I, retrospective study, 167 untreated patients with extra-skeletal malignant tumors by pathology were consecutively enrolled for staging with Tc-99m methyl-diphosphonate (99mTc-MDP) whole-body bone scan (WBS) and quantitative SPECT/CT, and a total of 396 bone lesions with abnormal radioactivity concentration in 167 patients were included from April 2019 to September 2020. The differences in SUVmax among the benign bone lesions, malignant bone lesions, and normal vertebrae were analyzed. The receiver operating characteristic (ROC) curve and cutoff value of SUVmax were obtained. Part II, prospective study, 49 solitary undetermined bone lesions in SPECT/CT in 49 untreated patients with extra-skeletal malignant tumors were enrolled from October 2020 to August 2022. The diagnostic efficacy of SUVmax in solitary undetermined bone lesions was assessed. The final diagnosis was based on follow-up imaging (CT, MRI, or 2-deoxy-2-[18F]fluoro-D-glucose-positron emission tomography/computed tomography) for at least 12 months.

Results

In Part I, a total of 156 malignant and 240 benign bone lesions was determined; the SUVmax of malignant lesions (26.49 ± 12.63) was significantly higher than those of benign lesions (13.92 ± 7.16) and normal vertebrae (6.97 ± 1.52) (P = 0.00). The diagnostic efficiency of the SUVmax of quantitative SPECT/CT revealed a sensitivity of 75.00% and a specificity of 81.70% at a cutoff value of 18.07. In Part II, 17 malignant and 32 benign lesions were determined. Using SUVmax ≥18.07 as a diagnostic criterion of malignancy, it has a sensitivity of 82.35%, a specificity of 93.75%, and an accuracy of 89.80%.

Conclusion

The SUVmax of quantitative SPECT/CT is valuable in evaluating solitary undetermined bone lesions. Using a cutoff SUVmax value of 18.07, quantitative SPECT/CT demonstrated high sensitivity, specificity, and accuracy in differentiating malignant from benign bone lesions.

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.

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.

A Review on the Usage of Bone Single-Photon Emission Computed Tomography/Computed Tomography in Detecting Skeletal Metastases in the Post-COVID-19 Era: Is it Time to Ditch Planar and Single-Photon Emission Computed Tomography only Gamma Camera Systems?

Planar whole-body bone scanning (WBS) is widely used to evaluate skeletal lesions seen in cancer and noncancer cases. Frequently, degenerative, or other benign bony changes may give rise to indeterminate lesions that mimic bone metastases. In the post-COVID-19 era, there is an evolutionary phase that puts importance on global development and adaptability, which encompasses to include nuclear medicine practices worldwide. Single-photon emission computed tomography/computed tomography (SPECT/CT) can be used to improve the characterization of these lesions and help to resolve the diagnostic conundrum while reducing the need for patients to undergo multiple different examinations at various imaging departments. The fusion of SPECT and CT allows morphological characterization of functional abnormality detected by focal tracer uptake on planar scintigraphy, which provides a one-stop center imaging in nuclear medicine departments. The objective of this study was to review the diagnostic accuracy of SPECT/CT in diagnosing bone metastases in a variety of oncology and nononcology cases and to determine the feasibility of performing bone SPECT/CT in all suspected cancer cases, including cases of bone infection instead of planar imaging alone. The utilization of hybrid SPECT/CT in indeterminate bone lesions detected on planar WBS can significantly increase the diagnostic confidence and accuracy of image interpretation. Recognition of patterns of disease identified using hybrid imaging can improve the management of patients with potentially lower costs in the long term. Currently, hybrid SPECT/CT machines are becoming a norm in nuclear medicine departments, thus potentially making single planar application machines obsolete in the near future. We hypothesize that in the interest of providing a meaningful interpretation of isotope bone scans, the default protocol should involve the option of acquiring SPECT/CT images rather than relying on whole-body scans only. Departments choosing to upgrade existing equipment or those choosing to invest in only one gamma camera should proactively opt for hybrid SPECT/CT systems.

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.

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.

Review of the role of bone-SPECT/CT in tarsal coalitions

Tarsal coalition (TC) is a congenital abnormal connection (fibrous, cartilaginous, or osseous) between two or more bones in the hind and midfoot, mostly consisting of calcaneonavicular or talocalcaneal coalition, and is often asymptomatic. However, TCs may result in foot motion limitation and pain with or without flatfoot (pes planus), arising in adolescents and young adults. Appropriate imaging is needed to pinpoint foot pain in the (suspected) TC, starting with plain radiographs. Still, normal radiographs do not exclude TCs. Computed tomography (CT) and MRI are frequently used advanced imaging techniques. CT alone has known limited sensitivity in cartilaginous and fibrous TCs and correlation between CT abnormalities and pain may be challenging, as solely anatomical changes in TCs are often asymptomatic. MRI can depict soft tissue abnormalities in TC with high accuracy. Nonetheless, after the implantation of metallic osteosynthesis material, MRI is often limited due to image distortion, signal loss, and misregistration. Bone scintigraphy with [99mTc]Tc-diphosphonate single photon emission computed tomography/CT (bone-SPECT/CT) is a known sensitive tool to detect osteoblastic bone pathology. However, the literature concerning bone-SPECT/CT in TC patients is limited. This article reviews bone-SPECT/CT patterns in TCs, how it complements other imaging techniques and their relation to clinical complaints. Bone-SPECT/CT excels in accurate bone pathology characterization in TC, confidently excluding synchronous lesions elsewhere, and offering optimal insight into osseous structures and 3D-localization of bone metabolism for surgery planning. Furthermore, even with implanted osteosynthesis material, bone-SPECT/CT can pinpoint the culprit pain generator, where MRI is either contra-indicated or considerably hampered.

Evaluation of standardized uptake value on 131I-6β-iodomethyl-19-norcholesterol scintigraphy for diagnosis of primary aldosteronism and correspondence with adrenal venous sampling

PURPOSE

Adrenal venous sampling (AVS) is a reliable method for lateralization of adrenal hormone secretion, which is important for discriminating between aldosterone-producing adenoma and bilateral adrenal hyperplasia, both of which cause primary aldosteronism (PA). The aim of this study was to evaluate the diagnostic accuracy of the maximum and mean standardized uptake values (SUV_max and SUV_mean, respectively) of ¹³¹I-6β-iodomethyl-19-norcholesterol (NP-59) single-photon emission computed tomography (SPECT) for PA and its correspondence with AVS.

METHODS

Adrenal NP-59 scintigraphy was performed in 14 patients with suspected PA, and AVS was also performed in 7 of them. SUV_max and SUV_mean of the adrenal lesions on the dominant side and their ratios to the values on the non-dominant side (SUVR_max and SUVR_mean, respectively) were calculated on SPECT images using ordered-subset conjugate gradient minimization (OSCGM) and three-dimensional ordered-subset expectation maximization (3D-OSEM) reconstruction algorithms.

RESULTS

SUV_max and SUV_mean on NP-59 SPECT images were significantly higher for aldosterone-producing adenoma than for bilateral adrenal hyperplasia or non-functioning adenoma and slightly superior to SUVR_max and SUVR_mean (P = 0.0475 and P = 0.0447 vs. P = 0.124 and P = 0.132, respectively, with OSCGM). The respective areas under the receiver-operating characteristic curve for SUV and SUVR were 0.933 and 0.725 with OSCGM and 0.844 and 0.750 with 3D-OSEM, while SUV_max and SUVR_max had exactly the same diagnostic accuracy as SUV_mean and SUVR_mean. SUV and SUVR were associated with the diagnostic features on AVS and consistent with lateralization by AVS in most patients.

CONCLUSION

In this study, SUV on NP-59 SPECT helped in the diagnosis of PA and was consistent with the results of AVS in nearly all cases.

Quantitative [99mTc]Tc-MDP SPECT/CT correlated with [18F]NaF PET/CT for bone metastases in patients with prostate cancer

BACKGROUND

The purpose of the present study was to elucidate the correlation between standardized uptake value (SUV) and volume-based parameters measured by quantitative [^99mTc]Tc-methylene diphosphonate (MDP) single photon emission computed tomography (SPECT)/CT and [¹⁸F]-sodium fluoride ([¹⁸F]NaF) positron emission tomography (PET)/CT in the assessment of bone metastases in patients with prostate cancer.

METHODS

The study included 26 male prostate cancer patients with confirmed or suspected bone metastases who underwent both [^99mTc]Tc-MDP SPECT/CT and [¹⁸F]NaF PET/CT studies. Skeletal lesions visible on both SPECT/CT and PET/CT were classified as benign or metastases. The maximum SUV (SUVmax), peak SUV (SUVpeak), mean SUV (SUVmean), metabolic bone volume (MBV), and total bone uptake (TBU) were calculated for every lesion showing abnormal uptake.

RESULTS

A total of 202 skeletal lesions (147 benign and 55 metastases) were detected in the 26 patients. Strong significant correlations were noted between SPECT/CT and PET/CT for the SUV- and volume-based parameters (all P < 0.001). The SUVmax, SUVpeak, SUVmean, and TBU values obtained with SPECT/CT were significantly lower than the corresponding values obtained with PET/CT (all P < 0.001). The MBV in SPECT/CT was significantly higher than that in PET/CT (P < 0.001). All SUV- and volume-based parameters obtained with both SPECT/CT and PET/CT for metastatic lesions were significantly higher than the corresponding parameters for benign lesions (P values from 0.036 to < 0.001).

CONCLUSIONS

These preliminary results demonstrate that the SUV- and volume-based parameters for bone uptake obtained with quantitative SPECT/CT and PET/CT are strongly correlated in patients with prostate cancer. The SUV parameters obtained with SPECT/CT were significantly lower than those obtained with PET/CT, whereas the uptake volume obtained with SPECT/CT was significantly higher than that obtained with PET/CT.

Impact of CT tube-voltage and bone density on the quantitative assessment of tracer uptake in Tc-99m bone SPECT/CT: A phantom study

PURPOSE

To evaluate the effect of computed tomography (CT) tube voltage and CT density for CT-based attenuation correction (CTAC) on quantification of tracer uptake in single photon emission computed tomography (SPECT)/CT.

METHODS

A cylindrical phantom contained 7 cylinders with diameter of 30 mm. The central cylinder and background part were filled with 17 kBq/ml of ^99mTc-pertechnetate solution. Of the remaining 6 cylinders, one cylinder was filled with water and 5 cylinders were filled with each own different concentration of K₂HPO₄ solution (120, 275, 450, 666, and 960 mg/cm³) to simulate different bone densities. The 6 cylinders also contained ^99mTc-pertechnetate solution with the same radioactivity concentration (207 kBq/ml). CT scans were performed with 4 different tube voltages of 80, 100, 120, and 140 kVp for CTAC. The radioactivity concentration in the 6 cylinders were measured on the SPECT images processed with 4 different attenuation coefficient maps derived from each tube voltage of CT images.

RESULTS

Compared with the water cylinder without K₂HPO₄ solution, the measured radioactivity of the highest density cylinder (K₂HPO₄ solution concentration: 960 mg/cm³) was found to be overestimated by 3.3 % and 4.3 %, respectively, when the tube voltage was 120 kVp and 140 kVp (p = 0.022). The use of low-tube voltage, such as 80 kVp, has improved the quantitative accuracy of bone SPECT/CT.

CONCLUSIONS

SPECT quantitative evaluation of tracers in high-density objects tends to overestimate as tube voltage for CTAC increases. However, the overestimation in quantitative SPECT/CT evaluation in simulated bone area is less than 5% at most.

Correlation analysis of I-131 SPECT/CT uptake parameters with the success ablation treatment of thyroid remnant in patients with low-intermediate-risk differentiated thyroid cancer

OBJECTIVE

To predict the successful outcome of radioactive iodine-131 (I-131) ablation treatment for differentiated thyroid cancer (DTC) patients using quantitative parameters from therapeutic I-131 SPECT/CT.

METHODS

This retrospective study enrolled 145 DTC patients (41 males and 104 females) who had radioactive iodine-131 (I-131) (RAI) ablation therapy following thyroidectomy surgery from July 2020 to May 2021. The median age was 47 years (24-65 years). All the patients underwent therapeutic I-131 thyroid SPECT/CT scan after RAI ablation. The I-131 uptake quantitative parameters SUV max , SUV mean %ID and ∆Tg (defined as the Tg level before RAI ablation minus the Tg level after six months) were assessem. Successful ablation treatment was defined as the level of TSH-stimulated Tg≤1 ng/mL and the disappearance of the thyroid bed on a whole-body I-131 scan six months or later after ablation treatment.

RESULTS

The quantitative parameters from therapeutic I-131 SPECT/CT of the successful ablation (n=130) group with SUV max 7.74 (3.84, 18.78) g/ml, SUV mean 4.02 (2.11, 6.39) g/ml and %ID 2.21% (0.67%, 7.30%) were significantly higher than those of the unsuccessful (n=15) group 0.75 (0.53, 1.28) g/ml, 0.44 (0.29, 0.79) g/ml and 0.16% (0.06%, 1.48%) (Z=-5.87, -5.71 and -4.99, all P < 0.001). SUV max , SUV mean and %ID were positively correlated with ΔTg (all P < 0.001). Receiver operating characteristics curve analysis showed that %ID performed better predict value than either SUV max (AUC=0.914, and 0.874, P=0.009) or SUV mean (AUC= 0.863 P=0.002). SUV max , SUV mean and%ID (OR =1.50, 2.85 and 1.01 all P < 0.001) were all independent predictors of successful RAI ablation.

CONCLUSION

The quantitative parameters of therapeutic I-131 SPECT/CT were related to the efficacy of ablation treatment, and %ID could predict the successful outcome of ablation treatment for DTC patients.

Quantitative myocardial perfusion SPECT/CT for the assessment of myocardial tracer uptake in patients with three-vessel coronary artery disease: Initial experiences and results

BACKGROUND

To evaluate quantitative myocardial perfusion SPECT/CT datasets for routine clinical reporting and the assessment of myocardial tracer uptake in patients with severe TVCAD.

METHODS

MPS scans were reconstructed as quantitative SPECT datasets using CTs from internal (SPECT/CT, Q_INT) and external (PET/CT, Q_EXT) sources for attenuation correction. TPD was calculated and compared to the TPD from non-quantitative SPECT datasets of the same patients. SUVmax, SUVpeak, and SUVmean were compared between Q_INT and Q_EXT SPECT datasets. Global SUVmax and SUVpeak were compared between patients with and without TVCAD.

RESULTS

Quantitative reconstruction was feasible. TPD showed an excellent correlation between quantitative and non-quantitative SPECT datasets. SUVmax, SUVpeak, and SUVmean showed an excellent correlation between Q_INT and Q_EXT SPECT datasets, though mean SUVmean differed significantly between the two groups. Global SUVmax and SUVpeak were significantly reduced in patients with TVCAD.

CONCLUSIONS

Absolute quantification of myocardial tracer uptake is feasible. The method seems to be robust and principally suitable for routine clinical reporting. Quantitative SPECT might become a valuable tool for the assessment of severe coronary artery disease in a setting of balanced ischemia, where potentially life-threatening conditions might otherwise go undetected.

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.

The Role of PSMA PET/CT in the Primary Diagnosis and Follow-Up of Prostate Cancer-A Practical Clinical Review

Simple Summary

The combination of positron emission tomography (PET)-diagnostics with ligands binding to the prostate-specific membrane antigen (PSMA) has been a diagnostic milestone in the situation of biochemical recurrence of prostate cancer and is gaining importance in primary diagnostics, providing a highly specific and sensitive diagnostic method in various clinical situations. However, the clinical application of this method requires a comprehensive knowledge of its advantages and disadvantages, potential pitfalls and influencing factors. This review aims to provide a practical clinical review of the currently available background data on PSMA PET/CT, as well as the clinical implications. Although a large amount of data already exist, a thorough analysis is complicated by study heterogeneity, showing the need for future systematic and prospective research.

Abstract

The importance of PSMA PET/CT in both primary diagnostics and prostate cancer recurrence has grown steadily since its introduction more than a decade ago. Over the past years, a vast amount of data have been published on the diagnostic accuracy and the impact of PSMA PET/CT on patient management. Nevertheless, a large heterogeneity between studies has made reaching a consensus difficult; this review aims to provide a comprehensive clinical review of the available scientific literature, covering the currently known data on physiological and pathological PSMA expression, influencing factors, the differences and pitfalls of various tracers, as well as the clinical implications in initial TNM-staging and in the situation of biochemical recurrence. This review has the objective of providing a practical clinical overview of the advantages and disadvantages of the examination in various clinical situations and the body of knowledge available, as well as open questions still requiring further research.

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.

Single-cell sequencing reveals MYC targeting gene MAD2L1 is associated with prostate cancer bone metastasis tumor dormancy

Background

Among malignant tumors, bone metastasis is frequently associated with prostate cancer which is seen in about 80% of patients. During cancer treatments, some tumor cells switch to a "dormant mode" to help tumor cells avoid attack from the immune system and anti-tumor therapies. In this dormant mode, tumor cells can be resuscitated, causing cancer to reoccur. The generally accepted explanation for this phenomenon is that the tumor cells have spread to the bone marrow before treatment and are dormant in the bone marrow. However, the key mechanism for inducing and maintaining the dormancy of these prostate cancer disseminated tumor cells in the bone marrow is still unclear. Therefore, studying the dormancy mechanism of tumor cells in bone metastasis is of great significance for the treatment and the prevention of recurrence of prostate cancer.

Methods

We obtained single-cell RNA-seq data of tumors from mouse models of prostate cancer bone metastasis mouse model numbered (GSE147150) from the GEO database, and obtained RNA-seq expression data and clinical information from The Cancer Genome Atlas Program (TCGA) of prostate cancer patients from the USCS Xena database. Screening of differential genes and annotation of GO functions were performed separately. Subsequently, the screened differential genes were compared and analyzed with 50 classic Hallmark signaling pathways, and the prognosis analysis of prostate cancer patients in TCGA data was performed to discover the key genes of the dormant mechanism of tumor cells in bone metastasis, and obtain new biomarkers that can be used to predict the prognosis of patients.

Results

A total of 378 differentially expressed genes were screened, of which 293 were significantly up-regulated and 85 were significantly down-regulated. Among them, the up-regulated genes were mainly related to the immune response, and the down-regulated genes were mainly related to the cell cycle. Through GSVA (Gene set variation analysis), it is found that there are differences in a total of 3 signal pathways: COMPLEMENT, MYC_TARGETS_V1 and MYC_TARGETS_V2. By comparing and analyzing the significantly down-regulated genes in dormant tumor cells with MYC_TARGETS_V1, MYC_TARGETS_V2, three significantly down-regulated genes were obtained: Ccna2, Mad2L1 and Plk1.

Conclusion

In summary, our findings indicate that the MYC targeting gene Mad2L1 is potentially related to the dormancy mechanism of prostate cancer. At the same time, Mad2L1, a gene associated with dormant prostate cancer cells, may be used as a biomarker for prognostic survival.

Three-dimensional CT for the diagnosis and management of bipartite scaphoids: a report of four cases in three patients

We investigated the role of three-dimensional (3-D) CT in the diagnosis and management of four bipartite scaphoids in three patients. We computed the volume ratio, moment of inertia ratio and direction vector from the centroid of the scaphoid to the os centrale carpi. We found that the os centrale carpi was always smaller than the scaphoid and showed an elongated shape in the scaphoid longitudinal axis. Its position was always posterior compared with the scaphoid anteroposterior axis. The main morphological feature of bipartite scaphoids was the continuity of the scaphoid from its proximal to distal aspect along the longitudinal axis. These criteria from 3-D imaging should be considered useful in the diagnosis of bipartite scaphoid as it allows differentiation from nonunion. 3-D single-photon emission computed tomography (SPECT)/CT was helpful in the surgical decision-making when the patient was symptomatic. 3-D imaging was also used for the preoperative simulation and planning of bone fusion as it simplifies surgery and makes it more accurate. Here we provide clear criteria for diagnosing bipartite scaphoids and for the planning when surgery is deemed necessary.

Clinical significance of quantitative bone SPECT/CT in the evaluation of hand and wrist pain in patients with rheumatic disease

We investigated the diagnostic value of the maximum standardized uptake value (SUV) at hand and wrist joints for differentiating rheumatic diseases via bone single-photon emission computed tomography (SPECT)/computed tomography (CT). A total of 84 patients manifesting hand and wrist pain (58 women; age, 49.8 ± 15.4 years) were finally diagnosed with rheumatoid arthritis (RA, n = 42), osteoarthritis (OA, n = 16), fibromyalgia (FM, n = 2), and other rheumatic diseases (n = 24). The SUV of each patient was measured in 32 joints including the distal interphalangeal (DIP), proximal interphalangeal (PIP), metacarpophalangeal (MCP), and wrist joints bilaterally. Differences in pain and SUVs between specific rheumatic diseases were assessed using the chi-squared test or one-way analysis of variance. Using the highest SUV (hSUV) in each patient, the diagnostic performance in differentiating specific diseases was evaluated by receiver operating characteristic (ROC) curve analysis. Pain symptoms were present in 886 (33.0%) sites in a total of 2688 joints. In four joint groups (DIP, PIP, MCP, and wrist), the SUVs of joints with pain were significantly higher than those of pain-free joints (all P < 0.001). Active joint sites with higher SUVs than the median value of each joint group were the most common in RA (55.1%). RA showed the greatest hSUV in the PIP (3.0 ± 2.4), MCP (3.5 ± 3.4), and wrist (3.3 ± 1.9) joint groups. FM was characterized by the lowest hSUV of all joint groups. In ROC curve analysis, the cumulative hSUV of the PIP, MCP, and wrist joint groups showed good performance for evaluating RA (area under the curve (AUC), 0.668; P = 0.005). The summation of the hSUVs at all joint groups had an excellent predictive performance for FM (AUC, 0.878; P < 0.001). Consequently, the arthritic activity of the hand and wrist joints based on SUV differed according to specific rheumatic diseases. Quantitative SPECT/CT may provide objective information related to arthritic activity for differentiating specific rheumatic diseases.

A novel approach for fibrous dysplasia assessment using combined planar and quantitative SPECT/CT analysis of Tc-99m-diphosphonate bone scan in correlation with biological bone turnover markers of disease activity

Purpose

To investigate the emerging role of Tc-99m-labeled diphosphonate (Tc-99m-DPD) uptake quantification by SPECT/CT in fibrous dysplasia (FD) bone lesions and its correlation with biological bone turnover markers (BTMs) of disease activity.

Materials and methods

Seven patients (49 ± 16 years) with a confirmed diagnosis of FD were included in this retrospective study. Bone scans with Tc-99m-DPD and quantitative SPECT/CT (xSPECT/CT) were performed. SUV_max (maximum standard unit value) and SUV_mean (mean standard unit value) were measured in all FD bone lesions. The skeletal burden score (SBS) was assessed on planar scintigraphy and multiplied by mean SUV _max and SUV_mean to generate two new parameters, SBS_SUV_max and SBS_SUV_mean, respectively. Planar and xSPECT/CT quantitative measures were correlated with biological BTMs of disease activity, including fibroblast growth factor 23 (FGF-23), alkaline phosphatase (ALP), procollagen 1 intact N-terminal propeptide (P1NP) and C-terminal telopeptide (CTX), as well as scoliosis angle measured on radiographs. Statistical significance was evaluated with Spearman's correlations.

Results

A total of 76 FD bone lesions were analyzed, showing an average SUV_max and SUV_mean (g/mL) of 13 ± 7.3 and 8 ± 4.5, respectively. SBS, SBS_SUV_max and SBS_SUV_mean values were 30.8 ± 25.6, 358 ± 267 and 220.1 ± 164.5, respectively. Mean measured values of FGF-23 (pg/mL), ALP (U/L), P1NP (μg/L) and CTX (pg/mL) were 98.4 (22-175), 283.5 (46-735), 283.1 (31-1,161) and 494 (360-609), respectively. Mean scoliosis angle was 15.7 (7-22) degrees. We found a very strong positive correlation between planar-derived SBS and CTX (r = 0.96, p = 0.010), but no significant correlation between SUV_max or SUV_mean and biological BTMs. SBS_SUV_max showed a strong to very strong positive correlation with CTX (ρ = 0.99, p = 0.002), FGF-23 (ρ = 0.91, p = 0.010), ALP (ρ = 0.82, p = 0.020), and P1NP (ρ = 0.78, p = 0.039), respectively.

Conclusion

This study showed that biological BTMs are significantly correlated with diphosphonate uptake on bone scan, quantified by a new parameter combining information from both planar and quantitative SPECT/CT. Further analysis of bone scan quantitative SPECT/CT data in a larger patient population might help better characterize the skeletal disease burden in FD, and guide treatment and follow-up.

Quantitative analysis in parathyroid adenoma scintigraphy

OBJECTIVE

Surgery is the only curative treatment for primary hyperparathyroidism. Parathyroid scintigraphy is one method used to preoperatively localize the lesion. We examined time-related changes in radiopharmaceutical uptake in parathyroid adenomas (PTAs) and thyroid gland by quantitative single-photon-emission computed tomography (SPECT) imaging to assess differences between rapid and delayed washout patterns.

PATIENTS AND METHODS

The study group consisted of 35 histologically verified PTAs after radio-guided surgery extirpation in 33 patients with primary hyperparathyroidism. Patients underwent a three-phase SPECT/CT study of the neck and upper thorax post 99mTc-methoxyisobutylisonitrile (MIBI) injection. Images were reconstructed using a proprietary ordered-subset-conjugate-gradient-maximization algorithm (Siemens xSPECT Quant). PTAs were divided into those with a rapid (group A) and those with a slow (group B) washout pattern. SUVmax values of PTAs and thyroid gland tissue at 10, 90 and 180 min post 99mTc-MIBI injection were recorded and statistically assessed. Retention indexes related to the early examination were calculated for PTA and thyroid gland (RI-PTA and RI-TG).

RESULTS

There were 11 PTAs in group A and 24 in group B. Significant between-group differences in PTA SUVmax and PTA/thyroid gland ratios were observed only at 180 min postinjection (P = 0.0297, P = 0.0222, respectively). RI-PTAs differed significantly at 90 and 180 min postinjection (P = 0.0298, P = 0.0431). No differences in PTA volumes, thyroid gland SUVmax values or RI-TG were observed between the groups.

CONCLUSION

PTAs with rapid and slow washout patterns have different characteristics on quantitative analysis in later phases. No significant differences in directly measurable quantitative values (SUVmax, PTA/thyroid gland ratio) at the early stages of multi-phase examination were observed.

Absolute Quantification in Diagnostic SPECT/CT: The Phantom Premise

The application of absolute quantification in SPECT/CT has seen increased interest in the context of radionuclide therapies where patient-specific dosimetry is a requirement within the European Union (EU) legislation. However, the translation of this technique to diagnostic nuclear medicine outside this setting is rather slow. Clinical research has, in some examples, already shown an association between imaging metrics and clinical diagnosis, but the applications, in general, lack proper validation because of the absence of a ground truth measurement. Meanwhile, additive manufacturing or 3D printing has seen rapid improvements, increasing its uptake in medical imaging. Three-dimensional printed phantoms have already made a significant impact on quantitative imaging, a trend that is likely to increase in the future. In this review, we summarize the data of recent literature to underpin our premise that the validation of diagnostic applications in nuclear medicine using application-specific phantoms is within reach given the current state-of-the-art in additive manufacturing or 3D printing.

Optimization of cross-calibration factor for quantitative bone SPECT without attenuation and scatter correction in the lumbar spine: head-to-head comparison with attenuation and scatter correction

OBJECTIVES

Quantitative single-photon emission computed tomography (SPECT) with computed tomography (SPECT/CT) is known to improve diagnostic performance. Although SPECT-alone systems are used widely, accurate quantitative SPECT using these systems is challenging. This study aimed to improve the accuracy of quantitative bone SPECT of the lumbar spine with the SPECT-alone system.

METHODS

The cross-calibration factor (CCF) was measured using three kinds of phantoms and the optimal values were determined. The recovery coefficient with and without attenuation and scatter correction (ACSC) were compared. Bone SPECT/CT was performed on 93 consecutive patients with prostate cancer, and the standardized uptake values (SUVs) were compared using the respective CCFs. The first 60 patients were classified according to body weight, and the correlation coefficient between SUVs with and without ACSC were calculated; the slopes were defined as body weight-based coefficients (BWCs). In the remaining 33 patients, the SUV was adjusted according to BWC, and the accuracy of the adjustment was verified.

RESULTS

The quantitative SPECT values obtained from the CCF using SIM2 bone phantom showed nearly accurate radioactivity concentrations, even without ACSC. The recovery coefficients with and without ACSC were similar. Unadjusted SUVs with and without ACSC were strongly correlated; however, SUVs without ACSC were significantly higher than those with ACSC (P < 0.0001). The mean difference between the SUVs with and without ACSC disappeared when the SUVs without ACSC were adjusted by BWC (P = 0.9814).

CONCLUSIONS

Our cross-calibration method for quantitative bone SPECT enables interpretation with a harmonized SUV even in SPECT-alone systems.

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.

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.

Progress in diagnosis of bone metastasis of prostate cancer

The diagnosis of bone metastasis of prostate cancer (PC) is of great significance to the treatment and prognosis of patients with PC.Bone scan is the most commonly used in the early diagnosis of bone metastasis, but its specificity is low and there is a high false positive.In recent years, with the in-depth study of the application of CT, MRI, emission computed tomography (ECT), positron emission computed tomography/computed tomography (PET/CT) and deep learning algorithm-convolutional neural networks (CNN) in the diagnosis of bone metastasis, the combined application of various auxiliary parameters in the diagnosis of bone metastasis has significantly been improved. The therapeutic effect of PC patients with bone metastasis can also be evaluated, which is expected to achieve the treatment of bone metastasis as well as diagnosis. By systematically expounding the research progress of the above-mentioned techniques in the diagnosis of bone metastasis, it can provide clinicians with new methods for the diagnosis of bone metastasis and improve the diagnostic efficiency for bone metastasis.

Polyethylene oxide-polyacrylic acid-folic acid (PEO-PAAc) nanogel as a 99m Tc targeting receptor for cancer diagnostic imaging

Nanoparticles are frequently used as targeting delivery systems for therapeutic and diagnostic radiopharmaceuticals. Polyethylene oxide-polyacrylic acid (PEO-PAAc) nanogel was prepared via γ-radiation-induced polymerization. Variable factors affecting nanoparticles size were investigated. The nanogel was radiolabeled with the imaging radioisotope ^99m Tc and finally conjugated with folic acid to target folate receptor actively. PEO-PAAc-folic acid gel was characterized by dynamic light scattering (DLS) and atomic force microscopy (AFM). Biodistribution was studied in normal mice and solid tumor-bearing mice via intravenous and intratumor injections of the radiolabeled PEO-PAAc-folic acid nanogel. Results of biodistribution showed high selective uptake of the prepared complex in tumor muscle compared with normal muscle for both intravenous and intratumor injections. The T/NT ratio was found to be 6.186 and 294.5 for intravenous and intratumor injections, respectively. Consequently, ^99m Tc-PEO-PAAc-folic acid complex could be a promising agent for cancer diagnostic imaging.

Monitoring jaw osteomyelitis therapy with single-photon emission computed tomography/computed tomography

OBJECTIVE

The aim of the study was to evaluate the value of single-photon emission computed tomography/computed tomography (SPECT/CT) for therapy response assessment of jaw osteomyelitis.

MATERIALS AND METHODS

Thirty-four baseline and 74 follow-up SPECT/CT examinations for therapy response assessment were performed in 34 patients with jaw osteomyelitis. SPECT/CT and planar late-phase bone scintigraphy images were assessed at baseline and follow-up, according to the following criteria: tracer uptake grade (0 = no uptake, 1 = low uptake, 2 = moderate uptake and 3 = high uptake); and morphologic signs (osteolysis, sequestration, sclerosis, periosteal reaction and pathologic fracture).

RESULTS

At baseline, SPECT/CT showed marked (grade 2 or 3) uptake in 91% (31/34) of the patients, osteolysis in 85% (29/34), sclerosis in 71% (24/34), periosteal reaction in 44% (15/34) and a sequestrum in 24% (8/34). In 24 patients with clinically complete remission during or after at least 12 months' therapy, bone scintigraphy showed grade 0 or 1 uptake in 100% (24/24) and SPECT/CT in 91% (22/24) of the patients. Sclerosis with the disappearance of osteolysis, sequestration and periosteal reactions was the predominant morphologic finding in complete responders (68%; 16/24). In 10 patients with symptoms of exacerbation of the osteomyelitis, 80% (8/10) showed increasing uptake, 90% (9/10) sclerosis, 80% osteolysis (8/10) and 40% (4/10) osteolysis and periosteal reactions.

CONCLUSION

SPECT/CT is a valuable tool to accurately assess therapy response, disease exacerbation and complications of jaw osteomyelitis. Low-grade (grade 1) residual tracer uptake is common in patients with clinically complete remission and is suggestive of ongoing bone remodeling and healing.

An analysis of clinical values of MRI, CT and X-ray in differentiating benign and malignant bone metastases

OBJECTIVE

To investigate the clinical values of magnetic resonance imaging (MRI), computed tomography (CT) and X-ray in differential diagnosis of benign and malignant bone metastases.

METHODS

A total of 80 patients with bone metastases admitted to our hospital were selected as the study subjects. X-ray, CT and MRI examinations were performed, respectively. The pathological examination results were taken as the gold standard to analyze the lesion sites of metastatic tumors in 80 subjects. The diagnostic sensitivity, specificity and accuracy of X-ray, CT and MRI examinations were calculated and compared.

RESULTS

Among the 80 patients, 71 cases were diagnosed as malignant bone metastases and 9 cases as benign lesions according to pathological examination. The diagnostic sensitivity, specificity and accuracy of X-ray, CT and MRI examinations were 63.38%, 33.33% and 60.00%, 84.51%, 66.67% and 82.50%, and 90.14%, 77.78% and 88.75%, respectively. MRI was superior to X-ray in the sensitivity, specificity and accuracy of differential diagnosis of benign and malignant bone metastases (P < 0.05). MRI was superior to CT, but there was no significant difference between the two groups (P < 0.05). The diagnostic sensitivity, specificity and accuracy of CT + MRI were significantly higher than those of any single detection method (P < 0.05).

CONCLUSION

MRI, CT and X-ray exhibit a good value in differential diagnosis of benign and malignant bone metastases. Overall, MRI is superior to CT and X-ray in the screening effects, and the combined detection methods are more satisfactory. It is recommended that CT should be used for primary screening, and CT + MRI should be implemented for a enhanced diagnosis.

Usefulness of Quantitative Bone Single-Photon Emission Computed Tomography/Computed Tomography for Evaluating the Treatment Response of Bone Metastasis in a Lung Cancer Patient

We report a case of bone metastasis arising from lung cancer, including quantitative values obtained with bone single-photon emission computed tomography/computed tomography (SPECT/CT), which were useful to evaluate the treatment response. The first bone SPECT/CT during pembrolizumab therapy for lung cancer recurrence showed intense ^99mTc-HMDP uptake of the right femur head and mild uptake of the left ribs. After the palliative radiotherapy for the right femur head metastasis and chemotherapy, the second bone SPECT/CT showed a decrease in focal uptake of the right femur hip and increasing uptake of the left ribs. There was also new uptake appearance in the sternum, right rib, spine (Th2, Th9, Th12, L4, S1), and bilateral pelvic bone (left ilium, acetabular cartridge, femur, right ilium and ischium). The change of maximum standardized uptake values (SUVmax) for the right femur head and left third and eighth rib bony metastases were −72.6% (from 22.96 to 6.28), +407.7% (from 2.97 to 15.08), and +229.2% (from 2.60 to 8.56), respectively. The change of whole-lesion metabolic bone volume and total bone uptake was +235.4% (from 22.75 to 76.3 cm³) and +219.1% (from 205.0 to 654.09), respectively. Two quantitative bone SPECT/CT images clearly showed the good response of femur head metastasis due to radiotherapy, and progression of other bone metastases regardless of chemotherapy.

Advancing frontiers in rheumatic and musculoskeletal imaging

In recent years, technological improvements allowed imaging modalities to become increasingly essential in achieving early and precise diagnoses in the field of rheumatic and musculoskeletal diseases (RMDs). To date, imaging examinations are routinely used in all steps of diagnostic and therapeutic care pathways of patients affected by RMDs. The articles published in this Article Collection clearly show the efforts of researchers to find innovative applications of musculoskeletal imaging in clinical practice and to face the crucial challenges that remain in the interpretation and quality control of images. Highly performing diagnostic technologies are currently available to early diagnose and accurately monitor several musculoskeletal disorders, but also to guide personalized interventional therapeutic procedures tailored to the individual patients in the emerging process of precision medicine. Among these new modalities, some are particularly promising and thereby subject to several lines of research in RMDs, including SPECT-CT and dual-energy CT, MRI sequences, high and ultra-high frequency ultrasound with effective tools like shear wave elastography.

Standardized uptake values of 99mTc-MDP in normal vertebrae assessed using quantitative SPECT/CT for differentiation diagnosis of benign and malignant bone lesions

BACKGROUND

Quantitative bone SPECT/CT is useful for disease follow up and inter-patient comparison. For bone metastatic malignant lesions, spine is the most commonly invaded site. However, Quantitative studies with large sample size investigating all the segments of normal cervical, thoracic and lumbar vertebrae are seldom reported. This study was to evaluate the quantitative tomography of normal vertebrae using ^99mTc-MDP with SPECT/CT to investigate the feasibility of standardized uptake value (SUV) for differential diagnosis of benign and malignant bone lesions.

METHODS

A retrospective study was carried out involving 221 patients (116 males and 105 females) who underwent SPECT/CT scan using ^99mTc-MDP. The maximum SUV (SUV_max), mean SUV (SUV_mean) and CT values (Hounsfield Unit, HU) of 2416 normal vertebrae bodies, 157 benign bone lesions and 118 malignant bone metastasis foci were obtained. The correlations between SUV_max of normal vertebrae and CT values of normal vertebrae, age, height, weight, BMI of patients were analyzed. Statistical analysis was performed with data of normal, benign and malignant groups corresponding to same sites and gender.

RESULTS

The SUV_max and SUV_mean of normal vertebrae in males were markedly higher than those in females (P < 0.0009). The SUV_max of each normal vertebral segment showed a strong negative correlation with CT values in both males and females (r = - 0.89 and - 0.92, respectively; P < 0.0009). The SUV_max of normal vertebrae also showed significant correlation with weight, height, and BMI in males (r = 0.4, P < 0.0009; r = 0.28, P = 0.005; r = 0.22, P = 0.026), and significant correlation with weight and BMI in females (r = 0.32, P = 0.009; r = 0.23, P = 0.031). The SUV_max of normal group, benign bone lesion group and malignant bone metastasis foci group showed statistical differences in both males and females.

CONCLUSION

Our study evaluated SUV_max and SUV_mean of normal vertebrae, benign bone lesion and malignant bone metastasis foci with a large sample population. Preliminary results proved the potential value of SUV_max in differentiation benign and malignant bone lesions. The results may provide a quantitative reference for clinical diagnosis and the evaluation of therapeutic response in vertebral lesions.

Recent Advances in Nanomedicine for the Diagnosis and Treatment of Prostate Cancer Bone Metastasis

Patients with advanced prostate cancer can develop painful and debilitating bone metastases. Currently available interventions for prostate cancer bone metastases, including chemotherapy, bisphosphonates, and radiopharmaceuticals, are only palliative. They can relieve pain, reduce complications (e.g., bone fractures), and improve quality of life, but they do not significantly improve survival times. Therefore, additional strategies to enhance the diagnosis and treatment of prostate cancer bone metastases are needed. Nanotechnology is a versatile platform that has been used to increase the specificity and therapeutic efficacy of various treatments for prostate cancer bone metastases. In this review, we summarize preclinical research that utilizes nanotechnology to develop novel diagnostic imaging tools, translational models, and therapies to combat prostate cancer bone metastases.

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.

Optimization of Number of Iterations as a Reconstruction Parameter in Bone SPECT Imaging Using a Novel Thoracic Spine Phantom

The aim of this study was to optimize the number of iterations in bone SPECT imaging using a novel thoracic spine phantom (ISMM phantom). Methods: The quality and quantitative accuracy of bone SPECT images were evaluated by changing the number of iterations and the size of the hot spot in the phantom. True SUVs in the vertebra, tumor, and background parts were 9.8, 52.2, and 1.0, respectively. The phantom image was reconstructed using the ordered-subset expectation-maximization algorithm with CT-based attenuation correction, scatter correction, and resolution recovery; the number of ordered-subset expectation-maximization subsets was fixed at 10, with iterations ranging from 1 to 40. Full width at half maximum, percentage coefficient of variation, contrast ratio for the sphere and background (contrast), and recovery coefficient were evaluated as a function of the number of iterations for a given number of subsets (10) using the reconstructed images. In addition, SUV_max, SUV_peak, and SUV_mean were calculated with various numbers of iterations for each sphere (13, 17, 22, and 28 mm) simulating a tumor. Results: Full width at half maximum decreased as the number of iterations was increased, and full width at half maximum converged uniformly when the number of iterations exceeded 10. The percentage coefficient of variation increased as the number of iterations was increased. Recovery coefficient decreased with decreasing sphere size. Contrast and all SUVs increased as the number of iterations was increased, and contrast and all SUVs converged uniformly when the number of iterations exceeded 5 and 10, respectively, for all sphere sizes. When the SUV was defined as the converged value for 10 iterations in the 28-mm sphere, the converged values of SUV_max, SUV_peak, and SUV_mean were 75.1, 66.5, and 55.6, respectively. The relative error in the converged values for SUV_max, SUV_peak, and SUV_mean were 43.8%, 27.3%, and 7.2% of the true value (52.2); all SUVs were overestimated. Conclusion: Using a thoracic spine phantom to evaluate the optimal reconstruction parameters in bone SPECT imaging, we determined the optimal number of iterations for 10 subsets to be 10.

A novel tool for improving the interpretation of isotope bone scans in metastatic prostate cancer

OBJECTIVES

The isotope bone scan (IBS) is the gold-standard imaging modality for detecting skeletal metastases as part of prostate cancer staging. However, its clinical utility for assessing skeletal metastatic burden is limited due to the need for subjective interpretation. We designed and tested a novel custom software tool, the Metastatic Bone Scan Tool (MetsBST), aimed at improving interpretation of IBSs, and compared its performance with that of an established software programme.

METHODS

We used IBS images from 62 patients diagnosed with prostate cancer and suspected bone metastases to design and implement MetsBST in MATLAB by defining thresholds used to identify the texture and size of metastatic bone lesions. The results of MetsBST were compared with those of the commercially available automated Bone Scan Index (aBSI) with regression analysis.

RESULTS

There was strong agreement between the MetsBST and aBSI results (R² = 0.9189). In a subregional analysis, MetsBST quantified the extent of metastatic disease in multiple bone sites in patients receiving multimodality therapy (radium-223 and external beam radiotherapy) to illustrate the differences in bone metastatic response to different treatments.

CONCLUSION

The results of MetsBST and the commercial software aBSI were highly consistent. MetsBST introduces novel clinical utility by its ability to differentiate between the responses of different bone metastases to multimodality therapies.

ADVANCES IN KNOWLEDGE

MetsBST reduces the variability in assessment of tumour burden caused by subjective interpretation. Therefore, it is a useful aid to physicians reporting nuclear medicine scans, and may improve decision-making in the treatment of metastatic prostate cancer.