Bloodpool SPECT as part of bone SPECT/CT in painful total knee arthroplasty (TKA): validation and potential biomarker of prosthesis biomechanics

Technical concepts on blood pool phase SPECT (acquisition, reconstruction)

Guidelines for bone scintigraphy are well established and recommend the use of planar early phase images to investigate a number of clinical indications. With recent advances in gamma camera technology the use of SPECT/CT imaging in the early phases is now possible, offering the potential of improved diagnostic confidence and prognostic value. To date little work has been carried out to optimize the acquisition of early phase bone images using SPECT/CT with most of the available studies acquiring SPECT images after the traditional planar images to allow comparison of the two techniques. Imaging durations of 7 to 10 minutes have been commonly used. However, the use of iterative reconstruction algorithms has been investigated with rapid SPECT imaging to allow imaging durations as low as 4 minutes. The use of CZT based systems with increased sensitivity and improved energy and spatial resolution also offers the potential to reduce imaging times. The optimization of projection measurement order has been investigated as a method of reducing image artefacts as a result of changing tracer distribution during the SPECT acquisition. In this article we consider the current state of early phase SPECT imaging and possible areas for future investigation as well as recommendations for departments looking to adopt blood pool SPECT imaging as part of their routine clinical practice.

Blood pool SPECT: rheumatological and orthopedic focus, a pictorial essay

Single photon emission computed tomography (SPECT) has revolutionized delayed bone scan acquisitions and promises to bring the same benefits to early acquisitions, especially in areas of complex anatomy. To date, however, only a few studies have been published about the utility of blood pool SPECT. The accurate assessment of inflammatory processes can be an indisputable added value to the diagnosis. We present here a series of clinical cases illustrating the utility of blood pool SPECT in various clinical situations in rheumatology and orthopedics. We grouped the cases according to three patterns that facilitate clinical reasoning: inflammatory osseous pathology (pattern A), inflammatory para-osseous pathology (pattern B) and inflammatory extra-osseous pathology (pattern C). A total of seventeen clinical cases are presented. This new semiology requires time and effort to be mastered but expands the diagnostic range offered by bone scintigraphy. More prospective studies on blood pool SPECT will be needed, especially those aiming to clarify its role.

Added value of early-phase SPECT over planar acquisition in bone imaging

BACKGROUND

The aim of this study is to evaluate the added value of early bone single photon emission computed tomography (SPECT) by comparison to pseudoplanar imaging.

METHODS

Fifty patients were retrospectively included from 3 centers. Reading sessions were organized using: late-phase acquisition alone; early SPECT and late-phase acquisition; early pseudoplanar and late-phase acquisition. The comparison between early SPECT and MIP was performed using a McNemar Test. Patients for whom early SPECT had provided additional information were also compared with patients for whom early SPECT had not.

RESULTS

Fifty patients were included. Early SPECT was superior to pseudoplanar MIP in 10/50 patients (20.0%, P=0.044). No significant difference was found between this group and the remainder. Early SPECT changed the diagnosis established from late-phase imaging in 21/50 patients.

CONCLUSIONS

Early SPECT is a promising tool in bone imaging and change the diagnosis in one fifth of the cases by comparison to pseudoplanar imaging.

The role of SPECT/CT in painful, noninfected knees after knee arthroplasty: a systematic review and meta-analysis-a diagnostic test accuracy review

PURPOSE

The aim of this systematic review was to present the current evidence on the clinical use of single-photon emission computed tomography/computed tomography (SPECT/CT) in the evaluation of noninfected painful knees after knee arthroplasty.

METHODS

Embase, PubMed, Google Scholar, Ovid, Scopus, Science Direct and the Cochrane Database of Systematic Reviews were searched from database inception to May 2022 following the PRISMA guidelines. As a primary outcome, we defined the role of SPECT/CT in the diagnostic approach to noninfected painful knee arthroplasty; as a secondary objective, we described the noninfection-related factors linked to painful knee arthroplasty. Pooled sensitivity, specificity, positive likelihood ratio, negative likelihood ratio, diagnostic odds ratio values and other indicators were calculated; receiver operating characteristic (ROC) curve analysis results and a summary of the areas under the curve (AUCs) from the included studies were reported. A Fagan plot, likelihood ratio plot and Deeks' funnel plot were generated and analysed. Methodological quality was assessed using the QUADAS-2 tool, and the certainty of evidence was assessed by the GRADE approach.

RESULTS

A total of 493 publications were identified, of which eight met the inclusion criteria, with a final pooled sample size of 308 patients. The pooled sensitivity and specificity of SPECT/CT in diagnosing the source of pain in painful knee prostheses were 0.86 (95% CI: 0.75-0.93) and 0.90 (95% CI: 0.79-0.96), respectively, with pooled +LR and -LR values of 8.9 (95% CI: 4.11-19.19) and 0.15 (95% CI: 0.09-0.28). The pooled diagnostic odds ratio was 57.35, and the area under the curve was 0.94. SPECT/CT highly accurately identified different sources of pain, such as loosening of the prosthetic components, patellofemoral overloading, instability, malalignment of the components and degeneration of the patellofemoral compartment. The confidence of the estimates was moderate according to the GRADE approach.

CONCLUSION

With demonstrated high sensitivity and specificity, as a diagnostic tool, SPECT/CT can identify the source of pain in painful knees after knee arthroplasty, particularly in cases of loosening, patellofemoral disorders and component malalignment (level of evidence III). These findings have significant clinical repercussions, such as in changing the initial diagnosis, identifying or excluding different causes of painful knee arthroplasties, guiding subsequent treatment and positively impacting the final clinical outcome. We moderately recommend the use of SPECT/CT for identifying the source of pain after knee arthroplasty according to the GRADE assessment. This review was preregistered in Prospero under code CRD42022320457.

The Temporal Impact of Prosthesis Implantation and Semi-Quantitative Criteria on the Diagnostic Efficacy of Triple-Phase Bone Scanning for Periprosthetic Joint Infection

Objective

To evaluate the diagnostic efficacy of triple‐phase bone scanning and the temporal impact of prosthesis implantation on the diagnostic efficacy of triple‐phase bone scanning for periprosthetic joint infection (PJI).

Methods

Patients who were admitted to our hospital for joint pain and dysfunction after total joint arthroplasty between 2014 and 2020 were retrospectively included. Triple‐phase bone scanning was performed, and the blood pool images were evaluated to obtain the semi‐quantitative criteria. The patients were then grouped into six groups according to the time interval from index primary arthroplasty to triple‐phase bone scanning. We examined whether there were significant differences in sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy between the groups.

Results

Overall, 66 patients who underwent total hip arthroplasty (THA) and 74 patients who underwent total knee arthroplasty (TKA) were analyzed. No significant differences were observed between visual analysis and semi‐quantitative measurement in terms of sensitivity, specificity, PPV, NPV, and accuracy. For patients with a time interval from prosthesis implantation to bone scanning of >1 year, visual analysis had a higher PPV (100%) in patients who underwent THA and the use of semi‐quantitative criteria had a higher NPV (85.7%) in patients who underwent TKA.

Conclusion

The semi‐quantitative criteria showed no advantages in the diagnosis of PJI. In addition, triple‐phase bone scanning demonstrated good clinical diagnostic efficacy when the time interval from prosthesis implantation to bone scanning was >1 year.

Bone SPECT/CT in the Evaluation of Painful Total Ankle Replacement: Validation of Localization Scheme and Preliminary Evaluation of Diagnostic Patterns

PURPOSE

Third-generation total ankle replacement (TAR) is an increasingly popular and effective treatment for end-stage osteoarthritis, yet identifying causes of failure remains challenging. We evaluated integrated bone SPECT/CT in recurrent pain after TAR by validating a standardized reporting scheme, identifying uptake patterns, and assessing diagnostic performance and impact on clinical management.

PATIENTS AND METHODS

A total of 24 TARs in 16 patients with persistent or recurrent pain received integrated bone SPECT/CT using diagnostic CT settings. Images were retrospectively reviewed, and a novel localization scheme was validated by assessing interrater agreement. Distinct uptake patterns were identified, and diagnostic test characteristics were estimated. Reference standard consisted of clinical follow-up, laboratory findings, and subsequent procedures, including revision surgery.

RESULTS

Standardized scoring of bone SPECT/CT uptake was highly reproducible (intraclass correlation coefficient, 0.79; 95% confidence interval [CI], 0.75-0.82). The final diagnoses were gutter impingement (n = 12), periprosthetic (stress) fracture (n = 5), loosening (n = 5), tarsal arthritis (n = 1), and erysipelas (n = 1). Overall, the diagnostic test characteristics of bone SPECT/CT were as follows: sensitivity of 100% (95% CI, 82%-100%), specificity of 80% (95% CI, 28%-99%), and accuracy of 96% (95% CI, 79%-100%). Gutter impingement, periprosthetic fracture, and loosening were correctly identified in all cases revealing distinct uptake patterns. Importantly, persistent diffuse uptake was frequently observed, warranting cautious interpretation. Bone SPECT/CT impacted clinical management in 86%, with symptomatic improvement in 83% of patients.

CONCLUSIONS

Integrated bone SPECT/CT of painful TARs may benefit from standardized localization to reveal distinct uptake patterns representing common complications after TAR. Initial results show highly promising diagnostic value with potentially important impact on clinical management.

The Added Value of Bloodpool SPECT/CT in Painful Non-Operated Foot and Ankle Undiagnosed With Standard Three-Phase Bone Scintigraphy

Purpose: To evaluate the interest of adding a bloodpool SPECT/CT to standard three-phase bone scintigraphy (BS) for etiological diagnosis of subacute and chronic lower extremity pains.

Methods: We prospectively included patients addressed for pain of lower extremities lasting for at least 6 weeks, without previous surgery. They underwent a standard three-phase BS including late phase SPECT/CT, modified with an additional bloodpool SPECT/CT acquisition. Two independent physicians interpreted the images provided by both protocols. Diagnostic conclusion, diagnostic confidence, and interrater agreements were compared.

Results: One hundred and eighteen lower extremities from 113 patients were analyzed (71 men, median age of 53 years). Adding bloodpool SPECT/CT to standard three-phase BS changed diagnostic conclusions in 24.6% (29/118) of lower extremities. The modified protocol revealed at least one diagnostic conclusion explaining the pain in 89% of extremities, rather than 83.1% with the standard protocol (p = 0.02). Tendinopathies were diagnosed in 12.7% of lower extremities, rather than 4.2% with standard BS (p = 0.002). Adding bloodpool SPECT/CT substantially increased overall confidence of each reader (p < 0.001). Inter-reader agreement was not significantly impacted.

Conclusion: Adding bloodpool SPECT/CT to standard three-phase BS impacted diagnostic conclusion in a quarter of the patients with painful lower extremities, notably by revealing significantly more tendonitis.

Blood-Pool SPECT/CT in Chronic Ankle Tendinopathy

We report 2 cases where blood-pool SPECT/CT had a high added value compared with standard 3-phase bone scintigraphy with only delayed SPECT/CT for the etiological diagnosis of painful ankles. Two men, aged 48 and 62 years, were referred for suspicions of medial and lateral malleoli stress fractures, respectively. Although standard planar blood-pool imaging and delayed SPECT/CT were inconclusive, blood-pool SPECT/CT showed markedly increased uptake along posterior tibial tendon and peroneal tendon, respectively, leading to diagnose tendonitises. These cases illustrate that blood-pool SPECT/CT can extend the diagnostic yield of bone scintigraphy to extraosseous origin, particularly in chronic lower extremities pain.

Computed Tomography (CT) Protocols Associated with Cardiac and Bone Single-Photon Emission Computed Tomography/CT (SPECT/CT) in Korea

PURPOSE

Single-photon emission computed tomography/computed tomography (SPECT/CT) is an advanced hybrid nuclear medicine technology that generates both functional and anatomical images in a single study. As utilization of SPECT/CT in Korea has been increasing, the purpose of this study was to survey its application of cardiac and skeletal SPECT/CT imaging for protocol optimization.

METHODS

We surveyed CT protocols established for cardiac and skeletal SPECT/CT. We searched the guidelines for the CT protocols for SPECT/CT and reviewed the literature recently published.

RESULTS

Among 36 hybrid SPECT scanners equipped with four or more multi-channel detector CTs (MDCTs), 18 scanners were used to perform cardiac studies at both very low current CT (30-80 mA; 11.1%) and ultra-low current CT (13-30 mA; 88.9%). Among the 33 canners, very low current (≤ 80 mA) CT or low current CT (80-130 mA) was used in 23.5%, and 41.8% for spine disorders, and in 36.4% or 30.3% for foot/ankle disorders, respectively. In the CT reconstructions, slice thickness of 5 mm for cardiac studies was most commonly used (94.4%); thinner slices (0.6-1.0 mm) for spine and foot/ankle studies were used in 24.2% and 45.5%, respectively. We also reviewed the international guidelines.

CONCLUSIONS

The results and current recommendations will be helpful for optimizing CT protocols for SPECT/CT. Optimization of SPECT/CT protocols will be required for generating the proper strategy for the specific lesions and clinical purpose.