Skeletal Metastases and Benign Mimics on NaF PET/CT: A Pictorial Review

Hyperostosis frontalis interna on fluorine-18 sodium fluoride PET/computed tomography of obese cancer patients: a potential mimicker of metastasis

OBJECTIVE

The objective of this retrospective study was to identify the uptake patterns and suggest a quantitative method to detect hyperostosis frontalis interna (HFI) on fluorine-18 sodium fluoride ([18F]NaF) PET/computed tomography (CT).

METHODS

Between January 2019 and December 2021, patients who underwent [18F]NaF PET/CT with a BMI of 30 and above, were included. Three nuclear medicine consultants reviewed the studies to determine the presence and identify the uptake patterns of HFI. Quantitative evaluation was performed on PET images using the total number of counts over the frontal bone and the ratio of counts between the frontal bone and iliac crest.

RESULTS

A total of 105 out of 249 cases were included in this study. Among these scans, there were 67 positive HFI in [18F]NaF PET scans representing 64% of the studied population. As for the [18F]NaF PET uptake pattern, there were 53 with uniformly diffused and 14 with heterogeneous uptake pattern. There were 17 out of 67 with positive HFI in [18F]NaF PET scans but negative CT scans.

CONCLUSION

HFI is a common finding on [18F]NaF PET in obese patients and is probably underdiagnosed. HFI may present with a heterogeneous and diffuse pattern of uptake on [18F]NaF PET. The proposed quantitative analysis using the count ratios is in agreement with the visual evaluation of [18F]NaF PET images regardless of the CT findings. Awareness of this condition and its scintigraphic patterns is warranted since it can have clinical significance and may mimic other pathologies including metastasis in cancer patients.

Review of the role of MRI and 18 F-sodium fluoride PET/computed tomography in the characterisation of spinal bone metastases in a cohort of patients with breast cancer

PURPOSE

The purpose of the study was to compare the diagnostic accuracy and relative usefulness of MRI and 18 F-NaF (sodium fluoride) PET/computed tomography (CT) for detection of spinal bone metastases in a cohort of patients with high-risk breast cancer (BrCa).

METHODS

A retrospective study was conducted of patient and lesion-based analyses on 66 consecutive patients (median age, 62.5 years; age range, 33-91 years) who underwent Spinal MRI as well as 18 F-NaF PET-CT for restaging of newly diagnosed recurrent BrCa with no previous bone metastases. Both scans were performed within 20 days of each other. Review of prior images, clinical decisions, multi-disciplinary team discussions and decisions as well as follow-up information including scans and definitive tests was performed at least 12 months after the initial scans.

RESULTS

Of the 66 patients reviewed, 26 patients had documented spinal bone metastases on one or both modalities, while 40 patients were considered bone disease free on both modalities and this was confirmed on follow-up. On lesion-based analysis, the findings of 18 F-NaF PET-CT and spinal MRI were concordant in 51 patients (77.3%). In the remaining patients, 18 F-NaF PET/CT detected more lesions in 4 patients (7.6%) and MRI detected more lesions in 10 patients (15.1%). Interestingly, there was a very high, 97 % concordance (64 patients) between spinal MRI and 18 F-NaF PET-CT when staging of spinal bone metastasis was taken into consideration. In one patient MRI identified two spinal bone metastases which were not seen on 18 F-NaF PET/CT; and, in one patient 18 F-NaF PET/CT showed few spinal bone metastases when no lesion was seen on MRI.

CONCLUSIONS

Our study showed a high level of concordance between 18 F NaF PET-CT and spinal MRI within the setting of detection of bone lesions in the spine in a cohort of patients with high-risk BrCa. In our opinion, this high level of concordance negates the need to perform both tests although each test may be indicated for slightly different reasons. Further longitudinal studies across a longer duration and more centres may provide more definitive answers.

Team Approach: Management of Pathologic Fractures

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Optimal care for pathologic fractures centers on the use of a multidisciplinary team; thus, whenever there is a concern for pathologic fracture and proper workup is unable to be performed, prompt referral to a center equipped to manage these injuries should occur.

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Fixation strategies for pathologic fractures must take into account patient characteristics, cancer subtypes, and overall goals of treatment.

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As the treatments of cancers improve, patient life expectancy with disease will improve as well. This will lead to an increase in the incidence of impending or completed pathologic fractures. The broader subspecialties of orthopaedics must be aware of general principles in the diagnosis and management of these injuries.

Preparation, biological characterization and preliminary human imaging studies of 68Ga-DOTA-IBA

Purpose

In this study, DOTA-IBA was radiolabeled with ⁶⁸Ga and we determined the optimum labelling conditions and assessed the biological properties of ⁶⁸Ga-DOTA-IBA. We investigated the biodistribution of ⁶⁸Ga-DOTA-IBA in normal animals and undertook PET/CT imaging in humans. Finally, we explored the feasibility ⁶⁸Ga-DOTA-IBA as a bone imaging agent and demonstrated its potential for the therapeutic release of ¹⁷⁷Lu/²²⁵Ac-DOTA-IBA.

Methods

The controlled variables method was used to assess the impact of variables on the radiochemical purity of ⁶⁸Ga-DOTA-IBA. The biological properties of ⁶⁸Ga-DOTA-IBA were investigated.⁶⁸Ga-DOTA-IBA micro-PET/CT imaging was performed on animals. Volunteers were recruited for ⁶⁸Ga-DOTA-IBA imaging and data were compared to ^99mTc-MDP imaging studies to calculate the target to non-target ratio (T/NT) of the lesions.

Results

The prepared ⁶⁸Ga-DOTA-IBA had a radiochemical purity of >97% and demonstrated good biological properties with a good safety profile in normal mice. PET/CT imaging of the animals showed rapid blood clearance with high contrast between the bone and stroma. Human imaging showed that ⁶⁸Ga-DOTA-IBA could detect more lesions compared to ^99mTc-MDP and had a higher targeted to untargeted ratio.

Conclusions

⁶⁸Ga-DOTA-IBA is an osteophilic radiopharmaceutical that can be synthesized using a simple labelling method. ⁶⁸Ga-DOTA-IBA has high radiochemical purity and is stable in vitro stability. It is rapidly cleared from the blood, has low toxicity and has strong targeting to the bone with long retention times. We also found that it is rapidly cleared in non-target tissues and has high contrast on whole-body bone imaging. ⁶⁸Ga-DOTA-IBA PET/CT has potential as a novel bone imaging bone modality in patients with metastatic disease.

Multidisciplinary management of spinal metastases: what the radiologist needs to know

The modern management of spinal metastases requires a multidisciplinary approach that includes radiation oncologists, surgeons, medical oncologists, and diagnostic and interventional radiologists. The diagnostic radiologist can play an important role in the multidisciplinary team and help guide assessment of disease and selection of appropriate therapy. The assessment of spine metastases is best performed on MRI, but imaging from other modalities is often needed. We provide a review of the clinical and imaging features that are needed by the multidisciplinary team caring for patients with spine metastases and stress the importance of the spine radiologist taking responsibility for synthesizing imaging features across multiple modalities to provide a report that advances patient care.

Hyperostosis fronto-parietalis - radiology mimic of metastasis: A case report

Hyperostosis frontalis interna (HFI) is a benign entity manifested by bony overgrowth in the frontal endocranial surface. It is most commonly reported incidentally among postmenopausal elderly women. Tracer uptake appearances of HFI can vary on planar bone scans, enabling it to be easily confounded with bone metastases. We report a case of HFI in a 69-year-old postmenopausal female with treated left breast cancer detected on bone scintigraphy, with subsequent confirmation by computed tomography. Our case highlights the importance of having awareness of HFI and its key pattern findings to avoid mistaking it for pathology, and to recognise the use of computed tomography and hybrid fusion imaging techniques as reliable diagnostic tools for HFI.

Osteitis Fibrosa Cystica Caused by Hyperparathyroidism Shown on 18F-NaF PET/CT

F-NaF PET/CT in hyperparathyroidism and osteitis fibrosa cystica is rarely reported. We report the case of a 16-year-old boy who underwent NaF PET/CT for the evaluation of bilateral bone destruction, which was incidentally noted on an abdominal x-ray. The PET/CT images identified multiple bony abnormalities in the skull, pelvis, and limbs. In addition, a hypodense nodule was found posterior to the inferior pole of the right lobe of thyroid gland. Subsequent Tc-sestamibi imaging showed abnormal uptake in the neck nodule, which was confirmed as parathyroid adenoma by the pathology.

18F-Sodium Fluoride PET: History, Technical Feasibility, Mechanism of Action, Normal Biodistribution, and Diagnostic Performance in Bone Metastasis Detection Compared with Other Imaging Modalities

The skeleton is the third most common site for metastasis overall, after the lungs and liver. Accurate diagnosis of osseous metastasis is critical for initial staging, treatment planning, restaging, treatment monitoring, and survival prediction. Currently, ^99mTc-methylene diphosphonate whole-body scanning is the cornerstone of imaging to detect osseous metastasis. Although ¹⁸F-sodium fluoride (¹⁸F-NaF) was one of the oldest medical tracers for this purpose, it was replaced by other tracers because of their better physical properties, until recently. Continued development of PET scanners has opened a new era for ¹⁸F-NaF, and given its higher sensitivity, there have been increasing applications in imaging. In this review, we will discuss the history, technical aspects, radiobiology, and biodistribution of this tracer. Finally, we compare the accuracy of ¹⁸F-NaF PET with other conventional imaging methods for detection of osseous metastasis.