Positron Emission Tomography–CT Imaging in Guiding Musculoskeletal Biopsy

First Experiences with Fusion of PET-CT and MRI Datasets for Navigation-Assisted Percutaneous Biopsies for Primary and Metastatic Bone Tumors

Background: The aim of this study was to compare the technique of navigation-assisted biopsy based on fused PET and MRI datasets to CT-guided biopsies in terms of the duration of the procedure, radiation dose, complication rate, and accuracy of the biopsy, particularly in anatomically complex regions. Methods: Between 2019 and 2022, retrospectively collected data included all navigated biopsies and CT-guided biopsies of suspected primary bone tumors or solitary metastases. Navigation was based on preoperative CT, PET-CT/-MRI, and MRI datasets, and tumor biopsies were performed using intraoperative 3D imaging combined with a navigation system. Results: A total of 22 navigated (main group: m/f = 10/12, mean age: 56 yrs.) and 57 CT-guided biopsies (reference group: m/f = 36/21, mean age: 63 yrs.) were performed. Patients were grouped according to anatomic sites (pelvis, spine, extremities, thorax). The duration of the procedure in the reference group was significantly shorter than in the main group, particularly in the spine. The effective radiation dose was in the same range in both groups (main/reference group: 0.579 mSv and 0.687 mSv, respectively). In the reference group, a re-biopsy had to be performed in nine patients (diagnostic yield: 84%). A total of four major and three minor complications occurred in the reference group. Conclusions: Navigation-assisted percutaneous tumor biopsy resulted in correct, histologically useable diagnoses in all patients and reached a higher accuracy and first-time success rate (diagnostic yield: 100%) in comparison to CT-guided biopsies. The fusion of PET, CT, and MRI datasets enables us to combine anatomical with metabolic information. Consequently, target selection was improved, and the rate of false negative/low-grade sampling errors was decreased. Radiation exposure could be kept at a comparable level, and the durations of both procedures were comparable to conventional methods.

Augmenting CT-Guided Bone Biopsies Using 18F-FDG PET/CT Guidance

Computer tomography (CT)-guided percutaneous core biopsies are currently the gold standard in diagnostic procedures for patients with bone lesions of unknown kind. CT-guided biopsies can lead to misdiagnosis or repetition of biopsies in case of small or heterogeneous lesions. We hypothesize that molecular image guidance could be used to optimize the biopsy strategy, by supporting the detection of heterogeneous lesions or lesions without radiographic substrate. To evaluate this hypothesis, we investigated if and how the addition of 2-deoxy-2-18F-fluoro-D-glucose-positron emission tomography (18F-FDG-PET)/CT could augment routine CT-guided bone biopsies. To this end, 106 patients who underwent a CT-guided bone biopsy between April 2019 and April 2020, obtained from either a vertebral or peripheral bone, were included. Patients were divided into 2 groups: 36 patients received an 18F-FDG-PET/CT scan prior to their CT-guided bone biopsy (PET group), while 70 patients only had a morphological CT scan (CT group). Histopathology was used to categorize biopsies into five subgroups (inconclusive, benign, malignant or infectious disease, or normal tissue). In the PET group, the number of conclusive biopsies was significantly higher compared to the CT group (N = 33/36 (92%) versus N = 53/70 (76%); p < 0.05). Furthermore, the number of first-try biopsies was lower in the PET group compared to the CT group (1.9 vs. 2.54, p = 0.051). In conclusion, 18F-FDG-PET/CT imaging significantly increased the success rate of first-try CT-guided bone biopsies by showing less inconclusive biopsies and misdiagnosis.

PET/CT-guided versus CT-guided percutaneous core biopsies in the diagnosis of bone tumors and tumor-like lesions: which is the better choice?

OBJECTIVE

The present study aimed to evaluate the diagnostic performance and safety of PET/CT-guided percutaneous core bone biopsy and to compare the PET/CT-guided method to conventional CT-guided percutaneous core biopsies to diagnose Chinese patients with bone tumors and tumor-like lesions.

METHODS

Data for 97 patients with bone tumors and tumor-like lesions diagnosed by percutaneous core bone biopsy from February 2013 to November 2018 were retrospectively analyzed. The study included 42 cases in the PET/CT group and 55 cases in the CT alone group. The diagnostic performance, cost and complications associated with the intervention were compared between the two groups. All patients were eventually confirmed to have bone tumors and tumor-like lesions according to surgical pathology findings.

RESULTS

There were no significant differences in patient characteristics (P > 0.05). For the patients in the PET/CT group, the overall diagnostic yield of the initial biopsies and the diagnostic accuracy derived from the surgically proven cases were both 97.62%, which was significantly higher than the values in the CT group during the same period (P < 0.05). No major biopsy-related complications (e.g., serious bleeding or tumor dissemination) occurred before, during, or after the intervention. Therefore, no significant difference was observed between the two groups with regard to the complication rate (P > 0.05).

CONCLUSION

Compared with CT-guided percutaneous bone biopsy, PET/CT-guided percutaneous bone biopsy is an effective and safe alternative with high diagnostic performance in the evaluation of hypermetabolic bone lesions to diagnose bone tumors and tumor-like lesions.

Advanced modalities of molecular imaging in precision medicine for musculoskeletal malignancies

Musculoskeletal malignancies consist of a heterogenous group of mesenchymal tumors, often with high inter- and intratumoral heterogeneity. The early and accurate diagnosis of these malignancies can have a substantial impact on optimal treatment and quality of life for these patients. Several new applications and techniques have emerged in molecular imaging, including advances in multimodality imaging, the development of novel radiotracers, and advances in image analysis with radiomics and artificial intelligence. This review highlights the recent advances in molecular imaging modalities and the role of non-invasive imaging in evaluating tumor biology in the era of precision medicine.

PET/CT-guided biopsy with respiratory motion correction

PURPOSE

Given the ability of positron emission tomography (PET) imaging to localize malignancies in heterogeneous tumors and tumors that lack an X-ray computed tomography (CT) correlate, combined PET/CT-guided biopsy may improve the diagnostic yield of biopsies. However, PET and CT images are naturally susceptible to problems due to respiratory motion, leading to imprecise tumor localization and shape distortion. To facilitate PET/CT-guided needle biopsy, we developed and investigated the feasibility of a workflow that allows to bring PET image guidance into interventional CT suite while accounting for respiratory motion.

METHODS

The performance of PET/CT respiratory motion correction using registered and summed phases method was evaluated through computer simulations using the mathematical 4D extended cardiac-torso phantom, with motion simulated from real respiratory traces. The performance of PET/CT-guided biopsy procedure was evaluated through operation on a physical anthropomorphic phantom. Vials containing radiolabeled 18F-fluorodeoxyglucose were placed within the physical phantom thorax as biopsy targets. We measured the average distance between target center and the simulated biopsy location among multiple trials to evaluate the biopsy localization accuracy.

RESULTS

The computer simulation results showed that the RASP method generated PET images with a significantly reduced noise of 0.10 ± 0.01 standardized uptake value (SUV) as compared to an end-of-expiration image noise of 0.34 ± 0.04 SUV. The respiratory motion increased the apparent liver lesion size from 5.4 ± 1.1 to 35.3 ± 3.0 cc. The RASP algorithm reduced this to 15.7 ± 3.7 cc. The distances between the centroids for the static image lesion and two moving lesions in the liver and lung, when reconstructed with the RASP algorithm, were 0.83 ± 0.72 mm and 0.42 ± 0.72 mm. For the ungated imaging, these values increased to 3.48 ± 1.45 mm and 2.5 ± 0.12 mm, respectively. For the ungated imaging, this increased to 1.99 ± 1.72 mm. In addition, the lesion activity estimation (e.g., SUV) was accurate and constant for images reconstructed using the RASP algorithm, whereas large activity bias and variations (± 50%) were observed for lesions in the ungated images. The physical phantom studies demonstrated a biopsy needle localization error of 2.9 ± 0.9 mm from CT. Combined with the localization errors due to respiration for the PET images from simulations, the overall estimated lesion localization error would be 3.08 mm for PET-guided biopsies images using RASP and 3.64 mm when using ungated PET images. In other words, RASP reduced the localization error by approximately 0.6 mm. The combined error analysis showed that replacing the standard end-of-expiration images with the proposed RASP method in PET/CT-guided biopsy workflow yields comparable lesion localization accuracy and reduced image noise.

CONCLUSION

The RASP method can produce PET images with reduced noise, attenuation artifacts and respiratory motion, resulting in more accurate lesion localization. Testing the PET/CT-guided biopsy workflow using computer simulation and physical phantoms with respiratory motion, we demonstrated that guided biopsy procedure with the RASP method can benefit from improved PET image quality due to noise reduction, without compromising the accuracy of lesion localization.

PET Molecular Imaging-Directed Biopsy: A Review

OBJECTIVE

The purpose of this review is to summarize the applications of PET molecular imaging-directed biopsy of a variety of organs in the management of various diseases with a focus on cancers.

CONCLUSION

PET can yield metabolic information at the cellular and molecular levels, and PET-directed biopsy is playing an increasing role in the diagnosis and staging of diseases.

Fluorodeoxyglucose-PET/Computed Tomography-Guided Biopsy

PET/computed tomography (CT) combines the anatomic information from CT with PET metabolic characterization. 18F-fluorodeoxyglucose (FDG) PET is helpful to differentiate malignant lesions from benign ones, that usually show lower or no uptake. However, active inflammation or infectious disease might also present FDG uptake. Studies confirm the great value of PET/CT as the imaging method of choice for guiding biopsy procedures. Novel PET radiopharmaceuticals are also being investigated for guiding biopsies.

Advantages of percutaneous abdominal biopsy under PET-CT/ultrasound fusion imaging guidance: a pictorial essay

Positron emission tomography (PET) is a functional imaging technique that can investigate the metabolic characteristics of tissues. Currently, PET images are acquired and co-registered with a computed tomography (CT) scan (PET-CT), which is employed for correction of attenuation and anatomical localization. In spite of the high negative predictive value of PET, false-positive results may occur; indeed, Fluorine 18 ((18)F)-fluorodeoxyglucose ((18)F-FDG) uptake is not specific to cancer. As (18)F-FDG uptake may also be seen in non-malignant infectious or inflammatory processes, FDG-avid lesions may necessitate biopsy to confirm or rule out malignancy. However, some PET-positive lesions may have little or no correlative ultrasound (US) and/or CT findings (i.e., low conspicuity on morphological imaging). Since it is not possible to perform biopsy under PET guidance alone, owing to intrinsic technical limitations, PET information has to be integrated into a CT- or US-guided biopsy procedure (multimodal US/PET-CT fusion imaging). The purpose of this pictorial essay is to describe the technique of multimodal imaging fusion between real-time US and PET/CT, and to provide an overview of the clinical settings in which this multimodal integration may be useful in guiding biopsy procedures in PET-positive abdominal lesions.

Improving CT-guided transthoracic biopsy of mediastinal lesions by diffusion-weighted magnetic resonance imaging

OBJECTIVES

To evaluate the preliminary results obtained using diffusion-weighted magnetic resonance imaging and the apparent diffusion coefficient for planning computed tomography-guided biopsies of selected mediastinal lesions.

METHODS

Eight patients with mediastinal lesions suspicious for malignancy were referred for computed tomography-guided biopsy. Diffusion-weighted magnetic resonance imaging and apparent diffusion coefficient measurement were performed to assist in biopsy planning with diffusion/computed tomography fused images. We selected mediastinal lesions that could provide discordant diagnoses depending on the biopsy site, including large heterogeneous masses, lesions associated with lung atelectasis or consolidation, lesions involving large mediastinal vessels and lesions for which the results of biopsy using other methods and histopathological examination were divergent from the clinical and radiological suspicion.

RESULTS

In all cases, the biopsy needle was successfully directed to areas of higher signal intensity on diffusion-weighted sequences and the lowest apparent diffusion coefficient within the lesion (mean, 0.8 [range, 0.6-1.1]×10-3 mm2/s), suggesting high cellularity. All biopsies provided adequate material for specific histopathological diagnoses of four lymphomas, two sarcomas and two thymomas.

CONCLUSION

Functional imaging tools, such as diffusion-weighted imaging and the apparent diffusion coefficient, are promising for implementation in noninvasive and imaging-guided procedures. However, additional studies are needed to confirm that mediastinal biopsy can be improved with these techniques.

Role of positron emission tomography/computed tomography in bone malignancies

This article presents an overview of positron emission tomography combined with computed tomography (PET/CT) imaging of bone tumors for the practicing radiologist. The clinical roles and utility of (18)F-labeled fluorodeoxyglucose PET/CT in patients with primary bone tumors, osseous metastases, and multiple myeloma are reviewed. The clinical and research data supporting the utility of PET/CT in the evaluation of skeletal malignancies continues to grow.

The impact of coaxial core biopsy guided by FDG PET/CT in oncological patients

OBJECTIVE

When deciding on therapy, FDG PET/CT-positive results should be confirmed by histology if possible. We evaluated the impact of percutaneous PET/CT-guided biopsies on histological confirmation of PET/CT-positive lesions.

METHODS

We prospectively evaluated 126 patients who had undergone a PET/CT scan with positive results with an indication for histological evaluation of lesions. Imaging was performed in a PET/CT scanner with a fluoroscopic imaging system. A total of 130 lesions were accessed by PET/CT-guided biopsy. The technical feasibility, clinical success and complication rates of PET/CT-guided biopsies were evaluated.

RESULTS

Of 130 PET/CT-positive lesions, 128 (98.5 %) were successfully accessed and representative tissue samples obtained. Two lesions were reaccessed due to inconclusive histological results. Histology showed that 99 of the 130 lesions (76.2 %) were malignant, and 31 lesions (23.8 %) were benign (inflammatory cells or necrotic tissue); these patients had no recurrence of disease after a minimum follow-up of 6 months. Also, in 23 of the 130 lesions (17.7 %), the patient was referred for the PET/CT-guided biopsy due to a previous nontumoral biopsy result, and of these 23 lesions, 21 were found to be malignant. The complication rates were: pneumothorax in 15/130 (11.5 %; resolved spontaneously), haemoptysis in 2/130 (1.5 %) and severe haemothorax in 1/130 (0.8 %); there was no procedure-related mortality.

CONCLUSION

PET/CT-guided biopsy is feasible and may optimize the diagnostic yield of image-guided interventions. Also, PET/CT-positive lesions with no morphological correlation may now be accessible to percutaneous interventions.

Percutaneous biopsy based on PET/CT findings in cancer patients: technique, indications, and results

OBJECTIVE

To describe a technique for CT-guided biopsy based on PET/CT findings and to evaluate the indications and results of the technique in cancer patients.

METHODS

We evaluated all patients receiving CT-guided percutaneous biopsies whose indication was based on PET/CT findings at an oncology reference center from October 2009 to December 2010. The PET/CT images were evaluated side by side with noncontrast CT images to identify the lesion or area of interest to be biopsied. Biopsies were guided by CT with the needle directed at the area of metabolic activity identified in the PET/CT examination performed before the procedure.

RESULTS

A total of 64 cases were included in this study. The most common lesion location was pulmonary (n = 28; 43.8%). The median of the lesions' greatest diameter and maximum SUV were 44.1 ± 31.6 mm (10-186 mm) and 8.4 ± 5.9 (2.1-34.0), respectively. The histologic results of the biopsies were negative for malignancy in 15 cases (23.4%), positive in 46 cases (71.9%), and inconclusive in 3 cases (4.7%). Lesions with an SUV ≥ 4.0 were more likely to be malignant (85.4% vs. 46.2%; P = 0.006).

CONCLUSIONS

CT-guided biopsies should be used routinely for lesions identified or better characterized by PET/CT. The results of this study demonstrate that this method is reliable, secure, and very accurate diagnostically, revealing a high percentage of malignant lesions.

The role of imaging for translational research in bone tumors

Sarcomas are a heterogeneous group of rare connective tissue tumors, representing 1% of adult and 15% of childhood cancers for which biological and pathological information is still incomplete. In bone tumors patients with metastatic disease at onset, those who relapse and those with post-surgical secondary lesions still have a dismal outcome because of poor response to current therapies. Different molecular biology approaches have identified activated cell signalling pathways or specific molecular endpoints that may be considered potential drug targets or markers useful for diagnosis/prognosis in musculoskeletal pathology. Recently, advances in the field of molecular imaging allow visualization of cell and metabolic functions with the use of targets that include cell membrane receptors, enzymes of intracellular transport. Moreover advanced non-invasive newer imaging techniques like 18-FDG PET, quantitative dynamic-contrast MR imaging, diffusion weighted imaging have all shown a potential in distinguish malignant from benign lesions, in revealing the efficacy of therapy in tumors, the onset of recurrence and a good reliability in reckoning the percentage of necrosis in Ewing sarcoma and osteosarcoma. Thus, in vivo detection of imaging cancer biomarkers may be useful to better characterize those complex pathologic processes, such as apoptosis, proliferation and angiogenesis that determine tumor aggressiveness, providing not only complementary information of prognostic metabolic indicators, but also data in real-time on the efficacy of the treatment through the modulation of the cell metabolism.

Hybrid imaging (SPECT/CT and PET/CT)--improving the diagnostic accuracy of functional/metabolic and anatomic imaging

In-line combined systems, single-photon emission computed tomography (SPECT)/computed tomography (CT) and positron emission tomography (PET)/CT, allow an instant generation of fused images of scintigraphy and CT data. The accumulated clinical data on the use of these systems in various clinical scenarios indicate that this hybrid technology improves the diagnostic accuracy as compared to scintigraphy and CT alone and even to side-by-side interpretation of scintigraphy and CT, which were acquired separately. The improved diagnostic accuracy is reflected by improving image quality of SPECT and PET, detection of more clinically relevant lesions, better localization of disease and differentiation between physiologic and pathologic uptake, characterization of disease by its functional and morphologic appearance before and after therapy and accurate delineation of disease, optimizing biopsy and therapy planning.