“Glowing Proof: ¹⁸F FDG PET/CT Confirms Biopsy Accuracy”

[¹⁸F]FDG PET/CT-Guided biopsy technique

A regional positron emission tomography/computed tomography (PET/CT) scan using 2-deoxy-2-[¹⁸F] fluoro-D-glucose ([¹⁸F] FDG) identified the most metabolically active portion of the rib lesion. With robotic assistance, the biopsy trajectory was planned, a coaxial needle was positioned, and 4–5 core samples were obtained, avoiding necrotic or hypometabolic areas [Fig 1].

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Fig 1: (a-d) Axial section post procedure check PET/CT (red and black arrow are PET/CT images and blue arrow is pure PET-AC images), confirming that the extracted tissue cores were correct representation of the hyper metabolic target region. This approach provides immediate visual confirmation of optimal tissue sampling. PET/CT: Positron emission tomography/computed tomography; PET-AC: Positron emission tomography with attenuation correction.

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Intra-procedural validation of sampling

To ensure sample adequacy, the extracted cores were placed in a beaker, and qualitative radioactivity measurement of retrieved specimens was acquired by imaging of the specimen container after the biopsy procedure under the PET/CT scanners for 15 minutes. Striking focal [¹⁸F]FDG uptake was observed in the cores, with minimal background activity, confirming that the specimens were truly representative of the hypermetabolic region [Fig 2]. This intra-procedural validation step is important in reducing the likelihood of non-diagnostic or necrotic sampling and improving diagnostic yield, as in previous studies.^[1–3] Final histopathology confirmed the diagnosis of perivascular epithelioid cell tumour (PEComa).

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Fig 2: Intra-procedural validation: (a and b) The extracted tissue cores, placed in a beaker, were scanned for 15 minutes in the PET/CT system. Striking focal ¹⁸F FDG uptake with minimal background activity was observed in MIP images (white arrows). (c and d) PET CT images of the core sample in beaker is confirming that the specimens were representative of the hyper metabolic target region (red arrows). This approach provided immediate visual confirmation of optimal tissue sampling prior to histopathological processing. MIP: Maximum intensity projection; PET/CT: Positron emission tomography/computed tomography; FDG: Fluorodeoxyglucose; CT: Computed tomography

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Validation of biopsy adequacy using [¹⁸F]FDG PET/CT has been described previously, particularly by groups from India and Europe.^[1,2] The current case illustrates the clinical utility of PET/CT-guided biopsy with real-time verification of sampling adequacy in a rare entity (PEComa). This approach may reduce the rate of inconclusive biopsies and improve diagnostic accuracy.^[2,3] In a study by Ferraro, D.A. et al., five consecutive patients with suspected Prostate carcinoma who underwent [¹⁸F]PSMA-1007 PET/CT scans followed by immediate PET/CT-guided and saturation template biopsy, the activity in biopsy cores was measured as counts per minute (CPM) in a gamma spectrometer. The mean CPM was overall significantly higher in needles with Prostate carcinoma compared to needles without Prostate carcinoma.^[4] Kaur N. et al studied the ex vivo measurement of the radioactivity of retrieved tissue specimens during PET/CT-guided biopsy and confirmed the sampling from the viable region and predicted the nature of the biopsied lesion before the histopathological analysis.^[5]

Most of the literature search mentions the measurement of the radioactivity of the extracted sample in a gamma spectrometer; however, we describe a practical one-stop approach of directly imaging the retrieved sample, and this technique is of relevance in ensuring accurate histopathological diagnosis, especially in lesions with necrotic or heterogeneous metabolic activity.