Real-time FDG PET guidance during biopsies and radiofrequency ablation using multimodality fusion with electromagnetic navigation

Abstract

Purpose: To assess the feasibility of combined electromagnetic device tracking and computed tomography (CT)/ultrasonography (US)/fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) fusion for real-time feedback during percutaneous and intraoperative biopsies and hepatic radiofrequency (RF) ablation.

Materials and methods: In this HIPAA-compliant, institutional review board-approved prospective study with written informed consent, 25 patients (17 men, eight women) underwent 33 percutaneous and three intraoperative biopsies of 36 FDG-avid targets between November 2007 and August 2010. One patient underwent biopsy and RF ablation of an FDG-avid hepatic focus. Targets demonstrated heterogeneous FDG uptake or were not well seen or were totally inapparent at conventional imaging. Preprocedural FDG PET scans were rigidly registered through a semiautomatic method to intraprocedural CT scans. Coaxial biopsy needle introducer tips and RF ablation electrode guider needle tips containing electromagnetic sensor coils were spatially tracked through an electromagnetic field generator. Real-time US scans were registered through a fiducial-based method, allowing US scans to be fused with intraprocedural CT and preacquired FDG PET scans. A visual display of US/CT image fusion with overlaid coregistered FDG PET targets was used for guidance; navigation software enabled real-time biopsy needle and needle electrode navigation and feedback.

Results: Successful fusion of real-time US to coregistered CT and FDG PET scans was achieved in all patients. Thirty-one of 36 biopsies were diagnostic (malignancy in 18 cases, benign processes in 13 cases). RF ablation resulted in resolution of targeted FDG avidity, with no local treatment failure during short follow-up (56 days).

Conclusion: Combined electromagnetic device tracking and image fusion with real-time feedback may facilitate biopsies and ablations of focal FDG PET abnormalities that would be challenging with conventional image guidance.

Figure 1:

Equipment setup for electromagnetic device tracking during percutaneous interventions. Electromagnetic field generator (arrow) with sterile cover is positioned in proximity to the sterile field and directed toward anticipated needle entry site. Sterile fiducials (arrowheads) are placed on skin surface near anticipated skin entry site.

Figure 2a:

Cervical biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 71-year-old man with history of B-cell chronic lymphocytic leukemia with FDG-avid focus (SUV_max, 7.2 g · mL⁻¹) within extensive left cervical adenopathy. Clinical concern was for Richter transformation (transformation to aggressive large cell lymphoma) within a background of chronic lymphocytic leukemia. (a) Axial PET/CT scan of the neck demonstrates focus of FDG avidity (SUV_max, 7.2 g · mL⁻¹) (arrow) within extensive left cervical adenopathy. (b) Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrates no discrete anatomic abnormality to specifically correspond to patient’s small focus of abnormal FDG uptake. (c–f) Multiplanar display of intraprocedural CT scans fused to preacquired PET scans. Tracked biopsy of abnormal FDG avidity (arrow), facilitated by electromagnetic device tracking; image fusion confirmed chronic lymphocytic leukemia without evidence for Richter transformation. After 14 months of clinical and imaging follow-up, no new evidence for Richter transformation was observed, and patient’s focal left cervical FDG abnormality resolved at follow-up imaging.

Figure 2b:

Cervical biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 71-year-old man with history of B-cell chronic lymphocytic leukemia with FDG-avid focus (SUV_max, 7.2 g · mL⁻¹) within extensive left cervical adenopathy. Clinical concern was for Richter transformation (transformation to aggressive large cell lymphoma) within a background of chronic lymphocytic leukemia. (a) Axial PET/CT scan of the neck demonstrates focus of FDG avidity (SUV_max, 7.2 g · mL⁻¹) (arrow) within extensive left cervical adenopathy. (b) Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrates no discrete anatomic abnormality to specifically correspond to patient’s small focus of abnormal FDG uptake. (c–f) Multiplanar display of intraprocedural CT scans fused to preacquired PET scans. Tracked biopsy of abnormal FDG avidity (arrow), facilitated by electromagnetic device tracking; image fusion confirmed chronic lymphocytic leukemia without evidence for Richter transformation. After 14 months of clinical and imaging follow-up, no new evidence for Richter transformation was observed, and patient’s focal left cervical FDG abnormality resolved at follow-up imaging.

Figure 2c:

Cervical biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 71-year-old man with history of B-cell chronic lymphocytic leukemia with FDG-avid focus (SUV_max, 7.2 g · mL⁻¹) within extensive left cervical adenopathy. Clinical concern was for Richter transformation (transformation to aggressive large cell lymphoma) within a background of chronic lymphocytic leukemia. (a) Axial PET/CT scan of the neck demonstrates focus of FDG avidity (SUV_max, 7.2 g · mL⁻¹) (arrow) within extensive left cervical adenopathy. (b) Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrates no discrete anatomic abnormality to specifically correspond to patient’s small focus of abnormal FDG uptake. (c–f) Multiplanar display of intraprocedural CT scans fused to preacquired PET scans. Tracked biopsy of abnormal FDG avidity (arrow), facilitated by electromagnetic device tracking; image fusion confirmed chronic lymphocytic leukemia without evidence for Richter transformation. After 14 months of clinical and imaging follow-up, no new evidence for Richter transformation was observed, and patient’s focal left cervical FDG abnormality resolved at follow-up imaging.

Figure 2d:

Cervical biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 71-year-old man with history of B-cell chronic lymphocytic leukemia with FDG-avid focus (SUV_max, 7.2 g · mL⁻¹) within extensive left cervical adenopathy. Clinical concern was for Richter transformation (transformation to aggressive large cell lymphoma) within a background of chronic lymphocytic leukemia. (a) Axial PET/CT scan of the neck demonstrates focus of FDG avidity (SUV_max, 7.2 g · mL⁻¹) (arrow) within extensive left cervical adenopathy. (b) Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrates no discrete anatomic abnormality to specifically correspond to patient’s small focus of abnormal FDG uptake. (c–f) Multiplanar display of intraprocedural CT scans fused to preacquired PET scans. Tracked biopsy of abnormal FDG avidity (arrow), facilitated by electromagnetic device tracking; image fusion confirmed chronic lymphocytic leukemia without evidence for Richter transformation. After 14 months of clinical and imaging follow-up, no new evidence for Richter transformation was observed, and patient’s focal left cervical FDG abnormality resolved at follow-up imaging.

Figure 2e:

Cervical biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 71-year-old man with history of B-cell chronic lymphocytic leukemia with FDG-avid focus (SUV_max, 7.2 g · mL⁻¹) within extensive left cervical adenopathy. Clinical concern was for Richter transformation (transformation to aggressive large cell lymphoma) within a background of chronic lymphocytic leukemia. (a) Axial PET/CT scan of the neck demonstrates focus of FDG avidity (SUV_max, 7.2 g · mL⁻¹) (arrow) within extensive left cervical adenopathy. (b) Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrates no discrete anatomic abnormality to specifically correspond to patient’s small focus of abnormal FDG uptake. (c–f) Multiplanar display of intraprocedural CT scans fused to preacquired PET scans. Tracked biopsy of abnormal FDG avidity (arrow), facilitated by electromagnetic device tracking; image fusion confirmed chronic lymphocytic leukemia without evidence for Richter transformation. After 14 months of clinical and imaging follow-up, no new evidence for Richter transformation was observed, and patient’s focal left cervical FDG abnormality resolved at follow-up imaging.

Figure 2f:

Cervical biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 71-year-old man with history of B-cell chronic lymphocytic leukemia with FDG-avid focus (SUV_max, 7.2 g · mL⁻¹) within extensive left cervical adenopathy. Clinical concern was for Richter transformation (transformation to aggressive large cell lymphoma) within a background of chronic lymphocytic leukemia. (a) Axial PET/CT scan of the neck demonstrates focus of FDG avidity (SUV_max, 7.2 g · mL⁻¹) (arrow) within extensive left cervical adenopathy. (b) Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrates no discrete anatomic abnormality to specifically correspond to patient’s small focus of abnormal FDG uptake. (c–f) Multiplanar display of intraprocedural CT scans fused to preacquired PET scans. Tracked biopsy of abnormal FDG avidity (arrow), facilitated by electromagnetic device tracking; image fusion confirmed chronic lymphocytic leukemia without evidence for Richter transformation. After 14 months of clinical and imaging follow-up, no new evidence for Richter transformation was observed, and patient’s focal left cervical FDG abnormality resolved at follow-up imaging.

Figure 3a:

Pelvic biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 19-year-old woman with undifferentiated round cell tumor of the right ilium, sacrum, and iliopsoas muscle after chemotherapy and radiation therapy, with foci of abnormal FDG avidity within the right iliopsoas muscle, anterior ilium, and posterior right sacroiliac joint (SUV_max, 2.2, 3.0, and 3.6 g · mL⁻¹, respectively) on surveillance PET/CT scans. Percutaneous biopsy was requested to exclude residual/recurrent tumor. (a) Axial PET/CT scan of pelvis demonstrates focus of FDG avidity (SUV_max, 3.0 g · mL⁻¹) within right iliopsoas muscle (arrow). Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrated a large osteolytic soft-tissue mass in right hemipelvis and involving right sacroiliac joint, but no focal anatomic abnormality to correspond to patient’s focus of FDG abnormality along anterior aspect of this large soft-tissue mass within the right iliopsoas muscle. (b, c) Intraprocedural CT scans coregistered to preacquired PET scans. Targeted focus of FDG avidity is displayed as a blue dot (arrow); tracked biopsy needle introducer is displayed as green line throughout the intervention. Intersecting red lines can be positioned to highlight either the location of the preselected target (b), or the tip of the tracked needle (c), as per the operator’s preference, thereby adding visual conspicuity to either target or tracked needle tip during the procedure. (d) CT scan confirms actual needle inserted to target immediately prior to sampling (arrowhead). Tracked biopsy facilitated by electromagnetic device tracking and image fusion confirmed necrotic round cell tumor (ghosts of round cells) and no evidence for viable malignancy. Follow-up through clinical assessment, contrast-enhanced CT, MR imaging, and PET/CT confirmed resolution of FDG PET abnormalities, with no evidence for local tumor progression since biopsy (follow-up, 1 year, 11 months).

Figure 3b:

Pelvic biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 19-year-old woman with undifferentiated round cell tumor of the right ilium, sacrum, and iliopsoas muscle after chemotherapy and radiation therapy, with foci of abnormal FDG avidity within the right iliopsoas muscle, anterior ilium, and posterior right sacroiliac joint (SUV_max, 2.2, 3.0, and 3.6 g · mL⁻¹, respectively) on surveillance PET/CT scans. Percutaneous biopsy was requested to exclude residual/recurrent tumor. (a) Axial PET/CT scan of pelvis demonstrates focus of FDG avidity (SUV_max, 3.0 g · mL⁻¹) within right iliopsoas muscle (arrow). Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrated a large osteolytic soft-tissue mass in right hemipelvis and involving right sacroiliac joint, but no focal anatomic abnormality to correspond to patient’s focus of FDG abnormality along anterior aspect of this large soft-tissue mass within the right iliopsoas muscle. (b, c) Intraprocedural CT scans coregistered to preacquired PET scans. Targeted focus of FDG avidity is displayed as a blue dot (arrow); tracked biopsy needle introducer is displayed as green line throughout the intervention. Intersecting red lines can be positioned to highlight either the location of the preselected target (b), or the tip of the tracked needle (c), as per the operator’s preference, thereby adding visual conspicuity to either target or tracked needle tip during the procedure. (d) CT scan confirms actual needle inserted to target immediately prior to sampling (arrowhead). Tracked biopsy facilitated by electromagnetic device tracking and image fusion confirmed necrotic round cell tumor (ghosts of round cells) and no evidence for viable malignancy. Follow-up through clinical assessment, contrast-enhanced CT, MR imaging, and PET/CT confirmed resolution of FDG PET abnormalities, with no evidence for local tumor progression since biopsy (follow-up, 1 year, 11 months).

Figure 3c:

Pelvic biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 19-year-old woman with undifferentiated round cell tumor of the right ilium, sacrum, and iliopsoas muscle after chemotherapy and radiation therapy, with foci of abnormal FDG avidity within the right iliopsoas muscle, anterior ilium, and posterior right sacroiliac joint (SUV_max, 2.2, 3.0, and 3.6 g · mL⁻¹, respectively) on surveillance PET/CT scans. Percutaneous biopsy was requested to exclude residual/recurrent tumor. (a) Axial PET/CT scan of pelvis demonstrates focus of FDG avidity (SUV_max, 3.0 g · mL⁻¹) within right iliopsoas muscle (arrow). Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrated a large osteolytic soft-tissue mass in right hemipelvis and involving right sacroiliac joint, but no focal anatomic abnormality to correspond to patient’s focus of FDG abnormality along anterior aspect of this large soft-tissue mass within the right iliopsoas muscle. (b, c) Intraprocedural CT scans coregistered to preacquired PET scans. Targeted focus of FDG avidity is displayed as a blue dot (arrow); tracked biopsy needle introducer is displayed as green line throughout the intervention. Intersecting red lines can be positioned to highlight either the location of the preselected target (b), or the tip of the tracked needle (c), as per the operator’s preference, thereby adding visual conspicuity to either target or tracked needle tip during the procedure. (d) CT scan confirms actual needle inserted to target immediately prior to sampling (arrowhead). Tracked biopsy facilitated by electromagnetic device tracking and image fusion confirmed necrotic round cell tumor (ghosts of round cells) and no evidence for viable malignancy. Follow-up through clinical assessment, contrast-enhanced CT, MR imaging, and PET/CT confirmed resolution of FDG PET abnormalities, with no evidence for local tumor progression since biopsy (follow-up, 1 year, 11 months).

Figure 3d:

Pelvic biopsy facilitated by electromagnetic needle navigation and multimodality image fusion in 19-year-old woman with undifferentiated round cell tumor of the right ilium, sacrum, and iliopsoas muscle after chemotherapy and radiation therapy, with foci of abnormal FDG avidity within the right iliopsoas muscle, anterior ilium, and posterior right sacroiliac joint (SUV_max, 2.2, 3.0, and 3.6 g · mL⁻¹, respectively) on surveillance PET/CT scans. Percutaneous biopsy was requested to exclude residual/recurrent tumor. (a) Axial PET/CT scan of pelvis demonstrates focus of FDG avidity (SUV_max, 3.0 g · mL⁻¹) within right iliopsoas muscle (arrow). Corresponding unenhanced CT scan at level of abnormal FDG-avid focus demonstrated a large osteolytic soft-tissue mass in right hemipelvis and involving right sacroiliac joint, but no focal anatomic abnormality to correspond to patient’s focus of FDG abnormality along anterior aspect of this large soft-tissue mass within the right iliopsoas muscle. (b, c) Intraprocedural CT scans coregistered to preacquired PET scans. Targeted focus of FDG avidity is displayed as a blue dot (arrow); tracked biopsy needle introducer is displayed as green line throughout the intervention. Intersecting red lines can be positioned to highlight either the location of the preselected target (b), or the tip of the tracked needle (c), as per the operator’s preference, thereby adding visual conspicuity to either target or tracked needle tip during the procedure. (d) CT scan confirms actual needle inserted to target immediately prior to sampling (arrowhead). Tracked biopsy facilitated by electromagnetic device tracking and image fusion confirmed necrotic round cell tumor (ghosts of round cells) and no evidence for viable malignancy. Follow-up through clinical assessment, contrast-enhanced CT, MR imaging, and PET/CT confirmed resolution of FDG PET abnormalities, with no evidence for local tumor progression since biopsy (follow-up, 1 year, 11 months).