Paul B. Shyn

Abdominal Masses Sampled at PET/CT-guided Percutaneous Biopsy: Initial Experience with Registration of Prior PET/CT Images

PURPOSE To establish the feasibility of performing combined positron emission tomography (PET)/computed tomography (CT)-guided biopsy of abdominal masses by using previously acquired PET/CT images registered with intraprocedural CT images. MATERIALS AND METHODS In this HIPAA-compliant institutional review board-approved study, 14 patients underwent clinically indicated percutaneous biopsy of abdominal masses (mean size, 3.3 cm; range, 1.2-5.0 cm) in the liver (n = 6), presacral soft tissue (n = 3), retroperitoneal lymph nodes (n = 2), spleen (n = 2), and pancreas (n = 1). PET/CT images obtained no more than 62 days (mean, 18.3 days) before the biopsy procedure were registered with intraprocedural CT images by using image registration software. The registered images were used to plan the procedure and help target the masses. RESULTS The image registrations were technically successful in all but one patient, who had severe scoliosis. The remaining 13 biopsy procedures yielded diagnostic results, which were positive for malignancy in 10 cases and negative in three cases. CONCLUSION PET/CT-guided abdominal biopsy with use of prior PET/CT images registered with intraprocedural CT scans is feasible and may be helpful when fluorine 18 fluorodeoxyglucose-avid masses that are not seen sufficiently with nonenhanced CT are sampled at biopsy.

PET/CT-guided Percutaneous Biopsy of Abdominal Masses: Initial Experience

PURPOSE To develop a technique for guiding percutaneous biopsies of abdominal masses in a positron emission tomography (PET)/computed tomography (CT) scanner, and test its feasibility and safety in patients. MATERIALS AND METHODS The authors conducted a prospective study in 12 patients who were in need of both a diagnostic (18)F-fluoro-deoxy-D-glucose (FDG) PET/CT scan and a percutaneous biopsy of an abdominal mass, located in the liver (n = 7), presacral soft tissue (n = 2), lymph node (n = 2), and kidney (n = 1). After completion of the PET/CT scan, with the patient remaining on the table, a one-table-position PET/CT scan was obtained with a radiopaque grid in place, and the biopsy procedure was planned. Then, a biopsy needle was placed into the mass using one-table-position CT scan registered to the planning PET scan. Masses were sampled after confirming accurate positioning of the needle tips with a final one-table-position PET/CT scan. Negative results were confirmed independently with follow-up imaging. RESULTS All biopsy procedures yielded diagnostic results; nine were positive for malignancy, and three were negative (fibrosis, steatosis, and Escherichia coli infection). One non-FDG-avid mass biopsy yielded a malignant result. Seven masses were either invisible or poorly depicted with unenhanced CT scan, and two masses contained FDG avidity in only a portion of the mass. There were no complications. CONCLUSIONS Although our data are preliminary, this initial experience suggests that abdominal masses can undergo successful biopsy in a PET/CT scanner. PET/CT guidance may be helpful when performing biopsy on FDG-avid masses that are either not visible with unenhanced CT or are FDG avid in only a portion.

Doppler color flow imaging of carotid artery dissection.

The incidence of carotid artery dissections complicating an aortic dissection is reported to be 15%. In the past, the radiographic identification of these dissections has been made primarily with arteriography. There have been three cases reported in the literature which describe the ability to identify carotid dissection with high resolution ultrasound. l.J This report describes two cases in which the diagnosis was made with the use of Doppler color flow imaging (Quantum Medical Systems; Issaquah, WA). With this new technique, the diagnosis of dissection can be made easily and rapidly, and direction of flow in both lumens can be identified and quantified. Preoperative evaluation of patients with suspected aortic dissection often includes angiography. Aortic dissections, however, may be missed by angiography alone when filling of the false lumen does not occur. •.s Ultrasonographic evaluation of accessible arteries offers the advantage of demonstrating a false lumen, even if this lumen is thrombosed. Two cases of aortic dissection with se£ondary common carotid artery dissections were evaluated postoperatively by Doppler color flow imaging. We discuss advantages of this new imaging modality in the preoperative and postoperative evaluation of carotid artery dissections. CASE REPORTS

Low-Dose 18F-FDG PET/CT Enterography: Improving on CT Enterography Assessment of Patients with Crohn Disease

The purpose of this study was to evaluate the diagnostic efficacy of low-dose, combined 18F-FDG PET/CT enterography (PET/CTE), compared with CT enterography (CTE) alone, in the assessment of patients with Crohn disease. Methods: Thirteen patients with Crohn disease were prospectively enrolled in this pilot study and underwent abdominal–pelvic 18F-FDG PET/CTE using neutral oral and intravenous contrast medium. The effective dose from PET/CTE was 17.7 mSv for the first 4 patients and 8.31 mSv for the last 9 patients. Six patients underwent surgical resection of the bowel, and 7 patients underwent colonoscopy with biopsies within 27 d (mean, 12 d) of PET/CTE. PET/CTE and CTE images were each visually assessed for Crohn disease involvement in 54 bowel segments with pathology correlation. Extraintestinal findings were recorded. A CTE severity score, maximum standardized uptake value (SUVmax), SUVmax ratio, simplified endoscopic score, and clinical parameters were correlated with pathology inflammation grade, on a per-patient basis and on a per-bowel-segment basis, using Spearman correlation. Results: In 3 (23.1%) of 13 patients, 18F-FDG uptake using PET/CTE revealed active inflammation in a bowel segment not evident using CTE (n = 2) or revealed an enterocolic fistula missed with CTE (n = 1). Visual interpretation of both PET/CTE and CTE images detected the presence of disease in all bowel segments with more than mild inflammation (sensitivity, 100%; specificity, 89.7%; positive predictive value, 78.9%; and negative predictive value, 100%). Correlation to inflammation grade per patient was the strongest for the SUVmax ratio (0.735, P = 0.004) and SUVmax (0.67, P = 0.013), as compared with the CTE score (0.62, P = 0.024). Correlation with inflammation per bowel segment was higher for the CTE score (0.79, P < 0.0001) than the SUVmax ratio (0.62, P < 0.0001) or SUVmax (0.48, P < 0.0001). SUVmax correlated strongly with serum C-reactive protein (0.82, P = 0.023), but CTE score did not. Conclusion: Low-dose 18F-FDG PET/CTE, compared with CTE, may improve the detection and grading of active inflammation in patients with Crohn disease. PET/CTE also may reveal clinically significant findings, such as enterocolic fistula, not evident on PET or CTE alone.

The challenging image-guided abdominal mass biopsy: established and emerging techniques ‘if you can see it, you can biopsy it’

Image-guided percutaneous biopsy of abdominal masses is among the most commonly performed procedures in interventional radiology. While most abdominal masses are readily amenable to percutaneous biopsy, some may be technically challenging for a number of reasons. Low lesion conspicuity, small size, overlying or intervening structures, motion, such as that due to respiration, are some of the factors that can influence the ability and ultimately the success of an abdominal biopsy. Various techniques or technologies, such as choice of imaging modality, use of intravenous contrast and anatomic landmarks, patient positioning, organ displacement or trans-organ approach, angling CT gantry, triangulation method, real-time guidance with CT fluoroscopy or ultrasound, sedation or breath-hold, pre-procedural image fusion, electromagnetic tracking, and others, when used singularly or in combination, can overcome these challenges to facilitate needle placement in abdominal masses that otherwise would be considered not amenable to percutaneous biopsy. Familiarity and awareness of these techniques allows the interventional radiologist to expand the use of percutaneous biopsy in clinical practice, and help choose the most appropriate technique for a particular patient.

Multimodality Non-rigid Image Registration for Planning, Targeting and Monitoring During CT-Guided Percutaneous Liver Tumor Cryoablation

RATIONALE AND OBJECTIVES The aim of this study was to develop non-rigid image registration between preprocedure contrast-enhanced magnetic resonance (MR) images and intraprocedure unenhanced computed tomographic (CT) images, to enhance tumor visualization and localization during CT imaging-guided liver tumor cryoablation procedures. MATERIALS AND METHODS A non-rigid registration technique was evaluated with different preprocessing steps and algorithm parameters and compared to a standard rigid registration approach. The Dice similarity coefficient, target registration error, 95th-percentile Hausdorff distance, and total registration time (minutes) were compared using a two-sided Students t test. The entire registration method was then applied during five CT imaging-guided liver cryoablation cases with the intraprocedural CT data transmitted directly from the CT scanner, with both accuracy and registration time evaluated. RESULTS Selected optimal parameters for registration were a section thickness of 5 mm, cropping the field of view to 66% of its original size, manual segmentation of the liver, B-spline control grid of 5 × 5 × 5, and spatial sampling of 50,000 pixels. A mean 95th-percentile Hausdorff distance of 3.3 mm (a 2.5 times improvement compared to rigid registration, P < .05), a mean Dice similarity coefficient of 0.97 (a 13% increase), and a mean target registration error of 4.1 mm (a 2.7 times reduction) were measured. During the cryoablation procedure, registration between the preprocedure MR and the planning intraprocedure CT imaging took a mean time of 10.6 minutes, MR to targeting CT image took 4 minutes, and MR to monitoring CT imaging took 4.3 minutes. Mean registration accuracy was <3.4 mm. CONCLUSIONS Non-rigid registration allowed improved visualization of the tumor during interventional planning, targeting, and evaluation of tumor coverage by the ice ball. Future work is focused on reducing segmentation time to make the method more clinically acceptable.

Interobserver variability in target definition for hepatocellular carcinoma with and without portal vein thrombus: radiation therapy oncology group consensus guidelines.

PURPOSE Defining hepatocellular carcinoma (HCC) gross tumor volume (GTV) requires multimodal imaging, acquired in different perfusion phases. The purposes of this study were to evaluate the variability in contouring and to establish guidelines and educational recommendations for reproducible HCC contouring for treatment planning. METHODS AND MATERIALS Anonymous, multiphasic planning computed tomography scans obtained from 3 patients with HCC were identified and distributed to a panel of 11 gastrointestinal radiation oncologists. Panelists were asked the number of HCC cases they treated in the past year. Case 1 had no vascular involvement, case 2 had extensive portal vein involvement, and case 3 had minor branched portal vein involvement. The agreement between the contoured total GTVs (primary + vascular GTV) was assessed using the generalized kappa statistic. Agreement interpretation was evaluated using Landis and Kochs interpretation of strength of agreement. The S95 contour, defined using the simultaneous truth and performance level estimation (STAPLE) algorithm consensus at the 95% confidence level, was created for each case. RESULTS Of the 11 panelists, 3 had treated >25 cases in the past year, 2 had treated 10 to 25 cases, 2 had treated 5 to 10 cases, 2 had treated 1 to 5 cases, 1 had treated 0 cases, and 1 did not respond. Near perfect agreement was seen for case 1, and substantial agreement was seen for cases 2 and 3. For case 2, there was significant heterogeneity in the volume identified as tumor thrombus (range 0.58-40.45 cc). For case 3, 2 panelists did not include the branched portal vein thrombus, and 7 panelists contoured thrombus separately from the primary tumor, also showing significant heterogeneity in volume of tumor thrombus (range 4.52-34.27 cc). CONCLUSIONS In a group of experts, excellent agreement was seen in contouring total GTV. Heterogeneity exists in the definition of portal vein thrombus that may impact treatment planning, especially if differential dosing is contemplated. Guidelines for HCC GTV contouring are recommended.

PET/CT-guided percutaneous liver mass biopsies and ablations: targeting accuracy of a single 20 s breath-hold PET acquisition.

AIM To determine whether a single 20 s breath-hold positron-emission tomography (PET) acquisition obtained during combined PET/computed tomography (CT)-guided percutaneous liver biopsy or ablation procedures has the potential to target 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG)-avid liver masses as accurately as up to 180 s breath-hold PET acquisitions. MATERIALS AND METHODS This retrospective study included 10 adult patients with 13 liver masses who underwent FDG PET/CT-guided percutaneous biopsies (n = 5) or ablations (n = 5). PET was acquired as nine sequential 20 s, monitored, same-level breath-hold frames and CT was acquired in one monitored breath-hold. Twenty, 40, 60, and 180 s PET datasets were reconstructed. Two blinded readers marked tumour centres on randomized PET and CT datasets. Three-dimensional spatial localization differences between PET datasets and either 180 s PET or CT were analysed using multiple regression analyses. Statistical tests were two-sided and p < 0.05 was considered significant. RESULTS Targeting differences between 20 s PET and 180 s PET ranged from 0.7-20.3 mm (mean 5.3 ± 4.4 mm; median 4.3) and were not statistically different from 40 or 60 s PET (p = 0.74 and 0.91, respectively). Targeting differences between 20 s PET and CT ranged from 1.4-36 mm (mean 9.6 ± 7.1 mm; median 8.2 mm) and were not statistically different from 40, 60, or 180 s PET (p = 0.84, 0.77, and 0.35, respectively). CONCLUSION Single 20 s breath-hold PET acquisitions from PET/CT-guided percutaneous liver procedures have the potential to target FDG-avid liver masses with equivalent accuracy to 180 s summed, breath-hold PET acquisitions and may facilitate strategies that improve image registration and shorten procedure times.

Percutaneous Imaging-Guided Cryoablation of Liver Tumors: Predicting Local Progression on 24-Hour MRI

OBJECTIVE The purpose of this study was to determine which MRI features observed 24 hours after technically successful percutaneous cryoablation of liver tumors predict subsequent local tumor progression and to describe the evolution of imaging findings after cryoablation. MATERIALS AND METHODS Thirty-nine adult patients underwent technically successful imaging-guided percutaneous cryoablation of 54 liver tumors (hepatocellular carcinoma, 8; metastases, 46). MRI features pertaining to the tumor, ablation margin, and surrounding liver 24 hours after treatment were assessed independently by two readers. Fisher exact or Wilcoxon rank sum tests (significant p values < 0.05) were used to compare imaging features in patients with and without subsequent local tumor progression. Imaging features of the ablation margin, treated tumor, and surrounding liver were evaluated on serial MRI in the following year. RESULTS A minimum ablation margin of 3 mm or less was observed in 11 (78.6%) of 14 tumors with and 15 of 40 (37.5%) without progression (p = 0.012). A blood vessel bridging the ablation margin was noted in 11 of 14 (78.6%) tumors with and nine of 40 (22.5%) without progression (p < 0.001). The incidence of tumor enhancement 24 hours after cryoablation was similar for tumors with (10/14, 71.4%) or without (25/40, 62.5%) local progression (p = 0.75). MRI enabled assessment of the entire cryoablation margin in 49 of 54 (90.7%) treated tumors. CONCLUSION MRI features at 24 hours after liver cryoablation that were predictive of local tumor progression included a minimum ablation margin less than or equal to 3 mm and a blood vessel bridging the ablation margin. Persistent tumor enhancement is common after liver cryoablation and does not predict local tumor progression.

PET/CT-guided Radiofrequency and Cryoablation: Is Tumor Fluorine-18 Fluorodeoxyglucose Activity Dissipated by Thermal Ablation?

PURPOSE To determine if tumor fluorine-18 fluorodeoxyglucose ((18)F-FDG) activity is dissipated by radiofrequency (RF) ablation or cryoablation during tumor ablation guided by positron emission tomography/computed tomography (PET/CT). MATERIALS AND METHODS This prospective study enrolled 12 patients (9 women and 3 men, 39-65 years old), each with at least one (18)F-FDG-avid liver, perihepatic, or lung tumor. Six patients (experimental group) underwent percutaneous PET/CT-guided RF ablation (n = 3) or cryoablation (n = 3). Six patients (control group) underwent diagnostic PET/CT-guided percutaneous biopsy. At a mean time of 103.5 minutes after a single intravenous (18)F-FDG dose, preprocedure and postprocedure PET/CT scans, separated by a mean time interval of 83.4 minutes, were obtained in all patients. Target tumor maximum standardized uptake value (TSUVmax) and ratio (SUVratio) of TSUVmax to normal liver average standardized uptake value (LSUVavg) were measured on all scans. Percentage changes in TSUVmax and SUVratio from preprocedure to postprocedure scans were compared for both groups and analyzed using the Student t test (P < .05 considered statistically significant). RESULTS For all patients in both groups, TSUVmax and SUVratio increased from preprocedure to postprocedure PET/CT scans without statistically significant differences. The mean percentage increase in TSUVmax for the ablation group was 32.5% (range 8.2%-46.7%) and for the biopsy group was 24.6% (3.7%-42.4%; P = .45). The mean percentage increase in SUVratio for the ablation group was 47.9% (18.8%-69.6%) and for the biopsy group was 37.6% (9.4%-65%; P = .37). CONCLUSIONS Tumor (18)F-FDG activity is not dissipated by percutaneous RF ablation or cryoablation. When performing (18)F-FDG PET/CT-guided RF ablation or cryoablation, changes in target tumor (18)F-FDG activity cannot be used to monitor treatment effects.