Servet Tatli

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.

MRI-guided cryotherapy

Over the last decade the focus of published research on MRI‐guided cryotherapy has switched from the study of experimental models to the clinical treatment of patients. The latter reports attest to the safety and feasibility of treating lesions in the liver, kidney, and other sites throughout the body. Further, the published images and initial results speak to the utility of MRI for the task of monitoring this specific procedure. This clinical utility is a realization of the promise of the earlier experimental work that showed the clarity with which interstitial ice is seen under MRI under various pulse sequence parameters. Early adopters have taken advantage of access to the patient that is provided by low and mid‐field open scanners; the near future will test the suitability of higher field systems. It has been critical that an FDA‐approved cryotherapy system and suitably thin probes were customized for the MRI environment a decade ago by which percutaneous cryotherapy could be performed. There is still work to be done to expand the role of percutaneous cryotherapy, to understand various tissue responses, and to optimize visualization of therapeutic isotherms. Also, long‐term outcomes need to be assessed. Overall, in a worldwide environment in which the practice of ablation is growing and an appreciation for such therapies is on the rise, the work of these recent years provides sound footing for the advances that lay ahead for clinical MRI‐guided cryotherapy. J. Magn. Reson. Imaging 2008;27:410–420.

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.

Inflammatory nodules mimic applicator track seeding after percutaneous ablation of renal tumors.

OBJECTIVE The objective of our study was to report the occurrence of benign inflammatory nodules that develop in or near applicator tracks after percutaneous radiofrequency ablation and cryoablation of renal tumors. CONCLUSION Benign inflammatory nodules occur rarely after percutaneous ablation of renal tumors and may mimic tumor seeding of the applicator track.

CT for intracardiac thrombi and tumors

Although cardiac tumors are rare, they nevertheless represent an important subgroup, the diagnosis of which is challenging for the primary care physician. Symptoms are not characteristic and serious complications including stroke, myocardial infarction and even sudden death from arrhythmia may be the first signs of tumor. The most common primary cardiac neoplasm is the benign myxoma and the most frequent primary malignant lesion is sarcoma. Cardiac metastases from distant primary carcinomas are now frequently encountered. Echocardiography until the past decade was the only consistently reliable and available non-invasive diagnostic tool. New non-invasive CT and MRI exams are changing the diagnostic approach. Echocardiography and angiocardiography with or without coronary arteriography remain routine methods for evaluating cardiac neoplasms. However, CT provides additional diagnostic information and is regarded as essential for adequate staging and treatment planning, particularly when surgical resection is being considered. This chapter reviews the wide spectrum of intracardiac thrombi and tumors including their incidence and imaging characteristics with particular reference to the CT findings and differential diagnosis.

Local staging of rectal cancer using combined pelvic phased-array and endorectal coil MRI

To assess the accuracy of MRI, using a pelvic phased‐array coil and an endorectal coil, for preoperative local staging of rectal cancer.

Percutaneous cryoablation techniques and clinical applications.

Once requiring surgery, cryoablation now can be performed percutaneously under image guidance, thanks to the development of small probes. Sonography was used to guide cryoablation performed surgically; now, computed tomography and magnetic resonance images are typically used to guide percutaneous cryoablation. Intraprocedural monitoring helps those performing the procedure to treat the tumor completely, while avoiding complications. Percutaneous cryoablation has been shown to be safe and effective for many clinical applications including kidney, liver, prostate, breast, and musculoskeletal cancers. In this article, we briefly review percutaneous cryoablation techniques and clinical applications.

Radiofrequency ablation: technique and clinical applications.

Radiofrequency ablation is the most commonly used percutaneous ablation technique and well-documented in the literature on focal therapies. It has become the image-guided ablation method of choice because of its efficacy, safety, and ease of use. Radiofrequency ablation has shown promise in treating selected solid tumors, particularly those involving the liver, kidneys, lungs, and the musculoskeletal system. It is a minimally invasive technique often used in inoperable patients with other comorbidities. Radiofrequency ablation requires a minimal hospital stay or can be performed on an outpatient basis. The aim of this article is to review radiofrequency ablation techniques and their clinical applications.

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.

Noninvasive Multidetector Computed Tomography Enterography in Patients with Small-Bowel Crohn's Disease : Is a 40-Second Delay Better than 70 Seconds?

Background: Multidetector computed tomography (MDCT) enterography combines neutral enteric contrast with intravenously administered contrast material. The optimal intravenous (IV) contrast material protocol has still not been established. Purpose: To determine the optimal delay time to image patients with small-bowel Crohns disease during MDCT enterography. Material and Methods: After oral administration of 1350 ml of neutral contrast medium, 26 patients with small-bowel Crohns disease underwent MDCT enterography; scans were obtained 40 s (enteric phase) and 70 s (parenchymal phase) after IV administration of 100 ml of iodinated contrast material. Three radiologists, blinded to clinical and pathological findings, independently and retrospectively evaluated each scan in two separate reading sessions for the presence or absence of CT features of Crohns disease activity. The interobserver agreement was evaluated, and the efficacy of each phase in detecting active disease in the terminal ileum for each reader was determined. The gold standard was pathology (n = 13), endoscopy (n = 3), and clinical evaluation (n = 10). Results: No statistically significant difference was present between the enteric and the parenchymal phase for each reader in each segment regarding the presence or absence of CT features of Crohns disease. The interobserver agreement for the presence of five main features of active Crohns disease in the terminal ileum ranged from poor to excellent. The sensitivity, specificity, negative predictive value, positive predictive value, and accuracy for active Crohns disease in the terminal ileum ranged from 40 to 90%, 88 to 100%, 70 to 94%, 44 to 100%, and 69 to 96%, respectively. There was no statistical difference between the two phases for each reader. Conclusion: MDCT enterography in patients with suspected active Crohns disease can be obtained at either 40 s or 70 s after IV contrast material.