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ABSTRACT |
Tuesday, May 2, 11:20 AM–12:30 PM
Abstracts 102–107
Moderators: Don C. Yoo, MD and Alan Siegel, MD
11:20 AM
102. Diagnosis of Richter's Transformation of Chronic Lymphocytic Leukemia by PET-CT Imaging
Bruzzi J.F.*; Truong M.; Marom E.; Sabloff B.; Macapinlac H.; Munden R.; Diagnostic Radiology, MD Anderson Cancer Center, Houston, TX.
Address correspondence to J.F. Bruzzi (jbruzzi{at}mdanderson.org)
Objective: Transformation of chronic lymphocytic leukemia (CLL) to diffuse large B cell lymphoma (Richter's transformation) or other malignancy occurs in 5% of patients with CLL and carries a poor prognosis. The objective of this study was to assess the diagnostic accuracy of PET-CT imaging in diagnosing malignant transformation of CLL.
Materials and Methods: A retrospective observational study was performed of all patients with CLL who underwent PET-CT imaging between May 2003 and April 2005. All PET-CT studies were performed on an integrated PET-CT scanner. CT, PET and fused PET-CT images from each of these PET-CT studies were reviewed together by two radiologists, who documented the following parameters: location of sites of abnormal FDG accumulation, defined as abnormal foci of FDG uptake with a maximum standard uptake value (SUVmax per body weight) of greater than 4; results from fine needle aspiration (FNA) or biopsy of enlarged lymph nodes or extranodal masses. Results of PET-CT scans were correlated with bone marrow biopsy analysis, and with clinical and laboratory data.
Results: 30 consecutive patients with CLL who underwent PET-CT during the study period (22 men, 8 women; mean age 61 years, range 40 – 82 years) were eligible for inclusion. PET-CT was performed to exclude malignant transformation of CLL in patients with clinically progressive disease (n = 21) and in peripheral stem cell transplant recipients (n = 9). In 16 patients (53%), PET-CT demonstrated foci of abnormally increased FDG uptake. Causes of increased FDG accumulation included histologically-confirmed transformation to diffuse large cell lymphoma or another malignancy (n = 10), accelerated phase CLL (n = 3), progressive CLL refractory to treatment (n = 2) and pneumonia (n = 1). Overall, PET-CT had a 63% positive predictive value for the diagnosis of malignant transformation of CLL. In 14 patients, PET-CT demonstrated lymphadenopathy with no or low-grade FDG uptake (SUVmax<4); none of these patients had malignant transformation according to bone marrow analysis and clinical follow-up over 4 months (negative predictive value, 100%).
Conclusion: In patients with CLL, abnormally elevated metabolic activity detected by PET-CT imaging indicates a poor clinical course with a high probability of transformation to a more aggressive malignancy. Normal or low-grade FDG uptake on PET-CT excludes malignant transformation with a high degree of confidence.
103. Non-Invasive Measurement of Temperature Distribution in Cryopreservation Solutions Using SMRI
Johnson S.A.1,3*; Thompson R.2; Lambert R.G.W.1; McGann L.E.3; 1. Department of Radiology and Diagnostic Imaging, University of Alberta, Edmonton, AB, Canada; 2. Department of Biomedical Engineering, University of Alberta, Edmonton, AB, Canada; 3. Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, AB, Canada.
Address correspondence to S.A. Johnson (saj{at}ualberta.ca)
Objective: Development of protocols for cryopreservation of tissues for transplant requires accurate monitoring of temperature and concentrations throughout samples during cooling and warming. In this study, spectroscopic magnetic resonance imaging (SMRI) is investigated as a noninvasive method for measuring spatial distribution of temperatures in cryoprotectant solutions used for cartilage preservation. SMRI provides a proton spectrum for each image voxel, and differentiates signals originating from water and cryoprotectant. We propose that chemical shift differences between water and cryoprotectant protons, measured directly from proton spectra, will correlate with sample temperature.
Materials and Methods: Cryoprotectant solutions of dimethyl sulfoxide (DMSO) in water at four different concentrations (range 1–5M) were cooled to -80°C. Samples were then warmed inside a 1.5 Tesla MRI system over 4 hours and imaged at 34 time points to sample a range of temperatures from -80°C to 0°C. The spectroscopic imaging pulse sequence was based on a conventional gradient echo approach, modified with a train of 1024 echoes, 1ms sampling interval and effective spectroscopic bandwidth of 1000 Hz. Imaging parameters were: 2 mm x 2 mm in-plane resolution, 8mm slice thickness, 2 second repetition time and total acquisition time of 2 minutes. Spectra from individual image voxels (32 µl) from each sample were analyzed.
Results: Spectroscopic analysis yielded significant variations in
several spectral properties including spin density (area under peaks), peak
line width, and chemical shift difference between water and DMSO peaks. All
four cryoprotectant concentrations yielded the same direct relationship
between temperature and chemical shift difference. At 1.5T, chemical shift
differences varied from 162 Hz at -80°C to 142 Hz at 0°C. Chemical
shift of a given peak could be detected with an accuracy of 
0.3 Hz based
on Monte-Carlo simulations. This translates to temperature measurement with
accuracy of 1.2°C.
Conclusion: These results confirm the potential for non-invasive temperature mapping of cryoprotected samples using SMRI. This approach allows measurement of absolute temperature independent of water mass, with high spatial resolution, and without need for reference information. This technique could resolve important limitations in current cryobiology research.
104. 18-FDG PET in the Evaluation of Malignant Pleural Mesothelioma and Evaluation of Standardized Uptake Values (SUV) as a Prognostic Marker
Chaudhry S.*; Vesselle H.J.; Department of Radiology, University of Washington, Seattle, WA.
Address correspondence to S. Chaudhry (SIDHARTH{at}U.WASHINGTON.EDU)
Objective: The incidence of malignant pleural mesothelioma is increasing while its prognosis remains poor. CT is suboptimal in characterizing pleural thickening. The aim of this study was to evaluate the utility of PET imaging in differentiating benign from malignant pleural thickening. Furthermore we evaluated standardized uptake values (SUV) as a prognostic marker for length of survival in patients with malignant pleural mesothelioma.
Materials and Methods: Between February 1999 and September 2001, 35 patients with clinical suspicion of mesothelioma and CT evidence of pleural thickening underwent F18-FDG PET examination. Axial, sagittal and coronal reconstruction images were visually interpreted and semi quantitative analysis performed using SUV measurement. The results of PET imaging were compared with pathology data. Patients were followed for up to 6 years. Maximum SUV was compared to length of patient survival.
Results: Out of 35 patients, histology demonstrated malignant pleural mesothelioma in 32 patients. One patient had malignant spindle cell neoplasm and 2 patients had benign pleural disease. Maximum SUV was 2.6 in patients with benign pleural disease. The solitary patient with malignant spindle cell neoplasm had maximum SUV of 4.2. The average maximum SUV among patients with mesothelioma was 8.5, and it ranged from 2.7 to 18.1. With a cutoff of 3, PET demonstrated a sensitivity of 96.9 %and specificity of 100% in differentiating benign from malignant pleural process. We subdivided mesothelioma patients into two groups. Those with maximum SUV up to 7 on the initial scan had a mean survival of 28 months from the date of scan, while those with SUV values above 7 had a mean survival of 8.5 months. Conversely, a subgroup of patients with survival of less than 12 months had average maximum SUV of 8.2 while another group with survival between 1 and 6 years had maximum SUV of 5.8.
Conclusion: This is the largest series to date evaluating PET imaging in malignant pleural mesothelioma. PET has proven to be a highly sensitive and specific modality to characterize pleural thickening. Furthermore, maximum SUV helps to predict long-term prognosis.
105. Accuracy of PET-CT in Detecting Ovarian Cancer Recurrence: Comparison with CT Alone and PET Alone
Sebastian S.1*; Fischman A.J.2; Horowitz N.S.2; Hahn P.F.2; Simeone J.F.2; Lee S.I.1,2; 1. Radiology, Emory University School of Medicine, Atlanta, GA; 2. Radiology, Massachusetts General Hospital, Boston, MA.
Address correspondence to S. Sebastian (Sunit.Sebastian{at}emoryhealthcare.org)
Objective: To investigate the relative accuracy of body CT, FDG-PET, and hybrid PET-CT for detection of recurrent ovarian carcinoma after primary treatment and debulking surgery.
Materials and Methods: Institutional review board approval was obtained for retrospective review of the scans and medical records. We reviewed 54 consecutive body CT, PET and PET-CT examinations on 53 patients presenting over a 15 month period with histologically proven ovarian cancer being evaluated for question of tumor recurrence. A PET scan and a CT of the neck, chest, abdomen and pelvis were performed without intravenous but with negative oral contrast on a fusion PET-CT scanner. One hour later, delayed PET images were obtained. These images were used for attenuation correction and fusion. Finally a diagnostic CT scan was performed with intravenous contrast and negative oral contrast. A body imager interpreted the diagnostic CT while a nuclear medicine expert independently reviewed the PET. Subsequently the two readers together interpreted the PET-CT fusion study in conjunction with the diagnostic CT. A gynecologic oncologist provided the gold standard for presence of recurrent disease based on review of the clinical records from the time of initial patient presentation to at least 3 months following the date of the scans. Pathology, radiology, and operative reports, laboratory values, treatment history, and physical exam records were included to establish the gold standard. The gynecologic oncologist and the readers were blinded to their respective findings.
Results: For the body overall, PET-CT demonstrates improved accuracy (49/53, 92%) over CT (44/53, 83%) and over PET (41/53, 77%). ROC analysis shows that this difference is statistically significant for CT (p < 0.01) but not for PET (p = 0.25). In the chest, PET-CT demonstrates improved accuracy (51/53, 96%) over CT (47/53, 89%) and PET (48/53, 90%). ROC analysis shows that this difference is not statistically significant either for CT (p = 0.07) or for PET (p = 0.33). In the abdomen, PET-CT again demonstrates improved accuracy (48/53, 91%) over CT (42/53, 79%) and PET (42/53, 79%). ROC analysis shows that this difference is statistically significant for CT (p < 0.01) but not for PET (p = 0.08).
Conclusion: The accuracy of PET-CT for detecting recurrent ovarian cancer is high. PET-CT is more accurate than CT alone or PET alone. For detecting disease either above or below the diaphragm, PET-CT is more accurate than CT alone or PET alone.
106. FDG-PET/CT in the Evaluation of Cutaneous T-cell Lymphoma
Kuo P.H.1*; McClennan B.L.1; Thompson K.2; Wilson L.3; Edelson R.2; Heald P.2; Girardi M.2; 1. Department of Diagnostic Radiology, Yale University School of Medicine, New Haven, CT; 2. Dermatology, Yale University School of Medicine, New Haven, CT; 3. Radiation Therapy, Yale University School of Medicine, New Haven, CT.
Address correspondence to P.H. Kuo (phillip.kuo{at}yale.edu)
Objective: To begin to assess the utility of utilizing combined fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) in the management of patients with cutaneous T cell lymphoma (CTCL), patients with varying stages of disease were full-body scanned using a General Electric Discovery ST 16-slice machine.
Materials and Methods: Patients were assessed by PET/CT for focal cutaneous and nodal FDG uptake, indicative of highly metabolically active (i.e. putatively malignant, cells), and comparisons were made to CT data alone and to the physical examination.
Results: Several key observations were made which suggested that information afforded by PET/CT scan was valuable. For example, the differing levels of FDG uptake in enlarged nodes found within an individual patient as well as among different patients may distinguish reactive from malignant adenopathy. Additionally, lymph nodes that would otherwise not meet pathologic size criteria (e.g., were not > 1 cm) were revealed in some cases to contain high metabolic activity. Thus, sub-centimeter nodes that would not meet size criteria for adenopathy may be marked for subsequent monitoring or targeted for biopsy. In addition, various cutaneous lesions, from thin subtle plaques to subcutaneous tumors, were revealed by focal FDG uptake and corresponded accurately (or were superior) to the cutaneous exam. Finally, serial PET/CT scans have also shown the ability to monitor response to a variety of therapeutic modalities.
Conclusion: In summary, PET/CT provides physiologic and anatomic information on the wide diversity of external and internal lesions in CTCL and therefore has great potential in improving the staging and monitoring of response to therapy of both the cutaneous and nodal disease.
107. Compensating Respiratory Blurring in PET/CT Imaging with the Respiratory-Aligned Summed-Phases (RASP) Method
MacDonald L.R.1*; Kinahan P.E.1; Alessio A.M.1; Segars W.P.2; Tsui B.M.2; 1. Radiology, University of Washington, Seattle, WA; 2. Radiology, Johns Hopkins University, Baltimore, MD.
Address correspondence to L.R. MacDonald (macdon{at}u.washington.edu)
Objective: PET/CT imaging has introduced new challenges in accurate quantitation of lung nodules due to respiratory motion and mismatches in CT-based attenuation correction (CTAC). We used Monte Carlo simulations to investigate how attenuation correction (AC) methods for PET can be optimized to account for mis-registration between the CTAC data and the PET data due to respiratory motion. This is a first step in developing a method of compensating for respiratory motion by non-rigid image registration and summation of separate respiratory phases (RASP).
Materials and Methods: The NCAT digital phantom was used to generate anthropomorphic distributions of radiotracer and linear attenuation coefficients that were used as source emission and attenuation data. A 2-cm diameter lesion, positioned in the lower right lung just above the liver, was added to the NCAT anatomy. The NCAT phantom models respiratory motion; Ten sets of both PET and CTAC data were generated at 0.5 sec. intervals covering one respiratory cycle. Simulated sinograms modeled the PET measurement process including the effects of attenuation, photon noise, and CTAC. The processed sinograms were then reconstructed with filtered back-projection with a Hanning filter. This process was repeated using a single respiratory frame for both PET and CTAC data (ideal case with RASP) and the same single frame CTAC data and the respiratory averaged PET data (current PET/CT CTAC method).
Results: Images that used the current method of CT-based attenuation correction in PET/CT imaging clearly showed distortions of the simulated lesion. This was caused by the respiratory mismatch between the respiratory averaged PET data and the single `snapshot', or respiratory phase, of the CTAC data. Images that used phase-matched data removed these distortions.
Conclusion: The idea of respiratory phase alignment and summing in PET/CT imaging can significantly improve image quality in terms of image fidelity and SNR.
* Will present paper
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