Ching-yee Oliver Wong

Fdg positron emission tomography/computed tomography scan may identify mantle cell lymphoma patients with unusually favorable outcome

ObjectivePatients diagnosed with mantle cell lymphoma (MCL) have generally poor prognosis, but a minority have a longer survival. There are no markers to identify this group and no generally established prognostic index for MCL. Our objective was to assess the prognostic value of the staging FDG PET/computed tomography (CT) scan. MethodsWe retrospectively analyzed initial scans performed at three institutions on biopsy-proven, cyclin D (+) MCL patients. The association of the SUVmax of the ‘hottest focus’ with overall survival (OS) and failure-free survival (FFS) was evaluated. Receiver operating characteristic analysis of SUVmax versus survival was used to establish a cut-off point of 4.83. In addition, PET findings were compared with contrast-enhanced CT performed within 3 weeks in patients from one institution. ResultsBoth the OS and FFS for patients with SUVmax greater than 5 were significantly decreased (P<0.01 and <0.001, respectively) as compared with the patients with SUV ≤5. The 5-year OS for group with SUVmax ≤5 was 87.7% and for SUVmax greater than 5 it was 34%. For SUVmax ≤5, the median FFS was 45.3 months as compared with 10.6 months for SUVmax greater than 5. PET changed the stage as compared with CT alone in 45% of patients. ConclusionStaging FDG PET/CT is superior to CT and may be used in the future for identification of a subset of MCL patients with a better outcome than otherwise expected.

Granulomatous disease: is it a nuisance or an asset during PET/computed tomography evaluation of lung cancers?

ObjectivesTo evaluate combined PET-computed tomography (CT) criteria for differentiating between granulomatous disease (GD) and malignancy (CA) in oncologic PET–CT studies. MethodsSixty-two patients who were referred for fluoro-2-deoxyglucose (FDG) PET–CT evaluation of pulmonary lesion(s) without a history of concurrent infection were studied. PET–CT was performed 1.5 h after intravenous administration of 555 MBq 18F-FDG in the fasting state with oral contrast. Combined PET–CT criteria including (i) calcifications (Ca2+) within lymph nodes, (ii) Ca2+ in lung nodules, (iii) liver and/or spleen Ca2+, (iv) locations of lung lesion(s), (v) hilar FDG uptake, (vi) comparison of lung versus maximum mediastinal FDG uptake, (vii) lymph node uptake not in the most probable lymphatic drainage pathway from a particular lung lesion, and (viii) extra pulmonary abnormal FDG uptake were each assigned a numerical score (0–3) with progressively higher score and sum of scores toward the increasing likelihood of GD. These patients either had pathological confirmation by biopsy/resection or were followed radiographically for a period of 2 years (CA=13; GD=49). Discriminant analysis was performed on all the above criteria with this gold standard. Simple t-test and box plot analysis were also performed on the summation of the scores (from 0 in CA to 13 in GD). ResultsWhen all eight criteria were entered into discriminant analysis, the combined PET–CT criteria classified correctly 71% of patients with a sensitivity of 65% and specificity of 92% for GD. The most significant discriminating criterion was FDG uptake in the lung lesion(s) less than maximum mediastinal uptake (P=0.01). The sum scores in GD and CA were significantly different (4.9±2.4 vs. 3.2±1.5, respectively, P=0.014). Box plots showed a clear separation at a cut-off value of around 3.5. ConclusionResults show that the set of combined PET–CT criteria are highly specific for GD, which is not necessarily a nuisance during oncologic evaluation. Knowledge of these criteria may attribute some of the abnormal PET findings to GD, which is a useful asset for quick recognition and clinical interpretation.

Dynamic PET-CT studies for characterizing nasopharyngeal carcinoma metabolism: comparison of analytical methods

ObjectivesTo investigate the optimal PET protocol and analytical method to characterize the glucose metabolism in nasopharyngeal carcinoma (NPC). MethodsNewly diagnosed NPC patients were recruited and a dynamic PET-CT scan was performed. The optimized threshold to derive the arterial input function (AIF) was studied. Two-tissue compartmental kinetic modeling using three, four, and five parameters, Patlak graphical analysis, and time sensitivity (S-factor) analysis were performed. The best compartmental model was determined in terms of goodness of fit, and correlated with Ki from Patlak graphical analysis and the S-factor. The methods with R>0.9 and P<0.05 were considered acceptable. The protocols using two static scans with its retention index (RI=(SUV2/SUV1−1)×100%, where SUV is the standardized uptake value) were also studied and compared with S-factor analysis. ResultsThe best threshold of 0.6 was determined and used to derive AIF. The kinetic model with five parameters yields the best statistical results, but the model with k4=0 was used as the gold standard. All Ki values and some S-factors from data between various intervals (10–30, 10–45, 15–30, 15–45, 20–30, and 20–45 min) fulfilled the criteria. The RIs calculated from the S-factor were highly correlated to RI derived from simple two-point static scans at 10 and 30 min (R=0.9, P<0.0001). ConclusionThe Patlak graphical analyses and even a 20-min-interval S-factor analysis or simple two-point static scans were shown to be sufficient to characterize NPC metabolism, confirming the clinical feasibility of applying a short dynamic with image-derived AIF or simple two-point static PET scans for studying NPC.

Exceptionally low metabolic activity in aggressive peripheral T-cell lymphoma.

PurposeTo investigate metabolic behavior of aggressive peripheral T-cell (PTC) lymphoma compared with other aggressive T-cell (OTC) nonHodgkins lymphomas (NHLs) and the various grades (1, 2, 3) of follicular B-cell (FC) NHL as a reference cell type for indolent to aggressive behavior. Materials and methodsPretreatment 2-deoxy-2-[18F] fluoro-d-glucose positron emission tomography-computed tomography scans of 33 patients with pathologic diagnosis of aggressive T-cell NHL and FC (FC1 = 6, FC2 = 8, FC3 = 9, PTC = 6, OTC = 4) were analyzed. The maximal standardized uptake value (SUV) was measured over biopsy region (BxSUV) and the highest tumor activity of the body (BmSUV). ResultsThere were significant differences in both BxSUV (P = 0.036) and BmSUV (P = 0.026) among these five groups with significantly lower metabolic activity in PTC compared with other aggressive NHL (FC3, OTC). BmSUV in PTC was significantly lower than that in OTC (8.2±2.5 vs. 22.3±7.0, P = 0.029) and was similar to that of FC1 (9.4±1.9) and FC2 (9.7±1.4) but lower than that of FC3 (14.6±2.7). Similar findings were noted in BxSUV between PTC and OTC (6.7±2.5 vs. 20.4±7.2, P = 0.035). ConclusionAlthough 2-deoxy-2-[18F]fluoro-d-glucose positron emission tomography has been found to reflect metabolic activity for the aggressiveness of B-cell NHL, PTC has an exceptionally low metabolic activity, similar to that of low-grade B-cell FC1 and FC2.

Tumor metabolic phenotypes on 18F FDG PET.

however, this technology may play an important role in allowing correction of misregistration due to patient motion or breathing artifacts, which may also arise from integrated SPECT/CT. Besides anatomic referencing, the added value of CT coregistration is also based on the attenuation correction capabilities of CT. Cardiac imaging poses a particular problem in attenuation correction because of respiratory and cardiac motion in the thorax. Individual CT-based attenuation correction of brain studies using SPECT may also lead to improved image quality and more accurate data evaluation. Furthermore, radionuclide treatment planning using attenuation correction of imaging data and assessment of organ or target volumes derived from simultaneously performed CT may be more accurate and potentially allows safe and effective therapy. A similar discussion on the need for integrated hybrid scanners has already been raised after the introduction of hybrid PET/CT systems to clinical medicine. As indicated for PET/CT, image fusion is faster, more reliable, and more accurate using an integrated scanner than using separately performed imaging modalities (4). In addition to these technical issues, hybrid image acquisition of both modalities in a single clinical visit (1stop) offers apparent logistic advantages and is obviously more comfortable for the patient. PET/CT scanners represent the imaging modality with the most rapid growth worldwide and play an increasing role in routine patient care, especially in oncologic applications. Yet, there is a lack of evidence that the same holds true for hybrid SPECT/CT systems. CT coregistration, however, has been recognized to result in higher specificity and sensitivity of scintigraphic imaging and to markedly reduce the number of indeterminate findings. The superiority of SPECT/CT over planar scintigrams or SPECT has been clearly demonstrated for imaging skeletal diseases, parathyroid adenomas, and neuroendocrine cancers and for mapping sentinel lymph nodes in various cancers (1). Studies demonstrating superiority in other clinical applications are lacking; however, pilot studies encourage the use of SPECT/CT in cardiac and neurologic imaging. Regarding the growing number of studies demonstrating an added value of hybrid SPECT/CT over separately performed imaging modalities (1), it appears likely that this promising technique will gain an important role in clinical routine practice. The broad spectrum of existing SPECT tracers and their widespread availability suggests SPECT/CT as a complementary imaging modality to PET/CT procedures. In summary, we agree with Knoll and colleagues that advanced software-based coregistration procedures do have a legitimate relevance for image fusion, particularly if no hybrid technology is available. However, we believe that hardware-based hybrid acquisition offers several apparent advantages regarding accuracy, reliability, logistics, and comfort for the patient, which cannot be easily outweighed by software-based image fusion approaches.

High Incidence of Initial Loss of Consciousness with Abnormal F-18 FDG and O-15 Water Brain PET in Patients with Chronic Closed Head Injury

Background: The purpose of this study is to evaluate the incidence of loss of consciousness (LOC) with functional abnormalities by brain positron emission tomography (PET) in patients with closed head injury using fluorine-18 labeled fluorodeoxyglucose (F-18 FDG) and O-15 water PET imaging. Methods: 36 sequential patients referred from rehabilitation service without known brain disease who had cognitive complaints months after head injury and had F-18 FDG and O-15 water PET, CT and/or MRI imaging were included. The image findings were compared and correlated with the incidence of initial LOC. Results: Significant difference was found in the association of abnormal imaging findings with LOC between functional (PET) and anatomical (CT or MRI) modalities. There was also significant discrepancy between PET and CT/MRI findings. Of the 28 patients with normal CT or MRI, 10 patients or 36% had abnormal PET findings (p=0.007). However, there was, however, high concordance (92%) between perfusion and metabolic PET images. Conclusion: There are significantly more functional than anatomic abnormalities in chronic closed head injury. PET may help in confirming the diagnosis and subsequent management when CT/MRI is normal. Those with normal PET are less likely to have LOC at the time of initial injury.