Effective reduction of brown fat FDG uptake by controlling environmental temperature prior to PET scan: an expanded case series.

INTRODUCTION: Brown fat uptake of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) on a positron emission tomography (PET) scan may limit the ability to assess for cancer. Previously, Garcia et al. demonstrated in ten patients a significant decrease in brown fat uptake of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) after controlling the patient's environmental temperature. OBJECTIVE: The objective of the current study is to validate the effectiveness of controlled environmental temperature (CET) to reduce physiologic brown fat (BF) FDG uptake on a PET scan in a larger series. METHOD: A retrospective review was performed from January 2002 to October 2007 of patients who had (1) a pattern of FDG uptake on PET scan consistent with BF, (2) no evidence of cancer by computed tomography in the regions of interest noted below, (3) repeat scan with CET within 4 months of the 1st PET scan, and (4) no use of drugs reported to reduce BF FDG uptake (e.g., benzodiazepine, beta-blockers, reserpine) unless they were used identically prior to and during both studies. The FDG-PET and controlled environmental temperature-positron emission tomography (CET-PET) scans were performed as per protocol. The non-CET and CET-PET images were blinded/randomized, and three physicians assessed three regions (right neck, left neck, and paraspinal area) semiquantitatively using the following scale: "0" (background [bkgd]), 1 + (> bkgd < liver), 2 + (equal to liver), 3 + (> liver). Standard uptake value (SUV) data was recorded. Results were analyzed using a two-tailed t test. RESULTS: Of 8,640 FDG-PET scans performed, 30 patients (four male, 26 female) met the above criteria. The median age was 36 years (range, 12-60 years). The mean (± 1 standard deviation) of differences in the scores between the two studies for right neck, left neck, and paraspinal regions, respectively, were for reader 1:(2.1 ± 1.37), (1.95 ± 1.43), and (1.85 ± 1.26); reader 2 (2.3 ± 1.40), (1.70 ± 1.13), and (1.77 ± 1.13); reader 3 (2.17 ± 1.17), (2.20 ± 1.18), and (0.50 ± 1.30); for maximum SUV score (3.4 ± 2.9), (3.3 ± 2.9), and (1.77 ± 1.13). All p values were <0.001. CONCLUSION: In this larger series, CET effectively reduced the false-positive (18)FDG uptake in BF on PET scans without the use of drugs.

Doxorubicin-induced cardiac toxicity and cardiac rest gated blood pool imaging.

Anthracyclines are one of the most commonly used and potent chemotherapeutic agents. Doxorubicin (Adriamycin) is one common anthracycline used to treat many solid tumors including breast, sarcomas, gynecologic and hematological malignancies, such as leukemias and lymphomas. However, its use is often limited due to dose-dependent cardiotoxicity. As a result, patients receiving doxorubicin should have close monitoring of their left ventricular function. The gated cardiac blood pool (GBP) study is one of the most accurate and reproducible methods of assessing left ventricular function. This report presents an overview of (1) the incidence, clinical course, mechanisms, pathology, prevention, and monitoring of doxorubicin-induced cardiotoxicity (DIC), (2) the use of GBP studies in monitoring for DIC, and (3) 2 algorithms for the use of GBP studies in monitoring for DIC. This report concludes with a proposed algorithm for the use of GBP studies in DIC. With an understanding of DIC, GBP studies, and various algorithms, the interpreting physician may help the oncologist identify DIC earlier, more accurately, and before it becomes clinically apparent.

The utility of radioiodine scans prior to iodine 131 ablation in patients with well-differentiated thyroid cancer.

BACKGROUND: The utility of radioiodine (RAI) scans prior to (131)I ablation is controversial. The objective of this study was to evaluate the utility of RAI scans prior to (131)I ablation in patient with well-differentiated thyroid cancer. METHOD: All RAI scans performed prior to (131)I ablation from July 2000 to November 2006 at Washington Hospital Center were reviewed retrospectively. Patients were excluded who were suspected of having 1) loco-regional disease, 2) distant metastases, and/or 3) physiological uptake that might alter management prior to the pre-ablation RAI scans. RAI scans were performed either 24 hours after dosing with 37-148 MBq of (123)I or 48 hours after dosing with 37-148 MBq of (131)I with imaging of the whole body, the thyroid bed/neck with a pinhole collimator, and the neck and chest with a parallel-hole collimator. One reviewer blindly evaluated each set of scans using six criteria, and for the purpose of this study, the thresholds for each criterion for which the patient's management may have been altered prior to (131)I ablation are noted in parentheses: 1) the number of foci of RAI uptake in thyroid bed/neck (0 or > or =6), 2) the location(s) of these foci in the thyroid bed/neck (outside the thyroid bed), 3) the size of the largest foci in thyroid bed/neck (> or =1 lobe), 4) the percent uptake in the thyroid bed/neck (> or =15%), 5) uptake suggestive of distant metastases, and 6) significant altered biodistribution (e.g., any breast, marked salivary gland, or marked gastrointestinal uptake). RESULTS: Of 355 sets of scans reviewed, 53% of patients had findings on the RAI scans that might have altered the patient's management prior to their (131)I ablation. The data grouped by the criteria noted above were 1) 12% with six or more foci suggesting local metastases and 6% (22) with no focal uptake, 2) 14% with suggestion of lymph node metastases, 3) 1.1% with at least one focus > or =1 lobe, 4) 8% with > or =15% uptake, 5) 4% with distant metastases, 6) 16% demonstrating altered distribution with 6% breast, 3% salivary, 10% GI, and 0.3% urinary bladder. CONCLUSION: Pre-ablation RAI scans demonstrate a significant number of findings that may alter the management of patients with well-differentiated thyroid cancer prior to (131)I ablation.

(18)F-FDG PET hemispheric cerebral hypometabolic activity: patient motion artifact.

A 51-y-old man underwent (18)F-FDG PET for disease restaging of non-Hodgkin's lymphoma. Initial attenuation correction images demonstrated unilateral hemispheric cerebral hypometabolic activity. The remainder of the scan was otherwise unremarkable. Non-attenuation correction images demonstrated a patient motion artifact attributable to lateral movement of the patient's head during image acquisition. Subsequent repeat (18)F-FDG PET showed normal cerebral cortical activity.

Benzodiazepine-resistant "brown fat" pattern in positron emission tomography: two case reports of resolution with temperature control.

PURPOSE: Supraclavicular uptake of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) on positron emission tomography (PET) scan is attributed to lymph node, muscle, or brown fat activity. Differentiation between physiological or pathological etiologies is necessary. Benzodiazepine premedication to reduce physiological uptake has been attempted with variable success. A relationship between brown-fat FDG uptake and cold temperature has also been established. To our knowledge, no case reports or studies have been published to demonstrate whether controlling the temperature can alter the physiological uptake in these regions. PROCEDURES: Two teenage female patients with these patterns on PET scans performed with oral benzodiazepine administration underwent repeat imaging with temperature-controlled environment settings. RESULTS: Resolution of supraclavicular FDG uptake with temperature control in two patients in whom benzodiazepine had no prior effect. CONCLUSION: Although the exact mechanism remains unknown, we propose that the control of temperature reduces the metabolism of glucose by brown fat. Further studies are warranted to confirm the above observations, and, if confirmed, to determine the most efficient and effective use of temperature control to minimize supraclavicular and axillary FDG uptake.

Dosimetrically determined doses of radioiodine for the treatment of metastatic thyroid carcinoma.

In the absence of definitive studies relating radioiodine dose to outcomes, selection of a dose of radioiodine to treat metastatic thyroid carcinoma is problematic, and several approaches have been used. These include empiric fixed doses and doses used on dosimetric approaches specific for each patient. This paper is a review of the rationale and technique for dosimetrically-determined doses of radioiodine for the treatment of metastatic thyroid carcinoma. This review (1) discusses the alternatives for selection of a dose, (2) discusses the two major approaches for determining radioiodine doses dosimetrically, (3) briefly reviews several modifications of these approaches, (4) reviews the literature regarding the results, (5) discusses the side effects of these different approaches, and (6) concludes with recommendations for patient management and future research. This review does not address use of dosimetrically-determined doses of radioiodine for the initial ablation of thyroid tissue postoperatively.