Alla Turlakow

Peritoneal carcinomatosis can be difficult to diagnose, as CT is insensitive, with peritoneal biopsy and lavage often subject to problems of sampling error. The aim of our study was to evaluate the role of (18)F-FDG PET in detecting peritoneal carcinomatosis in patients with stomach, ovarian, and adrenal cancer and mesothelioma and to compare the results with CT scans in the same patient group. Our secondary aim was to identify characteristic patterns of abdominal (18)F-FDG uptake in biopsy-proven peritoneal disease and to correlate these patterns with available histologic and anatomic findings after surgery and structural imaging. The medical records of 88 patients with stomach (n = 48), ovarian (n = 13), and adrenal cancer (n = 6) and mesothelioma (n = 21) were reviewed for the presence of peritoneal tumor on (18)F-FDG PET and CT scans. The results were correlated with either contemporaneous peritoneal biopsy or ascitic aspirate or with radiographic or clinical follow-up if histology was negative or unavailable. Of 24 patients with suspected peritoneal tumor, 17 had biopsy-proven findings of peritoneal disease. Of the 24 patients with suspected peritoneal tumor, (18)F-FDG PET was positive in 14 patients, with 1 of these scans being false-positive, CT was positive in 10 patients, and either PET or CT was positive in 18 patients. This yielded sensitivities of 57% (13/23), 42% (10/23), and 78% (18/23), with uniformly high positive predictive values of 93% (13/14), 100% (10/10), and 95% (18/19), respectively. We identified 2 distinctly abnormal scintigraphic patterns of focal and uniform (18)F-FDG uptake corresponding to nodular and diffuse peritoneal disease on pathologic examination. (18)F-FDG PET adds to conventional imaging in the staging of peritoneal carcinomatosis. It is also a useful diagnostic tool when peritoneal biopsy is either unavailable or inappropriate. We have identified 2 distinct scintigraphic patterns that appear to predict the presence of either nodular or diffuse peritoneal pathology.

To compare filtered back projection (FBP) and iterative reconstruction with segmented attenuation correction (IRSAC) in the local imaging of prostate cancer by positron emission tomography with 2-fluorodeoxyglucose (FDG-PET). We retrospectively identified 13 patients with primary (n=7) or recurrent (n=6) prostate cancer who had increased uptake in the prostate on FDG-PET performed without urinary catheterization, contemporaneous biopsy confirming the presence of active tumor in the prostate, and correlative cross-sectional imaging by MRI (n=8) or CT (n=5). FDG-PET images were reconstructed by FBP and IRSAC. Two independent nuclear medicine physicians separately rated FBP and IRSAC images for visualization of prostatic activity on a 4-point scale. Results were compared using biopsy and cross-sectional imaging findings as the standard of reference. IRSAC images were significantly better that FBP in terms of visualization of prostatic activity in 12 of 13 patients, and were equivalent in 1 patient (p<0.001, Wilcoxon signed ranks test). In particular, 2 foci of tumor activity in 2 different patients seen on IRSAC images were not visible on FBP images. In 11 patients who had a gross tumor mass evident on cross-sectional imaging, there was good agreement between PET and cross-sectional anatomic imaging with respect to tumor localization. In selected patients, cancer can be imaged within the prostate using FDG-PET, and IRSAC is superior to FBP in image reconstruction for local tumor visualization.

Case Report from JAMA Internal Medicine — Fludeoxyglucose Positron Emission Tomography in the Diagnosis of Giant Cell Arteritis

The purpose of this study was to compare the results of isotope injection the morning of surgery (1-d protocol) with isotope injection the day before surgery (2-d protocol) in patients having sentinel lymph node (SLN) biopsy for breast cancer. The 1-d (protocol 1) and 2-d (protocol 2) protocols included 514 and 152 patients, respectively, treated contemporaneously by surgeons experienced with the SLN biopsy technique. All had preoperative lymphoscintigraphy (LSG) and SLN biopsy using both blue dye and (99m)Tc-sulfur colloid. All patients had a single-site intradermal injection of unfiltered (99m)Tc-sulfur colloid in 0.05 mL normal saline: 3.7 MBq (0.1 mCi) on the morning of surgery for protocol 1 and 18.5 MBq (0.5 mCi) on the afternoon before surgery for protocol 2. The patients in protocols 1 and 2 were comparable in terms of age, tumor size, tumor location, histologic type, node positivity, and frequency of a previous surgical biopsy. Comparing protocols 1 and 2, early (30 min) LSG images found the SLN equally often (69% vs. 68%). Isotope identified the SLN equally often at surgery (93% vs. 97%) as did isotope plus dye (98% vs. 99%). A comparable number of SLNs was found (2.5 vs. 2.8 per axilla), and the concordance between isotope and dye in the SLN was also comparable (97% vs. 95%). Late LSG images (at 2 h, possible only for protocol 2) identified the SLN in significantly more patients compared with early images (86% vs. 68%). With unfiltered (99m)Tc-sulfur colloid injected intradermally, the results of SLN biopsy under the 1-d and 2-d protocols are virtually identical. A 2-d protocol allows increased efficiency in scheduling, both for nuclear medicine physicians and for the operating room, with no compromise in the effectiveness of SLN mapping.