Diagnostic Computed Tomography Coregistration With In-111-DTPA-Octreotide Single Photon Emission Tomography/Low-Dose Computed Tomography.

OBJECTIVES: In-111-DTPA-octreotide (OctreoScan) is still pivotal for neuroendocrine tumor imaging, despite the introduction of Ga-68-octreotide tracers. Low-dose computed tomography (LDCT) assists in the localization of SPECT findings but often results in uncertain interpretation. This retrospective study evaluates the impact of coregistration of In-111-DTPA-octreotide SPECT/LDCT with diagnostic CT on interpretation. METHODS: Thirty-five consecutive studies, in which coregistration was performed because of uncertain interpretation, were evaluated. Presence of somatostatin receptors was categorized retrospectively as definitely positive, probably positive, probably negative, or definitely negative with and without rigid registration with diagnostic CT, and possible added value of coregistration was evaluated. RESULTS: Coregistration was performed in 35 studies. However, on subsequent reading, 4 SPECT/CTs yielded definite results and were omitted. Coregistration was helpful in 30 of the remaining 31 cases, changing reading to definitely positive (7) or to definitely negative (23). In 13 of the 23 cases, diagnosis changed from probably positive to definitely negative. Coregistration contributed in 42 of 48 sites, with greatest benefit in the liver (13/14), pancreas (10/10), and lymph nodes (6/6). CONCLUSIONS: Coregistration is becoming increasingly easier and may be utilized when SPECT/LDCT is inconclusive.

Ga-68 DOTA-NOC uptake in the pancreas: pathological and physiological patterns.

OBJECTIVE: Gallium-68 (Ga-68) DOTA-1-NaI3-octreotide (DOTA-NOC) positron emission tomography (PET)/computed tomography (CT) is increasingly used for neuroendocrine tumors (NETs), often found primarily in the pancreas. However, physiologic uptake of DOTA-NOC has been described in the uncinate process of the pancreas. We studied DOTA-NOC uptake in this organ. MATERIALS AND METHODS: Ninety-six patients underwent 103 DOTA-NOC scans, with pathology-proven pancreatic NET (n = 40) and nonpancreatic NET or biochemical suspicion of NET (n = 63). RESULTS: DOTA-NOC uptake was detected in 35 documented pancreatic tumor sites (SUV: 5.5-165; mean: 25.7 ± 28.8; median: 17.8). Among 63 cases without previous known pathology, uptake was suspicious for tumor in 24 sites (SUV: 4.7-35; mean 16.3 ± 8.0; median: 14.1), and in 38 sites, it was judged as physiological, generally lower relative to adjacent structures (SUV: 2.2-12.6; mean: 6.6 ± 2.2; median: 6.2). In 24 scans with suspected tumor and in 37 of 38 scans with physiological uptake, diagnostic computed tomography or magnetic resonance imaging or endoscopic ultrasonography failed to detect tumor. CONCLUSIONS: Pancreatic DOTA-NOC uptake must be interpreted with caution, and further studies are required.

68Ga-DOTA-NOC PET/CT imaging of neuroendocrine tumors: comparison with ¹¹¹In-DTPA-octreotide (OctreoScan®).

PURPOSE: Recent data have indicated that 68Ga-DOTA-NOC positron emission tomography/X-ray computed tomography (PET/CT) may yield improved images in a shorter acquisition protocol than ¹¹¹In-DTPA-octreotide (OctreoScan®, OCT). Therefore, we performed a prospective comparison of 68Ga-DOTA-NOC and OCT for the detection of neuroendocrine tumors (NETs). METHODS: Nineteen patients (eight carcinoid, nine pancreatic NETs, and two NE carcinoma of unknown origin) with previous positive OCT scans underwent 68Ga-DOTA-NOC PET/CT and OCT single-photon emission computed tomography imaging for staging or follow-up. Findings were compared by region and verified with conventional imaging. RESULTS: All images of both modalities demonstrated focal uptake, often at multiple sites. 68Ga-DOTA-NOC images were clearer than OCT images, facilitating interpretation. Similar foci were identified with both modalities in 41 regions, with additional foci on 68Ga-DOTA-NOC in 21 and on OCT in 15 regions. CT, magnetic resonance imaging, or ultrasound confirmed the concordant findings in 31 of 41 regions and findings seen with 68Ga-DOTA-NOC only in 15 of 21 regions. Findings seen with OCT only were less clear and were only confirmed in 4 of 15 regions. 68Ga-DOTA-NOC had impact on staging in four patients and on management in three patients. CONCLUSIONS: Although 68Ga-DOTA-NOC and OCT images were similar, in this study, 68Ga-DOTA-NOC demonstrated more true positive tumor foci and was better tolerated by patients. This direct comparison supports replacement of OCT with 68Ga-DOTA-NOC-PET/CT in the evaluation of NETs.

Positron emission tomography in interstitial lung disease.

BACKGROUND AND OBJECTIVES: A high rate of glycolysis may reflect the inflammatory activity of interstitial lung disease (ILD). This prospective study investigated whether PET can distinguish IPF, a primarily fibrotic process, from other entities of ILD that have a marked inflammatory component. METHODS: Twenty-one patients referred for surgical lung biopsy because of diffuse ILD underwent PET at the time of the lung biopsy. PET transmission scans were obtained after injecting (18)FDG intravenously. Regions of interest (ROI) were drawn on the lung images, and the standardized uptake value (SUV) was calculated for these ROI. RESULTS: Of the 21 patients studied, 14 had IPF, four had non-specific interstitial pneumonia, and the remaining three patients each had respiratory bronchiolitis-ILD, sarcoidosis and Langerhan's cell histiocytosis. There was no statistically significant difference in the SUV between IPF patients and non-IPF patients (P = 0.26), although patients with IPF tended to have higher SUV. Radiographic changes tended to be more prominent in the lung bases in patients with IPF compared with non-IPF patients; however, the median ratio of SUV measured in the upper fields to the whole lungs in IPF patients was not significantly different compared with the median ratio in non-IPF patients (P = 0.31). CONCLUSION: PET does not allow differentiation of IPF from a non-IPF diffuse interstitial pulmonary process.

SPECT/CT hybrid imaging with 111In-pentetreotide in assessment of neuroendocrine tumours.

OBJECTIVE: Somatostatin receptor scintigraphy (SRS) of neuroendocrine (NE) tumours is often challenging because of minute lesion size and poor anatomic delineation. This study evaluates the impact of sequentially performed single-photon emission computed tomography (SPECT)/CT fusion on SRS study interpretation and clinical management of these tumours. PATIENTS AND DESIGN: Seventy-two patients were studied with routine SRS and SPECT/CT at 4, 24 and optionally 48 h after injection of 222 MBq 111In-pentetreotide. Forty-five patients were evaluated for carcinoid, 15 for islet cell tumour, seven for metastatic NE tumour, four for medullary thyroid carcinoma, and one patient had ophthalmopathy. SPECT/CT induced improvement in the interpretation of SPECT and conventional CT and resultant clinical management changes were recorded. RESULTS: SRS was negative in 28 patients and positive in 44 patients. SPECT/CT provided no additional information in 48 patients, including all 28 negative studies. SPECT/CT improved localization of the SPECT-detected lesions in 23 of the 44 positive studies. It defined the extent of disease in 17, showed unsuspected bone involvement in three, and differentiated physiological from tumour uptake in three studies. SPECT/CT affected the clinical management in 10 patients, altered the surgical approach in six, spared unnecessary surgery in two, and modified the therapeutic modality in two patients. CONCLUSIONS: SPECT/CT affected the diagnostic interpretation of SRS in 32% of the patients and induced changes in management in 14% of the patients.

Does streaming affect the cerebral distribution of infraophthalmic intracarotid chemotherapy?

BACKGROUND AND PURPOSE: The development of new non-ocular-toxic drugs has enabled infraophthalmic chemotherapeutic infusion. We assessed whether streaming occurs with infraophthalmic, high cervical internal carotid artery (ICA) delivery of chemotherapeutic agents by means of conventional angiographic catheters. METHODS: Six patients with high-grade gliomas treated with monthly carotid intraarterial chemotherapy were studied. Chemotherapy delivery and distribution was modeled by technetium 99m hexylmethyl-propyleneamine oxine (HMPAO), a first-pass agent. Each patient received 0.5 mCi (18.5 MBq) of (99m)Tc-HMPAO in 50-mL of saline intraarterially in the ICA at the C1-C2 level. Injections were given twice, at two different injection rates: 0.08 mL/s at one therapeutic session and 6 mL/s a month later. The slow injection rate modeled the slowest rate used in the delivery of chemotherapy into the ICA. The higher rate was selected to avoid any possibility of uneven mixing, by replacing intracarotid blood completely and by using a turbulent injection rate that destroys laminar flow and intraarterial streaming. Single photon emission CT (SPECT) was performed 2 hours after injection. For each patient, the corresponding SPECT sections at the two injection rates were compared. RESULTS: No differences were noted in (99m)Tc-HMPAO distribution between the two injection rates in any of the patients. However, some of the rapid injection rate SPECT scans showed extension of the (99m)Tc-HMPAO uptake into adjacent watershed territories. CONCLUSION: There was no evidence, in humans, of substantial streaming during slow infraophthalmic intracarotid injections. Slow rates of infusion are as good as high rates for infraophthalmic intracarotid drug delivery. This is of special importance for drugs that are not tolerated at high injection rates. Moreover, infraophthalmic intracarotid chemotherapeutic infusion does not require special injectors or catheters.