Robert J. Ackermann

Comparison of single time-point [111-In] pentetreotide SPECT/CT with dual time-point imaging of neuroendocrine tumors

Purpose: To determine whether single time-point single-photon emission computed tomography—computed tomography (SPECT/CT) somatostatin receptor imaging can replace traditional dual time-point planar and SPECT somatostatin receptor scintigraphy for evaluation of neuroendocrine tumors. Materials and Methods: Twenty-four patients (9 males, 15 females; mean age: 56 years; range: 14–82 years) underwent [111-In] pentetreotide scintigraphy, with planar whole-body images acquired at 24 and 48 hours after injection and abdominal SPECT/CT at 24 hours postinjection. Two blinded readers independently interpreted each study, using single time-point (24 hours planar and SPECT/CT) and separately using dual time-point (24- and 48-hours planar, and 24-hour SPECT without CT) image information. Consensus interpretations were compared with surgical pathology, or clinical and radiologic follow-up for at least 12 months. Results: Interobserver agreement was excellent (&kgr; = 0.86) for single time-point imaging, and good (&kgr; = 0.56) with dual time-point imaging. After consensus review, single time-point imaging identified pathologic lesions in 11 of 12 subjects with diagnosis of NET at follow-up, and in 0 of 12 subjects without NET (sensitivity 92%; specificity 100%). Dual time-point imaging performed similarly, but missed an additional NET case (sensitivity 83%; specificity 100%). After review of SPECT/CT, the readers considered that additional 48 hours imaging was not necessary in the majority of cases, indicating high degree of confidence with the single time-point imaging. Conclusion: [111-In] pentetreotide SPECT/CT imaging at 24 hours identifies pathologic disease sites and distinguishes physiologic activity equally well compared to traditional strategies using 2 imaging days. Routine use of SPECT/CT will allow single time-point imaging without loss of diagnostic accuracy, enhancing patient convenience, and clinical throughput.

Deadtime correction for two multihead Anger cameras in 131I dual-energy-window-acquisition mode.

Two side-by-side energy windows, one at the photopeak and one at lower energy, are sometimes employed in quantitative SPECT studies. We measured the count-rate losses at moderately high activities of 131I for two multihead Anger cameras in such a dual-window-acquisition mode by imaging a decaying source composed of two hot spheres within a warm cylinder successively over a total of 23 days. The window locations were kept fixed and the paralyzable model was assumed. In addition, for the Picker Prism 3000 XP camera, the source was viewed from three different angles separated by 120 degrees and the final results are from an average over these three angles. For the Picker camera, the fits to the data from the individual windows are good (the mean of the squared correlation coefficient equals 0.98) while for the Siemens Multispect camera fits to the data from head 1 and from the lower-energy, monitor window are relatively poor. Therefore, with the Siemens camera the data from the two windows are combined for deadtime computation. Repeated autopeaking might improve the fits. At the maximum count rate, corresponding to a total activity of 740 MBq (20 mCi) in the phantom, the multiplicative deadtime correction factor is considerably larger for the Picker than for the Siemens camera. For the Picker camera, it is 1.11, 1.12, and 1.12 for heads 1-3 with the photopeak window and 1.10 for all heads with the lower-energy monitor window. For the Siemens camera, the combined-window deadtime correction factor is 1.02 for head 1 and 1.03 for head 2. Differences between the deadtime correction factor for focal activity and for the total activity do not support the hypothesis of count misplacement between foci of activity at these count rates. Therefore, the total-image dead time correction is recommended for any and all parts of the image.

Delayed biliary drainage is common in asymptomatic post-cholecystectomy volunteers

A commonly used diagnostic criterion for sphincter of Oddi dysfunction is delayed drainage of contrast media from the bile ducts at endoscopic retrograde cholangiography (ERC), which is defined as the persistence of contrast greater than 45 min after injection. We performed ERC in 11 asymptomatic post-cholecystectomy volunteers for the purpose of evaluating biliary drainage time. In an attempt to more accurately quantify emptying, concomitant scintigraphy was performed at the time of ERC and contrast drainage. Sufficient contrast mixed with technetium-99m sulfur colloid to completely fill out the intra-hepatic tree was injected (mean volume, 9 ml) and the volunteers remained in the prone position during imaging. The length of time from cholecystectomy, bile duct size, volume of contrast injected, and scintigraphic T1/2s did not correlate with drainage time at ERC. At 45 min after injection the degree of residual contrast filling was scored as: empty in three volunteers, almost empty in one, one-fourth full in 5, and one-half full in two. Therefore, 7 of the 11 asymptomatic volunteers (63%) had delayed drainage. Even if more stringent criteria for delayed drainage were used (ducts one-half filled), 2 of the 11 (18%) had abnormal drainage. The frequent occurrence of delayed drainage in these asymptomatic post-cholecystectomy volunteers challenges the validity of the 45-min delayed drainage criterion for sphincter of Oddi dysfunction.

SPECT imaging of Moyamoya disease using 99mTc-HM-PAO comparison with computed tomography findings

99mTc-HM-PAO was used to evaluate regional cerebral blood flow in a 26-year-old woman with Moyamoya disease. This patient had an 18-month history of recurrent neurologic deficits and had angiographic evidence of Moyamoya disease. She had used oral contraceptives and cigarettes, but had no other risk factors for stroke. Single photon emission computed tomographic images showed bilateral and asymmetric reductions in blood flow to anterior and lateral brain regions. These findings correlated better with clinical symptomatology and suggested more extensive brain involvement than did computed tomography.

SPECT/CT Characterization of Oral Activity on Radioiodine Scintigraphy

CONTEXT Oral activity on radioiodine scintigraphy is commonly seen and may cause diagnostic dilemma. Determining the precise mechanism of oral uptake on radioiodine scintigraphy will increase the accuracy and confidence of interpretation and avoid possible misinterpretation. OBJECTIVE To determine the etiology of focal persistent radioiodine oral uptake seen on radioiodine scans. DESIGN Retrospective sequential series at a university clinic and a phantom study experiment. METHODS Preablation iodine-131 planar and single photon emission computed tomography/computed tomography (SPECT/CT) scans of 216 patients after total thyroidectomy were reviewed. Planar images were inspected for the presence of oral activity above the salivary gland background and SPECT/CT was reviewed to determine the location and nature of oral activity. A post-hoc phantom study was designed using typodont stone models fitted with various dental materials, immersed in a diluted iodine-131 solution, and imaged with SPECT/CT to characterize radioiodine uptake by high-attenuation dental materials. RESULTS Oral activity was seen on planar images in 123 of 216 (57%) patients; 12 patients were excluded from analysis because the SPECT/CT field of view did not cover the entire oral cavity. In the remainding 111 patients SPECT/CT images demonstrated focal uptake localizing to high-attenuation dental material on the CT in 95 of 111 (86%) patients. All cases of oral activity on planar imaging were interpreted as benign etiology on SPECT/CT. The phantom study confirmed focal in vitro uptake within high-attenuation dental materials representing a range of commonly used metal alloys. CONCLUSION Focal oral activity on diagnostic radioiodine scans frequently localizes to high-attenuation dental material on SPECT/CT. We postulate that an affinity between negatively charged iodide ions (I(-)) in saliva and positively charged metal ions (eg, Ag(+), Hg(+), Au(2+), Pd(2+)) within the dental materials is at the basis of persistent focal radioiodine uptake in the oral cavity. This represents a new mechanism underlying benign radioiodine activity not previously described in the medical literature.

Hypoalbuminemia and Osteoporosis: Reappraisal of a Controversy

CONTEXT Human studies have reported conflicting results on the association of hypoalbuminemia with osteoporosis. OBJECTIVE The aim of the study is to test the independent association between hypoalbuminemia and osteoporosis. DESIGN This is a cross-sectional observation. SETTING AND PARTICIPANTS Patients are the outpatient consecutive individuals with available clinical, laboratory, and densitometry data from 2001 to 2013 in our tertiary care academic medical center. EXPOSURE Exposure is hypoalbuminemia defined as serum albumin less than 3.5 g/dL. MAIN OUTCOME MEASURE Osteoporosis is defined as bone mineral density of 2.5 SD or less below the mean peak bone mass of young, healthy adults. RESULTS Overall, 21 121 patients were included. Mean of age was 61 years (SD 14). There were 4244 males (20.1%) and 1614 patients of African-American ethnicity (7.6%). There was a graded decrease in rate of osteoporosis from 28.0% (n = 33) at albumin of 3 g/dL or less to 9.3% (n = 1548) at albumin greater than 4 g/dL (P < .001) at the femoral neck and from 20.3% (n = 24) to 6.1% (n = 1011) at the total hip (P < .001). In a fully adjusted model, the odds of osteoporosis at albumin of 3 g/dL or less was 3.31-fold (95% confidence interval [CI] 2.08-5.28, P < .001) at the femoral neck, 2.98-fold (95% CI 1.76-5.01, P < .001) at the total hip, and 2.18-fold (95% CI 1.43-3.31, P < .001) at the lumbar spine as compared with albumin greater than 4 mg/dL. A similar independent association was identified with a longer-observed duration of hypoalbuminemia. CONCLUSION In a large population, we report an independent association of osteoporosis with lower levels of serum albumin and a longer-observed duration of hypoalbuminemia.

The use of a vasoconstrictor to improve tumour blood flow in intra-arterial chemotherapy: Preliminary report

The effectiveness of intra-arterial chemotherapy is dependent on a high tumour to normal blood flow ratio (T/NT). This report demonstrates the use of a vasoconstrictor (NE) to improve the relative blood flow to head and neck tumours by causing vasoconstriction and decreased blood flow to normal soft tissue. Five quantitative planar Tc-MAA perfusion studies were performed on three patients with increasing dose rates of norepinephrine (NE) to determine the optimal dose in each patient that would produce the best T/NT. All patients demonstrated a change in perfusion pattern with increasing dose rates (0.1 to 15 μg min-1), although there was considerable variation between patients. Quantitative SPECT was performed on two patients. In one, there was a 35% increase in the T/NT and a 16% decrease in arteriovenous (A-V) shunting to the lung.