Raghuveer Halkar

Reproducibility and Reliability of Anti-3-[18F]FACBC Uptake Measurements in Background Structures and Malignant Lesions on Follow-Up PET-CT in Prostate Carcinoma: an Exploratory Analysis

PurposeThe aim of this study is to examine the reproducibility of anti-1-amino-3-[18F]fluorocyclobutane-1-carboxylic acid (anti-3-[18F]FACBC) quantitative measurements in key background structures and untreated malignant lesions.ProceduresRetrospective review of 14 patients who underwent follow-up anti-3-[18F]FACBC positron emission tomography-X-ray computed tomography (PET-CT) for prostate carcinoma recurrence. Standard uptake values (SUV) were measured in both original and follow-up scans in key background structures and untreated malignant lesions. Absolute and percent mean difference in SUV between scans and interclass correlation coefficients (ICC) were also computed.ResultsMean (±SD, range) scan interval was 17.4 months (±7.1, 4–29). %Mean difference in SUVmean was <20 % in background structures with low absolute differences. ICCs were >0.6 except for early-phase blood pool (ICC = 0.4). SUVmax in malignant lesions without interim therapy increased or remained stable over time.ConclusionsDespite variable time interval between scans, FACBC PET-CT demonstrates acceptable reproducibility in key background structures. Untreated malignant lesions showed stable or increased uptake over time. A formal test-retest study is planned.

Incremental benefit of SPECT + CT bone scans over conventional planar and SPECT bone scans in vertebroplasty

Study design: Planar bone scans with SPECT and SPECT + CT were performed in those patients who underwent peri-operative evaluation for vertebroplasty. The scans were evaluated separately to identify the “culprit” vertebra (e) by two readers and their results were analyzed. Objective: Use of planar and SPECT bone scan for identifying the “culprit” vertebra (e) for vertebroplasty is well established. SPECT + CT is a relatively recent imaging tool providing co-registered fused images. Theoretical advantages of SPECT + CT over conventional SPECT imaging needs to be evaluated and documented. Summary of Background Data: Percutaneous stabilization of collapsed vertebra by bone cement has now become a standard procedure. However, it is essential to localize the correct vertebra. Imaging modalities like CT scan provides structural or anatomical information where as bone scan (planar + SPECT images) provides more functional or physiological information. Combination of these two imaging modalities is expected to provide much more than information obtained by any one imaging modality separately. To the best our knowledge, there is no reference available in the literature adopting this approach. Materials and Methods: Two expert readers, blinded to patient history, evaluated the scans. They independently analyzed planar + SPECT only images followed by SPECT/CT fused images with the aim to identify the acutely fractured vertebra for vertebroplasty. Results: Interpretations changed, on average, 50% of the time as a result of the additional information provided by SPECT + CT. SPECT + CT more precisely localizes tracer abnormalities in the vertebra compared to SPECT imaging alone Conclusion: The greatest value of co-registered SPECT + CT bone scan lies in the accurate localization of affected vertebrae in complicated cases of multiple collapsed vertebrae of different ages as well as in the post-vertebroplasty setting

Tc-99m DTPA and I-131 hippurate renography. Findings in hepatorenal syndrome.

Tc-99m DTPA and 1–131 OIH renography were performed simultaneously in a patient with hepatorenal syndrome. Blood flow was delayed and diminished bilaterally; there was Tc-99m DTPA and 1–131 OIH retention in the parenchyma with no evidence of tracer retention in the collecting systems. The 1–131 OIH renogram curve demonstrated a steadily rising pattern, whereas the Tc-99m DTPA curve demonstrated an initial vascular peak and was subsequently flat. There was no appreciable response to furosemide. These findings are not specific for hepatorenal syndrome, and the diagnosis is based on the characteristic clinical setting and the exclusion of other causes of renal failure. A brief literature review and a discussion of differential diagnosis are included.

Correct interpretation of a myocardial perfusion SPECT study in a patient with Ebstein’s anomaly through recognition of septal artifact

ConclusionQuantitative assessment by use of polar maps and normal files increases the confidence of interpretation in most cases.4,5 However, when altered anatomy not accounted for in the normal database is present, the results can be misleading. This case illustrates the necessity for complete review of the patient’s history, rotating planar images, oblique slices, and polar maps to properly interpret a study.

A Novel Timesaving Method for Hepatobiliary Imaging for Suspected Acute Cholecystitis

OBJECTIVE To optimize resource utilization of cholescintigraphy for suspected acute cholecystitis with a time-saving method without a loss in diagnostic accuracy. MATERIALS AND METHODS Institutional review board approval was obtained for this retrospective study. Hepatobiliary imaging data for 81 patients with suspected acute cholecystitis were recalled for modification into 2 summed static images, using only the first and last 5 minutes of the dynamic images, thereby eliminating the middle 50 minutes of imaging data. Two nuclear medicine physicians interpreted the summed images to assess visualization, and those interpretations were compared to the original reports based on using all 60 minutes of dynamic imaging. A third nuclear medicine physician mediated rare inter-reader interpretive disagreements. Comparison of interpretations of time-saving and conventional methods and also inter-observer variability was achieved using the Cohen κ coefficient analysis. RESULTS Interpretations rendered using the time-saving method showed near-perfect agreement with those based on the full dynamic imaging protocol (Cohen κ coefficient = 0.92 for both readers). Furthermore, nuclear medicine physician readers agreed with each other (Cohen κ coefficient = 0.95 between the 2 readers), indicating minimal inter-observer variability using this novel optimized technique. CONCLUSION In the setting of suspected acute cholecystitis, imaging resource utilization may be improved, via reduced gamma camera and technologist time, using a novel time-saving method without sacrificing diagnostic accuracy. Multicenter larger trials, however, will be necessary to establish reproducibility.