Ryan Avery

Low-dose, prospective triggered high-pitch spiral coronary computed tomography angiography: comparison with retrospective spiral technique.

RATIONALE AND OBJECTIVES Cardiac computed tomographic angiography algorithms emphasize radiation reduction while maintaining diagnostic image quality (IQ). The aim of this study was to evaluate IQ and interreader variability using prospective electrocardiographically triggered high-pitch spiral cardiac computed tomographic angiography (FLASH-CT) compared to retrospective electrocardiographic gating (RETRO-CT) for coronary artery disease evaluation in a patient population including overweight and obese individuals. MATERIALS AND METHODS Seventy patients (24 women; mean age, 60 years) matched for gender, age, body mass index (27.4 ± 5.5 kg/m(2)), and calcium score (184 ± 328) underwent cardiac computed tomographic angiography, 35 with FLASH-CT (Definition Flash) and 35 with RETRO-CT (Somatom Definition). Images were reconstructed using standard protocols and least motion phase for RETRO-CT acquisitions. Two independent, blinded readers evaluated the coronary arteries using an 18-segment model, grading IQ on a 5-point, Likert-type scale and coronary stenosis on a 5-point semiquantitative and binary scale. RESULTS Effective radiation dose (1.50 vs 17.3 mSv, P < .0001) and mean heart rate (58 vs 62 beats/min, P < .05) were significantly lower for FLASH-CT compared to RETRO-CT. Seven hundred forty segments (> 1.5 mm) were evaluated. There was no significant difference between FLASH-CT and RETRO-CT scans in overall per-segment IQ (3.11 ± 0.75 vs 3.10 ± 0.82, P = .94). FLASH-CT had noninferior IQ relative to RETRO-CT (95% confidence interval, -0.25 to 0.26). There was no significant difference in interreader variability in diagnosis between FLASH-CT and RETRO-CT for all coronary segments (77.5% vs 78.2%, P = .83). CONCLUSIONS FLASH-CT is an acceptable coronary computed tomographic angiographic method for reducing radiation dose without compromising IQ for a patient population including overweight and obese individuals.

18F sodium fluoride PET/CT detects osseous metastases from breast cancer missed on FDG PET/CT with marrow rebound.

Intense FDG uptake by bone marrow following recent chemotherapy limits evaluation for osseous metastases. The impact of marrow rebound on accuracy of (18)F-fluoride PET/CT is unclear. A 73-year-old woman with breast cancer presented for restaging FDG PET/CT, which showed intense activity throughout almost the entire axial skeleton and no osseous metastases. An (18)F-fluoride PET/CT performed 7 days later identified multiple osseous metastases in the spine, ribs, and pelvis. This case demonstrates that (18)F-fluoride PET/CT should be considered for the evaluation of osseous metastases in patients with rebound marrow uptake on FDG PET/CT.

Receiver-operating-characteristic analysis of an automated program for analyzing striatal uptake of 123I-ioflupane SPECT images: calibration using visual reads.

A fully automated objective striatal analysis (OSA) program that quantitates dopamine transporter uptake in subjects with suspected Parkinson’s disease was applied to images from clinical 123I-ioflupane studies. The striatal binding ratios or alternatively the specific binding ratio (SBR) of the lowest putamen uptake was computed, and receiver-operating-characteristic (ROC) analysis was applied to 94 subjects to determine the best discriminator using this quantitative method. Methods: Ninety-four 123I-ioflupane SPECT scans were analyzed from patients referred to our clinical imaging department and were reconstructed using the manufacturer-supplied reconstruction and filtering parameters for the radiotracer. Three trained readers conducted independent visual interpretations and reported each case as either normal or showing dopaminergic deficit (abnormal). The same images were analyzed using the OSA software, which locates the striatal and occipital structures and places regions of interest on the caudate and putamen. Additionally, the OSA places a region of interest on the occipital region that is used to calculate the background-subtracted SBR. The lower SBR of the 2 putamen regions was taken as the quantitative report. The 33 normal (bilateral comma-shaped striata) and 61 abnormal (unilateral or bilateral dopaminergic deficit) studies were analyzed to generate ROC curves. Results: Twenty-nine of the scans were interpreted as normal and 59 as abnormal by all 3 readers. For 12 scans, the 3 readers did not unanimously agree in their interpretations (discordant). The ROC analysis, which used the visual-majority-consensus interpretation from the readers as the gold standard, yielded an area under the curve of 0.958 when using 1.08 as the threshold SBR for the lowest putamen. The sensitivity and specificity of the automated quantitative analysis were 95% and 89%, respectively. Conclusion: The OSA program delivers SBR quantitative values that have a high sensitivity and specificity, compared with visual interpretations by trained nuclear medicine readers. Such a program could be a helpful aid for readers not yet experienced with 123I-ioflupane SPECT images and if further adapted and validated may be useful to assess disease progression during pharmaceutical testing of therapies.

Classification Schema of Symptomatic Enterogastric Reflux Utilizing Sincalide Augmentation on Hepatobiliary Scintigraphy

Enterogastric reflux (EGR) is the reflux of duodenal contents into the stomach. Hepatobiliary scintigraphy provides physiologic assessment of the biliary system and was used to test the hypothesis that presence and timing of EGR may be associated with infusion of sincalide, a surrogate of endogenous cholecystokinin. Methods: One hundred fifty-seven hepatobiliary scintigraphy studies were retrospectively reviewed. Data included EGR incidence on initial reports, incidence after masked second reads, and time of EGR onset in relation to sincalide infusion. EGR cases were then classified according to onset on pre-, post-, or both presincalide and postsincalide imaging. Results: Time of EGR onset at 19–24 minutes after start of a 15-min sincalide infusion differed significantly from normal (p<0.0001). EGR was initially reported in 14 of 157 cases (8.9%) but found in 38 of 157 cases on masked second reads (24.2%), corresponding to a 15.3% discrepancy rate. Conclusion: The temporal association of EGR onset with sincalide infusion may identify patients with EGR mimicking chronic cholecystitis or biliary dyskinesia. A novel classification schema was therefore developed as a framework for future research, utilizing EGR onset in relation to pre-, post-, or both presincalide and postsincalide imaging as a hypothetical biomarker of clinically significant EGR.

The Semicolon Sign: Dopamine Transporter Imaging Artifact from Head Tilt

Dopamine transporter (DAT) imaging is a valuable tool to aid in the diagnosis of Parkinson disease and other Parkinsonian syndromes. DAT imaging is special among clinical nuclear medicine scans in that the already small caudate and putamen are presented in multiple thin axial cuts. Because the imaged basal ganglia are small, slight differences in head tilt may result in a significant artifact that we have termed the semicolon sign. The semicolon sign occurs when forward head tilt creates select images that show the caudate nuclei separate from the putamen. This gives the false impression that DAT activity in the putamen is decreased or absent. To avoid falsely attributing this artifact to loss of putaminal activity, it is imperative that the interpreting physician first recognize the artifact and then mentally integrate all provided images to identify normal activity in the putamen on subsequent levels. Furthermore, quantitative software packages for automated DAT scan interpretation are now available. If images demonstrating the semicolon sign are used for automated interpretation, loss of activity in the putamen may be falsely calculated, thereby contributing to erroneous results. Quality control measures are essential to ensure that technologists correctly position each patient’s head to minimize head tilt artifact on DAT scan images. A protocol to obtain optimal head positioning is presented.

FDG-PET/CT for Monitoring Response of Melanoma to the Novel Oncolytic Viral Therapy Talimogene Laherparepvec

61-year-old woman with stage IIIa (T3a N1a M0) left lower leg melanoma with lesions suggestive of in-transit metastases 8 months following wide local excision and femoral nodal dissection. FDG-PET/CT demonstrated 5 FDG-avid in-transit nodal metastases in the distal left leg, confirmed on biopsy. Talimogene laherparepvec (T-VEC) oncolytic immunotherapy consisting of intralesional injections of modified herpes simplex virus-expressing granulocyte-macrophage colony-stimulating factor was completed over 6 months. Subsequent FDG-PET/CT demonstrated reduced or resolved FDG activity in the treated in-transit metastases and a new FDG-avid left thigh in-transit metastasis. FDG-PET/CT can monitor response to T-VEC and potentially other novel viral immunotherapies.

Evaluation of an Objective Striatal Analysis Program for Determining Laterality in Uptake of 123I-Ioflupane SPECT Images: Comparison to Clinical Symptoms and to Visual Reads

An automated objective striatal analysis (OSA) software program was applied to dopamine transporter 123I-ioflupane images acquired on subjects with varying severities of parkinsonism. The striatal binding ratios (SBR) of the left and right putamina (relative to the occipital lobe) were computed, and the laterality of that measure was compared with clinical symptoms and visual reads. The objective over-read of OSA was evaluated as an aid in confirming the laterality of disease onset. Methods: One hundred one 123I-ioflupane scans were acquired on clinically referred subjects. SPECT images were analyzed using the OSA software, which locates the slices containing the striatal and background (occipital) structures, positions regions over the left and right caudate nuclei and putamina, and calculates the background-subtracted SBR. Seven images were uninterpretable because of patient motion or lack of visualization of the striatum. The remaining 94 scans were analyzed with OSA. Differences between left and right putaminal SBR ranged from 0% to 36.6%, with a mean of 11.4%. When the difference between the SBR of the left and right putamina was greater than 6%, the lower side was taken as the side of onset. Left-to-right differences less than 6% were considered to be nonlateralizing (symmetric). The 94 scans were reviewed independently by 3 masked expert readers. By majority consensus, abnormal findings were seen on 67 of the 94 scans, of which 46 had available clinical findings. Results: Clinically, 34 subjects presented with lateralized tremors and 12 with symmetric or no tremors. Of the 34 cases of clinically lateralized tremors, 26 (76%) were concordant with the OSA findings, 5 were disparate with OSA (15%), and in 3 the OSA results were symmetric (9%). For the same 34 patients, the visual reads were concurrent with clinical tremor findings in 24 cases (71%), 1 was disparate (3%), and 9 visual reads were symmetric (26%). Of the 9 scans deemed symmetric by readers, 4 were correctly lateralized by OSA, and of the 3 symmetric OSA results, 2 were correctly lateralized visually. Conclusion: The OSA program may be a helpful aid in the interpretation of 123I-ioflupane SPECT images for determining laterality representing the asymmetric loss of dopamine transporters in the striata. OSA offers an objective, reproducible over-read evaluation for the laterality of onset in Parkinson disease.

18F-FDG PET/CT for Monitoring Response of Merkel Cell Carcinoma to the Novel Programmed Cell Death Ligand 1 Inhibitor Avelumab

An 85-year-old man with stage IIIA Merkel cell carcinoma of the left arm was initially treated with local excision and axillary node dissection followed by radiation therapy. Eight months after surgery, whole-body FDG PET/CT demonstrated intensely hypermetabolic hepatic metastases and abdominal lymphadenopathy. Given his age and comorbidities, he was considered a poor candidate for chemotherapy, and therefore the novel programmed cell death ligand 1 inhibitor avelumab was initiated. FDG PET/CT after 4 cycles showed complete resolution of hepatic and nodal metastases. Whole-body FDG PET/CT can be used for monitoring response of multisystem metastases from Merkel cell carcinoma to active immunotherapy.

Clinical outcomes meta-analysis: measuring subendocardial perfusion and efficacy of transmyocardial laser revascularization with nuclear imaging

IntroductionRandomized and nonrandomized clinical trials have tried to assess whether or not TMR patients experience an increase in myocardial perfusion. However there have been inconsistencies reported in the literature due to the use of different nuclear imaging modalities to test this metric. The primary purpose of this meta-analysis was to determine whether SPECT, MUGA and PET scans demonstrate changes in myocardial perfusion between lased and non-lased subjects and whether laser type affects myocardial perfusion. The secondary purpose was to examine the overall effect of laser therapy on clinical outcomes including survival, hospital re-admission and angina reduction.MethodsSixteen studies were included in the primary endpoint analysis after excluding all other non-imaging TMR papers. Standardized mean difference was used as the effect size for all quantitative outcomes and log odds ratio was used as the effect size for all binary outcomes.ResultsStatistically significant improvements in myocardial perfusion were observed between control and treatment groups in myocardial perfusion at 6-month follow up using PET imaging with a porcine model. However non-significant differences were observed in patients at 3 and 12 months using SPECT, PET or MUGA scans. Both CO2 and Ho:YAG laser systems demonstrated an increase in myocardial perfusion however this effect was not statistically significant. In addition both laser types displayed statistically significant decreases in patient angina at 3, 6 and 12 months but non-significant increases in survival rates and decreases in hospital re-admissions.ConclusionIn order to properly assess myocardial perfusion in TMR subjects, subendocardial perfusion needs to be analyzed via nuclear imaging. PET scans can provide this level of sensitivity and should be utilized in future studies to monitor and detect perfusion changes in lased and non-lased subjects.

The Pinwheel Sign: Artifact from Head Rotation During SPECT Acquisition for Dopamine Transporter Imaging

This case study illustrates the pattern and significance of the pinwheel sign, a SPECT artifact from rotational head motion that can complicate the diagnosis of Parkinson disease. Monitoring the patient during image acquisition is crucial since rotational motion artifacts are difficult to identify on raw or processed images and may lead to incorrect interpretation of findings.