Screening of Potential Cardiac Involvement in Competitive Athletes Recovering From COVID-19: An Expert Consensus Statement

As our understanding of the complications of coronavirus disease-2019 (COVID-19) evolve, subclinical cardiac pathology such as myocarditis, pericarditis, and right ventricular dysfunction in the absence of significant clinical symptoms represents a concern. The potential implications of these findings in athletes are significant given the concern that exercise, during the acute phase of viral myocarditis, may exacerbate myocardial injury and precipitate malignant ventricular arrhythmias. Such concerns have led to the development and publication of expert consensus documents aimed at providing guidance for the evaluation of athletes after contracting COVID-19 in order to permit safe return to play. Cardiac imaging is at the center of these evaluations. This review seeks to evaluate the current evidence regarding COVID-19-associated cardiovascular disease and how multimodality imaging may be useful in the screening and clinical evaluation of athletes with suspected cardiovascular complications of infection. Guidance is provided with diagnostic "red flags" that raise the suspicion of pathology. Specific emphasis is placed on the unique challenges posed in distinguishing athletic cardiac remodeling from subclinical cardiac disease. The strengths and limitations of different imaging modalities are discussed and an approach to return to play decision making for athletes post-COVID-19, as informed by multimodality imaging, is provided.

Diagnostic accuracy of dopaminergic imaging in prodromal dementia with Lewy bodies

BACKGROUND

Dopaminergic imaging has high diagnostic accuracy for dementia with Lewy bodies (DLB) at the dementia stage. We report the first investigation of dopaminergic imaging at the prodromal stage.

METHODS

We recruited 75 patients over 60 with mild cognitive impairment (MCI), 33 with probable MCI with Lewy body disease (MCI-LB), 15 with possible MCI-LB and 27 with MCI with Alzheimer's disease. All underwent detailed clinical, neurological and neuropsychological assessments and FP-CIT [123I-N-fluoropropyl-2β-carbomethoxy-3β-(4-iodophenyl)] dopaminergic imaging. FP-CIT scans were blindly rated by a consensus panel and classified as normal or abnormal.

RESULTS

The sensitivity of visually rated FP-CIT imaging to detect combined possible or probable MCI-LB was 54.2% [95% confidence interval (CI) 39.2-68.6], with a specificity of 89.0% (95% CI 70.8-97.6) and a likelihood ratio for MCI-LB of 4.9, indicating that FP-CIT may be a clinically important test in MCI where any characteristic symptoms of Lewy body (LB) disease are present. The sensitivity in probable MCI-LB was 61.0% (95% CI 42.5-77.4) and in possible MCI-LB was 40.0% (95% CI 16.4-67.7).

CONCLUSIONS

Dopaminergic imaging had high specificity at the pre-dementia stage and gave a clinically important increase in diagnostic confidence and so should be considered in all patients with MCI who have any of the diagnostic symptoms of DLB. As expected, the sensitivity was lower in MCI-LB than in established DLB, although over 50% still had an abnormal scan. Accurate diagnosis of LB disease is important to enable early optimal treatment for LB symptoms.

Opportunities for improvement on current nuclear cardiology practices and radiation exposure in Latin America: Findings from the 65-country IAEA Nuclear Cardiology Protocols cross-sectional Study (INCAPS)

BACKGROUND

Comparison of Latin American (LA) nuclear cardiology (NC) practice with that in the rest of the world (RoW) will identify areas for improvement and lead to educational activities to reduce radiation exposure from NC.

METHODS AND RESULTS

INCAPS collected data on all SPECT and PET procedures performed during a single week in March-April 2013 in 36 laboratories in 10 LA countries (n = 1139), and 272 laboratories in 55 countries in RoW (n = 6772). Eight "best practices" were identified a priori and a radiation-related Quality Index (QI) was devised indicating the number used. Mean radiation effective dose (ED) in LA was higher than in RoW (11.8 vs 9.1 mSv, p < 0.001). Within a populous country like Brazil, a wide variation in laboratory mean ED was found, ranging from 8.4 to 17.8 mSv. Only 11% of LA laboratories achieved median ED <9 mSv, compared to 32% in RoW (p < 0.001). QIs ranged from 2 in a laboratory in Mexico to 7 in a laboratory in Cuba. Three major opportunities to reduce ED for LA patients were identified: (1) more laboratories could implement stress-only imaging, (2) camera-based methods of ED reduction, including prone imaging, could be more frequently used, and (3) injected activity of 99mTc could be adjusted reflecting patient weight/habitus.

CONCLUSIONS

On average, radiation dose from NC is higher in LA compared to RoW, with median laboratory ED <9 mSv achieved only one third as frequently as in RoW. Opportunities to reduce radiation exposure in LA have been identified and guideline-based recommendations made to optimize protocols and adhere to the "as low as reasonably achievable" (ALARA) principle.

PREDICTION OF RELAPSE FROM HYPERTHYROIDISM FOLLOWING ANTITHYROID MEDICATION WITHDRAWAL USING TECHNETIUM THYROID UPTAKE SCANNING

OBJECTIVE

Technetium thyroid uptake (TTU) is not inhibited by antithyroid drugs (ATD) and reflects the degree of thyroid stimulation. We intended to predict the relapse rate from hyperthyroidism based on TTU measurement.

METHODS

Out of 44 initially enrolled subjects, 38 patients aged 41.6 ± 14.6 with Graves disease (duration: 84 ± 78 months) completed the study. TTU was performed with 40-second imaging of the neck and mediastinum 20 minutes after injection of 1 mCi technetium-99m pertechnetate. TTU was measured as the percentage of the count of activity accumulated in the thyroidal region minus the mediastinal background uptake to the count of 1 mCi technetium-99m under the same acquisition conditions. Then methimazole was stopped and patients were followed. The optimal TTU cutoff value for Graves relapse prediction was calculated using Youden's J statistic.

RESULTS

Hyperthyroidism relapsed in 11 (28.9%) patients 122 ± 96 (range: 15-290) days post-ATD withdrawal. The subjects in remission were followed for 209 ± 81 days (range: 88-390). TTU was significantly higher in patients with forthcoming relapse (12.0 ± 8.0 vs. 3.9 ± 2.0, P = .007). The difference was significant after adjustment for age, sex, history of previous relapse, disease duration, and thyroid-stimulating hormone (TSH) levels before withdrawal. The area under the receiver operative characteristic (ROC) curve was 0.87. The optimal TTU cutoff value for classification of subjects with relapse and remission was 8.7 with sensitivity, specificity, and positive and negative predictive value of 73%, 100%, 100%, and 90%, respectively (odds ratio [OR] = 10.0; 95% confidence interval [CI]: 3.4-29.3).

CONCLUSION

TTU evaluation in hyperthyroid patients receiving antithyroid medication is an accurate and practical method for predicting relapse after ATD withdrawal.

ABBREVIATIONS

ATD = antithyroid drugs RIU = radio-iodine uptake TSH = thyroid-stimulating hormone TSI = thyroid-stimulating immunoglobulin TTU = technetium thyroid uptake.

Patient doses from CT examinations in Turkey

PURPOSE

We aimed to establish the first diagnostic reference levels (DRLs) for computed tomography (CT) examinations in adult and pediatric patients in Turkey and compare these with international DRLs.

METHODS

CT performance information and examination parameters (for head, chest, high-resolution CT of the chest [HRCT-chest], abdominal, and pelvic protocols) from 1607 hospitals were collected via a survey. Dose length products and effective doses for standard patient sizes were calculated from the reported volume CT dose index (CTDIvol).

RESULTS

The median number of protocols reported from the 167 responding hospitals (10% response rate) was 102 across five different age groups. Third quartile CTDIvol values for adult pelvic and all pediatric body protocols were higher than the European Commission standards but were comparable to studies conducted in other countries.

CONCLUSION

The radiation dose indicators for adult patients were similar to those reported in the literature, except for those associated with head protocols. CT protocol optimization is necessary for adult head and pediatric chest, HRCT-chest, abdominal, and pelvic protocols. The findings from this study are recommended for use as national DRLs in Turkey.

Current status of nuclear cardiology in Japan: Ongoing efforts to improve clinical standards and to establish evidence

Nuclear cardiology imaging tests are widely performed in Japan as clinical practice. The Japanese nuclear cardiology community has developed new diagnostic imaging tests using (123)I-beta-methyl-p-iodophenyl-pentadecanoic acid, (123)I-metaiodobenzylguanidine, and (18)F-fluorodeoxyglucose PET for detecting cardiac involvement in sarcoidosis. These tests have become popular worldwide. The Japanese Circulation Society and the Japanese Society of Nuclear Cardiology have published clinical imaging guidelines showing indications and standards for the new imaging tests. JSNC is currently striving to improve the standard of clinical practice and is promoting research activities.

Russian practical guidance on radiological support for justification of X-ray and nuclear medicine examinations

An important part of the justification process is assessment of the radiation risks caused by exposure of a patient during examination. The authors developed official national methodology both for medical doctors and sanitary inspectors called 'assessment of radiation risks of patients undergoing diagnostic examinations with the use of ionizing radiation'. The document addresses patients of various age groups and a wide spectrum of modern X-ray and nuclear medicine examinations. International scale of risk categorisation was implemented by the use of effective dose with account for age dependence of radiation risk. The survey of effective doses in radiology, including CT, mammography, and intervention radiology, and nuclear medicine, including single-photon emission tomography and positron emission tomography, for patients of various age groups from several regions of Russia was used for the risk assessment. The output of the methodology is a series of tables for each diagnostic technology with lists of examinations for three age groups (children/adolescents, adults and seniors) corresponding to various radiation risk categories.

Internal dosimetry estimates using voxelized reference phantoms for thyroid agents

This work presents internal dosimetry estimates for diagnostic procedures performed for thyroid disorders by relevant radiopharmaceuticals. The organ doses for (131)Iodine, (123)Iodine and (99m)Tc incorporated into the body were calculated for the International Commission on Radiological Protection (ICRP) reference voxel phantoms using the Monte Carlo transport method. A comparison between different thyroid uptakes of iodine in the range of 0-55% was made, and the effect of various techniques for administration of (99m)Tc on organ doses was studied. To investigate the necessity of calculating organ dose from all source regions, the major source organ and its contribution to total dose were specified for each target organ. Moreover, we compared effective dose in ICRP voxel phantoms with that in stylized phantoms. In our method, we directly calculated the organ dose without using the S values or SAFs, as is commonly done. Hence, a distribution of the absorbed dose to entire tissues was obtained. The chord length distributions (CLDs) were also computed for the selected source-target pairs to make comparison across the genders. The results showed that the S values for radionuclides in the thyroid are not sufficient for calculating the organ doses, especially for (123)I and (99m)Tc. The thyroid and its neighboring organs receive a greater dose as thyroid uptake increases. Our comparisons also revealed an underestimation of organ doses reported for the stylized phantoms compared with the values based on the ICRP voxel phantoms in the uptake range of 5-55%, and an overestimation of absorbed dose by up to 2-fold for Iodine administration using blocking agent and for (99m)Tc incorporation.

Evaluation of imaging systems using the posterior variance of emission counts

We investigate an approach to evaluation of emission-tomography (ET) imaging systems used for region-of-interest (ROI) estimation tasks. In the evaluation we employ the concept of "emission counts" (EC), which are the number of events per voxel emitted during a scan. We use the reduction in posterior variance of ROI EC, compared to the prior ROI EC variance, as the metric of primary interest, which we call the "posterior variance reduction index" (PVRI). Systems that achieve a higher PVRI are considered superior to systems with lower PVRI. The approach is independent of the reconstruction method and is applicable to all photon-limited data types including list-mode data. We analyzed this approach using a model of 2-D tomography, and compared our results to the classical theory of tomographic sampling. We found that performance evaluations using the PVRI index were consistent with the classical theory. System evaluation based on EC posterior variance is an intuitively appealing and physically meaningful method that is useful for evaluation of system performance in ROI quantitation tasks.

Evaluation of [11C]-choline positron-emission/computed tomography in patients with increasing prostate-specific antigen levels after primary treatment for prostate cancer

OBJECTIVE

To evaluate [(11)C]-choline positron-emission tomography (PET)/computed tomography (CT) for detecting clinical recurrence after primary treatment for prostate cancer.

PATIENTS AND METHODS

In all, 50 patients with prostate cancer who had had initial therapy (radical prostatectomy in 40, external beam radiation in three and interstitial brachytherapy in seven) had PET/CT using [(11)C]-choline in the presence of an increased or increasing prostate-specific antigen (PSA) level. The mean (range) time to biochemical progression was 22 (2-136) months. Current PSA levels were determined in all patients at the time of examination. The results were correlated with the histopathology reports after targeted biopsy or surgery, and with the clinical follow-up.

RESULTS

The mean (median, range) PSA level in patients with positive PET/CT was 3.62 (2.42, 0.5-13.1) ng/mL, and that in patients with a negative scan was 0.90 (0.95, 0.41-1.40) ng/mL. PET/CT was positive in seven of 13 patients with a PSA level of <1.5 ng/mL, and histology was positive in this group in nine. In 17 patients with PSA levels of 1.5-2.5 ng/mL PET/CT was positive in all and the histology was positive in 13; in 11 men with a PSA level of 2.5-5 ng/mL PET/CT was positive in all 11 and the histology was positive in 10; in nine men with PSA levels of >5 ng/mL PET/CT identified all as positive and the histology was positive in eight. The sensitivity at a PSA level of <2.5 ng/mL of PET/CT for detecting recurrence was 91% (95% confidence interval, 71-99%) with a specificity of 50% (16-84)%.

CONCLUSION

[(11)C]-choline PET/CT seems to be useful for re-staging prostate cancer after curative therapy and with increasing PSA levels; this was verified by histological examination. We recommend this method at PSA levels of <2.5 ng/mL.

A priori selection of the regularization parameters in emission tomography by Fourier synthesis

This paper describes how the stability of the inverse problem underlying emission tomography can be measured and controlled in clinical settings. We show how the Lanczos approximation provides a way to regularize a certain class of iterative reconstruction algorithms through a given level of noise or resolution in the slices and for a given acquisition protocol. Moreover, we show how the same Lanczos approximation can be used to decide when the iterative reconstruction algorithm actually converges for a given machine precision. These ideas are illustrated by means of reconstructions of simulated and actual emission datasets.

Diagnostic accuracy of PET/CT in patients with extranodal marginal zone MALT lymphoma

BACKGROUND

(18)Fluoro-2-deoxyglucose ((18)FDG) positron emission tomography (PET) is widely used for initial staging and follow-up in patients with malignant lymphoma. While earlier studies suggested a limited role for PET in extranodal marginal zone mucosa-associated lymphoid tissue (MALT) lymphoma patients due to their non-FDG avidity, more recent reports have suggested that the issue is controversial. In the present study, we evaluated the diagnostic accuracy of PET integrated with CT (PETCT) in patients with MALT lymphoma and assessed its reliability in clinical staging and monitoring response.

METHODS

Thirty-three patients with biopsy proven MALT lymphoma in 37 sites, who underwent PET/CT at diagnosis, were enrolled. Medical records, PET/CT findings and data obtained by other diagnostic procedures were reviewed.

RESULTS

Common sites of MALT lymphoma were the stomach (18), lung (5), orbit (4), and parotid gland (3). PET/CT detected active disease in 18 of 33 patients (54.5%) at diagnosis. Sensitivity in gastric MALT (38.9%) was lower when compared with non-gastric MALT (75%). PET/CT detected active disease in 100% patients with advanced disease (stage III-IV) but only in 42.3% with early stage disease (I-II). The incidence of gastric FDG uptake was higher in patients showing gastric ulcer on gastroscopy than in subjects with minimal or no macroscopic findings. Of the 33 patients in the study cohort, 12 had a follow-up PET/CT which detected relapse in three patients.

CONCLUSIONS

These data suggest that PET/CT is a useful tool for both, initial staging and follow-up after therapy in patients with MALT lymphoma. Its sensitivity depends on disease location and stage at initial diagnosis.

Implications of full compliance with the computed tomography scanning recommendations of the National Institute for Clinical Excellence and Scottish Intercollegiate Guidelines Network guidelines for the management of head injury

A prospective study was conducted to examine clinical practices in the management of head-injured patients preinception and postinception of the Scottish Intercollegiate Guidelines Network guidelines. Comparison was made between the Scottish Intercollegiate Guidelines Network and National Institute for Clinical Excellence guidelines on their indications for computed tomography scanning. Information was available on 2827 adult patients. Two hundred and thirty-two patients satisfied one or more Scottish Intercollegiate Guidelines Network criteria for computed tomography scanning. Four hundred and seventy-eight patients fulfilled one or more National Institute for Clinical Excellence criteria for scanning. No patient with Scottish Intercollegiate Guidelines Network or National Institute for Clinical Excellence indications for computed tomography scanning and who was not scanned, subsequently required neurosurgical treatment for a complication related to their injury. Full compliance with the scanning recommendations in the Scottish Intercollegiate Guidelines Network and National Institute for Clinical Excellence guidelines will require a significant increase in scanning resource and is unlikely to lead to the identification of a significant additional number of patients with intracranial lesions requiring neurosurgical intervention.

[2005 monitoring report: use of positron emission tomography with fluorodeoxyglucose in the management of patients with breast cancer, ovarian cancer, and uterine cancer]

CONTEXT

The validity of the recommendations is based on their actualisation as well as on the quality of the initial elaboration process. Therefore the "Standards, Options and Recommendations" (SOR) from the National French federation of comprehensive cancer centres (FNCLCC) has set up a literature monitoring process.

OBJECTIVES

To identify new data, which are likely to modify existing recommendations, evaluate their impact and inform potential users on their validity.

METHODS

The monitoring process is based on 3 main steps lead in collaboration with experts: collect data, select and classify information and analyse information. Analysis of information consists of comparing the conclusions of new data with the conclusions of the initial report and then to identify the recommendations that need to be updated.

RESULTS

This article presents the 2005 monitoring report concerning "the use of positron emission tomography with FDG in the management of breast cancer, ovarian cancer and uterin cancer". Following the monitoring process,all the existing recommendations (initial report from 2003) are still valid. However three modifications have been proposed by the working group: 1) increased level of evidence concerning the use of PET-scan for suspicion of local or metastatic recurrence (option, level of evidence: A); 2) a new option for the use of PET-scan for revealed cervix cancer recurrence, especially for the therapeutic decision strategy (level of evidence: B2); and 3) new formulation (less strict) of the recommendation concerning the use of PET-scan in the management of endometrial cancer.

An analysis of the physiological FDG uptake pattern in the stomach

The purpose of this study was to clarify the normal gastric FDG uptake pattern to provide basic information to make an accurate diagnosis of gastric lesions by FDG PET. We examined 22 cases, including 9 of malignant lymphoma, 8 of lung cancer, 2 of esophageal cancer, and 3 of other malignancies. No gastric lesions were observed in any of the 22 cases on upper gastrointestinal examinations using either barium meal or endoscopic techniques. The intervals between FDG PET and the gastrointestinal examination were within one week in all cases. The stomach regions were classified into the following three areas: U (upper)-area, M (middle)-area, and L (lower)-area. The degree of FDG uptake in these three gastric regions was qualitatively evaluated by visual grading into 4 degrees, and then a semiquantitative evaluation was carried out using the standardized uptake value (SUV). Based on a visual grading evaluation, the mean FDG uptake score in the U-, M-, and L-areas was 1.14 +/- 0.96, 0.82 +/- 0.96, and 0.36 +/- 0.49 (mean +/- S.D.), respectively. The FDG uptake scores obtained in the three areas were significantly different (Friedman test, p < 0.05). Furthermore, the rank order of the FDG uptake score in each case (U > or = M > or = L) was found to be statistically significant (Cochran-Armitage trend test, p < 0.05). The mean SUVs of 11 cases in the three areas were 2.38 +/- 1.03, 1.91 +/- 0.71, and 1.34 +/- 0.44 (mean +/- S.D.), respectively. The SUV in the U-area was significantly higher than that in the L-area (Friedman test, p < 0.05). A significant difference in FDG uptake was observed among the three gastric areas, and the FDG uptake extent in all cases was U > M > L. In conclusion, the physiological gastric FDG uptake was significantly higher at the oral end. A stronger gastric FDG uptake at the anal end may therefore be suggestive of a pathological uptake.

Technical errors in planar bone scanning

Optimal technique for planar bone scanning improves image quality, which in turn improves diagnostic efficacy. Because planar bone scanning is one of the most frequently performed nuclear medicine examinations, maintaining high standards for this examination is a daily concern for most nuclear medicine departments. Although some problems such as patient motion are frequently encountered, the degraded images produced by many other deviations from optimal technique are rarely seen in clinical practice and therefore may be difficult to recognize. The objectives of this article are to list optimal techniques for 3-phase and whole-body bone scanning, to describe and illustrate a selection of deviations from these optimal techniques for planar bone scanning, and to explain how to minimize or avoid such technical errors.

Effects of noise, image resolution, and ROI definition on the accuracy of standard uptake values: a simulation study

Semiquantitative standard uptake values (SUVs) are used for tumor diagnosis and response monitoring. However, the accuracy of the SUV and the accuracy of relative change during treatment are not well documented. Therefore, an experimental and simulation study was performed to determine the effects of noise, image resolution, and region-of-interest (ROI) definition on the accuracy of SUVs.

METHODS

Experiments and simulations are based on thorax phantoms with tumors of 10-, 15-, 20-, and 30-mm diameter and background ratios (TBRs) of 2, 4, and 8. For the simulation study, sinograms were generated by forward projection of the phantoms. For each phantom, 50 sinograms were generated at 3 noise levels. All sinograms were reconstructed using ordered-subset expectation maximization (OSEM) with 2 iterations and 16 subsets, with or without a 6-mm gaussian filter. For each tumor, the maximum pixel value and the average of a 50%, a 70%, and an adaptive isocontour threshold ROI were derived as well as with an ROI of 15 x 15 mm. The accuracy of SUVs was assessed using the average of 50 ROI values. Treatment response was simulated by varying the tumor size or the TBR.

RESULTS

For all situations, a strong correlation was found between maximum and isocontour-based ROI values resulting in similar dependencies on image resolution and noise of all studied SUV measures. A strong variation with tumor size of > or =50% was found for all SUV values. For nonsmoothed data with high noise levels this variation was primarily due to noise, whereas for smoothed data with low noise levels partial-volume effects were most important. In general, SUVs showed under- and overestimations of > or =50% and depended on all parameters studied. However, SUV ratios, used for response monitoring, were only slightly dependent of ROI definition but were still affected by noise and resolution.

CONCLUSION

The poor accuracy of the SUV under various conditions may hamper its use for diagnosis, especially in multicenter trials. SUV ratios used to measure response to treatment, however, are less dependent on noise, image resolution, and ROI definition. Therefore, the SUV might be more suitable for response-monitoring purposes.

Differences between systematic reviews and health technology assessments: a trade-off between the ideals of scientific rigor and the realities of policy making

OBJECTIVES

To elucidate important differences between a health technology assessment (HTA) and a systematic review, using an HTA of positron emission tomography (PET) as an example.

METHODS

Interviews with seventeen individuals who were authors or users of the PET HTA.

RESULTS

Those interviewed identified seven areas in which HTAs often differ from traditional systematic reviews: (i) methodological standards (HTAs may include literature of relatively poor methodological quality if a topic is of importance to decision-makers), (ii) replication of previous studies (relatively common for HTAs but not systematic reviews), (iii) choice of topics (more policy oriented for HTAs, while systematic reviews tend to be driven by researcher interest), (iv) inclusion of content experts and policy-makers as authors (policy-makers more likely to be included in HTAs, although there are potential conflicts of interest), (v) inclusion of economic evaluations (more often with HTAs, although economic evaluations based upon poor clinical data may not be useful), (vi) making policy recommendations (more likely with HTAs, although this must be done with caution), and (vii) dissemination of the report (more often actively done for HTAs).

CONCLUSIONS

This case study of an HTA of PET scanning confirms that HTAs are a bridge between science and policy and require a balance between the ideals of scientific rigor and the realities of policy making.

Characterization of the normal adrenal gland with 18F-FDG PET/CT

Prior studies have documented increased (18)F-FDG adrenal activity in both benign and malignant pathologic conditions. When whole-body PET imaging is performed without CT anatomic coregistration, however, the normal adrenal gland is difficult to recognize. The purpose of this study was to investigate the normal adrenal appearance and standardized uptake value (SUV) using (18)F-FDG PET/CT imaging.

METHODS

Twenty patients with lymphoma with normal-appearing adrenal glands on prior CT examination (less than a 5% pretest likelihood of adrenal involvement) were studied. PET/CT imaging was performed 2 h after intravenous administration of (18)F-FDG. Unenhanced CT scans were acquired for attenuation correction and anatomic coregistration. PET images were reconstructed using an ordered-subsets expectation maximization algorithm and were corrected for body weight, dose, and radioactive decay. Ability to confirm visualization of the adrenal glands was determined for (18)F-FDG PET alone and for (18)F-FDG PET/CT by a consensus of 2 readers, and uptake of (18)F-FDG in the adrenal gland was compared with liver activity and scored visually (0 = no visualization, 1 = activity less than in liver, 2 = activity equal to liver activity, and 3 = activity greater than in liver).

RESULTS

The 2 readers agreed on visualization of the adrenal glands with PET alone for 2 of 40 (5%) glands. With PET/CT, the readers agreed on visualization of 27 of 40 (68%) adrenal glands. Visual scores for normal adrenal activity ranged from 0 to 3, and maximum SUVs ranged from 0.95 to 2.46. Visual scoring of adrenal activity correlated well with both mean and maximal SUV (mean SUV vs. visual score: slope = 0.96, r = 0.88; maximum SUV vs. visual score: slope = 0.99, r = 0.87).

CONCLUSION

PET/CT permits more reliable visualization of normal adrenal glands than does PET alone. Visual assessment of adrenal uptake correlates well with SUV measurement, and readers of PET/CT need to be aware of the wide range of normal adrenal uptake.

Single-Detector Helical CT in PET–CT: Assessment of Image Quality

OBJECTIVE

CT in positron emission tomography (PET)-CT imaging is often performed as a single scan from the base of the skull to the groin, potentially resulting in degradation of the quality of CT scans depending on the position of the patient's arms and mode of breathing and the use and timing of IV contrast injection. The aim of our study was to assess the impact of artifacts on the diagnostic quality of CT scans using a single-detector helical CT scanner in PET-CT imaging.

MATERIALS AND METHODS

Two radiologists retrospectively evaluated the diagnostic image quality of CT scans obtained with PET-CT in 81 patients with lymphoma. The severity of the artifacts related to the position of the patient's arms beside the body, the influence of breathing motion, and the presence of contrast material in the upper thoracic veins were ranked using a 4-point scale.

RESULTS

Performing CT with the patient's arms positioned beside the body resulted in streak artifacts, predominantly in the upper abdomen, that were graded as mild in 22%, moderate in 40%, and severe in 38% of the scans. A patient's weight significantly correlated with the degree of severity of the artifacts (p < 0.05). Shallow breathing by the patient during scanning caused blurring and double-imaging, again predominantly in the upper abdomen, that were graded as mild in 23%, moderate in 49%, or severe in 28% of the scans. In 84% of the CT scans obtained with IV contrast material, the image quality of the upper thoracic region was moderately (27%) or severely (57%) degraded by streak artifacts from highly concentrated contrast material in the upper thoracic veins.

CONCLUSION

The use of a single-detector CT scanner in whole-body PET-CT decreases the image quality of CT scans because of streak artifacts that occur predominantly in scans of the upper abdomen. Scanning with the patient's arms raised eliminates the streak artifacts in scans of the abdominal region. With the new generation of PET-CT devices equipped with MDCT scanners, breathing motion artifacts can be expected to be eliminated if protocols for breath-hold CT are applied. Reversing the direction of CT scanning allows one to avoid imaging the thoracic region at a time when undiluted IV contrast material is still present in the upper thoracic veins.

PET performance measurements for an LSO-based combined PET/CT scanner using the National Electrical Manufacturers Association NU 2-2001 standard

Results of performance measurements for a lutetium oxyorthosilicate (LSO)-based PET/CT scanner using new National Electrical Manufacturers Association (NEMA) NU 2-2001 standards are reported.

METHODS

Performance measurements following the NU 2-2001 standards were performed on an LSO-based PET/CT scanner. In addition, issues associated with the application of the NEMA standard to LSO-based tomographs in the presence of intrinsic radiation are discussed.

RESULTS

We report on some difficulties experienced in following the suggested NEMA measurement techniques and describe alternative approaches. Measurements with the new standard (as compared with NU-1994) incorporate the effects of activity outside the scanner and facilitate measurements of the entire axial field of view. Realistic clinical conditions are also simulated in image quality measurements of a torso phantom.

CONCLUSION

We find that, with appropriate modifications, NU 2-2001 can be successfully applied to LSO-based scanners.

NEMA NU 2 performance tests for scanners with intrinsic radioactivity

Performance tests on lutetium oxyorthosilicate (LSO)-based PET scanners cannot be conducted strictly according to the National Electrical Manufacturers Association (NEMA) NU 2 standards because of the presence of intrinsic radioactivity within the LSO crystal scintillator material. This background radiation gives rise mainly to random coincidence events but also to a small number of true coincidences, which cannot be eliminated from measurements on such scanners and must therefore be corrected for in the data analysis. The current NU 2 standards do not take account of these backgrounds and hence can lead to erroneous results on LSO-based machines. Nevertheless, the intent of the standards can be met with appropriate modifications to the acquisition and processing procedures. In this paper, we propose certain changes to the NEMA specifications to accommodate this class of scanners. These changes affect mainly the estimation of sensitivity, scatter, randoms, and count losses. Using these modified procedures, the NU 2 performance of LSO-based systems can accurately be measured.

Accuracy and Cost-Effectiveness of [18F]-2-Fluoro-Deoxy-D-Glucose-Positron Emission Tomography Scan in Potentially Resectable Non-small Cell Lung Cancer

STUDY OBJECTIVES

This retrospective study of patients who were referred for surgical resection of non-small cell lung cancer (NSCLC) assessed the accuracy and cost-effectiveness of positron emission tomography (PET) with radiolabeled [18F]-2-fluoro-deoxy-D-glucose (FDG) in staging mediastinal lymph nodes (MLNs).

DESIGN

From January 2001 to September 2002, 90 patients with suspected or proven NSCLC who had been referred for curative resection were retrospectively reviewed. All patients were without evidence of metastatic disease. Sixty-nine of the 90 patients had undergone thoracic FDG-PET imaging as part of their evaluation and are the focus of this study. Sensitivity, specificity, accuracy, and positive and negative predictive values for metastasis to the MLN were calculated for CT scanning vs FDG-PET scanning. Four algorithms for staging MLN with mediastinoscopy and/or FDG-PET scan were compared.

MEASUREMENTS AND RESULTS

Sixty-nine patients underwent preoperative CT and FDG-PET scans, and 32 of 69 patients underwent mediastinoscopy. Fifty-seven patients underwent thoracotomy with complete mediastinal lymphadenectomy. Sensitivity, specificity, accuracy, and positive and negative predictive values for CT scans and FDG-PET scans were 46%, 86%, 78%, 43%, and 87%, and 62%, 98%, 91%, 89% and 92%, respectively. Mediastinoscopy was accurate in 32 of 32 patients (100%). Routine mediastinoscopy remains the most economically reasonable strategy with excellent sensitivity. Selective FDG-PET imaging improved the sensitivity of noninvasive staging for patients with normal MLNs on CT scans.

CONCLUSIONS

Selective use of FDG-PET imaging improves staging accuracy compared to CT scanning alone and makes it a cost-effective adjunct to the preoperative staging of NSCLC. However, in patients with adenocarcinoma and MLNs of < 1 cm, FDG-PET scanning cannot yet replace mediastinoscopy.

Development and evaluation of an automated atlas-based image analysis method for microPET studies of the rat brain

An automated method for placement of 3D rat brain atlas-derived volumes of interest (VOIs) onto PET studies has been designed and evaluated. VOIs representing major structures of the rat brain were defined on a set of digitized cryosectioned images of the rat brain. For VOI placement, each PET study was registered with a synthetic PET target constructed from the VOI template. Registration was accomplished with an automated algorithm that maximized the mutual information content of the image volumes. The accuracy and precision of this method for VOI placement was determined using datasets from PET studies of the striatal dopamine and hippocampal serotonin systems. Each evaluated PET study could be registered to at least one synthetic PET target without obvious failure. Registration was critically dependent upon the initial position of the PET study relative to the synthetic PET target, but not dependent on the amount of synthetic PET target smoothing. An evaluation algorithm showed that resultant radioactivity concentration measurements of selected brain structures had errors=2% due to misalignment with the corresponding VOI. Further, radioligand binding values calculated from these measurements were found to be more precise than those calculated from measurements obtained with manually drawn regions of interest (ROIs). Overall, evaluation results demonstrated that this atlas-derived VOI method can be used to obtain unbiased measurements of radioactivity concentration from PET studies. Its automated features, and applicability to different radioligands and brain regions, will facilitate quantitative rat brain PET assessment procedures.

Establishing equivalence for activity standards of short-lived radionuclides using the NPL secondary standard radionuclide calibrator

Conventional comparison techniques used between National Metrology Institutes are not practicable for short-lived radionuclides because of geographical separations and transport difficulties. The NPL Secondary Standard Radionuclide Calibrator provides an alternative approach and a comparison was conducted with 18F to investigate its feasibility. The exercise was successful and the paper details the protocol used, the quality assurance mechanisms introduced to underpin the comparison and an analysis of the results. It was also demonstrated that this approach could be linked to the BIPM SIR system. Recommendations are presented for the extension of this work to other suitable, short-lived radionuclides.

Functional imaging of motor recovery after stroke: Remaining challenges

Stroke is a leading cause of disability in the United States and is likely to have an increasing impact on disability worldwide. In order to develop more effective rehabilitation techniques, it is critical to understand the mechanisms underlying the mature brain's capacity to reorganize and restore neurologic function. Over the past decade, functional brain imaging has been a principal investigational tool in elucidating mechanisms of stroke recovery. Functional imaging studies of motor performance in patients with stroke consistently demonstrate areas of brain activation not present in healthy subjects. The role of these additional areas in recovery after stroke remains uncertain. This review discusses methodologic and theoretical issues that impact on interpreting functional imaging studies of motor recovery after stroke.