Beth A. Harkness

Distinguishing tumor recurrence from irradiation sequelae with positron emission tomography in patients treated for larynx cancer.

PURPOSE Distinguishing persistent or recurrent tumor from postradiation edema, or soft tissue/cartilage necrosis in patients treated for carcinoma of the larynx can be difficult. Because recurrent tumor is often submucosal, multiple deep biopsies may be necessary before a diagnosis can be established. Positron emission tomography with 18F-2fluoro-2deoxyglucose (FDG) was studied for its ability to aid in this problem. METHODS AND MATERIALS Positron emission tomography (18FDG) scans were performed on 11 patients who were suspected of having persistent or recurrent tumor after radiation treatment for carcinoma of the larynx. Patients underwent thorough history and physical examinations, scans with computerized tomography, and pathologic evaluation when indicated. Standard uptake values were used to quantitate the FDG uptake in the larynx. RESULTS The time between completion of radiation treatment and positron emission tomography examination ranged from 2 to 26 months with a median of 6 months. Ten patients underwent computed tomography (CT) of the larynx, which revealed edema of the larynx (six patients), glottic mass (four patients), and cervical nodes (one patient). Positron emission tomography scans revealed increased FDG uptake in the larynx in five patients and laryngectomy confirmed the presence of carcinoma in these patients. Five patients had positron emission tomography results consistent with normal tissue changes in the larynx, and one patient had increased FDG uptake in neck nodes. This patient underwent laryngectomy, and no cancer was found in the primary site, but nodes were pathologically positive. One patient had slightly elevated FDG uptake and negative biopsy results. The remaining patients have been followed for 11 to 14 months since their positron emission studies and their examinations have remained stable. In patients without tumor, average standard uptake values of the larynx ranged from 2.4 to 4.7, and in patients with tumor, the range was 4.9 to 10.7. CONCLUSION Positron emission tomography with labeled FDG appears to be useful in distinguishing benign from malignant changes in the larynx after radiation treatment. This noninvasive technique may be preferable to biopsy, which could traumatize radiation-damaged tissues and precipitate necrosis.

Whole body FDG-PET for the evaluation and staging of small cell lung cancer: a preliminary study

[F18]-2-deoxy-2fluoro-D-glucose positron emission tomography (FDG-PET) is increasingly used in the diagnosis and staging of lung cancer. Despite its positive performance characteristics in non-small cell lung cancer (NSCLC), the role of FDG-PET in the staging of small cell lung cancer (SCLC) remains to be determined. We designed a prospective study to address this question. Eighteen patients with SCLC were enrolled prospectively to undergo total body FDG-PET in addition to conventional staging procedures (chest computed tomography (CT), abdominal CT, cranial CT or magnetic resonance imaging (MRI), and bone scan/bone marrow biopsy). The agreement between FDG-PET and conventional staging modalities in identifying the presence or absence of metastatic disease was compared using the Veterans Administration (VA) cooperative staging system for staging. Overall staging by FDG-PET agreed with conventional staging exams in 15/18 (83%) patients (kappa=0.67), which included eight extensive and seven limited cases. FDG-PET showed more extensive disease in two of the three patients for which FDG-PET and conventional staging disagreed. These data suggest that total body FDG-PET may be useful in the staging, treatment planning, and prognostication of SCLC. Whether FDG-PET will replace other more established staging modalities remains to be determined by larger prospective randomized controlled studies.

Evaluation of the quantitative capability of a high-resolution positron emission tomography scanner for small animal imaging.

Objective: The quantitative capability of a positron emission tomog-raphy scanner for small animal imaging was evaluated in this study. Methods: The microPET P4 (Concorde Microsystems, Knoxville, TN) scanners capability for dynamic imaging and corrections for radioactive decay, dead time, and attenuation were evaluated. Rat brain and heart studies with and without attenuation correction were compared. A calibration approach to convert the data to nanocuries per milliliter was implemented. Calibration factors were determined using calibration phantoms of 2 sizes with and without attenuation correction. Quantitation was validated using the MiniPhantom (Data Spectrum, Chapel Hill, NC) with hot features (5:1 ratio) of different sizes (4, 6.4, 8, 13, and 16 mm). Results: The microPET P4 scanners ability to acquire dynamic studies and to correct for decay, dead time, and attenuation was demonstrated. The microPET P4 scanner provided accurate quantitation to within 6% for features larger than 10 mm. Sixty percent of object contrast was retained for features as small as 4 mm. Conclusions: The microPET P4 scanner can provide accurate quantitation.

Reduced Regional and Global Cerebral Blood Flow During Fenoldopam-Induced Hypotension in Volunteers

Dopamine has a wide spectrum of receptor and pharmacologic actions that may affect cerebral blood flow (CBF). A new, selective dopamine-1 agonist, fenoldopam, is a potent systemic vasodilator with moderate &agr;2-receptor affinity. However, the effects of fenoldopam on the cerebral circulation are undefined. We therefore hypothesized that infusion of fenoldopam would decrease mean arterial blood pressure (MAP) and might concurrently decrease CBF via vascular &agr;2-adrenoreceptor activation in awake volunteers. We studied nine healthy normotensive subjects, using positron emission tomography to measure CBF in multiple cortical and subcortical regions of interest. In addition, bioimpedance cardiac output and middle cerebral artery blood flow velocity were determined during fenoldopam-induced hypotension. Three men and four women, aged 25–43 yr, completed the study. Fenoldopam infused at 1.3 ± 0.4 &mgr;g · kg−1 · min−1 (mean ± sd) reduced MAP 16% from baseline: from 94 (89–100) mm Hg (mean [95% confidence interval]) to 79 [74–85] mm Hg (P < 0.0001). During the fenoldopam infusion, both cardiac output (+39%), and heart rate (+45%) increased significantly, whereas global CBF decreased from baseline, 45.6 [35.6–58.5] mL · 100 g−1 · min−1, to 37.7 [33.9–42.0] mL · 100 g−1 · min−1 (P < 0.0001). Despite restoration of baseline MAP with a concurrent infusion of phenylephrine, global CBF remained decreased relative to baseline values at 37.9 [34.0–42.3] mL · 100 gm−1 · min−1 (P < 0.0001). Changes in middle cerebral artery velocity did not correlate with positron emission tomography-measured changes of CBF induced by fenoldopam, with or without concurrent phenylephrine.

Angular disparity in ETACT scintimammography.

Emission tuned aperture computed tomography (ETACT) has been previously shown to have the potential for the detection of small tumors (<1 cm) in scintimammography. However, the optimal approach to the application of ETACT in the clinic has yet to be determined. Therefore, we sought to determine the effect of the angular disparity between the ETACT projections on image quality through the use of a computer simulation. A small, spherical tumor of variable size (5, 7.5 or 10 mm) was placed at the center of a hemispherical breast (15 cm diameter). The tumor to nontumor ratio was either 5:1 or 10:1. The detector was modeled to be a gamma camera fitted with a 4-mm-diam pinhole collimator. The pinhole-to-detector and the pinhole-to-tumor distances were 25 and 15 cm, respectively. A ray tracing technique was used to generate three sets of projections (10 degrees, 15 degrees, and 20 degrees, angular disparity). These data were blurred to a resolution consistent with the 4 mm pinhole. The TACT reconstruction method was used to reconstruct these three image sets. The tumor contrast and the axial spatial resolution was measured. Smaller angular disparity led to an improvement in image contrast but at a cost of degraded axial spatial resolution. The improvement in contrast is due to a slight improvement in the in-plane spatial resolution. Since improved contrast should lead to better tumor detectability, smaller angular disparity should be used. However, the difference in contrast between 10 degrees and 15 degrees was very slight and therefore a reasonable clinical choice for angular disparity is 15 degrees.

Evaluation of brain activity in FDG PET studies.

PURPOSE A tool (Gemini) was developed for quantifying regions of interest (ROIs) in registered MR and PET data. Its use was validated through phantom and simulated studies. METHOD Hot spheres were imaged in a phantom (3:1 and 5:1 target-to-nontarget ratios). The computerized 3D Hoffman brain phantom was used to simulate PET studies. Spherical local activity features of two diameters (4 and 10 mm) and five intensities (5, 15, 25, 50, and 100% increase over gray matter) were added to the data in the thalamus and Brodmann area 37. The data were reprojected into sinograms and blurred with a 7 mm kernel. Poisson noise was added, and the sinograms were then reconstructed and analyzed using both SPM96 and Gemini spherical ROIs. RESULTS Based on phantom and simulated data, the 95th percentile of intensity within a Gemini ROI afforded a reasonable joint optimization of variance (reliability) and accuracy (validity). SPM96 and Gemini results were similar for the larger (10 mm) feature, but in this application, Gemini was more sensitive than SPM96 for the small feature (4 mm). CONCLUSION Gemini, a tool for display and measurement of spherical ROIs in registered PET and MR data, is precise and accurate for testing hypotheses of differences in localized brain activity, comparing favorably with SPM96.

Improved Nuclear Medicine Uniformity Assessment with Noise Texture Analysis

Because γ cameras are generally susceptible to environmental conditions and system vulnerabilities, they require routine evaluation of uniformity performance. The metrics for such evaluations are commonly pixel value–based. Although these metrics are typically successful at identifying regional nonuniformities, they often do not adequately reflect subtle periodic structures; therefore, additional visual inspections are required. The goal of this project was to develop, test, and validate a new uniformity analysis metric capable of accurately identifying structures and patterns present in nuclear medicine flood-field uniformity images. Methods: A new uniformity assessment metric, termed the structured noise index (SNI), was based on the 2-dimensional noise power spectrum (NPS). The contribution of quantum noise was subtracted from the NPS of a flood-field uniformity image, resulting in an NPS representing image artifacts. A visual response filter function was then applied to both the original NPS and the artifact NPS. A single quantitative score was calculated on the basis of the magnitude of the artifact. To verify the validity of the SNI, an observer study was performed with 5 expert nuclear medicine physicists. The correlation between the SNI and the visual score was assessed with Spearman rank correlation analysis. The SNI was also compared with pixel value–based assessment metrics modeled on the National Electrical Manufacturers Association standard for integral uniformity in both the useful field of view (UFOV) and the central field of view (CFOV). Results: The SNI outperformed the pixel value–based metrics in terms of its correlation with the visual score (ρ values for the SNI, integral UFOV, and integral CFOV were 0.86, 0.59, and 0.58, respectively). The SNI had 100% sensitivity for identifying both structured and nonstructured nonuniformities; for the integral UFOV and CFOV metrics, the sensitivities were only 62% and 54%, respectively. The overall positive predictive value of the SNI was 87%; for the integral UFOV and CFOV metrics, the positive predictive values were only 67% and 50%, respectively. Conclusion: The SNI accurately identified both structured and nonstructured flood-field nonuniformities and correlated closely with expert visual assessment. Compared with traditional pixel value–based analysis, the SNI showed superior performance in terms of its correlation with visual perception. The SNI method is effective for detecting and quantifying visually apparent nonuniformities and may reduce the need for more subjective visual analyses.

Adult Gamma Camera Myocardial Perfusion Imaging: Diagnostic Reference Levels and Achievable Administered Activities Derived From ACR Accreditation Data

PURPOSE The aim of this study was to glean from accreditation surveys of US nuclear medicine facilities the in-practice radiopharmaceutical diagnostic reference levels (DRLs) and achievable administered activities (AAAs) for adult gamma camera myocardial perfusion imaging (MPI). METHODS Data were collected from the ACR Nuclear Medicine Accreditation Program during one three-year accreditation cycle from May 1, 2012, to April 30, 2015. Data elements included radiopharmaceutical, administered activity, examination protocol, interpreting physician specialty, practice type, and facility annual examination volume. Facility demographics, DRLs, and AAAs were tabulated for analysis. RESULTS The calculated DRLs and AAAs are consistent with previously published surveys, and they adhere to national societal guidelines. Facilities seeking ACR accreditation are nearly evenly split between hospital based with multiple gamma cameras and office based with single gamma cameras. The majority of facilities use single-day, low-dosage/high-dosage (99m)Tc-based protocols; a small minority use (201)TlCl protocols. Administered activities show a consistency across facilities, likely reflecting adoption of standard MPI protocols. CONCLUSIONS This practice-based analysis provides DRL and AAA benchmarks that nuclear medicine facilities may use to refine gamma camera MPI protocols. In general, the protocols submitted for ACR accreditation are consistent with national societal guidelines. The results suggest that there may be opportunities to further reduce patient radiation exposure by using modified examination protocols and newer gamma camera software and hardware technologies.

AAPM/SNMMI Joint Task Force: report on the current state of nuclear medicine physics training

The American Association of Physicists in Medicine (AAPM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI) recognized the need for a review of the current state of nuclear medicine physics training and the need to explore pathways for improving nuclear medicine physics training opportunities. For these reasons, the two organizations formed a joint AAPM/SNMMI Ad Hoc Task Force on Nuclear Medicine Physics Training. The mission of this task force was to assemble a representative group of stakeholders to: Estimate the demand for board-certified nuclear medicine physicists in the next 5-10 years, Identify the critical issues related to supplying an adequate number of physicists who have received the appropriate level of training in nuclear medicine physics, and Identify approaches that may be considered to facilitate the training of nuclear medicine physicists. As a result, a task force was appointed and chaired by an active member of both organizations that included representation from the AAPM, SNMMI, the American Board of Radiology (ABR), the American Board of Science in Nuclear Medicine (ABSNM), and the Commission for the Accreditation of Medical Physics Educational Programs (CAMPEP). The Task Force first met at the AAPM Annual Meeting in Charlotte in July 2012 and has met regularly face-to-face, online, and by conference calls. This manuscript reports the findings of the Task Force, as well as recommendations to achieve the stated mission. PACS number: 01.40.G.The American Association of Physicists in Medicine (AAPM) and the Society of Nuclear Medicine and Molecular Imaging (SNMMI) recognized the need for a review of the current state of nuclear medicine physics training and the need to explore pathways for improving nuclear medicine physics training opportunities. For these reasons, the two organizations formed a joint AAPM/SNMMI Ad Hoc Task Force on Nuclear Medicine Physics Training. The mission of this task force was to assemble a representative group of stakeholders to: Estimate the demand for board‐certified nuclear medicine physicists in the next 5–10 years, Identify the critical issues related to supplying an adequate number of physicists who have received the appropriate level of training in nuclear medicine physics, and Identify approaches that may be considered to facilitate the training of nuclear medicine physicists. As a result, a task force was appointed and chaired by an active member of both organizations that included representation from the AAPM, SNMMI, the American Board of Radiology (ABR), the American Board of Science in Nuclear Medicine (ABSNM), and the Commission for the Accreditation of Medical Physics Educational Programs (CAMPEP). The Task Force first met at the AAPM Annual Meeting in Charlotte in July 2012 and has met regularly face‐to‐face, online, and by conference calls. This manuscript reports the findings of the Task Force, as well as recommendations to achieve the stated mission. PACS number: 01.40.G‐

The Current State of Nuclear Medicine Physics Training: Findings of the AAPM/SNMMI Task Force

The Society of Nuclear Medicine and Molecular Imaging (SNMMI) and the American Association of Physicists in Medicine (AAPM) decided in 2012 to establish a joint task force (Table 1) to review the state of nuclear medicine physics training and assess how to improve future training opportunities. The mission of the task force was to assemble a group of stakeholders in nuclear medicine and medical physics to estimate the demand for board-certified nuclear medicine physicists over the next 5–10 years, identify issues critical to supplying an adequate number of appropriately trained nuclear medicine physicists, and identify possible ways to facilitate that training. The chair of the task force was active within both the SNMMI and the AAPM. Other members of the task force included representatives from the SNMMI, the AAPM, the American Board of Science in Nuclear Medicine (ABSNM), the American Board of Radiology (ABR), and the Commission for the Accreditation of Medical Physics Educational Programs (CAMPEP). The task force first met in person in July 2012. Over the next 2 years, the members met regularly both face to face and through conference calls, as well as communicating by email. In 2014 the task force delivered its final report, which was approved by the boards of directors of both organizations and was recently published in the Journal of Applied Clinical Medical Physics (1). Here we summarize the findings, but readers are encouraged to review the full report. Since the earliest days of nuclear medicine, the physicist has been an essential member of the developmental and clinical nuclear medicine team. The construction and implementation of nuclear medicine instruments and the development of clinical protocols has relied on collaboration between physicians and physicists. The nuclear medicine physicist has a strong understanding of physics and physiology, is an expert in instruments for measuring and imaging radiopharmaceuticals and in dosimetry for diagnostic and therapeutic procedures, and is responsible for devising and maintaining a quality assurance program for all imaging and nonimaging nuclear medicine equipment, including hybrid devices that incorporate CT or MR into a PET scanner or g-camera. It is essential that the nuclear medicine physicist have a basic understanding of physiology and molecular processes because of the functional nature of nuclear medicine, as well as knowing the physical and dosimetric aspects of radionuclide therapy. Although the well-trained diagnostic medical physicist may have a good basic understanding of nuclear medicine physics and may have a skill set overlapping that of the nuclear medicine physicist, nuclear medicine physics includes unique and essential aspects that may not be routinely covered within diagnostic imaging training. The task force reviewed the current workforce of nuclear medicine physicists within the United States, using sources such as the membership database of the SNMMI, the certified medical physicist database of the Conference of Radiation Control Program Directors, and a 2012 professional survey by the AAPM. This review found that there were about 350–450 nuclear medicine physicists in the United States and that they composed less than 10% of the total number of medical physicists. It was estimated that fewer than 60 individuals classified themselves as primarily a nuclear medicine physicist. Two organizations certify nuclear medicine physicists in the United States: the ABR and the ABSNM. To receive ABR certification, potential diplomates are required to pass a 3-part examination. Before allowing them to sit for the examination, the ABR reviews their experience and training, which, since 2014, has included completion of a medical physics residency. The ABR also requires participation in its maintenance-of-certification program. Thirty-seven medical physicists were certified in nuclear medical physics by the ABR between 2010 and 2014. To receive ABSNM certification in nuclear physics and instrumentation, candidates must pass a 2-part examination after meeting certain training and experience requirements but are not required to complete a nuclear medical physics residency. In addition, on January 1, 2015, the ABSNM established a maintenance-of-certification policy. Thirty-four physicists were certified in nuclear physics and instrumentation by the ABSNM between 2010 and 2014. Because of the small number of currently certified nuclear medicine physicists, there is a critical need for CAMPEP-accredited residencies for clinical training in nuclear medicine physics. The models for medical physics residencies include 2-year programs in nuclear medicine physics, completion of an additional year in nuclear medicine physics after an imaging medical physics residency, and completion of a doctoral program in medical physics. There is also a hub-and-spoke model in which a central site administers the program and the residents receive instruction at associated sites. The CAMPEP website lists 11 residency programs for imaging medical physics, and these provide 10–15 residency slots within North America. No residencies exist that are specifically for Received Dec. 15, 2015; revision accepted Feb. 10, 2016. For correspondence or reprints contact: Beth A. Harkness, Department of Radiology, Henry Ford Hospital, 2799 W. Grand Blvd., Detroit, MI 48202. E-mail: bethh@rad.hfh.edu Published online Mar. 10, 2016. COPYRIGHT