Daniel F. Worsley

Ascending aortic dissection causing unilateral absence of perfusion on lung scanning

A case of an ascending aortic dissection occurring in a patient 8 years after an aortic valve replacement is presented. The patients initial clinical presentation was thought to be due to pulmonary embolism, and a ventilation- perfusion lung scan demonstrated mismatched absence of perfusion to the entire right lung. Aortography and findings at surgery demonstrated a type A dissection of the ascending aorta. The anatomic relationship of the aorta and pulmonary artery and their common tunica adventitia make the right pulmonary artery susceptible to extrinsic compression after aortic dissection. Although uncommon, dissection of the ascending aorta needs to be considered in patients who have undergone previous aortic valve surgery and demonstrate mismatched unilateral absence of perfusion to the right lung. Because anticoagulation is contraindicated in patients with acute aortic dissection, confirmation of the diagnosis with angiography usually is required.

Comparison of stress-only vs. stress/rest with technetium-99m methoxyisobutylisonitrile myocardial perfusion imaging

Unlike conventional thallium-201 myocardial imaging, technetium-99m methoxyisobutylisonitrile (MIBI) requires separate stress and rest injections. We prospectively studied 148 consecutive patients referred for myocardial perfusion studies to determine the diagnostic value of rest images once normal exercise or dipyridamole tomographic images had been obtained. In patients referred with no history of previous myocardial infarction in whom the diagnosis of coronary artery disease was suspected, 45 of 109 (41%) patients had normal stress tomographic images. Obtaining rest images did not alter the final interpretation in any of these cases. From this we infer that in patients with normal images after exercise or dipyridamole administration and no past history of myocardial infarction, 99mTc-MIBI rest images are not required. This provides several advantages including increased speed of diagnosis, decreased patient radiation exposure, improved cost efficiency and decreased demand on tomographic camera time.

Incorporating Quantitative Single Photon Emission Computed Tomography into Radiation Therapy Treatment Planning for Lung Cancer: Impact of Attenuation and Scatter Correction on the Single Photon Emission Computed Tomography–Weighted Mean Dose and Functional Lung Segmentation

PURPOSE To assess the impact of attenuation and scatter corrections on the calculation of single photon emission computed tomography (SPECT)-weighted mean dose (SWMD) and functional volume segmentation as applied to radiation therapy treatment planning for lung cancer. METHODS AND MATERIALS Nine patients with lung cancer underwent a SPECT lung perfusion scan. For each scan, four image sets were reconstructed using the ordered subsets expectation maximization method with attenuation and scatter corrections ranging from none to a most comprehensive combination of attenuation corrections and direct scatter modeling. Functional volumes were segmented in each reconstructed image using 10%, 20%, …, 90% of maximum SPECT intensity as a threshold. Systematic effects of SPECT reconstruction methods on treatment planning using functional volume were studied by calculating size and spatial agreements of functional volumes, and V(20) for functional volume from actual treatment plans. The SWMD was calculated for radiation beams with a variety of possible gantry angles and field sizes. RESULTS Functional volume segmentation is sensitive to the particular method of SPECT reconstruction used. Large variations in functional volumes, as high as >50%, were observed in SPECT images reconstructed with different attenuation/scatter corrections. However, SWMD was less sensitive to the type of scatter corrections. SWMD was consistent within 2% for all reconstructions as long as computed tomography-based attenuation correction was used. CONCLUSION When using perfusion SPECT images during treatment planning optimization/evaluation, the SWMD may be the preferred figure of merit, as it is less affected by reconstruction technique, compared with threshold-based functional volume segmentation.

Preoperative Imaging in Primary Hyperparathyroidism: Literature Review and Recommendations

Primary hyperparathyroidism is the third most common endocrine disorder after diabetes mellitus and hypothyroidism, and affects an estimated 0.3% of the general population [1,2]. Approximately 90% of such patients are subsequently found to have a single parathyroid adenoma, 10% are found to have multigland hyperplasia or multiple adenomas, and the rare patient is found to have parathyroid carcinoma [3]. Surgical removal of the hyperfunctioning parathyroid tissue is the only definitive cure and is warranted in symptomatic patients or in those who develop complications, as well as in all patients under 50 years of age [4]. Traditionally, this was done by way of a bilateral neck exploration with direct visualization of all 4 glands, with preoperative imaging studies rarely required. In 1986, interventional radiologist John L. Doppman remarked that ‘‘the only localising study indicated in untreated primary hyperparathyroidism is to localise an experienced parathyroid surgeon’’ [5]. Over the last 30 years improvements in imaging techniques have enabled radiologists to identify parathyroid adenomas with greater confidence and accuracy, allowing surgeons to perform unilateral or targeted parathyroidectomies. More recently, concerns regarding higher rates of recurrent or persistent disease have prompted some surgeons to abandon unilateral parathyroidectomy and return to the traditional bilateral neck exploration [6]. Nonetheless, targeted parathyroidectomy remains the preferred operative technique for many surgeons and is associated with a shorter operative duration, a lower risk of postoperative complications and greater patient satisfaction

Monitoring esophageal transit of wax-polished alendronate in healthy postmenopausal women: A new technique for the study of pill transit time

Abstract Background: Alendronate sodium is an oral nitrogen-containing bisphosphonate that has been proven effective in the prevention and treatment of osteoporosis. Although adverse events are no more common with alendronate than with placebo in clinical trials, there have been postmarketing case reports of esophagitis and esophageal erosions in alendronate-treated patients. Delay in the transit of the tablet through the esophagus may contribute to the development of upper gastrointestinal (GI) symptoms, but few published techniques exist for the study of esophageal pill transit. Objective: The purpose of this pilot study was to describe a novel method to investigate the esophageal transit time of pills, using alendronate as a model. Methods: A total of 30 bisphosphonate-naive, healthy postmenopausal women were administered alendronate 10-mg, oval wax-polished tablets labeled with technetium Tc 99m pertechnetate. Simultaneous emission/transmission images were acquired at 1 second per frame. Two measures of esophageal transit time were calculated from the images: time to pass below the diaphragm and time-activity curves in a region of interest (ROI) drawn over the esophagus. Results: Median transit time from oropharynx to below the diaphragm was 3 seconds (range, 2–6 seconds). Using the ROI technique, median transit time for the whole esophagus was 5 seconds (range, 2–17 seconds). In 25 of 30 subjects (83%), esophageal transit time was ≤6 seconds. In the 5 subjects in whom transit time was ≥6 seconds, virtually all of this time was in the distal third of the esophagus; transit through the proximal two thirds was ≤3 seconds in all 30 subjects. Conclusions: As measured by this technique, oval wax-polished alendronate tablets pass through the esophagus rapidly. This technique could be used to investigate the effect of tablet shape or coating on esophageal transit as well as changes in dosing regimens for patients with normal or abnormal upper GI anatomy.

Ventilation–perfusion–chest Radiograph Match Is Less Likely to Represent Pulmonary Embolism If Perfusion Is Decreased Rather Than Absent

Purpose The authors’ goal was to determine whether the prevalence of pulmonary embolism in patients with matching ventilation–perfusion (V–Q) defects and chest radiographic opacities differs depending on the degree of perfusion deficit (absent versus decreased). Methods The authors performed a retrospective analysis of the data obtained from the Prospective Investigation of Pulmonary Embolism Diagnosis (PIOPED) study. In 233 patients, angiograms were of diagnostic quality for 275 lung zones that showed matching V–Q defects and chest radiographic opacities (triple matches). Of these, V–Q scans and chest radiographs from 217 patients with triple matches in 255 lung zones were retrieved and reviewed. Areas corresponding to chest radiographic opacities were scored as having either decreased perfusion or absent perfusion by consensus. Information regarding the presence or absence of pulmonary embolism in corresponding lung zones was obtained from the PIOPED database. Results The overall prevalence of pulmonary embolism in all lung zones with triple matches was 27% (69 of 255). Of the 255 areas of triple matches, the perfusion was decreased in 153 (60%) and absent in 102 (40%). The prevalence of pulmonary embolism in areas of triple matches with decreased perfusion and triple matches with absent perfusion was 13% (20 of 153) and 48% (49 of 102), respectively (P = 0.0001 by the chi-square test). When these were divided further by lung zones, triple matches with decreased perfusion and triple matches with absent perfusion in the upper–middle lung zone were associated with a prevalence of 0% (0 of 44), and 25% (9 of 36), respectively. The prevalence of pulmonary embolism in areas of triple matches with decreased perfusion and triple matches with absent perfusion in the lower lung zone was 18% (20 of 109), and 61% (40 of 66), respectively. Conclusions A V–Q/chest radiographic match is less likely to represent pulmonary embolism if perfusion is decreased rather than absent. The overall prevalence of pulmonary embolism associated with all triple matches in all lung zones varied from very low (0% in this series) to upper intermediate (61%), depending on whether perfusion was decreased or absent and also on the location of the triple match.

Impact of F-18 Fluorodeoxyglucose Positron Emission Tomography–Computed Tomography on Oncologic Patient Management: First 2 Years' Experience at a Single Canadian Cancer Center

Purpose The purpose of this study was to assess the influence of positron emission tomography–computed tomography (PET-CT) results on patient management from a single Canadian oncology center during its first 2 years of operation. Methods A total of 3,779 consecutive patients, 18 years of age and older, who were referred for PET-CT imaging at the British Columbia Cancer Agency between July 1, 2005 and June 30, 2007, were included in this analysis. Results were tabulated from a standard questionnaire, which was given to referring physicians following completion of their patients PET-CT study. Results From July 1, 2005 to June 30, 2007, 3,779 consecutive fluoro-2-deoxyglucose PET-CT examinations were performed in patients aged 18 years or older. A total of 3,429 referring-physician surveys (90.7%) were returned. The results of the PET-CT study resulted in a change in treatment decision in 49.8% of the studies and resulted in improved decision making in 83.2% of the studies. Conclusion This series demonstrated that the results from PET-CT studies performed at a single Canadian oncology center during the first 2 years of its operation altered patient management in 50% of cases and resulted in improved decision making in the majority of cases.

SU‐FF‐J‐136: The Impact of Attenuation and Scatter Correction On the SPECT Guided Radiation Therapy for Lung Cancer Patients: Comparison of SPECT Weighted Mean Dose and Functional Lung Segmentation

Purpose: To investigate the impact of different types of image reconstruction and attenuation/scatter (A/S) correction on the calculation of dosimetric indices proposed to be used for Single Photon Emission Computed Tomography(SPECT) guided dose escalation in lungcancer patients. Methods and Materials:SPECTlung perfusion scans were obtained for nine lungcancer patients using 99mTc‐macroaggregated albumin. Four image sets were reconstructed from each scan: one using a vendor provided ordered subsets expectation maximization (OSEM) algorithm, two quantitative SPECTreconstructions using OSEM methods with different types of A/S corrections and the fourth an OSEM reconstruction without any A/S correction. SPECT weighted mean dose (SWMD), dose function histogram, and functional lung volume have been calculated from dose distributions and regional perfusion maps. To investigate the dependence of SWMDs on gantry angle, twelve equally spaced co‐planar open field radiation beams delivering the same MU were centered on the PTV. Three field sizes, 5×5, 7.5×7.5 and 10×10cm2 were considered. SWMDs were calculated for each field and reconstruction. Functional lung volumes were segmented in each reconstruction using 10, 20, …, 90% of maximum SPECT uptake as a threshold. Results: SWMDs calculated from reconstructions without A/S correction showed more than 5% average difference compared to those with corrections. With A/S corrections, more consistent SWMDs were found in all the three OSEM reconstructions (average difference ∼2%). However, a large variation was observed between segmented functional lung volumes and the V20 of these volumes in all four reconstructions. The difference between the volumes reached over 50% regardless of whether A/S correction was applied in the reconstruction.Conclusion: Functional volume segmentation is sensitive to the type of A/S correction. In contrast, SPECT weighted mean dose calculation produces more consistent results and appears to be a more robust choice for clinical outcome analysis and SPECT guided treatment planning.

Lung scanning in patients with suspected pulmonary embolism: a decade of PIOPED

In this months column we have another opportunity to hear about the PIOPED study. Dr. Abass Alavi, Chief of Nuclear Medicine at the University of Pennsylvania, has been directly involved with the program since the beginning. Dr. Daniel Worsley is an Assistant Professor in the Department of Radiology at the University of British Columbia in Vancouver, Canada. He has been involved in many aspects of data analysis with the PIOPED study over the last several years. They will report the important findings from the study. The information provided in Table 2 represents the current thinking on lung scan interpretation.