Surveillance imaging of Hodgkin lymphoma patients in first remission: a clinical and economic analysis.

BACKGROUND: The majority of patients with Hodgkin lymphoma (HL) achieve disease remission after primary therapy. To the best of the authors' knowledge, no consensus exists for postremission surveillance imaging. METHODS: Retrospectively analyzed were 192 adult patients with classic HL in first remission. Events were defined as recurrent HL or secondary malignancies. Primary outcome was positive predictive value (PPV) of surveillance positron emission tomography/computed tomography (PET/CT) and CT scans in event detection. Secondary outcomes were costs and radiation exposures of surveillance scans. RESULTS: Sixteen events (12 recurrent HL cases and 4 secondary malignancies) were detected during a median follow-up of 31 months. The PPV of surveillance PET/CT was 22.9% compared with 28.6% for CT (P=.73). Factors that were found to significantly improve the PPV of scans in detecting recurrent HL included PET and CT concordance, involvement of a prior disease site, or the occurrence of a radiographic abnormality within 12 months. There were too few events to determine whether event detection by PET/CT versus CT or the presence of symptoms at the time of event detection affected overall outcomes. The cost to detect a single event was approximately $100,000. Radiation exposure to detect a single event was 146.6 millisieverts per patient for each of 9 patients. CONCLUSIONS: For patients with HL in first disease remission, surveillance radiography appears to be expensive, with limited clinical impact. Surveillance CT is generally adequate.

Imaging features of sarcoidosis on MDCT, FDG PET, and PET/CT.

OBJECTIVE: The objectives of this article are to discuss the epidemiology and natural history of sarcoidosis; to review the classic imaging features of sarcoidosis on radiography, CT, and 67Ga nuclear medicine scans; and to present clinical examples of sarcoidosis as seen on PET and PET/CT in the chest, abdomen and pelvis, and bones. CONCLUSION: The imaging features of sarcoidosis are diverse and can be seen on a variety of imaging techniques. It is important for radiologists and nuclear medicine physicians to recognize the common imaging features and patterns of sarcoidosis in order to raise the possibility in the appropriate clinical setting.

Comparison of standard-dose vs low-dose attenuation correction CT on image quality and positron emission tomographic attenuation correction.

OBJECTIVE: To determine if low-dose attenuation correction computed tomography (CTAC) 1) provides images with acceptable anatomic definition and noise compared with standard-dose CTAC and 2) provides acceptable positron emission tomographic attenuation correction. METHODS: Positron emission tomography/computed tomography was performed on 78 patients. Forty-three patients underwent CTAC with tube current based on a standard weight-based scale. A second group of 35 patients underwent CTAC with tube current based on a low-dose weight-based scale. In a blinded review, two radiologists rated each examination for anatomic definition and image noise at 4 major anatomic levels using a 5-point scale. To evaluate for correct positron emission tomographic attenuation correction at the standard and reduced radiation doses on CTAC, water phantom studies using both imaging techniques were performed and compared. RESULTS: Patients who underwent low-dose CTAC received a mean 60.6% reduction in radiation dose compared with those who underwent standard-dose CTAC (P < .0001). Low-dose CTAC demonstrated statistically significant poorer ratings for anatomic detail and noise at each of the 4 anatomic levels (P < .0001) compared with standard-dose CTAC. Scans were graded acceptable for diagnostic interpretation if scores for image noise and anatomic definition were greater than 3 at all anatomic levels. There was a significant difference between the number of acceptable diagnostic scans in the standard-dose group (88.4%) compared with the low-dose group (17.1%) (P < .0001). There was no statistical difference in attenuation correction values in low-dose and standard-dose attenuation correction maps of the water phantom. CONCLUSION: Low-dose CTAC significantly reduced the effective dose while providing optimal positron emission tomographic attenuation correction. However, because of decreased image quality, low-dose CTAC was not acceptable for diagnostic interpretation.

Babesiosis: CT and hematologic findings.

Babesiosis is a tick-borne illness caused by the protozoan Babesia microti. Most patients are asymptomatic but the infection may produce a spectrum of symptoms in immunocomprimised patients, especially asplenic patients. These range from mild fever, sweats, fatigue, and myalgias to severe multiorgan failure, including acute respiratory distress syndrome and death. Radiographic appearances include bilateral patchy air space and interstitial opacities. We report the radiographic, high-resolution computed tomography (HRCT), and hematologic appearances in a 63-year-old man presenting with acute babesisois. HRCT images revealed smooth septal thickening and intralobular lines superimposed on ground glass opacities in both upper lobes. Follow-up HRCT after 2 weeks of therapy demonstrated resolution of the pulmonary parenchymal abnormalities.

Hybrid PET/CT of the thorax: when is computer registration necessary?

OBJECTIVE: To determine if computer registration improves the image fusion of hybrid positron emission tomography (PET)/computed tomography (CT) data sets in the thorax acquired during different breathing maneuvers. METHODS: Hybrid PET/CT scans were acquired with varying CT respiratory instructions. The scans of 64 patients with 5 different breathing maneuvers were reviewed, including expiration, suspended breath hold, quiet breathing, small breath in, and regular breath in. The PET/CT data sets were reviewed before registration, after linear registration, and combined linear/nonlinear registration. Each PET/CT data set was graded for the quality of alignment at 5 anatomical locations (diaphragm, aortic arch, heart, thoracic spine, and lung apices) and rated from 1 (very poor) to 5 (excellent). The Kruskal-Wallis test was used to compare alignment between the breathing protocols, and Wilcoxon signed rank test was used to compare the registration techniques. RESULTS: The quality of anatomical alignment between superimposed (nonregistered) PET and attenuation correction CT (CTAC) acquired during expiration, suspended breath hold, and quiet breathing was excellent, with no significant changes in alignment following registration. The quality of anatomical alignment between superimposed (nonregistered) PET and CTAC acquired during inspiration showed significant misalignment at the heart (P = 0.001, P < 0.0001) and diaphragm (P = 0.0001, P < 0.0001) which did not correct with linear registration. Alignment significantly improved with additional nonlinear registration at the diaphragm (P = 0.008, P = 0.0002), although cardiac misalignment remained. CONCLUSIONS: With hybrid PET/CT, excellent anatomical alignment between PET and CTAC scans can be achieved with CT acquisition during expiration, suspended breath hold, or quiet breathing, and additional software registration is not necessary. Nonlinear registration significantly improves alignment discrepancies at the diaphragm if inspiratory methods are used, however, cardiac misalignment remains.

Cardiac septal aneurysm mimicking pseudomass: appearance on ECG-gated cardiac MRI and MDCT.

OBJECTIVE: Cardiac septal aneurysms in adults are diagnosed when the interatrial or interventricular septal membrane deviates more than 10-15 mm to either side in the cardiac chamber. Routine non-ECG-gated chest CT does not have sufficient temporal and spatial resolution for adequate characterization of such an entity. We report the imaging findings of cardiac septal aneurysms depicted in two patients with ECG-gated cardiac MRI and in a third with ECG-gated cardiac 64-MDCT. Each aneurysm was initially believed to be a cardiac tumor on the basis of the appearance on non-ECG-gated chest CT or MRI. CONCLUSION: Nonopacified blood can fill a cardiac septal aneurysm and mimic a pseudomass. It is important that radiologists recognize such an entity on chest CT and MRI because of the association with intracardiac shunting and stroke and to avoid misdiagnosis of an aneurysm as a cardiac tumor.

FDG-PET and CT features of non-small cell lung cancer based on tumor type.

We determined if specific tumor types of non-small cell lung cancer can be identified by variance in FDG-PET standard uptake value (SUV) in combination with characteristics on CT. Staging FDG-PET and CT scans of 81 patients (34 men and 47 women, average age 67+/-11 years) with 82 lung cancers were analyzed. Mean tumor SUV was calculated at the location of maximum FDG uptake. Tumor size, margins, and location were analyzed on CT. Statistical analysis compared SUV between tumor subtypes, assessed relationship between tumor subtype and features on CT and determined if combination of CT and SUV patterns predicted tumor type. In total 35 adenocarcinomas (AC); 15 bronchioloalveolar cell carcinomas (BAC), 23 squamous cell carcinomas and 9 large cell carcinomas were evaluated. Significant differences were found between SUV of all AC and squamous cell (p<0.0001); between all AC and large cell (p=0.03); between non-BAC AC and squamous cell types (p=0.0005); BAC and non-BAC AC (p=0.04), BAC and squamous cell (p<0.0001); BAC and large cell (p=0.004). Ground glass was the most significant CT feature in distinguishing tumor types, which was seen in BAC (p<0.0003). In conclusion, SUVs for non-small cell lung cancer were most significantly different between BAC and all other NCLC cell subtypes. The presence of ground glass in a nodule on CT is a significant feature for BAC and should raise the suspicion for this tumor type despite low FDG uptake.

Significance of incidental thyroid lesions detected on CT: correlation among CT, sonography, and pathology.

OBJECTIVE: The purpose of our study was to determine the prevalence of malignancy in incidental abnormalities of the thyroid gland detected on CT and to determine the relative accuracy of characterizing these abnormalities on CT as compared with sonography and pathology. MATERIALS AND METHODS: We searched our department's computerized clinical database for all thoracic and cervical CT scans in which a new abnormality was incidentally identified in the thyroid gland from 1998-2001. Two hundred thirty patients with abnormal findings in the gland on CT subsequently underwent thyroid sonography, and 118 of the 230 patients underwent a diagnostic biopsy or resection. CT and sonographic images were directly reviewed to identify imaging features of each thyroid abnormality, including the location, size, appearance, and presence or absence of calcifications. Associations were evaluated using Fisher's exact test of significance and the Student's t test. The overall rate of malignant and potentially malignant lesions among these incidental abnormalities of the thyroid gland was calculated. RESULTS: CT findings matched the sonographic characterization in 122 patients (53.0%), correctly identified the dominant nodule but missed multinodularity in 69 (30.0%) patients, and underestimated the number of nodules in 24 (10.4%) patients. CT overestimated the number of nodules in 5 (2.2%) patients and was false-positive for lesions in 10 patients (4.3%). Ninety-one patients with a single or dominant nodule on CT had pathologic correlation: 7 nodules were malignant, 17 showed malignant potential, and 67 were benign. Of 27 patients with multinodular or enlarged thyroid glands on CT and histopathologic correlation, 2 lesions were malignant and 25 benign. The presence of punctate calcifications on CT significantly correlated to the presence of microcalcifications on sonography (p < 0.02). Benign nodules were significantly smaller (mean, 2.16 +/- 1.01 cm; range, 0.6-4.5 cm) than malignant and potentially malignant nodules (mean, 2.79 +/- 0.99 cm; range, 0.7-4.6 cm) (p = 0.01). Patients 35 years or younger who had a thyroid lesion on CT were more likely to have malignancy (p < 0.01). Overall, among incidentally detected lesions of the thyroid gland, there was at least a 3.9% rate of malignancy (95% CI: 1.8-7.3%) and 7.4% rate of malignant potential (95% CI: 4.4-11.6%). CONCLUSION: There is at least an 11.3% prevalence of malignant or potentially malignant lesions among incidental thyroid abnormalities detected on CT. Patients 35 years or younger who have incidental abnormalities have a significantly greater rate of malignancy. No CT feature reliably distinguishes benign from malignant lesions in the thyroid gland. CT underestimates the number of nodules relative to sonography, which suggests that sonography is a useful adjunctive test after the incidental detection of a thyroid abnormality on CT.

Optimal CT breathing protocol for combined thoracic PET/CT.

OBJECTIVE: The objective of this study was to determine the optimal breathing protocol for combined PET/CT scans of the thorax. SUBJECTS AND METHODS: Eighty combined PET/CT scans were obtained in 64 patients (30 women, 34 men; mean age, 57 years; range, 19-86 years). The 80 PET/CT scans consisted of five group of patients (16 PET/CT scans per group) who underwent whole-body combined 18F-FDG PET/CT with different CT breathing protocols: expiration, mid suspended breath-hold, quiet breathing, small breath in, and regular breath in. The quality of alignment was analyzed at the diaphragm, aortic arch, heart, thoracic spine, and lung apices using a scale of ratings from 1 (very poor) to 5 (excellent). The Kruskal-Wallis test was used to compare alignment between breathing protocols for each anatomic reference point. RESULTS: Alignment of the PET and CT data sets was excellent with three breathing protocols: expiration, mid suspended breath-hold, and quiet breathing, with no statistical differences. Significant misalignment occurred at the diaphragm (p < 0.0001) and heart (p < 0.0001) with the small breath-in and regular breath-in techniques. CONCLUSION: Excellent image fusion of combined PET/CT data sets in the thorax, especially at the diaphragm and heart, can be achieved with expiration, mid suspended breath-hold, or quiet breathing. Quiet breathing is recommended for optimal patient comfort during acquisition of attenuation-correction CT data sets.

Accuracy of transmission CT and FDG-PET in the detection of small pulmonary nodules with integrated PET/CT.

PURPOSE: The purpose of this study was to determine the accuracy of detection of small pulmonary nodules on quiet breathing attenuation correction CT (CTAC) and FDG-PET when performing integrated PET/CT, as compared with a diagnostic inspiratory CT scan acquired in the same imaging session. METHODS: PET/CT scans of 107 patients with a history of carcinoma (54 male and 53 female, mean age 57.3 years) were analyzed. All patients received an integrated PET/CT scan including a CTAC acquired during quiet respiration and a contrast-enhanced CT acquired during inspiration in the same session. Breathing CTAC scans were reviewed by two thoracic radiologists for the presence of pulmonary nodules. FDG-PET scans were reviewed to determine accuracy of nodule detection. Diagnostic CT was used as the gold standard to confirm or refute the presence of nodules. RESULTS: On the CTAC scans 200 nodules were detected, of which 183 were true positive (TP) and 17, false positive. There were 109 false negatives (FN). Overall, 51 (48%) patients had a false interpretation, including 19 in whom CT was interpreted as normal for lung nodules. The average size of the nodules missed was 3.8+/-2 mm (range 2-12 mm). None of the nodules missed on the CTAC scans were detected by PET. In the right lung there were 20 TP, 42 true negative (TN), 11 FP, and 34 FN interpretations with a sensitivity in nodule detection of 37% (CI 24-51%) and a specificity of 79% (CI 66-89%). In the left lungs there were 16 TP, 65 TN, 3 FP, and 23 FN interpretations, with a sensitivity of 41% (CI 26-58%) and a specificity of 96% (CI 88-99%). CONCLUSION: The detection of small pulmonary nodules by breathing CTAC and FDG-PET is relatively poor. Therefore an additional diagnostic thoracic CT scan obtained during suspended inspiration is recommended for thorough evaluation of those patients in whom detection of pulmonary metastases is necessary for management.

"Hot" spots in hybrid positron emission tomography/computed tomography scanning of the abdomen: protocols, indications, interpretation, responsibilities, and reimbursements.

Although introduction of hybrid positron emission tomography/computed tomography (PET/CT) scanners represents an important development in field of radiology, the alliance of functional imaging with structural imaging has raised many controversial issues. The present review describes some of the important issues in hybrid PET/CT such as specific indications, protocols that deliver diagnostic quality CT scans while ensuring radiation dose associated with hybrid PET/CT examination are minimized, and the feasibility, desirability, and timing of oral and intravenous contrast administration. The issues of clinical indications for hybrid PET/CT versus PET alone will be discussed as well as the role of the CT component (ie, for diagnosis or transmission source alone) are discussed. The logistics of hybrid PET/CT scan interpretation, including the roles of radiologists and nuclear medicine physicians, will be discussed. This review describes the pertinent medical literature and discusses our experience with suitable examples.

Does initial staging or tumor histology better identify asymptomatic brain metastases in patients with non-small cell lung cancer?

BACKGROUND: To determine whether the distribution, staging features, or tumor histology of non-small cell lung cancer (NSCLC) distinguishes neurologically symptomatic from asymptomatic patients initially diagnosed with lung cancer, and to determine whether these factors may predict the presence of brain metastasis. METHODS: We performed a retrospective review of 809 patients with NSCLC and brain metastases who were treated in our institution between January 1996 and March 2003. Patients who had brain metastasis on initial staging were included. Thoracic computed tomographic scans were reviewed for lung tumor features and staging. Neurological computed tomographic or magnetic resonance image scans were assessed for distribution of brain metastases. Medical records were reviewed for comprehensive staging, tumor histology, and neurological symptoms. Fisher's exact test was used to determine any differences among tumor histology, staging, and imaging features among patients with or without neurological symptoms. RESULTS: Of the 809 patients, 181 had brain metastasis at initial staging. Among these 181 patients, 120 (66%) presented with neurological symptoms (group 1); 61 (34%) patients were asymptomatic (group 2). Patients with adenocarcinoma and large-cell carcinoma had greater odds of brain metastases than patients with squamous cell carcinoma (p = 0.001). There were 106 (58.6%) patients with adenocarcinoma, 32 (17.7%) with large cell carcinoma, and 18 (9.9%) with squamous cell carcinoma. In both groups, most lung cancers were in the right lung with upper lobe dominance. No significant difference in tumor histology or T stage was found between groups, although group 2 was more likely to have a higher N stage. Of the 181 patients with brain metastasis, 60 (33.1%) had N0 disease, 51 (28.2%) had T1 disease, and 23 (19.2%) had no other metastasis. There was no correlation between number/distribution of brain metastases and tumor histology, although patients with disease in the cerebellum or temporal lobes had a greater likelihood of neurological symptoms (odds ratio 3.7). CONCLUSION: There was no significant difference in tumor histology, staging, or distribution between symptomatic or asymptomatic patients with NSCLC with brain metastases. The odds of brain metastases were greater in those with adenocarcinoma or large-cell carcinoma.

Lipomatous hypertrophy of the interatrial septum: prevalence and features on fusion 18F fluorodeoxyglucose positron emission tomography/CT.

OBJECTIVE: To determine the prevalence of lipomatous hypertrophy of the interatrial septum (LHIS) on CT and its metabolic pattern on 18F fluorodeoxyglucose (FDG)-positron emission tomography (PET). METHOD AND MATERIALS: Eight hundred two CT PET scans were reviewed. Patients were included if the interatrial septum was > or = 1 cm and excluded if there was evidence of malignancy in the adjacent lung, hilum, or mediastinum. CT scans were fused with PET scans, and the mean standardized uptake value (SUV) was calculated over the LHIS, chest wall (CW) fat, and mediastinal blood pool. CT scans were reviewed for presence of excessive fat in the mediastinum, pericardial, peridiaphragmatic, peritoneal, and retroperitoneal regions and for the presence of emphysema. Medical records were reviewed for body mass index (BMI) and history of arrhythmia. RESULTS: Twenty-three of 802 patients (2.8%) had LHIS on CT (9 women and 14 men); average age was 75.6 years (range, 58 to 95 years). Average BMI of 17 patients (+/- SD) was 31 +/- 4.9 (range, 22.1 to 39.9). Mean CT values were as follows: thickening of LHIS, 1.47 +/- 0.35 cm (range, 1.07 to 2.25 cm); LHIS, - 79.6 + 24.5 Hounsfield unit (HU) [range, - 11 to - 121 HU]. LHIS was dumbbell shaped in 18 patients. Mean SUVs were as follows: LHIS, 1.84 +/- 0.10 (range, 0.48 to 3.48); CW fat, 0.36 + 0.37 (range, 0.04 to 1.98); blood pool, 1.74 + 0.51 (range, 0.25 to 2.71). The SUV of LHIS was greater than the SUV of CW wall fat in all patients (p < 0.0001). There was significant correlation between SUV and thickness of the LHIS on CT (p < 0.0001, r = 0.883). Those with dumbbell-shaped LHIS (p < 0.003) and presence of emphysema (p < 0.0377) had greater LHIS mean SUV. CONCLUSION: The SUV of LHIS was greater than the SUV of CW fat in all patients. LHIS with greater thickness or dumbbell shape had greater FDG uptake. These findings on CT and PET are important to recognize in order to avoid false-positive FDG-PET interpretations.

Comparison of alignment of computer-registered data sets: combined PET/CT versus independent PET and CT of the thorax.

PURPOSE: To retrospectively determine whether alignment of registered positron emission tomographic (PET) and computed tomographic (CT) data sets obtained independently varies significantly from alignment of data sets acquired from a combined PET/CT scanner. MATERIALS AND METHODS: The study was approved by the institution's Human Research Committee with a waiver of informed consent and complied with HIPAA. Whole-body combined PET/CT data sets and separate routinely positioned thoracic CT data sets were obtained from 12 patients (six men, six women; mean age, 48.6 years; range, 24-62 years). Separate PET and thoracic CT data sets matched for patient positioning and respiration were acquired on the same day for nine patients (four men, five women; mean age, 71 years; range, 51-90 years). Computer nonlinear registration was performed on PET and CT data sets from combined PET/CT (fusion group 1), PET data sets from combined PET/CT with unmatched thoracic CT (fusion group 2), and data sets from separate PET and CT matched for patient positioning and respiration (fusion group 3). Quality of alignment was assessed by two radiologists in consensus blinded to the source of registered data in each fusion group at the following anatomic locations: diaphragm, aortic arch, heart, thoracic spine, and lung apices. Results were compared by using the Wilcoxon paired signed rank and unpaired rank sum tests. RESULTS: Quality of alignment did not significantly differ between fusion group 1 and fusion group 3. Fusion group 1 provided significantly better alignment in two of five anatomic locations (P = .008 for diaphragm and P = .031 for heart) than fusion group 2. Fusion group 3 provided significantly better alignment in two of five anatomic locations (P = .037 for diaphragm and P = .009 for heart) than fusion group 2. CONCLUSION: Thoracic anatomic alignment does not significantly differ between registered PET and CT data sets acquired on a combined PET/CT scanner or from separate PET and CT scanners obtained on the same day when carefully matched for anatomic positioning and respiration.

Chest CT performed with z-axis modulation: scanning protocol and radiation dose.

Institutional review board approval of the study protocol and waiver of informed consent were obtained. This study was compliant with the Health Insurance Portability and Accountability Act. The purpose of this study was to retrospectively assess the scanning protocol and radiation dose associated with z-axis automatic tube current modulation in multi-detector row CT scanning of the chest. Fifty-three patients (mean age, 54 years; age range, 26-77 years; 25 men, 28 women) underwent 16-detector row chest CT with z-axis modulation and noise indexes of 10.0, 12.5, and 15.0 HU. Two radiologists independently compared images acquired with z-axis modulation and fixed tube current (180-300 mA) techniques for image noise, diagnostic acceptability, and depiction of peripheral bronchovascular markings. Tube current-time product was calculated for each study. There was good interobserver agreement between the two readers (kappa = 0.72). Compared with the fixed tube current technique, z-axis modulation provides acceptable image noise for chest CT, with an 18% and 26% reduction in tube current-time product at 10.0- and 12.5-HU noise indexes, respectively.