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BACKGROUND. Homogeneous microscopic fat within adrenal nodules on chemical-shift MRI (CS-MRI) is diagnostic of benign adrenal adenoma, but the clinical relevance of heterogeneous microscopic fat is not well established. OBJECTIVE. This study sought to determine the prevalence of malignancy in adrenal nodules with heterogeneous microscopic fat on dual-echo T1-weighted CS-MRI. METHODS. We performed a retrospective study of adult patients with adrenal nodules detected on MRI performed between August 2007 and November 2020 at seven institutions. Eligible nodules had a short-axis diameter of 10 mm or larger with heterogeneous microscopic fat (defined by an area of signal loss of < 80% on opposed-phase CS-MRI). Two radiologists from each center, blinded to reference standard results, determined the signal loss pattern (diffuse, two distinct parts, speckling pattern, central loss, or peripheral loss) within the nodules. The reference standard used was available for 283 nodules (pathology for 21 nodules, ≥ 1 year of imaging follow-up for 245, and ≥ 5 years of clinical follow-up for 17) in 282 patients (171 women and 111 men; mean age, 60 ± 12 [SD] years); 30% (86/282) patients had prior malignancy. RESULTS. The mean long-axis diameter was 18.7 ± 7.9 mm (range, 10-80 mm). No malignant nodules were found in patients without prior cancer (0/197; 95% CI, 0-1.5%). Four of the 86 patients with prior malignancy (hepatocellular carcinoma [HCC], renal cell carcinoma [RCC], lung cancer, or both colon cancer and RCC) (4.7%; 95% CI, 1.3-11.5%) had metastatic nodules. Detected patterns were diffuse heterogeneous signal loss (40% [114/283]), speckling (28% [80/283]), two distinct parts (18% [51/283]), central loss (9% [26/283]), and peripheral loss (4% [12/283]). Two metastases from HCC and RCC showed diffuse heterogeneous signal loss. Lung cancer metastasis manifested as two distinct parts, and the metastasis in the patient with both colon cancer and RCC showed peripheral signal loss. CONCLUSION. Presence of heterogeneous microscopic fat in adrenal nodules on CS-MRI indicates a high likelihood of benignancy, particularly in patients without prior cancer. This finding is also commonly benign in patients with cancer; however, caution is warranted when primary malignancies may contain fat or if the morphologic pattern of signal loss may indicate a collision tumor. CLINICAL IMPACT. In the absence of prior cancer, adrenal nodules with heterogeneous microscopic fat do not require additional imaging evaluation.

BACKGROUND. A considerable fraction of pheochromocytomas initially suspected to be sporadic, whether or not symptomatic, are a result of germline mutations. OBJECTIVE. The purpose of this article is to compare imaging features between hereditary and sporadic pheochromocytomas. METHODS. This retrospective study included 71 patients (39 women, 32 men; median age, 48 years) who underwent adrenal pheochromocytoma resection from January 2002 to October 2021 after preoperative CT or MRI. Two radiologists independently reviewed examinations to assess features of the largest resected pheochromocytoma. Interreader agreement was assessed by prevalence-adjusted bias-adjusted kappa coefficients; a third radiologist resolved discrepancies for further analysis. Genetic testing was used to classify pheochromocytomas as hereditary or sporadic and to classify hereditary pheochromocytomas by germline mutation clusters. Symptoms associated with pheochromocytomas and preoperative biochemical laboratory values were recorded. Groups were compared using Kruskal-Wallis, Fisher exact, and chi-square tests, and false-discovery rate-adjusted p values were computed to account for multiple comparisons. RESULTS. Hereditary pheochromocytoma ( n = 32), compared with sporadic pheochromocytoma ( n = 39), was associated with younger median age (38 vs 52 years, p = .001) and smaller median size (24 vs 40 mm, p < .001). Interreader agreement for CT and MRI features, expressed as kappa, ranged from 0.44 to 1.00. Hereditary and sporadic pheochromocytoma showed no difference in frequency of calcifications, hemorrhage, cystic change/necrosis, or macroscopic fat on CT, or in frequency of hemorrhage, cystic change/necrosis, macroscopic fat, or microscopic fat on MRI ( p > .05). When combining CT and MRI, cystic change/necrosis was observed in 35% of hereditary versus 67% of sporadic pheochromocytomas ( p = .10). Hereditary pheochromocytoma, compared with sporadic, had lower frequency of symptoms (31% vs 74%; p = .004) and lower 24-hour urinary normetanephrines (1.1 vs 5.1 times upper limits of normal, p = .006). Among hereditary pheochromocytomas, cystic change/necrosis (when assessable on imaging) was present in 18% and 45% of those with cluster 1 ( n = 11) and cluster 2 ( n = 21) germ-line mutations, respectively. CONCLUSION. Hereditary pheochromocytomas, compared with sporadic, are detected at a younger age and smaller size, produce lower 24-hour urinary normetanephrines, are less often symptomatic, and may less frequently show cystic change/necrosis. CLINICAL IMPACT. Imaging findings may complement clinical and biochemical features in raising suspicion for a previously unsuspected germline mutation in patients with pheochromocytoma.

OBJECTIVE. The objective of this study was to compare image quality and clinically significant lesion detection on deep learning reconstruction (DLR) and iterative reconstruction (IR) images of submillisievert chest and abdominopelvic CT. MATERIALS AND METHODS. Our prospective multiinstitutional study included 59 adult patients (33 women, 26 men; mean age ± SD, 65 ± 12 years old; mean body mass index [weight in kilograms divided by the square of height in meters] = 27 ± 5) who underwent routine chest ( n = 22; 16 women, six men) and abdominopelvic ( n = 37; 17 women, 20 men) CT on a 640-MDCT scanner (Aquilion ONE, Canon Medical Systems). All patients gave written informed consent for the acquisition of low-dose (LD) CT (LDCT) after a clinically indicated standard-dose (SD) CT (SDCT). The SDCT series (120 kVp, 164-644 mA) were reconstructed with interactive reconstruction (IR) (adaptive iterative dose reduction [AIDR] 3D, Canon Medical Systems), and the LDCT (100 kVp, 120 kVp; 30-50 mA) were reconstructed with filtered back-projection (FBP), IR (AIDR 3D and forward-projected model-based iterative reconstruction solution [FIRST], Canon Medical Systems), and deep learning reconstruction (DLR) (Advanced Intelligent Clear-IQ Engine [AiCE], Canon Medical Systems). Four subspecialty-trained radiologists first read all LD image sets and then compared them side-by-side with SD AIDR 3D images in an independent, randomized, and blinded fashion. Subspecialty radiologists assessed image quality of LDCT images on a 3-point scale (1 = unacceptable, 2 = suboptimal, 3 = optimal). Descriptive statistics were obtained, and the Wilcoxon sign rank test was performed. RESULTS. Mean volume CT dose index and dose-length product for LDCT (2.1 ± 0.8 mGy, 49 ± 13mGy·cm) were lower than those for SDCT (13 ± 4.4 mGy, 567 ± 249 mGy·cm) ( p < 0.0001). All 31 clinically significant abdominal lesions were seen on SD AIDR 3D and LD DLR images. Twenty-five, 18, and seven lesions were detected on LD AIDR 3D, LD FIRST, and LD FBP images, respectively. All 39 pulmonary nodules detected on SD AIDR 3D images were also noted on LD DLR images. LD DLR images were deemed acceptable for interpretation in 97% (35/37) of abdominal and 95-100% (21-22/22) of chest LDCT studies ( p = 0.2-0.99). The LD FIRST, LD AIDR 3D, and LD FBP images had inferior image quality compared with SD AIDR 3D images ( p < 0.0001). CONCLUSION. At submillisievert chest and abdominopelvic CT doses, DLR enables image quality and lesion detection superior to commercial IR and FBP images.

Objective: The objective of our study was to evaluate three commercially available iterative reconstruction (IR) algorithms-ASiR, iDOSE, and SAFIRE-and conventional filtered back projection (FBP) on image quality and radiation dose in kidney stone CT examinations., Materials and Methods: During the 6-month study period, 684 unenhanced kidney stone CT examinations of consecutive adults were performed on 17 CT scanners (GE Healthcare [vendor 1], n = 12 scanners; Philips Healthcare [vendor 2], n = 2; Siemens Health-care [vendor 3], n = 3); these examinations were retrieved using dose-monitoring software (eXposure). A total of 347 kidney stone CT examinations were reconstructed using FBP, and 337 examinations were processed using IR (ASiR, n = 248; iDOSE, n = 50; SAFIRE, n = 39). The standard-dose scanning parameters for FBP scanners included a tube potential of 120 kVp, a tube current of 75-450 mA for vendor 1 and a Quality Reference mAs of 160-180 for vendor 3, and a slice thickness of 2.5 or 5 mm. The dose-modified protocol for the IR scanners included a higher noise index (1.4 times higher than the standard-dose FBP protocol) for vendor 1, a lower reference tube current-exposure time product for vendor 2 (150 reference mAs), and a lower Quality Reference mAs for vendor 3 (120 Quality Reference mAs). Three radiologists independently reviewed 60 randomly sampled kidney stone CT examinations for image quality, noise, and artifacts. Objective noise and attenuation were also determined. Size-specific dose estimates (SSDEs) were compared using ANOVA., Results: Significantly higher subjective and objective measurements of image noise were found in FBP examinations compared with dose-modified IR examinations (p < 0.05). The radiation dose was substantially lower for the dose-modified IR examinations than the standard-dose FBP examinations (mean SSDE ± SD: 8.1 ± 3.8 vs 11.6 ± 3.6 mGy, respectively) (p < 0.0001), but the radiation dose was comparable among the three IR techniques (ASiR, 7.8 ± 3.1 mGy; iDOSE, 7.5 ± 1.9 mGy; SAFIRE, 7.6 ± 3.2 mGy) (p > 0.05)., Conclusion: The three IRs enable 20-33% radiation dose reduction in kidney stone CT examinations compared with the FBP technique without any image quality concerns. The radiation dose and image quality were comparable among these three IR algorithms.

Objective: The purpose of our study was to analyze the effect of lesion location and morphologic appearance on CT on the positive predictive value (PPV) for malignancy of all extrapulmonary lesions that were (18)F-FDG avid on PET/CT and that were biopsied under imaging guidance., Materials and Methods: Between January 2004 and December 2010, 227 patients underwent imaging-guided biopsy of 231 PET-positive extrapulmonary lesions with diagnostic pathologic results. The PET PPV for malignancy was retrospectively calculated and stratified according to lesion location and morphologic appearance., Results: The overall PET PPV for malignancy was 72%. Inflammatory processes accounted for the majority of benign biopsy results. Lesion location significantly affected the PPV (p < 0.001). Bone (96%) and liver (90%) lesions had significantly higher PPVs for malignancy compared with other locations, whereas lymph nodes (60%) had a significantly lower PPV for malignancy. Lesions that were morphologically suspicious and morphologically benign according to CT findings alone were associated with PPVs of 74% and 57%, respectively (p = 0.05). FDG-avid subcentimeter lymph nodes (n = 8) had a PPV for malignancy of 38%., Conclusion: Over half of PET-avid morphologically benign-appearing lesions and one third of PET-avid subcentimeter lymph nodes were found to be malignant at biopsy, suggesting that benign morphologic appearance alone should not preclude further workup of a PET-positive lesion. Biopsies of FDG-avid lesions in liver and bone yielded high rates of true malignancy, whereas biopsies of lymph nodes yielded a lower rate of malignancy compared with other lesion locations.

Objective: Our objective was to evaluate the accuracy of MDCT features of pancreatic cystic lesions in cyst characterization and in predicting cyst biologic aggressiveness., Subjects and Methods: In this prospective study, 114 patients (40 men and 74 women; age range, 23-89 years) with 130 cystic lesions (size range, 31-160 mm) in the pancreas underwent contrast-enhanced dual-phase (n = 92) and portal phase (n = 22) examinations with 16- or 64-MDCT scanners. Using defined morphologic features of cystic lesions on MDCT, two readers performed blinded evaluations for cystic characterization and predicting biologic aggressiveness (invasive lesions, carcinoma in situ, and moderate grade dysplasias) before pancreatic surgery. Receiver operating characteristic analysis was performed to assess the accuracy of MDCT using pathologic evaluation of the surgical specimen as a reference standard., Results: On the basis of MDCT features, the radiologic accuracy (reader 1 and reader 2) for stratifying lesions into mucinous and nonmucinous subtypes was 85% and 82% and for recognizing cysts with aggressive biology was 86% and 85%, respectively. Predictive values of MDCT were superior for lesions > 30 mm and nonmucinous lesions. Features favoring aggressive biology were main pancreatic duct dilation > 10 mm (p < 0.0001), biliary obstruction (p=0.01), mural nodule (p < 0.0001), main-duct intraductal papillary mucinous neoplasm (p < 0.0001), and advanced age (p = 0.0001). Sensitivity of detecting morphologic features was higher with the dual-phase pancreatic protocol CT., Conclusion: Morphologic features of pancreatic cystic lesions on MDCT allow reliable characterization into mucinous and nonmucinous subtypes and enable prediction of biologic aggressiveness.

Objective: The objective of this article is to illustrate the spectrum of imaging findings of polypropylene (Prolene) plug hernia repair., Conclusion: Knowledge of patient history and awareness of postsurgical imaging appearances are of importance because Prolene plugs are often incidentally encountered and if misdiagnosed may lead to erroneous patient disease staging and management.

Objective: Adrenal nodules are frequently encountered on current high-resolution imaging, and accurate characterization of such lesions is critical for appropriate patient care. Our article highlights how imaging techniques such as CT densitometry, CT washout characteristics, chemical shift MRI, PET, and PET/CT help characterize most adrenal lesions. We focus on these techniques as well as specifically, because of space constraints, the varied imaging appearances of adrenocortical carcinoma, pheochromocytoma, and lymphoma on these techniques., Conclusion: The imaging characterization of adrenal lesions has continued to advance over the past decade as new technologies have evolved. CT, MRI, PET, and PET/CT are now established clinical techniques capable of differentiating benign from malignant adrenal lesions.

Objective: The purpose of this article is to review the role of FDG PET/CT in ovarian cancer, which is the leading cause of death among gynecologic cancers., Conclusion: FDG PET/CT can significantly modify the assessment of the extent of primary and recurrent ovarian cancer and, hence, often alters patient management substantially. FDG PET/CT has thus become a critical tool for the preoperative evaluation of women with primary ovarian cancer and for postoperative follow-up assessment for evidence of recurrence in these patients.

Objective: The purpose of our study was to determine the frequency of discrepancies in side of findings (side discrepancies) in the body and the impression sections of radiology reports. In addition, we determined the frequency of corrected side discrepancies between radiology reports and images in a larger database of radiology reports., Materials and Methods: In this cross-sectional study, all radiology reports from January 1, 2007, through December 31, 2007 (n = 1,065,322), that had an addendum were assessed using a radiology reports search engine and searching for the words "left," "right," and "addendum" to locate laterality errors between the body of the report and the impression section. For reports with discrepancies, we recorded the patient's sex, true side of the lesion, and the imaging technique. All reports with an addendum (n = 13,821) in January 2007 containing the words "left" and "right" were evaluated using the same search engine for similar discrepancies. Imaging studies of reports with errors were reviewed to determine the correct side of the lesion and the clinical significance of the errors., Results: Of the 1,065,322 reports, 88 side discrepancies were reported in addenda. The errors in mislabeling the side of the lesion were more common in female (n = 58) than in male (n = 30) patients. Of the 88 errors reported in addenda, 27 were labeled incorrectly in the body of the report, 29 in the impression section, and 32 in both the body and impression sections. In January 2007, 36 of 13,821 (0.26%) reports had no correction for mislabeling of side. Most errors (70.9%) were graded as clinically important., Conclusion: Clinically significant errors were found in reporting the body side of the lesion in radiology reports between the body and impression sections.

Objective: The objective of our study was to evaluate a large cohort of patients with PET/CT to determine whether qualitative (visual) assessment, quantitative standardized uptake value (SUV), or standardized uptake ratio (SUR) techniques should be used when attempting to characterize adrenal masses in patients with cancer., Materials and Methods: The study group was composed of 150 consecutive patients (78 men, 72 women; mean age, 60 years; range, 24-88 years) with documented adrenal lesions. All patients were known to have an underlying primary malignancy and were referred for PET/CT to evaluate the underlying primary and metastatic tumor burden. Definitive lesion characterization was determined by evaluating all histologic adrenal specimens and all relevant prior and follow-up CT scans, including unenhanced, contrast-enhanced, and delayed contrast-enhanced washout studies., Results: Of the 139 benign lesions, 109 were considered benign by CT densitometry measurements and 135 by qualitative PET data. Qualitative PET characterized 28 of 30 benign lesions that were considered indeterminate by unenhanced CT. All 26 malignant lesions were characterized by PET: All showed qualitative and quantitative signal intensity greater than the liver. By combining unenhanced and qualitative CT data with the retrospective PET data, the analysis yielded a sensitivity of 100% for the detection of malignancy, a specificity of 99%, a positive predictive value (PPV) of 93%, a negative predictive value (NPV) of 100%, and an accuracy of 99% (Table 1). Conversely, for the detection of benignity, the sensitivity, specificity, PPV, NPV, and accuracy were 99%, 100%, 100%, 93%, and 99%, respectively., Conclusion: PET/CT is a highly accurate method for differentiating benign from malignant adrenal masses particularly when using qualitative, rather than quantitative, PET data. The routine use of quantitative mean or maximal SUV or SUR data may be unnecessary. Occasional benign lesions do show mild to moderate increased FDG uptake compared with that of the liver and may mimic some malignant lesions. Without evidence that these lesions are benign by unenhanced CT densitometry or adrenal mass stability or growth from previous CT scans, we recommend that these lesions be characterized using contrast-enhanced washout tests and that if those tests are inconclusive, using percutaneous biopsy if early lesion characterization is mandatory.

Objective: The purpose of our study was to evaluate a visual PET/CT scoring system for the differentiation of benign and early malignant esophageal uptake., Materials and Methods: Thirty-six consecutive patients with precancerous or early malignant esophageal lesions including Barrett's esophagus, Tis, T1, and T2 adenocarcinomas were eligible. Findings of these patients were compared with 66 patients who had reported increased esophageal (18)F-FDG uptake due to benign esophageal disorders. Lesions were evaluated with scores using the following characteristics in PET/CT: FDG uptake intensity (low = 0, moderate = 1, high = 2), FDG uptake eccentricity (concentric = 0, eccentric = 1), FDG uptake focality (diffuse = 0, segmental = 1, focal = 2), esophageal thickness on the CT component (normal = 0, thickening = 1, mass = 2), and location (distal third of the esophagus = 0, middle third of the esophagus = 1, proximal third of the esophagus = 2)., Results: Early malignant lesions had higher scores in FDG uptake intensity (p = 0.003; chi-square), eccentricity (p < 0.001), and focality (p < 0.001) compared with benign lesions. No significant difference was seen in esophageal thickness on CT (p = 0.168) and in location of the lesion (p = 0.291). Binary logistic regression analysis with a stepwise forward inclusion of all score components including the maximum standardized uptake value (SUV) of the lesions revealed that a total score combining eccentricity and focality scores has the highest accuracy of predicting early malignant disease. Using a threshold of equal or higher than 2 in the combined total focality-eccentricity score, the sensitivity was 83.3% and specificity was 68.2% for predicting early malignant disease., Conclusion: Focality and eccentricity of FDG uptake prove to be valuable PET/CT characteristics for the differentiation of nonspecific FDG uptake in the esophagus.

Objective: The purposes of this study were to validate a natural language processing program for extraction of recommendation features, such as recommended time frames and imaging technique, from electronic radiology reports and to assess patterns of recommendation features in a large database of radiology reports., Materials and Methods: This study was performed on a radiology reports database covering the years 1995-2004. From this database, 120 reports with and without recommendations were selected and randomized. Two radiologists independently classified these reports according to presence of recommendations, time frame, and imaging technique suggested for follow-up or repeated examinations. The natural language processing program then was used to classify the reports according to the same criteria used by the radiologists. The accuracy of classification of recommendation features was determined. The program then was used to determine the patterns of recommendation features for different patients and imaging features in the entire database of 4,211,503 reports., Results: The natural language processing program had an accuracy of 93.2% (82/88) for identifying the imaging technique recommended by the radiologists for further evaluation. Categorization of recommended time frames in the reports with the 88 recommendations obtained with the program resulted in 83 (94.3%) accurate classifications and five (5.7%) inaccurate classifications. Recommendations of CT were most common (27.9%, 105,076 of 376,918 reports) followed by those for MRI (17.8%). In most (85.4%, 322,074/376,918) of the reports with imaging recommendations, however, radiologists did not specify the time frame., Conclusion: Accurate determination of recommended imaging techniques and time frames in a large database of radiology reports is possible with a natural language processing program. Most imaging recommendations are for high-cost but more accurate radiologic studies.

Objective: Retroperitoneal fibrosis is a rare collagen vascular disorder of unclear cause. Both benign and malignant associations have been described, rendering differentiation of these entities of paramount importance because sinister pathology alters the diagnosis. Thus, a high level of diligence is required in the investigation of this condition, particularly in patients with concomitant systemic conditions., Conclusion: Familiarity with the realm of imaging manifestations of retroperitoneal fibrosis is vital to ensure correct diagnosis and optimal treatment.

Objective: The purpose of this study was to evaluate the feasibility of performing CT-guided interventional procedures with a very low radiation dose., Materials and Methods: We performed 291 CT-guided interventional procedures using a low dose of radiation. The subjects were 165 men and 126 women 22-89 years old with a mean age of 65 years. CT fluoroscopy was not used. The procedures were 201 percutaneous biopsies and 90 percutaneous aspiration or drainage procedures. Before the procedure, images were obtained with standard mAs of 175-250 mAs. All subsequent CT was performed at a reduced mAs. Technical success of catheter placement and biopsy was calculated, and the results were compared with those of procedures performed over the previous 12 months with standard radiation doses. Patient weight, lesion size, and number of CT acquisitions needed to complete the procedure were recorded., Results: All but three aspiration or drainage procedures performed at 30 mAs were successful, for a success rate of 96.7%. The technical success rate of biopsy performed at 30 mAs was 93.5%. In the cases of 13 patients undergoing biopsy, the masses were not identified with low-dose technique, and these procedures were completed at a higher dose. Results were independent of patient weight and lesion size. The technical success rate was 98% for percutaneous drainage performed at a standard radiation dose in the 12 months before introduction of the low-dose technique. The technical success rate was 87.5% for biopsy performed at a standard radiation dose in the 12 months before introduction of the low-dose technique. The complication rate of the low-dose technique was comparable to that of the standard-dose technique., Conclusion: Low-dose radiation technique using 30 mAs results in technical success for both catheter placement and percutaneous biopsy comparable to standard radiation dose.

Objective: The purpose of this study was to characterize pathologically proven adrenocortical carcinoma by examination of washout attenuation characteristics on contrast-enhanced CT images., Conclusion: Adrenocortical carcinoma has relative contrast retention on delayed contrast-enhanced CT. All tumors in this series had a relative percentage washout less than 40%, a finding consistent with malignant disease.

Objective: The objective of our study was to compare image quality and radiation dose associated with abdominopelvic CT using combined modulation, angular modulation, and constant tube current., Conclusion: Compared with using a constant tube current to scan the abdomen and pelvis, the use of a combined modulation technique results in a substantial reduction (42-44%) in radiation dose with acceptable image noise and diagnostic acceptability.

Objective: The objective of our study was to assess the relative performance of mangafodipir trisodium-enhanced liver MRI and whole-body FDG PET for the detection of liver metastases from adenocarcinoma of the colon and pancreas., Materials and Methods: Imaging data of 34 patients (23 men, 11 women; age range, 44-78 years) with adenocarcinoma of the colon (n = 27) or adenocarcinoma of the pancreas (n = 7) who had undergone mangafodipir trisodium-enhanced liver MRI and whole-body FDG PET were retrospectively reviewed for the presence and number of liver metastases. Histopathology (n = 25) or follow-up imaging (n = 9) served as the standard of reference. Breath-hold T1-weighted gradient-recalled echo, respiratory-triggered T2-weighted fast spin-echo, and mangafodipir trisodium-enhanced axial fat-saturated high-spatial-resolution (256 x 512) T1-weighted gradient-recalled echo images were obtained on a 1.5-T scanner. FDG PET was performed after the injection of 15-20 mCi (555-740 MBq) of FDG. The sensitivity, positive predictive value, and accuracy were calculated for each technique. The performances of the two techniques were compared using the Fisher's exact test., Results: Thirty patients had hepatic metastases and four had no hepatic metastases according to the standard of reference. The total number of metastases was 79, including 33 that measured less than 1 cm. Based on a per-patient analysis, MRI and FDG PET showed sensitivities of 96.6% and 93.3%, positive predictive values of 100% and 90.3%, and accuracies of 97.1% and 85.3%, respectively. According to a per-lesion analysis, MRI and FDG PET showed sensitivities of 81.4% and 67.0%, positive predictive values of 89.8% and 81.3%, and accuracies of 75.5% and 64.1%, respectively. MRI detected more hepatic metastases than FDG PET (p = 0.016). Of the 33 subcentimeter lesions confirmed on the standard of reference, all were identified on MRI, whereas only 12 were detected on FDG PET (p = 0.0001)., Conclusion: In patients with colon and pancreatic adenocarcinoma, high-spatial-resolution mangafodipir trisodium-enhanced liver MRI and whole-body FDG PET were comparable in the detection of patients with liver metastases. FDG PET provided additional information about extrahepatic disease and was useful in initial staging. However, significantly more and smaller liver metastases were detected on MRI than on FDG PET.

Objective: Our objective was to assess the effect of orthopedic metallic prostheses on radiation dose associated with MDCT using z-axis automatic tube-current modulation and a fixed tube current in a phantom and patient study., Conclusion: Z-modulation is associated with a 34.1% increase in the mean tube current-time product and no change in the extent of streak artifacts in patients with a metallic prosthesis, compared with patients without a prosthesis. However, compared with the fixed-tube-current technique, z-modulation is associated with a 28.9% decrease in the mean tube current-time product.

Objective: Attenuation values on CT of less than 10 H are considered characteristic of adrenal adenomas. Adrenal pheochromocytomas can infrequently contain fat that could result in low attenuation on CT. The purpose of our study was to determine if pheochromocytomas could be confused with adenomas by virtue of their attenuation values on unenhanced CT., Materials and Methods: CT attenuation and size of nine adrenal nodules producing pheochromocytoma syndrome were measured on unenhanced CT in nine patients. For five patients who received IV contrast material, washout profiles were also calculated., Results: Two of the nine patients had adrenal lesions with attenuation values of less than 10 H; one had a pheochromocytoma with an attentuation of 9.0 H, and the other had a medullary hyperplasia with an attenuation of 1.8 H. These two nodules showed evidence of microscopic fat at histologic examination. No macroscopic fat was seen on the CT scans. The remaining seven patients had lesions with attenuation values exceeding 10 H (mean value, 25.6 H; range, 1.8-41 H). Mean diameter of the nine tumors (including the hyperplastic nodule) was 3.2 cm (range, 0.8-6.7 cm; SD, +/- 2.3 cm). The two low-attenuation lesions also mimicked adenomas by displaying more than 60% contrast washout on 10-min-delayed contrast-enhanced scans, unlike the other three pheochromocytomas for which we had washout data., Conclusion: On CT, pheochromocytomas may have attenuation values less than 10 H and also may display more than 60% washout of contrast agents on delayed scanning. Adrenal pheochromocytomas should be included with adenomas in the differential diagnosis both for masses with low attenuation on unenhanced CT and for lesions exhibiting a high percentage of contrast washout.

Objective: We hypothesized that radiation doses for abdominal CT could be reduced by adjusting the dose for a patient's weight and cross-sectional abdominal dimensions, with the resultant scans still being of diagnostic quality., Subjects and Methods: Using a multidetector CT scanner, we prospectively studied 39 patients who were 65 years and older who had a known history of cancer. After performing a diagnostic contrast-enhanced CT examination, we obtained four slices each (centered at the top of the right kidney) at a standard radiation dose (240-300 mA) and at a 50% reduced dose (120-150 mA) at a constant kilovoltage of 140. Scans were obtained during a single breath-hold, with a 2.5-mm detector configuration and a slice pitch of 6:1. Reconstructed slice thickness was 5 mm. In a blinded review, two radiologists rated the randomized CT scans for overall image quality and anatomic details of liver, spleen, adrenal glands, kidneys, pancreas, and abdominal wall, using a 5-point scale (1 = unacceptable, 2 = substandard, 3 = acceptable, 4 = above average, and 5 = superior). Patients' weight and abdominal circumference, area, and anteroposterior and transverse diameters were correlated with image quality of scans obtained at standard-dose and 50% reduced-dose CT. Statistical analysis of the data was performed using Wilcoxon's signed rank test., Results: Overall, the image quality score was significantly higher (p < 0.005) on the scans obtained with standard-dose CT. No statistically significant difference in image quality was noted in the 50% reduced- and standard-dose CT scans in patients who weighed less than 180 lb, or 81 kg, (p > 0.05) and who had a transverse abdominal diameter of less than 34.5 cm (p > 0.05), an anteroposterior diameter of less than 28 cm (p > 0.05), a cross-sectional circumference of less than 105 cm (p > 0.05), and a cross-sectional area of less than 800 cm(2) (p > 0.05). Good interobserver agreement (p > 0.5) was found between the two reviewing radiologists., Conclusion: Abdominal CT scan quality appears to be acceptable even with a 50% reduction in radiation dose except in patients with large anthropometric measurements. A reduction in CT radiation dose is possible if the tube current is optimized for the patient's weight and abdominal dimensions.