The Incidental Pancreatic Cyst: When to Worry About Cancer.

Incidental pancreatic cystic lesions are a common challenge encountered by diagnostic radiologists. Specifically, given the prevalence of benign pancreatic cystic lesions, determining when to recommend aggressive actions such as surgical resection or endoscopic ultrasound with sampling is difficult. In this article, we review the common types of cystic pancreatic lesions including serous cystadenoma, intraductal papillary mucinous neoplasm, and mucinous cystic neoplasm with imaging examples of each. We also discuss high-risk or worrisome imaging features that warrant a referral to a surgeon or endoscopist and provid several examples of these features. These imaging features adhere to the latest guidelines from the International Consensus Guidelines, American Gastroenterological Association (2015), American College of Gastroenterology (2018), American College of Radiology (2010, 2017), and European Guidelines (2013, 2018). Our focused article addresses the imaging dilemma of managing incidental cystic pancreatic lesions, weighing the options between imaging follow-up and aggressive interventions.

The Need for Practical and Accurate Measures of Value for Radiology.

Radiologists play a critical role in helping the health care system achieve greater value. Unfortunately, today radiology is often judged by simple "checkbox" metrics, which neither directly reflect the value radiologists provide nor the outcomes they help drive. To change this system, first, we must attempt to better define the elusive term value and, then, quantify the value of imaging through more relevant and meaningful metrics that can be more directly correlated with outcomes. This framework can further improve radiology's value by enhancing radiologists' integration into the care team and their engagement with patients. With these improvements, we can maximize the value of imaging in the overall care of patients.

How the radiologist can add value in the evaluation of the pre- and post-surgical pancreas.

Disease involving the pancreas can be a significant diagnostic challenge to the interpreting radiologist. Moreover, the majority of disease processes involving the pancreas carry high significant morbidity and mortality either due to their natural process or related to their treatment options. As such, it is critical for radiologists to not only provide accurate information from imaging to guide patient management, but also deliver that information in a clear manner so as to aid the referring physician. This is no better exemplified than in the case of pre-operative staging for pancreatic adenocarcinoma. Furthermore, with the changing healthcare landscape, it is now more important than ever to ensure that the value of radiology service to other providers is high. In this review, we will discuss how the radiologist can add value to the referring physician by employing novel imaging techniques in the pre-operative evaluation as well as how the information can be conveyed in the most meaningful manner through the use of structured reporting. We will also familiarize the radiologist with the imaging appearance of common complications that occur after pancreatic surgery.

Review of small-bowel obstruction: the diagnosis and when to worry.

This is a review of small-bowel obstruction written primarily for residents. The review focuses on radiography and computed tomography (CT) for diagnosing small-bowel obstruction and CT for determining complications. (©) RSNA, 2015.

Dual-Energy MDCT for Imaging the Renal Mass.

OBJECTIVE: The purpose of this article is to provide the reader with a comprehensive overview of dual-energy MDCT applications for imaging renal masses. CONCLUSION: Dual-energy MDCT has the potential to substantially improve the ability of radiologists to diagnose renal masses compared with conventional MDCT, potentially streamlining patients' clinical management.

Impact of dual-energy multi-detector row CT with virtual monochromatic imaging on renal cyst pseudoenhancement: in vitro and in vivo study.

PURPOSE: To investigate whether dual-energy multi-detector row computed tomography (CT) with virtual monochromatic imaging can overcome renal cyst pseudoenhancement in a phantom experiment and a clinical study. MATERIALS AND METHODS: This retrospective single-center HIPAA-compliant study was approved by the institutional review board, with waiver of informed consent. Four renal compartments inserted into torso phantoms were filled with saline to simulate the unenhanced state and with iodinated solutions to simulate the three levels of renal parenchyma enhancement (140, 180, and 240 HU). Saline-filled spheres simulating renal cysts (15 and 18 mm in diameter) were serially suspended in the renal compartments and imaged with dual-energy and single-energy multi-detector row CT at four different energy levels (80, 100, 120, and 140 kVp). In addition, 28 patients (mean age, 66 years ± 10; mean body mass index, 31.3 kg/m(2) ± 6.2) with 34 intrarenal cysts were included. Virtual monochromatic images were reconstructed in 10-keV increments at energy levels ranging from 40 to 140 keV. Phantom and clinical data were analyzed by using multivariate regression analysis. RESULTS: In the phantom experiment, all polychromatic image data sets showed pseudoenhancement (postcontrast attenuation increase >10 HU) in all investigated conditions, with a significant effect on cyst size (P <.001), location (P <.001), and renal background attenuation level (P <.001). Virtual monochromatic images at energy levels ranging from 80 to 140 keV did not show pseudoenhancement, with the minimum attenuation increase (mean, 6.1 HU ± 1.6; range, 1.6-7.7 HU) on 80-keV images. In patients, pseudoenhancement never occurred on virtual monochromatic images at energy levels ranging from 90 to 140 keV. Patient body size had a significant effect (P = .007) on selection of the optimal monochromatic energy level. CONCLUSION: Dual-energy multi-detector row CT with reconstruction of virtual monochromatic images at an optimal energy level can overcome renal cyst pseudoenhancement.

Pediatric chest and abdominopelvic CT: organ dose estimation based on 42 patient models.

PURPOSE: To estimate organ dose from pediatric chest and abdominopelvic computed tomography (CT) examinations and evaluate the dependency of organ dose coefficients on patient size and CT scanner models. MATERIALS AND METHODS: The institutional review board approved this HIPAA-compliant study and did not require informed patient consent. A validated Monte Carlo program was used to perform simulations in 42 pediatric patient models (age range, 0-16 years; weight range, 2-80 kg; 24 boys, 18 girls). Multidetector CT scanners were modeled on those from two commercial manufacturers (LightSpeed VCT, GE Healthcare, Waukesha, Wis; SOMATOM Definition Flash, Siemens Healthcare, Forchheim, Germany). Organ doses were estimated for each patient model for routine chest and abdominopelvic examinations and were normalized by volume CT dose index (CTDI(vol)). The relationships between CTDI(vol)-normalized organ dose coefficients and average patient diameters were evaluated across scanner models. RESULTS: For organs within the image coverage, CTDI(vol)-normalized organ dose coefficients largely showed a strong exponential relationship with the average patient diameter (R(2) > 0.9). The average percentage differences between the two scanner models were generally within 10%. For distributed organs and organs on the periphery of or outside the image coverage, the differences were generally larger (average, 3%-32%) mainly because of the effect of overranging. CONCLUSION: It is feasible to estimate patient-specific organ dose for a given examination with the knowledge of patient size and the CTDI(vol). These CTDI(vol)-normalized organ dose coefficients enable one to readily estimate patient-specific organ dose for pediatric patients in clinical settings. This dose information, and, as appropriate, attendant risk estimations, can provide more substantive information for the individual patient for both clinical and research applications and can yield more expansive information on dose profiles across patient populations within a practice.

Dose coefficients in pediatric and adult abdominopelvic CT based on 100 patient models.

Recent studies have shown the feasibility of estimating patient dose from a CT exam using CTDI(vol)-normalized-organ dose (denoted as h), DLP-normalized-effective dose (denoted as k), and DLP-normalized-risk index (denoted as q). However, previous studies were limited to a small number of phantom models. The purpose of this work was to provide dose coefficients (h, k, and q) across a large number of computational models covering a broad range of patient anatomy, age, size percentile, and gender. The study consisted of 100 patient computer models (age range, 0 to 78 y.o.; weight range, 2-180 kg) including 42 pediatric models (age range, 0 to 16 y.o.; weight range, 2-80 kg) and 58 adult models (age range, 18 to 78 y.o.; weight range, 57-180 kg). Multi-detector array CT scanners from two commercial manufacturers (LightSpeed VCT, GE Healthcare; SOMATOM Definition Flash, Siemens Healthcare) were included. A previously-validated Monte Carlo program was used to simulate organ dose for each patient model and each scanner, from which h, k, and q were derived. The relationships between h, k, and q and patient characteristics (size, age, and gender) were ascertained. The differences in conversion coefficients across the scanners were further characterized. CTDI(vol)-normalized-organ dose (h) showed an exponential decrease with increasing patient size. For organs within the image coverage, the average differences of h across scanners were less than 15%. That value increased to 29% for organs on the periphery or outside the image coverage, and to 8% for distributed organs, respectively. The DLP-normalized-effective dose (k) decreased exponentially with increasing patient size. For a given gender, the DLP-normalized-risk index (q) showed an exponential decrease with both increasing patient size and patient age. The average differences in k and q across scanners were 8% and 10%, respectively. This study demonstrated that the knowledge of patient information and CTDIvol/DLP values may be used to estimate organ dose, effective dose, and risk index in abdominopelvic CT based on the coefficients derived from a large population of pediatric and adult patients.

Comparison of conventional and simulated reduced-tube current MDCT for evaluation of suspected appendicitis in the pediatric population.

OBJECTIVE: The purpose of this study was to compare CT with conventional and simulated reduced-tube current in the evaluation for acute appendicitis in children. MATERIALS AND METHODS: Validated noise-addition (tube current-reduction) software was used to create 50% and 75% tube current reductions in 60 CT examinations performed for suspected appendicitis, resulting in 180 image sets. Three blinded pediatric radiologists scored the randomized studies for the following factors: presence of the normal appendix or appendicitis (5-point scale; 1=definitely absent and 5=definitely present), presence of alternate diagnoses, and overall image quality (1=nondiagnostic and 5=excellent). Truth was defined by the interpretation of the conventional examination. RESULTS: For conventional examinations, the total number of reviews (60 cases×3 readers=180) in which the normal appendix was identified was 120 of 180 (66.7%), compared with 108 of 180 (60%) in the 50% (p=0.19) and 91 of 180 (50.6%) in the 75% (p=0.002) tube current-reduction groups. Appendicitis was identified in a total of 39 of 180 (21.7%), 38 of 180 (21.1%), and 37 of 180 (20.6%) examinations, respectively (p>0.05). This translates to sensitivities of 97% and 95% for the 50% and 75% tube current-reduction groups, respectively. Alternate diagnoses were detected in 14%, 16%, and 13% of scans, respectively. Compared with conventional-tube current examinations, reader confidence and assessment of image quality were significantly decreased for both tube current-reduction groups. CONCLUSION: Simulated tube current-reduction technology provides for systematic evaluation of diagnostic thresholds. Application of this technology in the setting of suspected appendicitis shows that tube current can be reduced by at least 50% without significantly affecting diagnostic quality, despite a decrease in reader confidence and assessment of image quality.

FDG-PET/CT characterization of adrenal nodules: diagnostic accuracy and interreader agreement using quantitative and qualitative methods.

PURPOSE: To determine interreader agreement and diagnostic accuracy across varying levels of reader experience using qualitative and quantitative methods of evaluating adrenal nodules using ((18)F)-fluorodeoxyglucose-positron emission tomography/computed tomography. METHODS: 132 adrenal nodules (96 adenomas, 36 metastases) were retrospectively identified in 105 patients (49 men and 56 women, mean age 66 years, age range 45-85 years) with a history of lung cancer who underwent ((18)F)-fluorodeoxyglucose-positron emission tomography/computed tomography. For each nodule, three readers independently performed one qualitative and two quantitative measurements: visual assessment, standardized uptake value (SUVmax), and standard uptake ratio (SUVratio). Interreader agreement was calculated using percent agreement with κ statistic for qualitative analysis and intraclass correlation coefficient (ICC) for quantitative analysis. Accuracy, sensitivity, and specificity for distinguishing benign from malignant adrenal nodules were calculated for each method. RESULTS: Percent agreement between readers for visual (qualitative) assessment was 92% to 96% and κ statistic was 0.79 to 0.90 (95% confidence limits 0.66-0.99). ICC for SUVmax was 92% to 99% (95% CL 0.8-1.0), and ICC for SUVratio was 89% to 99% (95% CL 0.74-0.99). For diagnosis of malignancy, mean sensitivity and specificity for visual assessment were 80% and 97%, respectively. Mean sensitivity and specificity for SUVmax were 91% and 81%, respectively; for SUVratio, 90% and 80%. Mean diagnostic accuracy was 93%, 83%, and 84% for visual assessment, SUVmax, and SUVratio, respectively. CONCLUSION: Excellent interreader agreement is seen for quantitative and qualitative methods of distinguishing benign from malignant adrenal nodules. Qualitative analysis demonstrated higher accuracy but lower sensitivity compared with quantitative analysis.

Effects of protocol and obesity on dose conversion factors in adult body CT.

PURPOSE: In computed tomography (CT), organ dose, effective dose, and risk index can be estimated from volume-weighted CT dose index (CTDI(vol)) or dose-length product (DLP) using conversion coefficients. Studies have investigated how these coefficients vary across scanner models, scan parameters, and patient size. However, their variability across CT protocols has not been systematically studied. Furthermore, earlier studies of the effect of patient size have not included obese individuals, which currently represent more than one-third of U.S. adults. The purpose of this study was to assess the effects of protocol and obesity on dose and risk conversion coefficients in adult body CT. METHODS: Whole-body computational phantoms were created from clinical CT images of six adult patients (three males, three females), representing normal-weight patients and patients of three obesity classes. Body CT protocols at our institution were selected and categorized into ten examination categories based on anatomical region examined. A validated Monte Carlo program was used to estimate organ dose. Organ dose estimates were normalized by CTDI(vol) and size-specific dose estimate (SSDE) to obtain organ dose conversion coefficients (denoted as h and h(ss) factors, respectively). Assuming each phantom to be 20, 40, and 60 years old, effective dose and risk index were calculated and normalized by DLP to obtain effective dose and risk index conversion coefficients (denoted as k and q factors, respectively). Coefficient of variation was used to quantify the variability of each conversion coefficient across examination categories. The effect of obesity was assessed by comparing each obese phantom with the normal-weight phantom of the same gender. RESULTS: For a given organ, the variability of h factor across examination categories that encompassed the entire organ volume was generally within 15%. However, k factor varied more across examination categories (15%-27%). For all three ages, the variability of q factor was small for male (<10%), but large for female phantoms (21%-43%). Relative to the normal-weight phantoms, the reduction in h factor (an average across fully encompassed organs) was 17%-42%, 17%-40%, and 51%-63% for obese-class-I, obese-class-II, and obese-class-III phantoms, respectively. h(ss) factor was not independent of patient diameter and generally decreased with increasing obesity. Relative to the normal-weight phantoms, the reduction in k factor was 12%-40%, 14%-46%, and 44%-59% for obese-class-I, obese-class-II, and obese-class-III phantoms, respectively. The respective reduction in q factor was 11%-36%, 17%-42%, and 48%-59% at 20 years of age and similar at other ages. CONCLUSIONS: In adult body CT, dose to an organ fully encompassed by the primary radiation beam can be estimated from CTDI(vol) using a protocol-independent conversion coefficient. However, fully encompassed organs only account for 50% ± 19% of k factor and 46% ± 24% of q factor. Dose received by partially encompassed organs is also substantial. To estimate effective dose and risk index from DLP, it is necessary to use conversion coefficients specific to the anatomical region examined. Obesity has a significant effect on dose and risk conversion coefficients, which cannot be predicted using body diameter alone. SSDE-normalized organ dose is not independent of diameter. SSDE itself generally overestimates organ dose for obese patients.

Characterization of adrenal nodules with dual-energy CT: can virtual unenhanced attenuation values replace true unenhanced attenuation values?

OBJECTIVE: The purpose of our study was to investigate whether virtual unenhanced adrenal nodule attenuation values can replace true noncontrast attenuation values. MATERIALS AND METHODS: Twenty-three incidentally discovered adrenal nodules (19 adenomas and four metastases) were identified in 19 patients (11 men and eight women; mean age, 65 years; age range, 38-84 years) who underwent unenhanced single-energy CT followed by contrast-enhanced dual-energy CT on the same scanner. A virtual unenhanced imaging dataset was generated from each dual-energy CT dataset. CT attenuation of each adrenal nodule was measured at the same location on virtual unenhanced images and true unenhanced images by three radiologists and mean values compared using the Student t test. Correlation between virtual unenhanced and true unenhanced values was determined using linear regression analysis. The mean difference and percentage of diagnostic agreement were also determined. Interreader variability was assessed using the intraclass correlation coefficient (ICC). RESULTS: The mean ± SD attenuation values for virtual unenhanced images and true unenhanced images were 14.7 ± 15.1 HU and 12.9 ± 13.4 HU, respectively (p = 0.2). Strong positive correlation was observed between virtual unenhanced images and true unenhanced images (R = 0.83-0.87). The mean difference between virtual unenhanced images and true unenhanced images was 1.8 ± 1.7 HU. Diagnostic agreement between virtual unenhanced images and true unenhanced images was 83-91% for three radiologists. No malignant nodules were misclassified as benign on virtual unenhanced images. The ICC was 0.88 and 0.96 for virtual unenhanced images and true unenhanced images, respectively, indicating high interreader agreement. CONCLUSION: Virtual unenhanced and true unenhanced attenuation measurements of adrenal nodules were not significantly different and showed strongly positive linear correlation. This finding resulted in substantial diagnostic agreement between virtual unenhanced images and true unenhanced images for distinguishing benign from malignant nodules.

Vascular surgery collaboration during pancreaticoduodenectomy with vascular reconstruction.

BACKGROUND: Once thought to have unresectable disease, pancreatic cancer patients with portal venous involvement are now reported to have comparable survival after pancreaticoduodenectomy (PD) with vascular reconstruction (VR) as compared with patients without vascular involvement. We hypothesize that a multidisciplinary approach involving a vascular surgeon will minimize morbidity and improve patency of VRs. METHODS: We identified 204 patients who underwent PD for pancreatic adenocarcinoma from 1997 to 2008. Patients who underwent PD with VR (N = 42) were compared with those who underwent standard PD (N = 162). VRs were performed by a vascular surgeon and involved primary repair (N = 8), vein patch (N = 25), or interposition grafting (N = 9) with femoral or other venous conduit. RESULTS: Patients undergoing PD with VR had larger tumors (3.0 cm vs. 2.5 cm, P < 0.01) but did not have different rates of tumor-free margins (73% vs. 72%, P = 0.84) or lymph nodes metastases (50% vs. 38%, P = 0.14). The VR group had higher median blood loss (875 mL vs. 550 mL, P = 0<0.01), but no differences in mortality, complication rates, length of stay, or readmission rates were found in a median follow-up of 29 months. Overall survival rates were similar. Predictors of mortality on multivariate analysis included increasing histological grade (P = 0.01), positive lymph nodes (P = 0.01), and increasing tumor size (P = 0.01), but not VR (P = 0.28). When evaluated by computed tomography scans within 6 months postoperatively, 97% of reconstructions remained patent. CONCLUSIONS: The need for VR is not a contraindication to potentially curative resection in patients with pancreatic adenocarcinoma. Assistance of a vascular surgeon during VR may allow moderate-volume centers to achieve outcomes comparable with high-volume centers.

Rate of contrast material extravasations and allergic-like reactions: effect of extrinsic warming of low-osmolality iodinated CT contrast material to 37 degrees C.

PURPOSE: To retrospectively determine whether extrinsic warming of the low-osmolality contrast material iopamidol to 37°C prior to intravenous administration at computed tomography (CT) affects extravasation and allergic-like reaction rates. MATERIALS AND METHODS: The need to obtain informed patient consent was waived for this HIPAA-compliant and institutional review board-approved analysis. All adverse events related to the intravenous administration of iopamidol during CT examinations occurring 200 days before (period 1) and 200 days after (period 2) the cessation of extrinsic contrast material warming (37°C) for intravenous injections of less than 6 mL/sec at Duke University Medical Center (Durham, NC) were retrospectively reviewed. Adverse event rates were compared by using χ2 statistics. RESULTS: There were 12,682 injections during period 1 (10,831 injections of iopamidol 300 and 1851 injections of iopamidol 370) and 12,138 injections (10, 064 injections of iopamidol 300 and 2074 injections of iopamidol 370) during period 2. Adverse event rates for iopamidol 300 were not affected by extrinsic warming (extravasation rates: 0.30% [32 of 10,831] in period 1 vs 0.23% [23 of 10,064] in period 2, P=.64; allergic-like reaction rates: 0.39% [42 of 10,831] in period 1 vs 0.46% [46 of 10,064] in period 2, P=.74; overall adverse events: 0.68% [74 of 10,831] in period 1 vs 0.69% [69 of 10,064] in period 2, P=.99). Discontinuation of extrinsic warming was associated with significantly increased extravasation and overall adverse event rates for iopamidol 370 (extravasation rates: 0.27% [five of 1851] vs 0.87% [18 of 2074], P=.05; allergic-like reaction rates: 0.16% [three of 1851] vs 0.39% [eight of 2074], P=.42; overall adverse events: 0.43% [eight of 1851] vs 1.25% [26 of 2074], P=.02). CONCLUSION: Extrinsic warming (to 37°C) does not appear to affect adverse event rates for intravenous injections of iopamidol 300 of less than 6 mL/sec but is associated with a significant reduction in extravasation and overall adverse event rates for the more viscous iopamidol 370.

Imaging-guided preoperative hookwire localization of nonpalpable extramammary lesions.

OBJECTIVE: Imaging-guided hookwire localization of nonpalpable lesions in the breast is frequently performed preoperatively. Outside the breast, this procedure is useful for planning resection of lesions in anatomic regions without intrinsic landmarks. The purpose of this study was to review an experience with hookwire localization of nonpalpable extramammary lesions. CONCLUSION: Preoperative imaging-guided hookwire localization is a useful technique that allows precise exploration and resection of nonpalpable lesions and increases confidence that the lesions have been entirely resected.

Effect of organ enhancement and habitus on estimation of unenhanced attenuation at contrast-enhanced dual-energy MDCT: concepts for individualized and organ-specific spectral iodine subtraction strategies.

OBJECTIVE: The purpose of this study was to assess whether habitus and organ enhancement influence iodine subtraction and should be incorporated into spectral subtraction algorithms. SUBJECTS AND METHODS: This study included 171 patients. In the unenhanced phase, MDCT was performed with single-energy acquisition (120 kVp, 250 mAs) and in the parenchymal phase with dual-energy acquisitions (80 kVp, 499 mAs; 140 kVp, 126 mAs). Habitus was determined by measuring trunk diameters and calculating circumference. Iodine subtraction was performed with input parameters individualized to muscle, fat, and blood ratio. Attenuation of the liver, pancreas, spleen, kidneys, and aorta was assessed in truly and virtually unenhanced image series. Pearson analysis was performed to correlate habitus with the input parameters. Analysis of truly unenhanced and virtually unenhanced images was performed with the Student t test; magnitude of variation was evaluated with Bland-Altman plots. Correction strategies were derived from organ-specific regression analysis of scatterplots of truly unenhanced and virtually unenhanced attenuation and implemented in a pixel-by-pixel approach. Analysis of individual organ correction and truly unenhanced attenuation was performed with the Student t test. RESULTS: The correlations between habitus and blood ratio (r = 0.694) and attenuation variation of fat at 80 kVp (r = -0.468) and 140 kV (r = -0.454) were confirmed. Although overall mean attenuation differed by no more than 10 HU between truly and virtually unenhanced scans overall, these differences varied by organ and were large in individual patients. Paired comparisons of truly and virtually unenhanced measurements differed significantly for liver, spleen, pancreas, kidneys, and aortic blood pool (p < 0.001 for all comparisons), but paired comparisons of truly unenhanced and individually organ-corrected measurements did not differ when organ- and habitus-based correction strategies were applied (p > 0.38 for all comparisons). CONCLUSION: Habitus and organ enhancement influence virtually unenhanced imaging and should be incorporated into spectral subtraction algorithms.

Detection of renal lesion enhancement with dual-energy multidetector CT.

PURPOSE: To determine whether dual-energy multidetector CT enables detection of renal lesion enhancement by using calculated nonenhanced images with spectral-based extraction in a non-body weight-restricted patient population. MATERIALS AND METHODS: Between January 2008 and December 2009, 139 patients were enrolled in this prospective HIPAA-compliant, institutional review board-approved study. Written informed consent was obtained from all patients. After single-energy nonenhanced 120-kVp CT images were acquired, contrast material-enhanced dual-energy multidetector CT images were acquired at 80 and 140 kVp. Calculated nonenhanced images were generated by using spectral-based iodine extraction. Lesion attenuation was measured on the acquired nonenhanced, calculated nonenhanced, and 140-kVp contrast-enhanced nephrographic images. Enhancement, defined as a 15-HU or greater increase in attenuation on the nephrographic images, was assessed by using the baseline attenuation on the acquired and calculated nonenhanced images. Acquired nonenhanced versus calculated nonenhanced image attenuation, as well as enhancement values, were compared by using paired Student t tests and Bland-Altman plots. RESULTS: Hypoattenuating (n = 66) and hyperattenuating (n = 28) cysts, angiomyolipomas (n = 18), and solid enhancing lesions (n = 27) were detected. Mean attenuation values for hypoattenuating cysts on the acquired and calculated nonenhanced CT images were 6.5 HU ± 5.8 (standard deviation) and 8.1 HU ± 3.1 (P = .13), respectively, with corresponding enhancement values of 1.1 HU ± 5.2 and -0.5 HU ± 6.2 (P = .12), respectively. Mean values for hyperattenuating cysts were 29.4 HU ± 5.6 on acquired images and 31.7 HU ± 5.1 on calculated images (P = .39) (corresponding enhancement, 4.7 HU ± 3.3 and 2.3 HU ± 4.1, respectively; P = .09). Mean values for fat-containing enhancing lesions were -90.6 HU ± 24.7 on acquired images and -85.9 HU ± 23.7 on calculated images (P = .57) (corresponding enhancement, 18.2 HU ± 10.1 and 13.6 HU ± 10.7, respectively; P = .19). Mean attenuation values for solid enhancing lesions were 26.0 HU ± 15.0 on acquired images and 27.7 HU ± 14.9 on calculated images (P = .45) (corresponding enhancement, 60.3 HU ± 13.1 and 58.3 HU ± 15.5, respectively; P = .38). CONCLUSION: Dual-energy CT acquisitions with spectral-based postprocessing enabled accurate detection of renal lesion enhancement across the attenuation spectrum of frequently encountered renal lesions in a non-body habitus-restricted patient population.

Low dose computerized tomography for detection of urolithiasis--its effectiveness in the setting of the urology clinic.

PURPOSE: Low dose noncontrast computerized tomography is becoming a common imaging tool to diagnose urolithiasis. We investigated its usefulness as a diagnostic tool in the outpatient setting. MATERIALS AND METHODS: A total of 62 patients with suspected urolithiasis underwent standard renal stone protocol computerized tomography with a tube current of 160 mA. Images were modified by adding image noise to simulate tube currents of 70, 100 and 130 mA. Three urologists independently interpreted the original and simulated dose scans for stone number, location and associated signs of obstruction. In addition, the investigators rated the ease of interpreting the scans and their overall level of confidence. RESULTS: There were no statistically significant differences in interobserver and intra-observer variability for stone detection or obstruction signs except significant interobserver variability in hydronephrosis and intra-observer variability in stranding categories. Each 1 mm increase in stone size increased the likelihood of a concordant response 3.55, 2.7 and 2-fold when reducing the tube current level by 19%, 38% and 56%, respectively (p=0.001, 0.008 and 0.021, respectively). Multiple stones or index stone location were not associated with agreement. The overall level of confidence decreased with lower simulated doses, particularly in the bony pelvis (p<0.02). CONCLUSIONS: Low dose computerized tomography may serve as an effective tool in the setting of the urology clinic in patients with urolithiasis. This imaging tool can better assess urolithiasis and associated obstruction than plain abdominal radiographs, but it may be problematic with small stones (less than 2 mm) and evidence of distal ureteral obstruction. Its effectiveness as a long-term followup tool requires further prospective trials.

Imaging appearance of surgical sponges at 1.5 T MRI: an in vitro study.

OBJECTIVE: To predict the MR appearance of retained surgical textiles in the acute setting by using an in vitro phantom and body MR imaging protocols. METHODS: Three surgical sponges were embedded in clear gelatin. One of these sponges was soaked in fresh human blood and the other two sponges were embedded dry. The following sequences were acquired at 1.5 T: T1W 3D gradient echo with chemical shift saturation (VIBE, volumetric interpolated breath-hold examination), 3D gradient dual echo T1W (in and opposed phase), 2D T2W single shot fast spin echo (HASTE, half-fourier acquisition single shot turbo spin echo), and 3D T2W fast spin echo (SPACE, sampling perfection with application optimized contrast using different flip angle evolutions). RESULTS: The radiopaque marker within the surgical sponge appears as a linear hypointense structure on T1W and T2W images. Slightly increased conspicuity of the radiopaque marker is seen on the in phase gradient dual echo images compared with the opposed phase gradient dual echo images, likely due to magnetic susceptibility effect. The surgical sponge material is invisible on the T1W images and appears hypointense on the T2W images. Owing to the T1W hyperintensity and T2W hypointensity of blood, the radiopaque marker within the blood soaked gauze is visible on the T1W images but obscured on the T2W images. CONCLUSIONS: We describe the in vitro MR appearance of retained surgical sponges in order to simulate their appearance in the acute setting prior to the mass-like foreign body reaction which may occur in the chronic phase.