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OBJECTIVE. The objective of our study was to determine the utility of radiomics features in differentiating CT cases of pancreatic ductal adenocarcinoma (PDAC) from normal pancreas. MATERIALS AND METHODS. In this retrospective case-control study, 190 patients with PDAC (97 men, 93 women; mean age ± SD, 66 ± 9 years) from 2012 to 2017 and 190 healthy potential renal donors (96 men, 94 women; mean age ± SD, 52 ± 8 years) without known pancreatic disease from 2005 to 2009 were identified from radiology and pathology databases. The 3D volume of the pancreas was manually segmented from the preoperative CT scans by four trained researchers and verified by three abdominal radiologists. Four hundred seventy-eight radiomics features were extracted to express the phenotype of the pancreas. Forty features were selected for analysis because of redundancy of computed features. The dataset was divided into 255 training cases (125 normal control cases and 130 PDAC cases) and 125 validation cases (65 normal control cases and 60 PDAC cases). A random forest classifier was used for binary classification of PDAC versus normal pancreas of control cases. Accuracy, sensitivity, and specificity were calculated. RESULTS. Mean tumor size was 4.1 ± 1.7 (SD) cm. The overall accuracy of the random forest binary classification was 99.2% (124/125), and AUC was 99.9%. All PDAC cases (60/60) were correctly classified. One case from a renal donor was misclassified as PDAC (1/65). The sensitivity was 100%, and specificity was 98.5%. CONCLUSION. Radiomics features extracted from whole pancreas can be used to differentiate between CT cases from patients with PDAC and healthy control subjects with normal pancreas.

Volume-of-interest (VOI) imaging is a strategy in computed tomography (CT) that restricts x-ray fluence to particular anatomical targets via dynamic beam modulation. This permits dose reduction while retaining image quality within the VOI. VOI-CT implementation has been challenged, in part, by a lack of hardware solutions for tailoring the incident fluence to the patient and anatomical site, as well as difficulties involving interior tomography reconstruction of truncated projection data. We propose a general VOI-CT imaging framework using multiple aperture devices (MADs), an emerging beam filtration scheme based on two binary x-ray filters. Location of the VOI is prescribed using two scout views at anterior-posterior (AP) and lateral perspectives. Based on a calibration of achievable fluence field patterns, MAD motion trajectories were designed using an optimization objective that seeks to maximize the relative fluence in the VOI subject to minimum fluence constraints. A modified penalized-likelihood method is developed for reconstruction of heavily truncated data using the full-field scout views to help solve the interior tomography problem. Physical experiments were conducted to show the feasibility of noncentered and elliptical VOI in two applications-spine and lung imaging. Improved dose utilization and retained image quality are validated with respect to standard full-field protocols. We observe that the contrast-to-noise ratio (CNR) is 40% higher compared with low-dose full-field scans at the same dose. The total dose reduction is 50% for equivalent image quality (CNR) within the VOI.

A novel beam filter consisting of multiple aperture devices (MADs) has been developed for dynamic fluence field modulation (FFM) in CT. Each MAD achieves spatial modulation of x-ray through fine-scale, highly attenuating tungsten bars of varying widths and spacings. Moiré patterns produced by relative motions between two MADs provide versatile classes of modulation profiles. The dual-MAD filter can be designed to achieve specific classes of target profiles. The designed filter was manufactured through a laser-sintering process and integrated to an experimental imaging system that enables linear actuation of the MADs. Dynamic FFM was achieved through a combination of beam shape modulation (by relative MAD motion) and amplitude modulation (by view-dependent mAs). To correct for gains associated with the MADs, we developed an algorithm to account for possible focal spot changes during/between scans and spectral effects introduced by the MADs. We performed FFM designs for phantoms following two imaging objectives: (1) to achieve minimum mean variance in filtered backprojection (FBP) reconstruction, and (2) to flatten the fluence behind the phantom. Comparisons with conventional FFM strategies involving a static bowtie and pulse width modulation were performed. The dual-MAD filter produced modulation profiles closely matched with the design target, providing varying beam widths not achievable by the static bowtie. The entire range of modulation profiles was achieved by 0.373 mm of MAD displacement. The correction algorithm effectively alleviated ring artifacts as a result of MADs while preserving phantom details such as wires and tissue boundaries. Dynamic FFM enabled by the MADs were effective in achieving the imaging objectives and demonstrated superior FFM capabilities compared to the static bowtie. In an ellipse phantom, the FFM of objective 1 achieved the lowest mean variance in all cases investigated. The FFM of objective 2 produce nearly isotropic local noise power spectrum and homogeneous noise magnitude. The dual-MAD filter provides an effective tool for fluence control in CT to overcome limitations of conventional static bowties and to further enable patient-specific FFM studies for a wide range of dose and image quality objectives.

Pancreatic cancer remains a major health problem, and only less than 20% of patients have resectable disease at the time of initial diagnosis. Systemic chemotherapy is often used in the patients with borderline resectable, locally advanced unresectable disease and metastatic disease. CT is often used to assess for therapeutic response; however, conventional imaging including CT may not correctly reflect treatment response after chemotherapy. Dual-energy (DE) CT can acquire datasets at two different photon spectra in a single CT acquisition, and permits separating materials and extract iodine by applying a material decomposition algorithm. Quantitative iodine mapping may have an added value over conventional CT imaging for monitoring the treatment effects in patients with pancreatic cancer and potentially serve as a unique biomarker for treatment response. In this pictorial essay, we will review the technique for iodine quantification of pancreatic cancer by DECT and discuss our observations of iodine quantification at baseline and after systemic chemotherapy with conventional cytotoxic agents, and illustrate example cases.

A Multiple Aperture Device (MAD) is a novel x-ray beam modulator that uses binary filtration on a fine scale to spatially modulate an x-ray beam. Using two MADs in series enables a large variety of fluence profiles by shifting the MADS relative to each other. This work details the design and control of dual MADs for a specific class of desired fluence patterns. Specifically, models of MAD operation are integrated into a best fit objective followed by CMA-ES optimization. To illustrate this framework we demonstrate the design process for an abdominal phantom with the goal of uniform detected signal. Achievable fluence profiles show good agreement with target fluence profiles, and the ability to flatten projections when a phantom is scanned is demonstrated. Simulated data reconstruction using traditional tube current modulation (TCM) and MAD filtering with TCM are investigated with the dual MAD system demonstrating more uniformity in noise and illustrating the potential for dose reduction under a maximum noise level constraint.

We introduce a novel strategy for fluence field modulation (FFM) in x-ray CT using multiple aperture devices (MADs). MAD filters permit FFM by blocking or transmitting the x-ray beam on a fine (0.1-1 mm) scale. The filters have a number of potential advantages over other beam modulation strategies including the potential for a highly compact design, modest actuation speed and acceleration requirements, and spectrally neutral filtration due to their essentially binary action. In this work, we present the underlying MAD filtration concept including a design process to achieve a specific class of FFM patterns. A set of MAD filters is fabricated using a tungsten laser sintering process and integrated into an x-ray CT test bench. A characterization of the MAD filters is conducted and compared to traditional attenuating bowtie filters and the ability to flatten the fluence profile for a 32 cm acrylic phantom is demonstrated. MAD-filtered tomographic data was acquired on the CT test bench and reconstructed without artifacts associated with the MAD filter. These initial studies suggest that MAD-based FFM is appropriate for integration in clinical CT system to create patient-specific fluence field profile and reduce radiation exposures.

Objective: The objective of our study was to determine how often symptomatic Meckel diverticulum and asymptomatic Meckel diverticulum are detected on CT in patients with known Meckel diverticulum and to evaluate factors that influence detection., Materials and Methods: A total of 85 CT examinations of 40 patients (eight pediatric patients and 32 adult patients; 29 male patients and 11 female patients; average age, 46.2 ± 23.7 [SD] years) with a pathologic diagnosis of Meckel diverticulum were retrospectively evaluated. These patients included 26 adult patients with incidentally found asymptomatic Meckel diverticulum and 14 patients (eight pediatric and six adult patients) with symptomatic Meckel diverticulum. The CT technical factors and patients' morphologic factors were compared with the detection of Meckel diverticulum using mixed-effect logistic regression models., Results: Meckel diverticulum was detected on at least one CT examination in eight of 14 (57.1%) symptomatic patients (two of four patients with bleeding, two of six patients with small-bowel obstruction, two of two patients with acute diverticulitis, one of one patient with incisional hernia, and one of one patient with inverted Meckel diverticulum) and in 13 of 23 (56.5%) total CT examinations. Asymptomatic Meckel diverticulum was detected on at least one CT examination in 11 of 26 (42.3%) patients and in 16 of 62 (25.8%) total CT examinations. The amount of peritoneal fat was related to the detection of Meckel diverticula (p = 0.02). Although not statistically significant, the subjective quality of axial CT (p = 0.05) tended to be related to detection, whereas the use of IV (p = 0.59) or positive oral (p = 0.41) contrast material was unrelated to detection. In the original CT reports, none of the asymptomatic cases of Meckel diverticulum was prospectively detected, whereas Meckel diverticulum was detected or mentioned as a possibility in 64% of the symptomatic cases., Conclusion: In patients with known Meckel diverticulum, CT can detect Meckel diverticulum in up to 47.5% of all patients. Meckel diverticulum is more commonly detected in symptomatic patients than in asymptomatic patients, and detection is related to the amount of peritoneal fat.

Objective: The aim of this study was to evaluate the ability of computed tomography (CT) in differentiating between intrapancreatic accessory spleen (IPAS) from pancreatic neuroendocrine tumor (PanNET)., Methods: Eight IPASs and 12 PanNETs in the pancreatic tail were retrospectively evaluated by 2 radiologists. Readers assigned a diagnosis to each examination and evaluated for the presence or absence of 9 CT findings that may aid in the diagnosis., Results: Reader 1 had a sensitivity of 0.83 and a specificity of 1; reader 2 had a sensitivity of 0.78 and a specificity of 0.86. Three of the 9 CT findings were found to be statistically significant in IPASs: the lesion present along the pancreatic dorsal surface, the lesion demonstrating the same enhancement as the spleen on venous phase, and heterogeneous enhancement during arterial phase., Conclusions: CT can be used to differentiate between IPAS and PanNET with good specificity and sensitivity. The IPAS mirrors the spleen's enhancement and is usually located along the dorsal surface of the pancreas.

Objective: The objective of our study was to determine the prevalence and CT appearance of cystlike changes of pancreatic neuroendocrine tumor (NET), particularly of small (≤ 3 cm) tumors., Materials and Methods: The clinical records, images, and pathologic reports of 74 consecutive patients (average age, 55.5 years) with surgically resected pancreatic NETs who underwent preoperative CT were retrospectively reviewed. The size and location of the pancreatic NETs were recorded. The tumors were classified on the basis of CT appearance as small (≤ 3 cm) or large (> 3 cm) and as solid, partially (≤ 50% or > 50%) cystic, or purely (≈ 100%) cystic. Peripheral contrast enhancement on CT was characterized, and lymph node and liver metastases found by pathologic examination were recorded., Results: A total of 78 pancreatic NETs were reviewed. Five were not visualized on CT, leaving 73 pancreatic NETs in 69 patients (multiple tumors were visualized on CT of three patients) for analysis. The mean size of the 73 tumors was 3.0 ± 2.6 (SD) cm (range, 0.7-13.1 cm); 52 tumors were 3 cm or smaller and 21 tumors were larger than 3 cm. Gross pathologic results confirmed that 13 of the 73 (17.8%) tumors were predominantly (> 50% or ≈ 100%) cystic: 10 of the 52 (19.2%) tumors 3 cm or smaller and three of the 21 (14.3%) tumors larger than 3 cm. Peripheral contrast enhancement was seen in 11 of the 13 (85%) predominantly cystic pancreatic NETs. Compared with solid pancreatic NETs, predominantly cystic pancreatic NETs were less commonly associated with lymph node and liver metastases., Conclusion: Cystic pancreatic NETs are not rare and should be included in the differential diagnosis of a cystic pancreatic mass, particularly if the cystic mass is associated with peripheral contrast enhancement. A minority of cystic pancreatic NETs can present with no peripheral enhancement.

Objective: The criteria for resection of solitary pancreatic side-branch intraductal papillary mucinous neoplasm (IPMN) have been well described by the Sendai consensus statement. However, the management of multiple pancreatic cystic lesions is less certain, with no clear guidelines in the literature to date. The purpose of this study was to evaluate the histopathologic findings in pancreatic IPMNs in patients with multiple (≥ 4) pancreatic cysts., Materials and Methods: The CT scans of all patients with a pathologically proven IPMN at our institution were reviewed, and a total of 52 patients with four or more pancreatic cysts were found. Each case was reviewed for the number of cysts and the presence of signs of invasive malignancy including a coexistent solid pancreatic mass, pancreatic ductal dilatation, and mural nodularity., Results: A total of 52 patients (19 men, 33 women; mean age, 71.8 years) were found to have multifocal IPMNs, defined as four or more cysts, on CT. Of these 52 patients, nine also had evidence of a solid pancreatic mass on CT. Retrospective review of the pathologic results for the remaining 43 patients (17 men, 26 women; mean age, 71.76 years) showed 18 cases of an IPMN with either high-grade dysplasia or a coexistent invasive carcinoma. Most important, 37% (7/19 patients) had no CT findings of an invasive malignancy according to the Sendai criteria (i.e., cysts ≥ 3 cm in the axial plane, main pancreatic ductal dilatation ≥ 6 mm, or mural nodularity within a cyst) but were found to have an IPMN with either high-grade dysplasia or invasive carcinoma. When the pancreas contained 10 or more cysts, high-grade dysplasia or invasive carcinoma tended to be more likely than low- or intermediate-grade dysplasia (odds ratio, 3.83; 95% CI, 0.87-16.8; p = 0.075)., Conclusion: The presence of multiple pancreatic cysts should be looked on with suspicion, particularly when there are a large number of cysts, even when none of the cysts individually meet the imaging criteria for resection according to the Sendai consensus recommendations. At the very least, these patients need to be followed very closely.

Objective: After traumatic splenic injury or splenectomy, small isolated spleens may develop. These implants are not limited to the left upper quadrant, and splenosis in other locations can mimic other pathologic entities. This pictorial essay presents the range of appearances of intraabdominal and pelvic splenosis., Conclusion: Radiologists can suggest or establish the correct diagnosis of splenosis in the appropriate clinical setting, particularly in less typical cases, to avert unnecessary tissue sampling.

Objective: This article reviews the pattern of anastomotic leak after robot-assisted laparoscopic radical prostatectomy (RALRP) on MDCT cystography with multiplanar reformatting and 3D display and discusses key surgical procedures to explain intraperitoneal leak and the incidence and clinical significance of anastomotic leak., Conclusion: RALRP is a minimally invasive surgery for localized prostate cancer, and its use has increased recently. Intraperitoneal extension of vesicourethral anastomotic leak after RALRP can occur, which is not associated with radical retropubic prostatectomy. MDCT cystography is a fast and accurate method for detection and evaluation of the extent of anastomotic leak after RALRP.

Objective: The aim of this in vitro study was to examine the capability of three protocols of dual-energy CT imaging in distinguishing calcium oxalate, calcium phosphate, and uric acid kidney stones., Materials and Methods: A total of 48 calcium oxalate, calcium phosphate, and uric acid human kidney stone samples were placed in individual containers inside a cylindric water phantom and imaged with a dual-energy CT scanner using the following three scanning protocols of different combinations of tube voltage, with and without a tin filter: 80 and 140 kVp without a tin filter, 100 and 140 kVp with a tin filter, and 80 and 140 kVp with a tin filter. The mean attenuation value (in Hounsfield units) of each stone was recorded in both low- and high-energy CT images in each protocol. The dual-energy ratio of the mean attenuation values of each stone was computed for each protocol., Results: For all three protocols, the uric acid stones were significantly different (p < 0.001) from the calciferous stones according to their dual-energy ratio values. For differentiating calcium oxalate and calcium phosphate stones, the difference between their dual-energy ratio values was statistically significant, with different degrees of significance (range, p < 0.001 to p = 0.03) for all three protocols. On the basis of the values of the area under receiver operating characteristic curve (AUC) of calcified stone differentiation, the three protocols were ranked in the following order: the 80- and 140-kVp tin filter protocol (AUC, 0.996), the 100- and 140-kVp tin filter protocol (AUC, 0.918), and the 80- and 140-kVp protocol (AUC, 0.871)., Conclusion: The tin filter added to the high-energy tube and the use of a wider dual-energy difference are important for improving the stone differentiation capability of dual-energy CT imaging.

Objective: Pancreatic neuroendocrine tumors expressing serotonin (carcinoid tumors) account for a small portion of pancreatic neuroendocrine tumors. The purpose of this study was to describe cases of small serotonin-producing pancreatic neuroendocrine tumors associated with pancreatic duct obstruction., Conclusion: Serotonin produced by pancreatic neuroendocrine tumors can induce fibrosis and pancreatic duct obstruction. Pancreatic neuroendocrine tumors should be considered when CT shows a small hypervascular mass associated with upstream pancreatic duct dilatation or atrophy. Evidence of small pancreatic neuroendocrine tumors should be sought in cases of idiopathic pancreatic duct stenosis.

Objective: The purpose of this article is to discuss and illustrate the MDCT findings of potential complications after cystectomy and urinary diversion., Conclusion: Multiple complications may occur after urinary diversion. Tumor recurrence is a major concern in patients with bladder cancer. CT has an important role in postoperative evaluation of patients with urinary diversion to identify correctable causes early to prevent deterioration in renal function and detect tumor recurrence in patients who had bladder cancer.

Objective: The purpose of this study was to evaluate interpretative performance with different MDCT reconstruction parameters in adult patients with suspected appendicitis., Materials and Methods: MDCT scans of 212 adult patients obtained in an emergency department with a 64-MDCT scanner were prospectively collected. Acquisition technique included 24 x 1.2 mm detector configuration and IV contrast administration with or without oral contrast administration. Data sets were reconstructed with three techniques: 5 x 5 mm, 3 x 3 mm, and 2 x 1 mm (section thickness x interval). Each of the 212 sets of images (grouped by reconstruction technique) was reviewed retrospectively using axial sections by two independent readers blinded to diagnosis. Medical record review was conducted to identify patients with appendicitis. Visualization of the appendix, confidence in visualization, confidence for presence or absence of specific CT findings, diagnostic accuracy, and diagnostic confidence were compared across reconstruction techniques. Data were analyzed with simple and ordinal logistic regression with adjustment for multiple observations derived from each patient and for reader differences., Results: Progressively thinner reconstruction section thickness was associated with a significant increase in the rate of visualization of the appendix (p < 0.001 for 5 x 5 vs 3 x 3; p = 0.03 for 3 x 3 vs 2 x 1), visualization confidence (p < 0.001 for 5 x 5 vs 3 x 3 and 3 x 3 vs 2 x 1), and confidence for presence or absence of findings. Seventeen subjects (8%) had appendicitis. Correctness of diagnosis was not significantly associated with reconstruction method. However, for correctly diagnosed cases interpreted as normal, impression confidence increased with progressively thinner section thickness (p < 0.001 for 5 x 5 vs 3 x 3 and 3 x 3 vs 2 x 1)., Conclusion: In this investigation of contrast-enhanced MDCT of the appendix, visual ization of the appendix and confidence in interpretation of axial images progressively improved with use of thinner reconstruction sections.

Objective: Current generation MDCT technology facilitates identification of small, nonenhancing lesions in the pancreas. The objective of this study was to determine the prevalence of findings of unsuspected pancreatic cysts on 16-MDCT in a population of adult outpatients imaged for disease unrelated to the pancreas., Materials and Methods: Contrast-enhanced MDCT scans of the abdomen were reviewed from 2,832 consecutive examinations to identify pancreatic cysts. Patients with a history of pancreatic lesions or predisposing factors for pancreatic disease or who were referred for pancreatic CT were excluded., Results: A total of 73 patients had pancreatic cysts, representing a prevalence of 2.6 per 100 patients (95% CI, 2.0-3.2). Cysts ranged in size from 2 to 38 mm (mean, 8.9 mm) and were solitary in 85% of cases. Analysis of demographic information showed a strong correlation between pancreatic cysts and age, with no cysts identified among patients under 40 years and a prevalence of 8.7 per 100 (95% CI, 4.6-12.9) in individuals from 80 to 89 years. After controlling for age, cysts were more common in individuals of the Asian race than all other race categories, with an odds ratio of 3.57 (95% CI, 1.05-12.13). There was no difference by sex in the prevalence of cysts (p = 0.527); however, cysts were on average 3.6 mm larger (p = 0.014) in men than women., Conclusion: In this outpatient population, the prevalence of unsuspected pancreatic cysts identified on 16-MDCT was 2.6%. Cyst presence strongly correlated with increasing age and the Asian race.

Objective: MDCT has become a valuable tool with high sensitivity for detecting transitional cell carcinoma of the upper urinary tract., Conclusion: In this article, we discuss and illustrate the spectrum of the appearances of transitional cell neoplasm of the upper urinary tract on 16- and 64-MDCT with multiplanar reformation and 3D imaging.

Objective: The purpose of our study was to evaluate factors predictive of the presence of invasive carcinoma associated with intraductal papillary mucinous neoplasm (IPMN) of the pancreas on MDCT., Materials and Methods: Preoperative MDCT of 36 consecutive patients (23 men, 13 women; mean age, 66.6 years) who had undergone surgical resection and had a pathologic diagnosis of IPMN were retrospectively assessed. CT was performed with a 4-MDCT scanner with 120 mL of IV contrast material at an injection rate of 3 mL/sec. Arterial and venous phase images were acquired at 25 and 50-60 sec from the start of IV contrast administration. Type of ductal involvement, location, tumor size in branch duct type and combined type lesions, caliber of the main pancreatic duct, caliber of the common bile duct or common hepatic duct, and solid appearance of the lesion were assessed on CT and correlated with pathologic findings for invasive carcinoma., Results: Pathologic analysis revealed carcinoma in situ in seven patients (19%) and invasive carcinoma in 15 patients (42%) arising from the IPMN. With invasive carcinoma, the size of the tumor in branch duct type and combined type, and the caliber of the main pancreatic duct were significantly larger compared with the lesions without invasive carcinoma (4.7 +/- 1.7 cm vs 2.6 +/- 1.4 cm [p = 0.0007] and 9.3 +/- 5.5 mm vs 4.6 +/- 4.1 mm [p = 0.006], respectively). A solid mass (p < 0.001), dilatation of the common bile duct or common hepatic duct (> or = 15 mm), and the presence of a stent (p = 0.0004) were correlated with the presence of associated invasive carcinoma., Conclusion: MDCT helped to predict invasive carcinoma associated with IPMN.

Objective: The objectives of our study were to define CT and MRI features that distinguish pathologic fractures from stress fractures and to compare the performance of CT and MRI with radiography., Materials and Methods: Two reviewers retrospectively reviewed 45 MR images, 37 CT scans, and 43 radiographs in 59 patients (30 biopsy-proven pathologic fractures and 29 stress fractures followed to resolution). The features observed on MRI were abnormal bone marrow (well-defined, ill-defined); intracortical, periosteal, or muscle T1 or T2 signal; endosteal scalloping; and a soft-tissue mass. The features seen on CT were marrow abnormality and character (well-defined, ill-defined, permeative, moth-eaten), endosteal scalloping, periosteal reaction (benign, aggressive), and a soft-tissue mass. Reviewers rated their confidence for diagnosing a pathologic fracture on a 1-3 scale (< 50%, 50-95%, > 95% sure, respectively) with each technique. Performance of each technique was defined by reviewer accuracy and area under the receiver operating characteristic curve (Az); the frequency with which the MRI and CT features were associated with pathologic and stress fractures was calculated., Results: For both reviewers, accuracy for differentiating pathologic from stress fractures was highest on MRI (accuracy/Az: reviewer 1, 98%/0.97; reviewer 2, 93%/0.99); CT (reviewer 1, 88%/0.83; reviewer 2, 82%/0.90) was less accurate than radiography (reviewer 1, 94%/0.98; reviewer 2, 88%/0.96). On MRI, pathologic fractures compared with stress fractures exhibited well-defined T1 marrow signal (83% vs 7%, respectively; p < 0.001), endosteal scalloping (58% vs 0%, p < 0.001), muscle signal (83% vs 48%, p = 0.026), and a soft-tissue mass (67% vs 0%, p < 0.001). On CT, pathologic fractures compared with stress fractures exhibited marrow abnormality (84% vs 17%, respectively; p = 0.001), endosteal scalloping (44% vs 0%, p = 0.006), and aggressive periosteal reaction (36% vs 0%, p = 0.04)., Conclusion: MRI is useful for distinguishing pathologic from stress fractures, especially after inconclusive radiographic findings. Specifically, pathologic fractures exhibit well-defined T1 marrow alterations, endosteal scalloping, and adjacent soft-tissue abnormalities.

Whereas stress fractures occur in normal or metabolically weakened bones, pathologic fractures occur at the site of a bone tumor. Unfortunately, stress fractures may share imaging features with pathologic fractures on plain radiography, and therefore other modalities are commonly utilized to distinguish these entities. Additional cross-sectional imaging with CT or MRI as well as scintigraphy and PET scanning is often performed for further evaluation. For the detailed assessment of a fracture site, CT offers a high-resolution view of the bone cortex and periosteum which aids the diagnosis of a pathologic fracture. The character of underlying bone marrow patterns of destruction can also be ascertained along with evidence of a soft tissue mass. MRI, however, is a more sensitive technique for the detection of underlying bone marrow lesions at a fracture site. In addition, the surrounding soft tissues, including possible involvement of adjacent muscle, can be well evaluated with MRI. While bone scintigraphy and FDG-PET are not specific, they offer a whole-body screen for metastases in the case of a suspected malignant pathologic fracture. In this review, we present select examples of fractures that underscore imaging features that help distinguish stress fractures from pathologic fractures, since accurate differentiation of these entities is paramount.

Objective: The objective of our study was to assess whether both renal arteries and renal veins can be evaluated using single-phase MDCT data sets alone to eliminate the need for both arterial and venous phase data sets., Materials and Methods: One hundred consecutive potential living renal donors who underwent 4-MDCT were evaluated. CT was performed with 120 mL of IV contrast material at an injection rate of 3 mL/sec. Both late arterial and venous phase acquisitions were obtained at 25 and 55 sec from the start of IV contrast injection, respectively. The number of the right and left renal veins and its anatomic variations were assessed by two reviewers. Late arterial phase images were evaluated initially, and then venous phase images were analyzed to assess opacification of the renal vein and to see whether venous phase data sets changed or added information about the venous anatomy as seen on late arterial phase images., Results: The retroaortic left renal vein was found in two subjects, and the circumaortic left renal vein was detected in three subjects. The renal veins were adequately opacified on late arterial phase images in all subjects. There were six subjects who had a normal left renal vein with a small posterior branch coursing posterior to the aorta and draining into the inferior vena cava, which were difficult to differentiate from the lumbar vein or ascending lumbar vein; in three of these six subjects, the small posterior branch was opacified only on venous phase images., Conclusion: Late arterial phase images obtained at 25 sec after the start of contrast injection can reveal the renal vein anatomy except for a small posterior branch of the left renal vein difficult to differentiate from the lumbar or ascending lumbar vein, as seen in three subjects. The data suggest that venous phase imaging is not necessary for the evaluation of renal vein anatomy.

Objective: The clinical presentation of lymphoplasmacytic sclerosing pancreatitis (LPSP) can be very similar to that of pancreatic cancer, with no statistically significant differences in the rates of abdominal pain, weight loss, jaundice, or levels of carcinoembryonic agent or cancer antigen 19-9. The purpose of this study is to describe and illustrate the CT features of LPSP presenting with obstructive jaundice and to correlate CT and pathology findings., Materials and Methods: Five patients with LPSP were evaluated. Morphologic features of the pancreas on CT scans, including the size of the pancreas, presence or absence of a mass, segmental difference of contrast enhancement, pancreatic duct, major pancreatic vasculature, and biliary tract, were retrospectively evaluated and correlated with histopathology. The degree of contrast enhancement of the pancreas was compared in 10 patients without LPSP, who were scanned with the same protocol., Results: CT scans showed diffuse (n = 2) or focal (n = 3) enlargement of the pancreatic head. The normal lobular appearance of the pancreas was effaced, and the gland appeared featureless in the involved region. Enlarged areas showed an enhancement pattern similar to that of the rest of the pancreas, and no segmental difference of contrast enhancement was identified. Pancreatic duct dilatation was not seen in any patient. Thickening and contrast enhancement of the common bile duct wall (n = 4) and gallbladder wall (n = 3) were observed and were pathologically correlated with inflammatory infiltrate and fibrosis of the common bile duct (n = 3) and gallbladder (n = 1)., Conclusion: When these findings are encountered, further evaluation with serologic tests or biopsy may aid in the diagnosis of LPSP.

Excretory phase computed tomography (CT) urography obtained with a 16-slice multidetector CT scanner using thin-section images (slice thickness = 0.75 mm, reconstruction increment = 0.5 mm) combined with interactive reformatted and 3-dimensional reconstruction techniques, high spatial resolution images of the urinary tract similar to those of classic intravenous urography can be produced. The purpose of this pictorial essay is to review the early experience of the authors and to show the wide range of abnormalities of the urinary tract detected with this technique.

Purpose: To choose an efficacious renal functional MRI contrast agent to image early renal tubular damage. We synthesized and compared smaller polyamine dendrimer-based MRI contrast agents (<60 kD) that, unlike Gd-[DTPA], transiently accumulate in renal tubules and can be used to visualize renal structural and functional damage., Materials and Methods: Six dendrimer-based MRI contrast agents smaller than 60 kD were studied by high resolution dynamic micro-MRI and compared to Gd-[DTPA]-dimeglumine and Gadomer-17. The best agent, DAB-G2, was further tested in a mouse ischemia/reperfusion model to validate its efficacy., Results: Despite unequal renal clearance rates, all polyamine dendrimer agents visualized the renal functional anatomy of the mice better than Gd-[DTPA]-dimeglumine and Gadomer-17. DAB-G2 was excreted most rapidly, yet was able to visualize mild renal tubular injury very early after injury., Conclusion: DAB-G2 was found to be the best candidate for functional kidney imaging and enabled early diagnosis of acute renal injury.

Background: The presence of lymph node metastases is an important factor in breast cancer patient prognosis. Therefore, the precise identification of sentinel lymph nodes in these patients is critical. Improving current magnetic resonance (MR) imaging methods using a newly synthesized nano-size paramagnetic molecule, G6, as a contrast agent, provides an attractive means toward attaining this goal., Methods: A four-dimensional method of micro-MR lymphangiography using G6 (9 nm/240 kd) was developed to visualize the lymphatic ducts and lymph nodes draining mouse mammary tumors over time. The ability of micro-MR lymphangiography with the G6 contrast agent to visualize lymphatic drainage of normal mouse mammary tissue was compared with that of the conventional MR contrast agent, Gd-[DTPA]-dimeglumine (<1 kd). Lymphatic drainage in spontaneous and xenografted breast tumor models was visualized using the G6 contrast agent., Results: Draining lymphatic ducts and lymph nodes were clearly visualized in the mammary tissue of normal mice and in spontaneous and xenografted breast tumor models after a direct mammary gland or peritumoral injection of G6. Gd-[DTPA]-dime-glumine, by contrast, failed to depict lymphatic flow from the mammary tissue in normal mice using the same method. Micro-MR lymphangiography using the G6 contrast agent revealed the absence of filling in the metastatic foci of affected lymph nodes., Conclusions: The superior temporal and spatial resolution of micro-MR lymphangiography using the contrast agent G6 may facilitate the study of tumor lymphatic drainage and lymphatic metastasis in both experimental animals and clinical medicine. In addition, this may be a powerful new method for sentinel lymph node localization in human breast cancer.

Background: Mouse models of disease, especially using transgenic and knockout technologies, are powerful tools to analyze the molecular basis of disease. We recently reported that a new dynamic micro-MRI method with dendrimer-based contrast agents can visualize renal structure and function in normal living mice and mice with acute renal failure. While MRI contrast enhancement is useful for detecting functional impairment of the kidneys, this technology has limitations in assessing morphologic changes, particularly cystic disease, because contrast-enhanced micro-MRI depicts cysts as low-intensity areas that cannot be distinguished from fibrotic foci., Methods: In the current study, we evaluated if micro-MRI employing a new three-dimensional MR hydrography signal sequence [three-dimensional fast imaging employing steady-state acquisition (3D-FIESTA)] can visualize chronic cystic changes without any contrast agents., Results: We were able to positively depict multiple renal cortical cysts of approximately 0.2 mm diameter in a mouse model of sickle cell disease and observe serial changes of renal cysts (>0.2 mm diameter) in cyclooxygenase-2 (COX-2) knockout mice during a 21/2-month period. Some cysts decreased in size over time., Conclusions: Micro-MRI with 3D-FIESTA can depict cyst formation in the diseased kidneys of living mice without injection of contrast agents.

Since its introduction in 1995, laparoscopic nephrectomy has become the preferred technique at many medical centers for the harvesting of kidneys from living donors for transplantation. Because the field of view at laparoscopic surgery is limited, preoperative radiologic evaluation of the donor's anatomy---the renal veins and arteries, collecting system, and parenchyma--is critical. Spiral computed tomographic (CT) angiography is a fast, safe, minimally invasive, and generally accepted method for preoperative evaluation of the renal vessels. Multi-detector row CT scanners offer shorter image acquisition time, narrower collimation, better spatial resolution, and less tube heating than do single-detector row CT scanners. Multi-row scanners also provide more complete anatomic coverage, increased contrast enhancement of the arteries, and greater longitudinal spatial resolution--all of which are important both for accurate imaging of the renal vasculature and for three-dimensional postprocessing of image data. Dual-phase multi-detector row CT angiography combined with three-dimensional postprocessing enables minimally invasive and highly accurate depiction of the preoperative donor anatomy. To make the most effective use of this method, radiologists must be familiar with its technical aspects, advantages, and potential pitfalls. They also must be able to identify variations in vasculature and in renal and extrarenal anatomy that are important for laparoscopic donor nephrectomy., (Copyright RSNA, 2004)

Few methods are currently available to visualize the entire lymphatic system. A method known as micro-magnetic resonance lymphangiography (MRL), which employs a dendrimer-based MRI contrast agent (PAMAM-G8) and a clinical-grade 1.5T MRI instrument, was recently developed for use in mice. In the present study, three dendrimer-based MRI contrast agents (PAMAM-G8, DAB-G5, and PAMAM-G4) with different pharmacokinetic characteristics were compared to determine the best reagent to visualize the lymphatic system under physiological or pathological conditions. In addition, two established MRI contrast agents (Gadomer-17 and Gd-[DTPA]-dimeglumine (Magnevist)) were used as control agents. In experiments with mice, most of the deep lymphatic system was visualized by micro-MRL with all agents except Gd-[DTPA]-dimeglumine. PAMAM-G8 was best for visualizing lymphatic vessels, whereas DAB-G5 was better for visualizing lymph nodes. PAMAM-G4 was intermediate in character between PAMAM-G8 and DAB-G5, except in exhibiting a low background signal (especially in the liver). The lymphatic system was not clearly visualized with Gd-[DTPA]-dimeglumine; however, the lymph nodes were visualized with Gadomer-17, although not as well as with dendrimer-based agents. In conclusion, DAB-G5 and PAMAM-G4 can be used to identify lymph nodes and lymphatic vessels, respectively. Their rapid excretion makes these compounds potentially attractive for human use.

The enhancement characteristics of a contrast agent are dependent on its pharmacokinetics within the body. In the case of macromolecular contrast agents, prolonged enhancement of the blood pool is seen after the first dose, limiting opportunities for repeated injection in the same session. If the enhancement within the blood pool could be intentionally switched off, the macromolecular contrast agents could be used both to define blood volume and vessel permeability, properties that could be useful in studying angiogenesis. In the current study, the avidin-biotin system was coupled to a dendrimer-based macromolecular MRI contrast agent to switch enhancement from the blood pool to the liver. Because avidin causes rapid trapping of the contrast agent in the liver, the blood pool cleared within 2 min of the injection of avidin. This system can be applied to all dendrimer-based macromolecular MRI contrast agents to investigate blood volume and vascular permeability. Moreover, it permits the repeated injection of the contrast agent and the "avidin switch" during a single MR experiment.

Objective: The purpose of this study was to determine the accuracy of multidetector CT (MDCT) angiography as the primary imaging technique in the evaluation of living kidney donors., Subjects and Methods: Seventy-four consecutive living kidney donors (30 men, 44 women; mean age, 41.7 years) who underwent MDCT were evaluated. CT examination was performed with 120 mL of IV contrast material at an injection rate of 3 mL/sec and a pitch of 6. In every case, arterial and venous phase volumetric data sets were acquired at 25 and 55 sec, respectively. Scans were reconstructed at 1-mm intervals for three-dimensional (3D) imaging using a volume-rendering technique. Axial CT images and 3D CT angiography were evaluated prospectively by one reviewer and retrospectively by two reviewers who had no knowledge of surgical results. Surgical correlation for the location of primary and accessory renal arteries, early branching of the renal arteries, and renal vein anomalies was made., Results: Seventy-two subjects underwent left nephrectomy, and two subjects underwent right nephrectomy because supernumerary left renal arteries were detected on preoperative CT angiography. Eighteen supernumerary renal arteries (two arteries to 16 kidneys and three arteries to one kidney) to 74 kidneys underwent nephrectomy. CT and surgical findings agreed in 93% of subjects (the average of three reviewers; range, 89-97%). Two small accessory renal arteries were missed by all three reviewers. Those arteries were diminutive and were thought to be insignificant by the surgeons. Early branching of the renal arteries was shown in 14 arteries, and CT and surgical findings agreed in 96% (the average of three reviewers; range, 93-97%). Renal vein anomalies were present in eight subjects, and CT and surgical findings agreed in 99% of the cases (range, 96-100%)., Conclusion: MDCT angiography is highly accurate for detecting vascular anomalies and providing anatomic information for laparoscopic living donor nephrectomy.

Large macromolecular MRI contrast agents with albumin or dendrimer cores are useful for imaging blood vessels. However, their prolonged retention is a major limitation for clinical use. Although smaller dendrimer-based MRI contrast agents are more quickly excreted by the kidneys, they are also able to visualize vascular structures better than Gd-DTPA due to less extravasation. Additionally, unlike Gd-DTPA, they transiently accumulate in renal tubules and thus also can be used to visualize renal structural and functional damage. However, these dendrimer agents are retained in the body for a prolonged time. The purpose of this study was to obtain information from which a macromolecular dendrimer-based MRI contrast agents feasible for use in further clinical studies could be chosen. Six small dendrimer-based MRI contrast agents were synthesized, and their pharmacokinetics, whole-body retention, and dynamic MRI were evaluated in mice to determine an optimal agent in comparison to Gd-[DTPA]-dimeglumine. Diaminobutane (DAB) dendrimer-based agents cleared more rapidly from the body than polyamidoamine (PAMAM) dendrimer-based agents with the same numbers of branches. Smaller dendrimer conjugates were more rapidly excreted from the body than the larger dendrimer conjugates. Since PAMAM-G2, DAB-G3, and DAB-G2 dendrimer-based contrast agents showed relatively rapid excretion, these three conjugates might be acceptable for use in further clinical applications.

Major advances in cancer biology and immunology have been gained using mouse models. However, very few methods are currently available to visualize the deep lymphatic system. A new micro-magnetic resonance lymphangiography (MRL) method in mice, which uses dendrimer-based magnetic resonance imaging contrast agents, was developed. Micro-MRL imaging clearly visualized most of the mouse lymphatic system, including both lymphatics and lymph nodes. This method could detect and distinguish among dilation of lymphatic vessels in a lymphangitis model, proliferative or neoplastic lymph node swellings in a lymphoproliferative model, and inflammatory lymph node swellings in an infection/inflammation model. Changes in the lymphoid system of transgenic mice overexpressing interleukin-15 could be visualized. Abnormal enlarged lymph nodes identified by micro-MRL were selectively removed and analyzed to demonstrate their cell type, receptor expression, and clonality in individual mice. We conclude that the enhanced resolution of this noninvasive micro-MRL can detect and classify lymphatic and lymph node abnormalities in mice, which should have wide applicability to the study of immunology and cancer in both experimental animals and clinical medicine.

Background: A noninvasive technique to evaluate the structure and function of the kidney would be useful to investigate renal diseases, especially acute renal failure. We have developed a novel technique to visualize functional micro-magnetic resonance (MR) images of the mouse kidney with a dendrimer-based macromolecular renal MR contrast agent., Method: Mice were injected with cisplatin or vehicle, then examined three days later by contrast-enhanced, dynamic high-resolution micro-MRI with 160 microm spatial resolution using a 1.5 T clinical MRI unit, a surface coil, and the renal contrast agent G4D-(1B4M-Gd)64., Results: The cortex and outer stripe of the outer medulla of the mouse kidney were clearly visualized in the normal mice. In animals treated with cisplatin, the gradation of tubular damage as assessed by contrast enhanced dynamic MRI correlated with renal function., Conclusion: Contrast-enhanced, dynamic high-resolution micro-MRI with a novel dendrimer-based macromolecular renal MR contrast agent can be a powerful tool for in vivo observation of renal structural and functional damage.

The rapid blood flow and perfusion of macromolecules in the inflammatory breast cancer xenograft (WIBC-9), which exhibits a "vasculogenic mimicry" type of angiogenesis without the participation of endothelial cells and expresses high levels of the HER-2/neu antigen, was evaluated in mice using 3D-micro-MR angiography using a novel macromolecular MR contrast agent [G6-(1B4M-Gd)(256)]. Herceptin, which recognizes the HER-2/neu antigen and has similar size (10 nm) to G6-(1B4M-Gd)(256), accumulated and internalized in the WIBC-9 tumors more quickly than in the control MC-5 tumors that progress with normal angiogenesis. Three dimensional micro-MRI with the G6-(1B4M-Gd)(256) macromolecular MRI contrast agent distinguishes between the different types of angiogenesis and is predictive of the rapid accumulation and internalization of Herceptin in the WIBC-9 inflammatory breast cancer xenograft.

In the present study, we examined hemodynamics in vasculogenic mimicry (VM) and angiogenesis of inflammatory breast cancer (IBC) xenografts (WIBC-9), having previously reported on the unique histological features and molecular basis of these processes (K. Shirakawa et al., Cancer Res., 61: 445-451, 2001). Histologically, the WIBC-9 xenografts exhibited invasive ductal carcinoma with a hypervascular structure (angiogenesis) in the tumor margin and VM without endothelial cells, central necrosis, or fibrosis in the tumor center. Results of molecular analysis indicated that WIBC-9 had a vasculogenic phenotype, including expression of Flt-1 and Tie-2. Comparison of WIBC-9 with an established non-IBC xenograft (MC-5), using time-coursed dynamic micromagnetic resonance angiography analysis (with our newly developed intravascular macromolecular magnetic resonance imaging contrast agent), electromicroscopy, and immunohistochemistry, demonstrated blood flow and a VM-angiogenesis junction in the central area of the WIBC-9 tumor. It has previously been considered impossible to prove a connection between VM and angiogenesis using angiography, because there are no intravascular macromolecular magnetic resonance imaging contrast agents that do not exhibit significant leakage through the vascular wall. In the present study, laser-captured microdissection was performed in regions of WIBC-9 tumors that exhibited VM without endothelial cells, central necrosis, or fibrosis, revealing expression of human-Flt-1 and human-Tie2 and the absence of human-CD31, human-endothelin B receptor, and human-thrombin receptor. These facts led us to hypothesize that the VM of WIBC-9 involves hemodynamics that serve to feed WIBC-9 cells, and this in turn suggests a connection between VM and angiogenesis.