Helical computed tomography of the pancreas: potential impact of higher concentrated contrast agents and multidetector technology.

The introduction of multidetector helical computed tomography (CT) has revolutionized the field of pancreatic imaging and has created a new dimension of temporal and spatial resolution. The speed of multidetector CT can either be used to reduce the time needed to cover a given volume or to increase the resolution along the z-axis, thereby resulting in nearly isotropic voxels. Pancreatic perfusion phases can thus be more clearly differentiated and small structures are better delineated, leading to an improvement in the diagnostic value of pancreatic CT. Contrast media with a higher iodine concentration seem to be superior to lower concentrated contrast agents, mainly because of the better evaluability of the vessels in the arterial examination phase. This manuscript reports current CT imaging strategies for patients with pancreatic cancer with emphasis on vascular invasion, lymph node metastasis, liver metastasis, and peritoneal carcinomatosis.

Multislice helical CT of the pancreas and spleen.

Multislice helical CT (MSCT) with its multidetector technology and faster rotation times, has led to new dimensions in spatial and temporal resolution in CT imaging. In contrast to single-slice CT, smaller slice collimations can be applied that lead to almost isotropic voxels and allow high quality multiplanar and 3-D image reconstructions. The high speed of multislice CT can be used to reduce the time needed to cover a given volume, to increase the spatial resolution along the z-axis by applying thinner slice collimations, and to cover longer anatomic volumes. The speed of MSCT allows organ imaging in clearly defined perfusion phases, e.g. the arterial, parenchymal, and portal venous perfusion phases. Contrast agents with higher iodine concentrations (400 mg iodine per ml compared with 300 mg iodine per ml) lead to higher contrast enhancement of the pancreas (arterial+portal venous phases), the kidneys (arterial+portal venous phases), the spleen (arterial phase), the wall of the small intestine (arterial+portal venous phases), the larger and smaller arteries (arterial phase), and the portal vein (portal venous phase). All of these advancements lead to improved visualization of small structures and of various pathologies, such as pancreatic tumors, liver metastases, vessel infiltration, and vascular diseases.

Intraoperative MR imaging.

Intraoperative MR imaging has become a safe and effective technology that has revolutionized the way neurosurgery is performed. Benefits include the ability to update data sets for navigational systems, to monitor tumor resections, to adjust the approach to intracranial lesions, and to guide functional and drug or cell delivery procedures. Use of this technique can help avoid inadvertent injury of important anatomic and vascular structures. In addition, complications such as ischemia or hemorrhage can be detected early. Intraoperative MR imaging is particularly useful for ensuring that brain biopsies yield diagnostic tissue and for assessing the completeness of tumor resection. As is true for any new technology, the benefits of intraoperative MR imaging must be examined carefully to guarantee appropriate use. Many neurosurgical procedures do not require real-time image guidance and can be performed safely using current surgical techniques, including microsurgical methods and frameless and frame-based stereotaxy. Other tumor resections, tumor biopsies, and surgical and interventional procedures distinctly benefit from the sophisticated information provided by intraoperative imaging techniques. In surgery for low-grade gliomas, intraoperative MR imaging has found general acceptance, whereas its usefulness to monitor the resection of high-grade gliomas remains controversial. The economic issues related to intraoperative MR imaging cannot be overlooked. The acquisition of an intraoperative MR imaging system is associated with considerable expense, and its performance increases the cost of equipment and the operating time. Despite these additional expenses, intraoperative MR imaging can lead to a potential overall cost reduction in the treatment of certain patients if long-term cure can be achieved, repeat resection can be avoided, or procedure-associated morbidity can be reduced. Although intraoperative MR imaging techniques hold tremendous potential, the definition of their appropriate role in the delivery of successful and cost-effective medical care awaits further study.

Contrast-enhanced 3D MRA of the aortoiliac and infrainguinal arteries when conventional transfemoral arteriography is not feasible.

PURPOSE: To evaluate whether contrast-enhanced 3-dimensional (3D) magnetic resonance angiography (MRA) can substitute for transaxillary or transbrachial catheter access when angiography via the transfemoral route is not possible. METHODS: Contrast-enhanced 3D MRA was performed in 14 patients (12 men; mean 66.1 +/- 12.4 years, range 48-98) with atherosclerotic disease of the aorta or lower extremities in whom conventional transfemoral arteriography was not feasible. The images were evaluated for their ability to identify and characterize lesions directly responsible for the patient's symptoms, adequately depict the vascular anatomy for therapy planning, and identify additional lesions not directly responsible for the patient's symptoms. The arterial system was divided into 15 segments, and image quality and the presence of occlusive disease were determined. RESULTS: MRA adequately depicted 387 (95%) of 406 arterial segments in 14 patients. Nineteen (5%) arterial segments were inadequately delineated because of low signal intensity distal from severe stenoses (n = 11), venous overlap (n = 6), or metallic clip-induced signal voids (n = 2). The lesions directly responsible for the patients' symptoms were identified in all 14 patients (2 aortic occlusions [Leriche's syndrome] and 12 iliac occlusions or severe stenoses). Visualization of the vascular anatomy was adequate for therapy planning in 13 of 14 patients, and 3D MRA satisfactorily identified other lesions not directly responsible for the current symptoms. CONCLUSIONS: When transfemoral catheter angiography of the aortoiliac and lower extremities is not feasible, contrast-enhanced 3D MRA is suitable for determining and planning therapy and can be used instead of angiography via the transaxillary or transbrachial routes.

Asymptomatic adnexal masses: correlation of FDG PET and histopathologic findings.

PURPOSE: To analyze asymptomatic adnexal masses at positron emission tomography (PET) with fluorodeoxyglucose (FDG) in correlation with histopathologic findings and evaluate FDG PET for assessing malignancy in comparison with transvaginal B-mode and Doppler ultrasonography (US) and magnetic resonance (MR) imaging. MATERIALS AND METHODS: Ninety-nine patients underwent static FDG PET of the abdomen. US scans were evaluated according to sonomorphologic scoring systems. Resistance index of tumor blood vessels was calculated. Transverse and sagittal T1-weighted MR images obtained before and after intravenous administration of gadopentetate dimeglumine with a fat-saturation technique and T2-weighted MR images were acquired at 1.5 T. Adnexal mass malignancy was first assessed with each modality and then with a combination of the three techniques. Final diagnosis was made with histopathologic evaluation. RESULTS: FDG PET depicted seven of 12 malignant and 66 of 87 benign asymptomatic adnexal tumors. False-negative PET results were obtained in five of seven stage pT1a cystadenocarcinomas and tumors of low malignant potential but not in advanced-stage ovarian carcinomas. Small moderately intense FDG accumulations in the lower pelvis were caused by benign adnexal tumors or gastrointestinal activity in 21 of 27 cases. The overall sensitivities and specificities were 58% (95% CI: 27.7, 84.8) and 76% (95% CI: 65.5, 84.4), respectively, for FDG PET; 92% (95% CI: 61.5, 99.8) and 60% (95% CI: 48.7, 70.1), respectively, for US; 83% (95% CI: 51.6, 97.7) and 84% (95% CI: 74.5, 90.9), respectively, for MR imaging; and 92% (95% CI: 61.5, 99.8) and 85% (95% CI: 75.8, 91.8), respectively, for the combination of three modalities. CONCLUSION: Since the sensitivity of US is as high as that of PET, MR imaging, and the combination of three modalities, it remains the method of choice for diagnosis and assessment of asymptomatic adnexal masses.