Nikolaos L. Kelekis

Cholangiocarcinoma: Spectrum of appearances on mr images using current techniques

This study describes the spectrum of appearances of cholangiocarcinoma on magnetic resonance (MR) sequences, including gadolinium-enhanced, fat-suppressed spoiled gradient echo images and MR cholangiography. Fifteen patients were included in the study. Histologic diagnosis was established in 11 patients by surgical resection (6 patients), percutaneous biopsy (4 patients), and open liver biopsy (1 patient). The final diagnosis was determined by correlation of the MR findings with cholangiographic studies and laboratory studies in 4 patients. MR studies were performed at 1.5 T, and the following sequences were obtained: T1-weighted spoiled gradient echo (SGE), T1-weighted fat-suppressed spin echo or SGE, T2-weighted fat-suppressed conventional or turbo spin echo, MR cholangiography, and gadolinium-enhanced T1-weighted fat-suppressed SGE images. The following determinations were made: tumor location, tumor extent, ductal dilatation, ductal wall thickness, signal intensity, enhancement pattern, and associated findings. Mass-like neoplasms were peripheral (6 patients), hilar (1 patient), and extrahepatic (2 patients). Circumferential tumors were hilar (2 patients) and extrahepatic (4 patients). All peripheral tumors were multifocal. Mass-like tumors were well-defined, rounded, and ranged from 1 to 14 cm in diameter. Circumferential tumors had less well-defined margins and measured from 3 to 15 mm in thickness. All mass-like tumors were moderately hypointense on T1-weighted images and mildly to moderately hyperintense on T2-weighted images. The circumferential tumors were iso- to moderately hypointense on T1-weighted images and iso- to mildly hyperintense on T2-weighted images. Mass-like tumors were generally well shown on non-contrast and immediate gadolinium-enhanced images, whereas circumferential tumors were poorly seen on non-contrast images and best shown on gadolinium-enhanced T1-weighted fat-suppressed images. The degree of enhancement ranged from minimal to intense on immediate gadolinium-enhanced images, with all tumors becoming more homogeneous in signal intensity on images obtained between 1 and 5 min following contrast administration. Tumor-containing lymph nodes greater than or equal to 1 cm in diameter were demonstrated in 11 out of 15 patients (73.3%). These were best shown on T2-weighted fat-suppressed images and gadolinium-enhanced fat-suppressed SGE images. MR cholangiography demonstrated the level of obstruction and degree of dilatation of the proximal biliary system in 5 out of 6 patients who underwent MR cholangiography. The spectrum of appearances of cholangiocarcinoma is demonstrable on MR images. Mass-like tumors are well shown on both pre- and post-gadolinium sequences. Circumferential tumors may cause minimally increased duct wall thickness and are most clearly shown on gadolinium-enhanced fat-suppressed SGE images obtained 1 to 5 min following gadolinium administration.

MRI of pancreatic metastases from renal cancer

OBJECTIVE Our goal was to describe the MR features of pancreatic metastases from renal cancer. MATERIALS AND METHODS Five patients with pancreatic metastases from renal cancer were imaged with MR. Imaging was performed on a 1.5 T MR imager using excitation-spoiled fat-suppressed T1-weighted SE images (all patients), T1-weighted spoiled GE images (all patients), T2-weighted fast SE (one patient) and excitation-spoiled fat-suppressed T2-weighted fast SE (one patient) images, serial postgadolinium spoiled GE images (all patients), and postcontrast excitation-spoiled fat-suppressed T1-weighted SE images (two patients). RESULTS Multiple pancreatic lesions (n = 6) were present in two patients, solitary tumors in two patients, and diffuse micronodular pancreatic enlargement in one patient. All lesions were hypointense compared to normal pancreas on T1-weighted fat-suppressed SE images. Lesions were high in SI on T2-weighted images in two of two patients. All lesions demonstrated enhancement on the immediate postgadolinium spoiled GE images with the smaller tumors (<1.5 cm, three individual and the micronodular tumors) showing diffuse enhancement and the larger tumors (>1.5 cm, five tumors) showing predominantly rim enhancement. CONCLUSION Pancreatic metastases from renal cell carcinoma have distinctive MR features that include diffuse enhancement in small lesions and rim enhancement in large lesions on immediate postgadolinium images and high SI on T2-weighted images.

Focal hepatic lymphoma: Magnetic resonance demonstration using current techniques including gadolinium enhancement

This study demonstrates the appearance of focal hepatic lymphoma using current magnetic resonance techniques including gadolinium enhancement. Fifteen patients with hepatic lymphoma were imaged at 1.5T. T1-weighted, T2-weighted, immediate, and 5-10-min delayed T1-weighted spoiled gradient echo images were acquired in all patients. Determination was made of lesion size, number, morphology, and signal intensity of lesions on all sequences. Seven patients had solitary lesions and 8 patients had multiple lesions. Focal lesions of hepatic lymphoma ranged in size from 5 mm to 15 cm. They were well defined masses with mild to moderate low signal intensity relative to liver on T1-weighted images. Lymphoma lesions in 6 patients were moderately high in signal intensity on T2-weighted images compared with liver (Type I lesions), and enhancement of lesions was intense on early post-gadolinium images in 5 of these patients. Lymphoma lesions in 6 patients were mildly hypointense to mildly hyperintense on T2-weighted images compared to liver (Type II lesions), and lesions in 5 of these patients enhanced minimally on the early post-gadolinium spoiled gradient echo images. The remaining 3 patients had received chemotherapy before the magnetic resonance examination, and the imaging findings varied reflecting presumed differences in treatment responses. Transient ill defined perilesional enhancement on immediate post-gadolinium spoiled gradient echo images was observed in 9 patients including patients with either type of lesion. Focal lesions of hepatic lymphoma are usually low in signal intensity on T1-weighted images but have variable signal intensity on T2-weighted images. In general, lesions that are mildly hypointense to minimally hyperintense in signal intensity on T2-weighted images enhance minimally, and lesions moderately high in signal intensity of T2-weighted images enhance intensely. Transient increased perilesional enhancement is common.

Magnetic resonance imaging of neuroblastoma using current techniques

We evaluated the ability of current magnetic resonance (MR) scanning techniques to detect and stage neuroblastoma in children, using surgical and histopathologic correlation. We prospectively and retrospectively reviewed 16 MR examinations from 14 patients with neuroblastoma (13 patients) or ganglioneuroblastoma (1 patient) and compared these to computed tomography (CT) (5 patients) and pathology (all patients). Sequences included: precontrast T1-weighted and T2-weighted images, and gadolinium-enhanced T1-weighted images. The study time for each MR exam was also calculated. Five primary tumors were intrathoracic paraspinous masses, eight were adrenal, and 1 was presacral. Neural foraminal invasion was demonstrated on MR in four of 14 patients. Three of the four patients had undergone CT and neural foraminal invasion was shown in one. Vascular encasement was demonstrated in five of 14 patients on MR images. Three of the five patients had undergone CT and vascular involvement was shown in two. All cases of neural foramina invasion and vascular encasement were proven at surgery. There were no false positive or false negative MR studies of neural foraminal invasion or vascular encasement. Bone marrow invasion was shown in two of 14 patients on MR images which were confirmed by bone marrow aspirate. No false negative cases of bone marrow invasion was shown. In one patient, CT considered one neuroblastoma to be adrenal in location which was correctly shown to be intrathoracic on MR. The mean study time for MR imaging was 49 min. Current MR techniques are accurate at detecting and staging neuroblastoma, and coverage of chest, abdomen, and pelvis can be performed in less than one hour.

Role of radiotherapy in the management of hepatocellular carcinoma: A systematic review.

Many patients with hepatocellular carcinoma (HCC) present with advanced disease, not amenable to curative therapies such as surgery, transplantation or radiofrequency ablation. Treatment options for this group of patients include transarterial chemoembolization (TACE) and radiation therapy. Especially TACE, delivering a highly concentrated dose of chemotherapy to tumor cells while minimizing systemic toxicity of chemotherapy, has given favorable results on local control and survival. Radiotherapy, as a therapeutic modality of internal radiation therapy with radioisotopes, has also achieved efficacious tumor control in advanced disease. On the contrary, the role of external beam radiotherapy for HCC has been limited in the past, due to the low tolerance of surrounding normal liver parenchyma. However, technological innovations in the field of radiotherapy treatment planning and delivery, have provided the means of delivering radical doses to the tumor, while sparing normal tissues. Advanced and highly conformal radiotherapy approaches such as stereotactic body radiotherapy and proton therapy, evaluated for efficacy and safety for HCC, report encouraging results. In this review, we present the role of radiotherapy in hepatocellular carcinoma patients not suitable for radical treatment.

Diagnosis and Monitoring Response to Treatment of Hepatosplenic Candidiasis in Patients with Acute Leukemia Using Magnetic Resonance Imaging

Hepatosplenic candidiasis (HSC) is a morbid complication encountered in immunocompromised individuals, especially, those being treated with intensive chemotherapy protocols for acute leukemia. Immediate recognition of this complication and initiation of appropriate treatment is crucial in order to control the infection, decrease the morbidity and mortality, and avoid delays in treatment of the underlying condition. The definitive diagnosis requires either positive blood cultures for yeasts in the presence of abnormal findings on imaging studies consistent with HSC, or liver biopsy demonstrating yeast forms or pseudohyphae. We describe our experience in the evaluation of 15 patients with HSC using magnetic resonance imaging (MRI) as a diagnostic and follow-up tool. The diagnosis of HSC was established by liver biopsy in 11 patients (73%), and by positive blood cultures for Candida in 4 patients (27%). All patients had MRI findings consistent with HSC during the study period. Amphotericin B was administered intravenously to all 15 patients (median duration of treatment, 62 days). Repeat MR images were obtained at 2 weeks, 6 weeks and then at monthly intervals until the resolution of abnormalities. The median time for the disappearance of MRI lesions was 9 weeks. Alterations in the appearance of lesions on MRI were noted throughout chemotherapy in all the 13 (86.6%) responding patients. Our results suggest that MRI when used in patients with high clinical suspicion for HSC provide an alternative for liver biopsy or other invasive diagnostic procedures and that appropriate response to treatment can be safely monitored by obtaining sequential MRI studies.

Chemotherapy-treated liver metastases mimicking hemangiomas on MR images.

AbstractBackground: To report the observation that chemotherapy-treated liver metastases may mimic the appearance of hemangiomas on T2-weighted and serial postgadolinium gradient-echo magnetic resonance (MR) images. Methods: T2-weighted and serial postgadolinium spoiled gradient-echo images were prospectively and retrospectively analyzed in six patients. All patients had been treated with chemotherapy for a duration of 2–12 months. Histopathologic evaluation of liver lesions was performed in three patients. Results: Twelve lesions that resembled hemangiomas were identified. Lesions were 0.8–5.5 cm in diameter. All were well defined, oval or lobulated, and demonstrated decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. On immediate postgadolinium images, all lesions demonstrated peripheral nodular enhancement, which coalesced on delayed imaging. Final histopathologic diagnoses were as follows: hepatic metastases from colon cancer (two patients), ovarian cancer (two patients), pancreatic islet cell tumor (one patient), and breast cancer (one patient). Conclusions: Metastases treated by chemotherapy may mimic the appearance of hemangiomas on a variety of commonly employed MR techniques. In patients undergoing MR imaging for the evaluation of liver metastases, a history of prior chemotherapy administration and duration should be sought to prevent inaccurate staging and inappropriate therapeutic decision making.

Angiosarcoma of the liver: MR imaging pre- and post-chemotherapy

Angiosarcoma of the liver is a rare tumor of mesenchymal origin. We report the MR appearance of angiosarcoma of the liver on T1-weighted, T2-weighted, and serial gadolinium enhanced spoiled gradient echo images pre- and post-intravenous chemotherapy. On pre-treatment images, angiosarcoma lesions were well defined, high signal with central regions of low signal on T2-weighted images, and showed peripheral nodular enhancement on serial post gadolinium images. Lesions resembled hemangiomas, however low signal central regions on T2-weighted images was a distinguishing feature. Post-treatment images acquired 11, 15, and 17 months after initiation of therapy, demonstrated decrease in diameter or resolution of angiosarcoma masses. Lesions increased in signal on T1 weighted images and decreased in signal on T2 weighted images approaching the signal intensity of liver. Treated liver lesions enhanced negligibly on gadolinium enhanced images.

A new era in computed tomographic dose optimization: the impact of iterative reconstruction on image quality and radiation dose.

Abstract The ongoing evolution of computer technology has made the use of iterative reconstruction (IR) algorithms clinically applicable. We reviewed current literature on the clinical use of IR against filtered back projection algorithms in terms of image quality and radiation dose. Iterative reconstruction algorithms provide equal or better image quality compared with filtered back projection, with dose reduction ranging from 25% to 98.6%. However, several studies have reported that the superior results of IR regarding objective evaluation are not always favorably interpreted by radiologists. Further clinical evaluation is needed to certify the optimal tradeoff between imaging quality and radiation dose, and radiologists need to become more familiar with the new appearance of computed tomographic images.

Magnetic resonance imaging of the abdominal aorta and iliac vessels using combined 3-D gadolinium-enhanced MRA and gadolinium-enhanced fat-suppressed spoiled gradient echo sequences

This study evaluates a combined protocol consisting of breath hold immediate post gadolinium 3-D gradient echo MR angiography and blood pool phase gadolinium-enhanced breath hold 2-D fat-suppressed spoiled gradient echo (SGE) sequences in the examination of diseases of the abdominal aorta and iliac vessels. Thirty-two patients with suspected disease of the abdominal aorta, major aortic branches, or iliac vessels underwent MR angiographic study from January 1996 to January 1997. Examinations were performed on a 1.5 T MR imager using 2-D axial SGE, coronal 3-D fast imaging in steady state precession (3-D FISP) following bolus administration of 40 mL of gadolinium, and axial and coronal blood pool phase gadolinium-enhanced fat-suppressed SGE. Post-processed data, including 3-D reconstructions using maximum intensity projection (MIP), targeted MIP, and multiplanar reconstruction (MPR) were evaluated. MR findings in all patients were correlated as follows: surgery (13 patients), angiography (11 patients), contrast enhanced CT (3 patients), non-contrast enhanced CT (1 patient), color doppler US (2 patients), and previous MR study (2 patients). MR findings correlated closely with findings at surgery or other imaging studies in 31 of 32 patients. One patient had renal artery occlusion that was misinterpreted as mild stenosis. The following vascular diseases were present: aneurysm disease [10 patients: aortic aneurysm (8 patients), inflammatory aneurysm (2 patients)], thoracoabdominal aortic dissection (2 patients), arteriovenous fistula (1 patient), stenoses and/or occlusion of the abdominal aorta, major aortic branches and iliac vessels [12 patients: stenoses and/or occlusion of the abdominal aorta with stenoses of the iliac vessels (9 patients), renal artery stenosis (2 patients), occlusion of the abdominal aorta (1 patient)], and occluded artery to pancreatic transplant artery (1 patient). Five patients had normal studies. The 3-D FISP technique accurately defined the luminal contours of vessels, allowing precise depiction of vessel stenosis (i.e., renal artery stenosis or common iliac artery stenosis) and clear demonstration of relationship of aortic branch vessels (i.e., renal arteries) to underlying aortic pathology (i.e., aortic aneurysm or dissection). Blood pool phase gadolinium-enhanced fat-suppressed SGE images were useful in the evaluation of the external surface of vessel walls, and providing accurate measurement of aneurysm diameter and other associated vascular entities (i.e., inflammatory aneurysm, left-sided IVC). Targeted MIP or MPR reconstruction were important for assessing stenoses of medium sized vessels such as renal arteries and branches of the iliac arteries, and for identifying accessory arteries. The combination of immediate post gadolinium 3-D FISP and blood pool phase gadolinium-enhanced fat-suppressed SGE is useful in the evaluation of the abdominal aorta, major aortic branches and iliac vessels. Immediate post gadolinium 3-D FISP images provides diagnostically useful information regarding vessel luminal contour, while blood pool phase gadolinium-enhanced fat-suppressed SGE provides ancillary information on the vessel wall and surrounding tissue.