Ahmed M. Tawfik

Dual-Energy CT Applications in Head and Neck Imaging

OBJECTIVE Dual-energy scanning is a breakthrough in CT technology that has several applications in chest and abdominal imaging. Dual-energy CT also has potential for head and neck imaging. This review describes the role of dual-energy CT in head and neck imaging. CONCLUSION As with other body regions, both image fusion and material characterization dual-energy applications can be used for head and neck imaging. Early results are promising, and further research is encouraged.

Perfusion CT of head and neck cancer

We aim to review the technique and clinical applications of perfusion CT (PCT) of head and neck cancer. The clinical value of PCT in the head and neck includes detection of head and neck squamous cell carcinoma (HNSCC) as it allows differentiation of HNSCC from normal muscles, demarcation of tumor boundaries and tumor local extension, evaluation of metastatic cervical lymph nodes as well as determination of the viable tumor portions as target for imaging-guided biopsy. PCT has been used for prediction of treatment outcome, differentiation between post-therapeutic changes and tumor recurrence as well as monitoring patient after radiotherapy and/or chemotherapy. PCT has a role in cervical lymphoma as it may help in detection of response to chemotherapy and early diagnosis of relapsing tumors.

De-novo portal vein thrombosis in liver cirrhosis: risk factors and correlation with the Model for End-stage Liver Disease scoring system.

Background and objectivesPortal vein thrombosis (PVT) is a potential lethal complication in late liver cirrhosis. There is a lack of knowledge of the clinical features and risk factors of PVT. We aimed to investigate the clinical and radiological characteristics, and biochemical markers of cirrhotic patients to determine the high-risk individuals for PVT attending our center. Patients and methodsOf 426 cirrhotic patients, only 120 consecutive patients were included. Clinical, biochemical, immunological, Model for End-stage Liver Disease (MELD) score, portal vein patency, and flow velocity were measured in all patients at baseline and every 6 months thereafter. Variables that could predict the development of PVT within 1 year were identified by multiple logistic regression. ResultsOnly 95 patients completed the study; PVT was found in 17 (17.9%) patients. PVT was observed mainly in the portal trunk, superior mesenteric vein, and splenic vein. Univariate analysis showed that diabetes mellitus, lower levels of hemoglobin, platelet counts, and portal vein flow velocity as well as increased MELD scores, platelet indices, portal vein diameter, and splenic thickness were associated with PVT patients than in non-PVT patients (all P<0.01). ConclusionThe incidence of PVT was 17.9%. PVT occurred mainly in the portal vein trunk, superior mesenteric vein, and splenic vein. Diabetes mellitus, lower levels of hemoglobin, platelet count and portal vein flow velocity as well as increased MELD score, platelet indices, portal vein diameter, and splenic thickening were associated with PVT. Splenic thickening, marked reduced of mean portal flow velocity, and diabetes mellitus may be risk factors for PVT.

Polysplenia syndrome: a review of the relationship with viscero-atrial situs and the spectrum of extra-cardiac anomalies

Polysplenia syndrome is classified as one of the situs ambiguous or heterotaxy syndromes and is classically termed left isomerism or bilateral left-sidedness. However, polysplenia is a controversial and complex entity with no fixed pathognomonic features but rather a broad spectrum of abnormalities. In many published case series, polysplenia was neither associated with viscero-atrial heterotaxy nor with duplication of left-sided structures. The relationship between polysplenia and viscero-atrial situs is not clear. Several recent case reports describe the association of polysplenia with situs inversus totalis or with pancreatic; venous and other anomalies or with several types of malignancy. This article provides the reader with a review of the literature as well as our own experience aiming at better understanding of the polysplenia syndrome, its relationship with viscero-atrial situs and the spectrum of associated extra-cardiac anomalies.

Perfusion CT of Head and Neck Cancer: Effect of Arterial Input Selection

OBJECTIVE The purpose of this study is to evaluate the effect of arterial input selection on perfusion CT parameters of head and neck tumors. MATERIALS AND METHODS Perfusion calculations were done for 50 cases using deconvolution-based software. Peak enhancement values of the ipsilateral internal carotid artery (ICA) and external carotid artery (ECA) were recorded. Blood flow (BF), blood volume (BV), mean transit time (MTT), and permeability surface area product were calculated using ipsilateral ECA, ipsilateral ICA, and contralateral ICA as input arteries. Values were compared using Wilcoxons matched pair test and Pearsons correlation coefficients (r). RESULTS A highly significant correlation was observed between peak enhancement values of the ICA and ECA (r = 0.97; p < 0.0001). A high correlation was observed between perfusion calculations obtained using ipsilateral ICA and ECA (BF, r = 0.98; BV, r = 0.92; MTT, r = 0.91; and permeability surface area product, r = 0.89), ipsilateral and contralateral ICA (BF, r = 0.97; BV, r = 0.95; MTT, r = 0.93; and permeability surface area product, r = 0.89), as well as left and right ICA (BF, r = 0.97; BV, r = 0.95; MTT, r = 0.94; and permeability surface area product, r = 0.88). All correlations were statistically significant (p < 0.0001). No significant differences were observed between perfusion calculations obtained using ipsilateral ICA versus ECA, ipsilateral versus contralateral ICA, or left versus right ICA (p > 0.05). CONCLUSION Arterial input selection has no significant effect on perfusion CT calculation of head and neck cancer. For standardization and simplification of postprocessing, we recommend the use of the ICA instead of the ECA as the arterial input because of its better visualization, perpendicular course, and larger caliber, all of which decrease partial volume effects.

Could serotonin be a potential marker for hepatocellular carcinoma? A prospective single-center observational study.

Background Hepatocellular carcinoma (HCC) is the third most common cause of cancer mortality among men worldwide. Serotonin is a biogenic amine, which may be involved in the tumorigenesis of HCC. Aim We aimed to determine whether serotonin is a dependable marker for the diagnosis of HCC in cirrhotic patients in comparison with &agr;-fetoprotein protein (AFP) and prothrombin induced by vitamin K absence-II (PIVKA-II). Patients and methods Serum serotonin, AFP, and PIVKA-II were measured in 262 patients with chronic hepatitis C (CHC): 82 cirrhotic patients with HCC (group I), 80 cirrhotic patients without HCC (group II), and 100 CHC-infected patients without cirrhosis (group III); in addition, 60 healthy controls were studied (group IV). Results AFP showed significant statistical differences among the groups studied (P<0.001). PIVKA-II and serotonin levels showed no statistically significant differences between the patients with CHC group and the healthy controls (P1=0.614 and P1=0.13, respectively), whereas their levels were statistically higher in cirrhotic patients than patients with CHC (all P values <0.001) and in the cirrhotic patients with HCC group than the cirrhotic patients without HCC (P<0.001). A significant positive correlation was found between serum serotonin and AFP (rho=0.794; P<0.001) and serum serotonin and PIVKA-II (rho=0.889; P<0.001) among the patient groups. The receiver operator characteristic curve showed a higher area under the curve for serotonin than AFP and PIVKA-II (0.942, 0.824, and 0.921, respectively). Conclusion Serotonin may be used together with PIVKA-II to screen for HCC in cirrhotic patients with CHC.

Pre-, Intra- and Post-Operative Imaging of Cochlear Implants.

The purpose of this review is to present essential imaging aspects in patients who are candidates for a possible cochlear implant as well as in postsurgical follow-up. Imaging plays a major role in providing information on preinterventional topography, variations and possible infections. Preoperative imaging using DVT, CT, MRI or CT and MRI together is essential for candidate selection, planning of surgical approach and exclusion of contraindications like the complete absence of the cochlea or cochlear nerve, or infection. Relative contraindications are variations of the cochlea and vestibulum. Intraoperative imaging can be performed by fluoroscopy, mobile radiography or DVT. Postoperative imaging is regularly performed by conventional X-ray, DVT, or CT. In summary, radiological imaging has its essential role in the pre- and post-interventional period for patients who are candidates for cochlear implants.

Whole-body MR angiography: first experiences with the new TimCT technology with single contrast injection.

To assess image quality, presence of artifacts, arterial stenosis, and interobserver agreement of Tim‐CT in assessment of the arterial system using contrast‐enhanced whole‐body‐MRA (CE‐Wb‐MRA) with a single contrast‐medium injection in patients with arteriosclerosis.

Effect of increasing the sampling interval to 2 seconds on the radiation dose and accuracy of CT perfusion of the head and neck.

Purpose To evaluate the effect of increasing the sampling interval from 1 second (1 image per second) to 2 seconds (1 image every 2 seconds) on computed tomographic (CT) perfusion (CTP) of head and neck tumors. Materials and Methods Twenty patients underwent CTP studies of head and neck tumors with images acquired in cine mode for 50 seconds using sampling interval of 1 second. Using deconvolution-based software, analysis of CTP was done with sampling interval of 1 second and then 2 seconds. Perfusion maps representing blood flow, blood volume, mean transit time, and permeability surface area product (PS) were obtained. Quantitative tumor CTP values were compared between the 2 sampling intervals. Two blinded radiologists compared the subjective quality of CTP maps using a 3-point scale between the 2 sampling intervals. Radiation dose parameters were recorded for the 2 sampling interval rates. Results No significant differences were observed between the means of the 4 perfusion parameters generated using both sampling intervals; all P >0.05. The 95% limits of agreement between the 2 sampling intervals were −65.9 to 48.1) mL/min per 100 g for blood flow, −3.6 to 3.1 mL/100 g for blood volume, −2.9 to 3.8 seconds for mean transit time, and −10.0 to 12.5 mL/min per 100 g for PS. There was no significant difference between the subjective quality scores of CTP maps obtained using the 2 sampling intervals; all P > 0.05. Radiation dose was halved when sampling interval increased from 1 to 2 seconds. Conclusions Increasing the sampling interval rate to 1 image every 2 seconds does not compromise the image quality and has no significant effect on quantitative perfusion parameters of head and neck tumors. The radiation dose is halved.

Dual-Energy Computed Tomography Applications for the Evaluation of Cervical Lymphadenopathy

There is recent interest in the use of dual-energy computed tomography (CT) in head and neck imaging, and the results are encouraging. This article reviews dual-energy CT applications as complementary tools to conventional CT scanning in the evaluation of cervical lymphadenopathy. The article cites the most relevant studies and highlights their results. Single-source and dual-source dual-energy applications including virtual noncontrast images, linear and nonlinear image blending, monochromatic images, iodine quantification, and spectral Hounsfield unit attenuation curve analysis are reviewed. Future directions and research suggestions are discussed in brief.