Imaging modalities in head-and-neck cancer patients.

Accurate staging and timely assessment is critical in head-and-neck cancer patients for formulating the appropriate treatment strategy. Therefore, optimizing pretreatment imaging for diagnosis is of great importance. Computerized tomography (CT), introduced in the early 70s, followed by magnetic resonance imaging (MRI) and positron emission tomography (PET), refinements in ultrasonography (USG), advances in nuclear medicine, and applications such as sentinel node lymphoscintigraphy have greatly added to diagnostic accuracy. Post-treatment CT or MRI is of value when a recurrent tumor is suspected. It can confirm the presence of such a lesion and determine its extent. This is important information for determining the possibility of salvage therapy.

Using Multidetector-Row CT for the Diagnosis of Afferent Loop Syndrome Following Gastroenterostomy Reconstruction

PURPOSE: To assess the clinical manifestations and multidetector-row computed tomography (MDCT) findings of afferent loop syndrome (ALS) and to determine the role of MDCT on treatment decisions. MATERIALS AND METHODS: From January 2004 to December 2008, 1,100 patients had undergone gastroenterostomy reconstruction in our institution. Of these, 22 (2%) patients were diagnosed as ALS after surgery that included Roux-en-Y gastroenterotomy (n=9), Billroth-II gastrojejunostomy (n=7), and Whipple's operation (n=6). Clinical manifestations and MDCT features of these patients were recorded and statistically analyzed. The presumed etiologies of obstruction shown on the MDCT were correlated with clinical information and confirmed by surgery or endoscopic biopsy. RESULTS: The most common clinical symptom was acute abdominal pain, presenting in 18 patients (82%). We found that a fluid-filled C-shaped afferent loop in combination with valvulae conniventes projecting into the lumen was the most common MDCT features of ALS. Malignant causes of ALS, such as local recurrence and carcinomatosis, are the most common etiologies of obstruction. These etiologies and associated complications can be predicted 100% by MDCT. CONCLUSION: Our results suggest that MDCT is a reliable modality for assessing the etiologies of ALS and guiding treatment decisions.

Pitfalls in the use of Multidetector Row CT Angiography for Identification of Intracranial Vascular Abnormalities : Focus on the Various Radiological Findings / 대한뇌혈관외과학회지

OBJECTIVE: Multidetector-Row computed tomographic angiography (MDCTA) is a promising method for detection and surgical planning of intracranial vascular abnormalities. However, there are several problems, such as image degradation due to inevitable patients movement, venous contamination, kissing vessel artifact, demonstration of venous structures mimicking aneurysm and bone artifacts. The purpose of our study is to review our recent experience with false negative or positive cases on MDCTA. METHODS: Between May 2007 and May 2010, 259 consecutive patients, who were diagnosed with intracranial aneurysms or other vascular abnormalities by MDCTA, were retrospectively reviewed. Among the 259 patients, 172 patients who underwent digital subtraction angiography (DSA), which was considered as the standard of reference, were included in the study. Two neuroradiologists and two neurosurgeons evaluated independently and separately all of the MDCTA images. RESULTS: A total 26 cases (15.3%) were revealed abnormal vascular findings on MDCTA. There were 11 false negatives on MDCTA including incomplete scanning range of lesion site (n=3), a blood blister aneurysm (n=1), severe vasospasm (n=4) and bone artifacts (n=3). Also there were 15 false positives on MDCTA; venous contamination over the lesion site (n=6), focal dilation of the bifurcation or branching site of major vessels (n=6) and poor quality of the images due to inevitable patients movement (n=3). CONCLUSIONS: MDCTA is clearly not the total answer for aneurysm diagnosis. We recommend that MDCTA scanning range is planned to encompass the whole intracerebral vasculature. Close attention to image acquisition and interpretation are required to reduce errors in MDCTA of intracranial aneurysms.

Estudio vascular renal por TC multidetector de 64 canales / 64-Multidetector row CT for the Renal Vascular Study

Objetivo: Mostrar las diversas variantes anatómicas vasculares tanto arteriales como venosas en el estudio angiográfico renal por tomografìa computada multidetector (TCMD) de 64 canales, dada su implicancia en un eventual planeamiento quirúrgico. Material y métodos: Evaluamos retrospectivamente 26 estudios realizados con tomógrafo Philips Brilliance de 64 canales. Se obtuvieron secuencias sin contraste y postcontraste e.v. en fases arterial y venosa, administrado con bomba inyectora doble cabezal. Para una fase arterial apropiada se utilizó técnica de bolus track. Las imágenes fueron posteriormente procesadas en Workstation Philips Brilliance 190P en un tiempo promedio de 30 minutos y reconstruidas con técnicas MIP y volumétrica. Resultados: Dentro de las variantes anatómicas arteriales, encontramos: bifurcaciones prehiliares (n=3), arterias accesorias (n=4) y arterias polares (n=9). Dentro de las variantes venosas fueron halladas: venas renales múltiples (n=5), venas circumaórticas (n=2), retroaórticas (n=2) y vena tributaria lumbar prominente (n=1). Conclusión: El estudio vascular renal adquiere importancia en el planeamiento quirúrgico en casos de nefrectomías parciales, laparoscópicas y en el transplante renal. Esto otorga suma utilidad al estudio de TCMD de 64 canales por su eficacia diagnóstica, dada la alta calidad de las reconstrucciones obtenidas, llegando a igualar a la angiografía digital, sin ser un método invasivo.

Purpose: To show the wide range of anatomical vascular variants, arterial and venous, that can be seen in the angiographic renal study using 64-multidetector-row computed tomography (64-MDCT), due to its importance in an eventual surgical planning. Material and Methods: We have evaluated retrospectively 26 studies that have been done using a 64 channels Philips Brilliance CT scanner. We have obtained non enhanced and both in arterial and venous enhanced sequences. For the injection of the contrast material we have used a double head injector bomb. The arterial phase was acquired using the bolus track technique. The raw data has then been post processed in a 190P Philips Brilliance workstation in a mean time of 30 minutes. The reconstructions have been obtained both with MIP and volumetric technique. Conclusion: The renal vascular study has importance for the surgical planning in cases of parcial nephrectomies or laparoscopic nephrectomies as well as in renal transplant. This makes the 64-MDCT a very useful non invasive imaging tool due to its high accuracy similar to digital angiography.

Reviews of Radiation Protection and Shielding for Computed Tomography in Foreign Countries / 의학물리

A computed tomography (CT) is a powerful system for the effectively fast and accurate diagnosis. The CT system, therefore, has used substantially and developed for improving the performance over the past decade, resulting in growing concerns over the radiation dose from the CT. Advanced CT techniques, such as a multidetector row CT scanner and dual energy or dual source CT, have led to new clinical applications that could result in further increases of radiation does for both patients and workers. The objective of this study was to review the international guidelines of the shielding requirements for a CT facility required for a new installation or when modifying an existing one. We used Google Search Engine to search the following keywords: computed tomography, CT regulation or shield or protection, dual energy or dual source CT, multidetector CT, CT radiation protection, and regulatory or legislation or regulation CT. In addition, we searched some special websites, that were provided for sources of radiation protection, shielding, and regulation, RSNA, AAPM, FDA, NIH, RCR, ICRP, IRPA, ICRP, IAEA, WHO (See in Table 1 for full explanations of the abbreviations). We finally summarized results of the investigated materials for each country. The shielding requirement of the CT room design was very well documented in the countries of Canada, United States of America, and United Kingdom. The wall thickness of the CT room could be obtained by the iso-exposure contour or the point source method. Most of documents provided by international organizations were explained in importance of radiation reduction in patients and workers. However, there were no directly-related documents of shielding and patient exposure dose for the dual energy CT system. Based international guidelines, the guideline of the CT room shielding and radiation reduction in patients and workers should be specified for all kinds of CT systems, included in the dual energy CT. We proposed some possible strategies in this paper.

Multidector CT Imaging of Coronary Artery Stents: Is This Method Ready for Use?

Coronary artery stenting has become the most important nonsurgical treatment for coronary artery disease. However, in-stent restenosis occurs at a relatively high rate and this problem has led to the routine use of invasive angiography for assessing stent patency. Although coronary angiography is the clinical gold standard and it is a very effective diagnostic tool for detecting such in-stent restenosis, it's clearly an invasive procedure with its associated morbidity and mortality risks. Therefore, a noninvasive technique for detecting in-stent restenosis would be of great interest and use for following up patients after coronary angioplasty. Multidetector-row CT (MDCT) is being increasingly used for noninvasive coronary artery imaging as it has high diagnostic accuracy for detecting coronary artery stenosis in native, non-stented, coronary arteries. However, the application of MDCT to stent imaging is somewhat difficult. It is generally accepted that visualizing the in-stent lumen with using 4-slice MDCT is impossible because of the modality's low temporal and spatial resolution. There is increased visualization of the stent lumen on 16-slice MDCT, and so in-stent restenosis can be detected in assessable stents. Yet for stents with small diameters (<3 mm) and/or thicker struts, visualization of instent stenosis remains a problem. The recently introduced 64-slice CT offers more improved spatial and temporal resolution than does 16-slice CT and this results in superior visualization of the stent lumen and in-stent restenosis. However, although 64-slice MDCT allows for improved stent visualization, a relevant part (up to 47%) of the stent lumen is still not assessable. There are many factors that interfere with the assessment of the real stent lumen even on 64-slice CT. The metal of the stents can cause blooming artifacts that prevent the accurate interpretation of a lumen's patency. The blooming effect is caused by a combination of partial volume averaging and beam hardening, and this results in higher CT attenuation values in the stent lumen and this enlarges the apparent size of the stent struts, thus leading to a pseudo-narrowing of the lumen. Regarding the type of stent, the gold or gold-coated stents along with the stents made of tantalum, cause the most severe artifacts, while the stainless steel and cobalt stents can be more accurately visualized. Cardiac motion, poor contrast filling, the oblique course of the coronary vessels and calcification may also decrease the ability to assess a stent's lumen. To improve a stent's visualization, numerous methods have been attempted such as dedicated post-processing or the use of dual-source CT. However, because of its presently limited sensitivity and high radiation exposure, MDCT should not be used as the first-line test to screen for in-stent restenosis in asymptomatic patients. Given its high specificity and negative predictive value, MDCT might be valuable for confirming stent occlusion in symptomatic patients. Such stent evaluation should focus on the proximal coronary artery segments and on those stents with a diameter greater than 3 mm.