Diagnostic approach to retromolar trigone cancer by multiplanar computed tomography reconstructions.

Neoplasms of retromolar trigone have important peculiarities due to their spatial relationships with the surrounding structures. Tumours that involve this area can extend to nearby muscles; adipose spaces; and other anatomic structures, such as the soft palate, the tonsillar fossa, the parapharyngeal space, and the floor of the mouth. In spite of a relatively quick diagnosis, the real extent of these tumours is typically underestimated at clinical examination. Our purpose was to propose a systematic approach to the use of multiplanar computed tomography reconstructions to evaluate normal retromolar trigone anatomy and the main pathways of spread for tumours that arise in this area. To our knowledge, only few reports exist in literature about this topic and none are about the usefulness of multidetector computed tomography and multiplanar reconstructions.

A method to evaluate the dose increase in CT with iodinated contrast medium.

PURPOSE: The objective of this study is to develop a method to calculate the relative dose increase when a computerized tomography scan (CT) is carried out after administration of iodinated contrast medium, with respect to the same CT scan in absence of contrast medium. METHODS: A Monte Carlo simulation in GEANT4 of anthropomorphic neck and abdomen phantoms exposed to a simplified model of CT scanner was set up in order to calculate the increase of dose to thyroid, liver, spleen, kidneys, and pancreas as a function of the quantity of iodine accumulated; a series of experimental measurements of Hounsfield unit (HU) increment for known concentrations of iodinated contrast medium was carried out on a Siemens Sensation 16 CT scanner in order to obtain a relationship between the increment in HU and the relative dose increase in the organs studied. The authors applied such a method to calculate the average dose increase in three patients who underwent standard CT protocols consisting of one native scan in absence of contrast, followed by a contrast-enhanced scan in venous phase. RESULTS: The authors validated their GEANT4 Monte Carlo simulation by comparing the resulting dose increases for iodine solutions in water with the ones presented in literature and with their experimental data obtained through a Roentgen therapy unit. The relative dose increases as a function of the iodine mass fraction accumulated and as a function of the Hounsfield unit increment between the contrast-enhanced scan and the native scan are presented. The data shown for the three patients exhibit an average relative dose increase between 22% for liver and 74% for kidneys; also, spleen (34%), pancreas (28%), and thyroid (48%) show a remarkable average increase. CONCLUSIONS: The method developed allows a simple evaluation of the dose increase when iodinated contrast medium is used in CT scans, basing on the increment in Hounsfield units observed on the patients' organs. Since many clinical protocols employ multiple scans at different circulatory phases after administration of contrast medium, such a method can be useful to evaluate the total dose to the patient, also in view of potential clinical protocol optimizations.

Evaluation of the anterior ethmoidal artery by 3D dual volume rotational digital subtraction angiography and native multidetector CT with multiplanar reformations. Initial findings.

Our purpose is to codify the anterior ethmoidal artery (AEA) course and its relationship with adjacent structures. Twenty patients with cerebrovascular disease underwent selective internal carotid dual volume angiography. Fusion of the vascular and bony images was obtained successively on a second console. MDCT of the cranium was performed in all patients. To identify the AEA course, multiplanar CT reformations were obtained. In all cases the entry-point of AEA and its course were identified by means of dual volume angiography. The information was confirmed by MDCT. In a second phase, we studied another 78 patients affected by inflammatory disease and polyposis only by means of MDCT, in order to confirm the previous data obtained by comparison between angiography and MDCT. In this second phase, 110/156 vessels were indirectly detected by means of visualization of the ethmoidal entry point. In the remaining cases, AEA was directly shown due to integrity of the thin ethmoidal bone lamellae or bony canal. Dual volume angiography is essential to identify the course of the AEA (standard of reference for the interpretation of CT). In patients with benign rhinosinusal pathology, where invasivity techniques are not justified, MPR reconstructions were of pivotal importance in the evaluation of the course of the artery with particular reference to its relationship with the frontal recess.

Combined magnetic resonance urography and targeted helical CT in patients with renal colic: a new approach to reduce delivered dose.

PURPOSE: To determine whether magnetic resonance urography (MRU), obtained before helical computed tomography (CT) in patients with acute renal colic, can help delimit the obstructed area to be subsequently examined by a targeted CT scan, thus reducing the dose of radiation. MATERIALS AND METHODS: Patients (51) with symptoms of acute renal colic underwent MRU and a total urinary tract helical CT. CT images from the 5 cm below the level of ureteral obstruction as demonstrated by MRU were selected out. Combined interpretation of MRU and selected CT images constituted protocol A. Protocol B consisted of the entire unenhanced helical CT of the urinary tract. The two protocols were compared regarding the following points: 1) sensitivity in diagnosing the presence of obstructing urinary stones, and 2) the delivered radiation dose. RESULTS: Protocol A and protocol B had, respectively, 98% and 100% sensitivity in demonstrating ureteral stone as a cause of renal colic. Estimated average dose calculated from phantom study was 0.52 mSv for protocol A and 2.83 mSv for protocol B. Therefore, the effective radiation dose was 5.4 times lower in protocol A compared to protocol B. CONCLUSION: Combined MRU and short helical CT has a high sensitivity in detecting ureteral calculi with a reduced radiation dose.

Virtual endoscopy of the nasopharynx in the evaluation of its normal anatomy and alterations due to lymphoid hyperplasia: preliminary report.

The purpose of this study was to evaluate the diagnostic usefulness of virtual endoscopy in establishing the anatomic appearance of nasopharynx, both normal and affected by lymphoid hyperplasia. Thirty-seven patients affected by chronic rhinosinusal and otomastoid pathology, all studied by rhinoscopy, were examined with multislice computed tomography (CT) and virtual endoscopy of the nasopharynx. Rhinoscopy showed a completely normal nasopharynx in 15 cases and a variable grade of lymphoid hypertrophy in 22 patients. A general agreement was observed between traditional and virtual endoscopy findings in both subgroups. The tasca of Luschka was detected in 13/15 of normal subjects and only in 3/22 patients. The Rosenmuller fossae appeared deeper in normal subjects and their symmetry could be considered an important criterion of normality. In all cases, a good evaluation of the tubaric ostium was obtained. Differentiation between hyperplasic lymphoid tissue and neoplasms is possible only in lymphoid hyperplasia characterized by median crest-like swelling with a narrow base. In most cases, differential diagnosis cannot be based only on morphological criteria of virtual endoscopy, but it should be evaluated considering the overall CT findings and clinical presentation.

Magnetic resonance imaging findings of osteoid osteoma of the proximal femur.

Osteoid osteoma (OO) is a benign bone tumor whose main radiological finding is nidus. OO of the proximal femur can also result in non-specific findings such as hip joint effusion, perinidal bone marrow edema and soft tissue mass. Since the nidus may be difficult to identify with MR, these non-specific findings can lead to erroneous diagnosis. Therefore, MR imaging technique should be optimized in order to identify nidus. Since MR imaging has assumed increasing importance in the evaluation of disorders of the hip, radiologists must be aware of the spectrum of findings of OO of the proximal femur. The aim of this pictorial review is to show the MR imaging findings of intra-articular and extra-articular OO of the proximal femur.