Maria Raissaki

Determination of normal splenic volume on computed tomography in relation to age, gender and body habitus

Abstract The purpose of our study was to examine variations in normal splenic size in relation to age, gender and body habitus in vivo, and to determine normative data for splenic volume on CT. The width (W), length (L), thickness (Th), cross-sectional areas and volume (Vol) of the spleen were obtained from abdominal CT examinations of 140 patients who underwent CT for indications unrelated to splenic disease. Splenic volume did not vary significantly (–0.04 < r < 0.05, p > 0.10) with the patients age, gender, height, weight, body mass index or the diameter of the first lumbar vertebra, the latter considered as representative of body habitus on CT. The mean value of the measured splenic volume (S Vol) was 214.6 cm3 with a range from 107.2 to 314.5 cm3. S Vol correlated well with all the linear and the maximal cross-sectional area measurements and could be calculated using the formula: S Vol = 30 + 0.58 (W × L × Th.). Employing the same formula splenic volume was reliably assessed in 47 patients with clinically evident splenomegaly. Quantitative assessment of splenic volume might be of value in assessing mild variations in splenic size, because splenomegaly is the most common manifestation of splenic involvement in many disorders.

Acute abdomen due to torsion of wandering spleen: CT diagnosis

Abstract. Two adults and a child with acute abdomen and surgically confirmed torsion of wandering spleen are presented. Computed tomography provided a spectrum of findings including an ovoid or comma-shaped abdominal mass, hypertrophy of the livers left lobe, a whirled appearance of hyperdense, nonenhancing splenic vessels, and an enlarged spleen, exhibiting minimal or no enhancement. Computed tomography also indicated the point of torsion and the viability of splenic parenchyma.

Reduction of eye lens radiation dose by orbital bismuth shielding in pediatric patients undergoing CT of the head: a Monte Carlo study.

Our aim in the study was to assess the eye lens dose reduction resulting from the use of radioprotective bismuth garments to shield the eyes of pediatric patients undergoing head CT. The Monte Carlo N-particle transport code and mathematical humanoid phantoms representing the average individual at different ages were used to determine eye lens dose reduction accomplished with bismuth shielding of the eye in the following simulated CT scans: (a) scanning of the orbits, (b) scanning of the whole head, and (c) 20 degrees angled scanning of the brain excluding the orbits. The effect of bismuth shielding on the eye lens dose was also investigated using an anthropomorphic phantom and thermoluminescence dosimetry (TLD). Eye lens dose reduction achieved by bismuth shielding was measured in 16 patients undergoing multiphase CT scanning of the head. The patients scans were divided in the following: CT examinations where the eye globes were entirely included (n=5), partly included (n=6) and excluded (n=5) from the scanned region. The eye lens dose reduction depended mainly on the scan boundaries set by an operator. The average eye lens dose reduction determined by Monte Carlo simulation was 38.2%, 33.0% and <1% for CT scans of the orbits, whole head, and brain with an angled gantry, respectively. The difference between the Monte Carlo derived eye lens dose reduction factor values and corresponding values determined directly by using the anthropomorphic phantom head was found less than 5%. The mean eye lens dose reduction achieved by bismuth shielding in pediatric patients were 34%, 20% and <2% when eye globes were entirely included, partly included and excluded from the scanned region, respectively. A significant reduction in eye lens dose may be achieved by using superficial orbital bismuth shielding during pediatric head CT scans. However, bismuth garments should not be used in children when the eyes are excluded from the primarily exposed region.

The effect of z overscanning on radiation burden of pediatric patients undergoing head CT with multidetector scanners : A Monte Carlo study

The purpose of this study was to investigate the effect of z overscanning on eye lens dose and effective dose received by pediatric patients undergoing head CT examinations. A pediatric patient study was carried out to obtain the exposure parameters and data regarding the eye lens position with respect to imaged volume boundaries. This information was used to simulate CT exposures by Monte Carlo code. The Monte Carlo N-Particle (MCNP, version 4C2) radiation transport code and five mathematical anthropomorphic phantoms representing newborn, 1-, 5-, 10-, and 15-year-old patient, were employed in the current study. To estimate effective dose, the weighted computed tomography dose index was calculated by cylindrical polymethyl-methacrylate phantoms of 9.7, 13.1, 15.4, 16.1, and 16.9 cm in diameter representing the pediatric head of newborn, 1-, 5-, 10-, and 15-year-old individuals, respectively. The validity of the Monte Carlo calculated approach was verified by comparison with dose data obtained using physical pediatric anthropomorphic phantoms and thermoluminescence dosimetry. For all patients studied, the eye lenses were located in the region -1 to 3 cm from the first slice of the imaged volume. Doses from axial scans were always lower than those from corresponding helical examinations. The percentage differences in normalized eye lens absorbed dose between contiguous axial and helical examinations with pitch=1 were found to be up to 10.9%, when the eye lenses were located inside the region to be imaged. When the eye lenses were positioned 0-3 cm far from the first slice of region to be imaged, the normalized dose to the lens from contiguous axial examinations was up to 11 times lower than the corresponding values from helical mode with pitch=1. The effective dose from axial examinations was up to 24% lower than corresponding values from helical examinations with pitch=1. In conclusion, it is more dose efficient to use axial mode acquisition rather than helical scan for pediatric head examinations, if there are no overriding clinical considerations.

Childhood encephalitis in Crete, Greece.

This study included all 18 cases of children hospitalized for encephalitis in the referral university hospital of Heraklion, Crete, Greece, during the 5-year period from 2000 to 2004. Encephalitis was attributed to viral infection (echovirus, herpes simplex virus 1, varicella-zoster virus, cytomegalovirus, and influenza A) in eight children and to bacteria (Mycoplasma pneumoniae, group A β-hemolytic streptococcus, and Rickettsia typhi) in a further five cases. Multiple hyperintense brain lesions on magnetic resonance imaging (MRI) were associated with a severe clinical presentation but not with a guarded long-term outcome. Five children still presented with mild to moderate sequelae after 1.5 to 5.3 (median 4.0) years. Our findings confirm the elimination of measles, mumps, and rubella—associated encephalitis in the postvaccine era. MRI appeared to be of great diagnostic value. Although no fatalities were observed, deficits did persist in several patients. (J Child Neurol 2006;21:910—912; DOI 10.2310/7010.2006.00217).

Radiation dose and cancer risk to children undergoing skull radiography

Background: Limited data exist in the literature concerning the patient-effective dose from paediatric skull radiography. No information has been provided regarding organ doses, patient dose during PA skull projection, risk of cancer induction and dose to comforters, i.e. individuals supporting children during exposure. Objective: To estimate patient-effective dose, organ doses, lifetime cancer mortality risk to children and radiation dose to comforters associated with skull radiography. Materials and methods: Data were collected from 136 paediatric examinations, including AP, PA and lateral skull radiographs. Entrance-surface dose (ESD) and dose to comforters were measured using thermoluminescent dosimeters. Patients were divided into the following age groups: 0.5–2, 3–7, 8–12 and 13–18 years. The patient-effective dose and corresponding organ doses were calculated using data from the NRPB and Monte Carlo techniques. The risk for fatal cancer induction was assessed using appropriate risk coefficients. Results: For AP, PA and lateral skull radiography, effective dose ranges were 8.8–25.4, 8.2–27.3 and 8.4–22.7 μSv respectively, depending upon the age of the child. For each skull projection, the organs receiving doses above 10 μGy are presented. The number of fatal cancers was found to be less than or equal to 2 per 1 million children undergoing a skull radiograph. The mean radiation dose absorbed by the hands of comforters was 13.4 μGy. Conclusions: The current study provides detailed tabular and graphical data on ESD, effective dose, organ doses and lifetime cancer mortality risk to children associated with AP, PA and lateral skull projections at all patient ages.

Normalized dose data for upper gastrointestinal tract contrast studies performed to infants

The aim of the current study was to (a) provide normalized dose data for the estimation of the radiation dose from upper gastrointestinal tract contrast (UGIC) studies carried out to infants and (b) estimate the average patient dose and risks associated with radiation from UGIC examinations performed in our institution. Organ and effective doses, normalized to entrance skin dose (ESD) and dose area product (DAP) were estimated for UGIC procedures utilizing the Monte Carlo N-particle (MCNP) transport code and two mathematical phantoms, one corresponding to the size of a newborn and one to the size of a 1-year-old child. The validity of the MCNP results was verified by comparison with dose data obtained in physical anthropomorphic phantoms simulating a newborn and a 1-year-old infant using thermoluminescence dosimetry (TLD). Data were also collected from 25 consecutive UGIC examinations performed to infants. Study participants were (a) 12 infants aged from 0.5 to 5.9 months (group 1) and (b) 13 infants aged from 6 to 15 months (group 2). For each examination, ESD and dose to comforters were measured using TLD. Patient effective doses were estimated using normalized dose data obtained in the simulation study. The risk for fatal cancer induction was estimated using appropriate coefficients. The results consist of tabulated dose data normalized to ESD or DAP for the estimation of patient dose. Conversion coefficients were estimated for various tube potentials and beam filtration values. The mean total fluoroscopy time was 1.26 and 1.62 min for groups 1 and 2, respectively. The average effective dose was 1.6 mSv for group 1 and 1.9 mSv for group 2. The risk of cancer attributable to the radiation exposure associated with a typical UGIC study was found to be up to 3 per 10 000 infants undergoing an UGIC examination. The mean radiation dose absorbed by the hands of comforters was 47 microGy. In conclusion, estimation of radiation doses associated with UGIC studies performed to infants can be made using the normalized dose data provided in the current study. Radiation dose values associated with UGIC examinations carried out to infants are not low and should be minimized as much as possible.

Insulin‐induced oedema in children and adolescents

Abstract:  Oedema is an uncommon complication of insulin therapy, which has only rarely been reported in childhood. We describe a case of a 12‐year‐old girl with newly diagnosed type 1 diabetes, who presented with oedema of the lower extremities and periorbitally, one day after the initiation of insulin treatment. Other causes of oedema were excluded. Following administration of frusemide, oedema resolved within ten days. An extended review of the literature revealed only nine cases of insulin‐induced oedema in children and adolescents aged ≤16 years. In conclusion, insulin‐induced oedema should be considered during the introduction of insulin therapy in children and adolescents with newly diagnosed type 1 diabetes. Loop diuretics and ephedrine may be beneficial when spontaneous resolution does not occur.

Hepatodiaphragmatic interposition of the colon in the upright and supine position

OBJECTIVE Hepatodiaphragmatic interposition of the colon (HDIC) has been previously evaluated with chest radiography (CR) of patients examined in an erect position. In this work the presence of HDIC was assessed in patients who underwent CT in the supine position. MATERIALS AND METHODS In 1,440 patients, 806 men and 634 women, 19-83 years old subjected to CR and abdominal CT for various indications, HDIC was retrospectively evaluated. RESULTS In 2.4% of the patients HDIC was found using CT in the supine position but in only 0.3% on CR. The variation appeared more frequently in men than in women and in older adults and individuals with an increased amount of intraabdominal fat. This latter finding may represent an additional factor favoring malposition of the colon. CONCLUSION The results of this study indicate that HDIC has a significantly greater incidence in the supine position of patients, and it can not be excluded on the basis of negative CR.

Effect of x-ray tube parameters and iodine concentration on image quality and radiation dose in cerebral pediatric and adult CT angiography: a phantom study.

ObjectivesThe aim of the present phantom study was to investigate the effect of x-ray tube parameters and iodine concentration on image quality and radiation dose in cerebral computed tomographic (CT) angiographic examinations of pediatric and adult individuals. Materials and MethodsFour physical anthropomorphic phantoms that represent the average individual as neonate, 1-year-old, 5-year-old, and 10-year-old children and the RANDO phantom that simulates the average adult individual were used. Cylindrical vessels were bored along the brain-equivalent plugs of each physical phantom. To simulate the brain vasculature, vessels of 0.6, 1, 2, and 3 mm in diameter were created. These vessels were filled with contrast medium (CM) solutions at different iodine concentrations, that is, 5.6, 4.2, 2.7, and 1.4 mg I/mL. The phantom heads were scanned at 120, 100, and 80 kV. The applied quality reference tube current-time product values ranged from a minimum of 45 to a maximum of 680. The CT acquisitions were performed on a 16-slice CT scanner using the automatic exposure control system. Image quality was evaluated on the basis of image noise and contrast-to-noise ratio (CNR) between the contrast-enhanced iodinated vessels and the unenhanced regions of interest. Dose reduction was calculated as the percentage difference of the CT dose index value at the quality reference tube current-time product and the CT dose index at the mean modulated tube current-time product. ResultsImage noise that was measured using the preset tube current-time product settings varied significantly among the different phantoms (P < 0.0001). Hounsfield unit number of iodinated vessels was linearly related to CM concentration (r2 = 0.907) and vessel diameter (r2 = 0.918). The Hounsfield unit number of iodinated vessels followed a decreasing trend from the neonate phantom to the adult phantom at all kilovoltage settings. For the same image noise level, a CNR improvement of up to 69% and a dose reduction of up to 61% may be achieved when CT acquisition is performed at 80 kV compared with 120 kV. For the same CNR, a reduction by 25% of the administered CM concentration may be achieved when CT acquisition is performed at 80 kV compared with 120 kV. ConclusionsIn cerebral CT angiographic studies, appropriate adjustment of the preset tube current-time product settings is required to achieve the same image noise level among participants of different age. Cerebral CT angiography at 80 kV significantly improves CNR and significantly reduces radiation dose. Moreover, at 80 kV, a considerable reduction of the administered amount of the CM may be reached, thus reducing potential risks for contrast-induced nephropathy.