Kilovoltage Technique Research Articles

Radiation dose reduction for chest radiography of infants in intensive care units using a high peak kilovoltage-technique.

Chest radiography is an important tool in the care of infants in intensive care units. Image optimization must be monitored to minimize radiation exposure in this susceptible population. To examine the use of a high tube peak kilovoltage technique to achieve radiation dose reduction while maintaining adequate image quality. A retrospective study was conducted. Radiation doses of chest radiographs performed in the pediatric intensive care units in our institution were calculated. The radiographs were divided into two groups based on the value of the peak kilovoltage used: above and below 60 kilovolts (kV). Image quality was blindly assessed by two fellowship-trained pediatric radiologists. Air kerma, effective dose and quality score for the high versus the low peak kilovoltage group were compared and analyzed. The study included 376 radiographs. One hundred and seven radiographs were performed using peak kilovoltage values equal to or above 60kV and 269 radiographs were performed using values under 60kV. The average air kerma for the lower peak kilovoltage group was 56.6 microgray (µGy) (30.7-81.9) vs. 22.9µGy (11.8-34.4) for the higher peak kilovoltage group (P<0.0001). The mean difference in effective dose between the groups was 11.68 (P<0.0001). The mean difference for the quality score was 0.06 (±0.03, P=0.10), not statistically significant. A high peak kilovoltage technique may enable a statistically significant radiation dose reduction without compromising the diagnostic value of the image.

CT of cardiac and extracardiac vascular anomalies: embryological implications

BackgroundCongenital heart disease (CHD) is the most common neonatal anomaly. Extracardiac findings are commonly associated with CHD. It is mandatory to evaluate extracardiac structures for potential associated abnormalities that might impact the surgical planning for these patients. The purpose of this study was to determine the extracardiac abnormalities that could associate cardiac anomalies and to give insights into their embryological aberrations.ResultsThirty-two pediatric patients (22 males and 10 females) underwent CT angiography to assess CHD. Diagnosis of the CHD and associated extracardiac findings were recorded and tabulated by organ system and type of CHD. Retrospective ECG-gated low-peak kilovoltage (80Kvp) technique was used on 128MDCT GE machine. Patients were diagnosed according to their CHD into four groups: chamber anomalies 90%, septal anomalies 81.3%, conotruncal anomalies 59.4%, and valvular anomalies 59.4%. Extracardiac findings were found in 28 patients (87.5%) with a total of 76 findings. Vascular findings were the most prevalent as 50 vascular findings were observed in 28 patients. Aortic anomalies were the commonest vascular anomalies. Fourteen thoracic findings were observed in 12 patients; of them lung consolidation patches were the most common and 12 abdominal findings were found in seven patients, most of findings were related to situs abnormalities.ConclusionExtracardiac abnormalities especially vascular anomalies are commonly associating CHD. Along with genetic basis, aberrations in dynamics of blood flow could represent possible causes of this association.

Contrast Opacification Using a Reduced Volume of Iodinated Contrast Material and Low Peak Kilovoltage in Pulmonary CT Angiography: Objective and Subjective Evaluation

The purpose of our study was to evaluate whether a reduced volume of iodinated contrast material for pulmonary CT angiography (CTA) using a low peak kilovoltage (kVp) technique yields equivalent opacification in all vessels. Four hundred fifty-two consecutive pulmonary CTA patients (265 women and 187 men; age range, 18-91 years; mean age, 56.2 years) were retrospectively evaluated. Patients were grouped into those receiving 125 mL (n = 229) and 75 mL (n = 223) of 370 mg I/mL iodinated contrast material. Low kVp was used in all patients. Hounsfield units were measured at lobar, posterobasal segment, posterobasal ramus, and medial basal subsegmental ramus in the left lower lobe. Three thoracic radiologists blinded to contrast dose independently and randomly evaluated the quality of enhancement using a 3-point scale at the same levels. The two-sample Student's t test was used to compare contrast opacification between groups; Spearman's correlation and the C-statistic were used to assess objective and subjective measurements. Interreader agreement was measured using Kendall's coefficient. Mean contrast opacification differences between 125 mL versus 75 mL were not statistically significant (p > 0.21) at the lobar, segmental, and posterior basal rami, although the mean trended (p = 0.07) toward higher opacification of the medial basal ramus among 75 mL patients. Across all four pulmonary artery segments, there was good concordance between subjective and objective measurements, significantly higher than the null value of 0.50 (p > 0.05). For subsegmental arteries, concordance between objective and subjective measures was greater for the 75 mL group (p < 0.05). There was good interreader concordance, with a concordance coefficient of 0.70 (95% CI, 0.66-0.74). Both objective and subjective measures of contrast opacification support a reduction from 125 to 75 mL of contrast medium required for pulmonary CTA.

Avaliação das doses de radiação em uretrocistografia miccional de crianças

OBJETIVO: Analisar o produto dose-área, a dose de entrada na pele do paciente e as doses relativas à fluoroscopia e às radiografias em exames de cistouretrografia miccional em crianças. MATERIAIS E MÉTODOS: Foram avaliados os procedimentos em 37 pacientes, realizados por quatro médicos do serviço. As medições foram realizadas com um equipamento composto de uma câmara de ionização acoplada diretamente à saída do tubo de raios X e um eletrômetro (Diamentor) ligado diretamente ao computador, para a coleta dos dados. RESULTADOS: Foi observada alguma heterogeneidade na realização do procedimento, que não segue padrão de técnica radiográfica. São realizadas em média 11 radiografias por exame, usando tempo longo de fluoroscopia, com dose média final mais alta que a encontrada em referências da literatura. CONCLUSÃO: A adoção da técnica de alta quilovoltagem nas radiografias e o uso restrito da fluoroscopia podem proporcionar importante redução das doses durante a realização deste procedimento, porque o maior contribuinte para as altas doses verificadas foi a utilização da fluoroscopia.

Dual-source CT angiography of the thoracic aorta using prospective cardiac gating and a low kilovoltage technique

Dual-source CT angiography of the thoracic aorta using prospective cardiac gating and a low kilovoltage technique

Estudo dosimétrico de radiografias de tórax com o emprego de técnicas de alta quilovoltagem

Neste trabalho foi realizado estudo comparativo em radiografias de tórax empregando técnicas de alta e baixa quilovoltagens, tendo como objetivo uma melhoria da qualidade técnica das radiografias, associada a uma redução nas doses fornecidas aos pacientes. O estudo foi realizado em 48 pacientes randomizados, com realização de 70 radiografias de tórax em incidência póstero-anterior, utilizando técnicas de alta quilovoltagem (120 kVp) e carga transmitida de 2,3 mAs, e técnicas de baixa quilovoltagem (70 kVp) e carga transmitida de 5 a 10 mAs. Os valores de doses de entrada na pele foram medidos com um Diamentor. A técnica de baixa quilovoltagem apresentou um aumento de 326% na dose fornecida ao paciente, quando comparada com a técnica de alta quilovoltagem. Com o uso das técnicas de alta quilovoltagem foi constatada, ainda, uma diminuição do número de radiografias de má qualidade que necessitavam repetição, poupando os equipamentos e reduzindo custos por conta da melhoria da qualidade da imagem radiográfica.

Urography with metrizamide in children.

Noionic contrast material could have particular value in pediatric urography because of the absence of osmotic diuresis and associated fluid loss. Excretory urograms were obtained in 23 children using metrizamide at 300 mg l/ml and administered at a dose of 2.2 ml/kg. The radiographs gave excellent urinary tract opacification without changes in serum osmolality. The calyces appeared sharp but undistended, there was increased occurrence of ureteral ridging, and the urinary bladders often remained undistended at the completion of the studied. The dense opacification attainable with isoosmolar metrizamide also gave the opportunity for performing urography with higher than normal kilovoltage and thus reducing radiation exposure to the child. Also in vitro studies demonstrated the significant radiation dose reduction possible with the higher kilovoltage technique.

Predicting brain tumor histology: change of effective atomic number with contrast enhancement.

Thirty-eight enhancing intracranial neoplasms were evaluated with a dual kilovoltage technique to measure the change of effective atomic number (delta Z), and linear attenuation coefficients with the use of iodinated contrast material. The change of effective atomic number was found to separate intracranial neoplasms into three major groups: gliomas, meningiomas, and metastases. Other parameters, including linear attenuation coefficients and CT numbers, varied from less accurate to inaccurate. The change of effective atomic number with contrast enhancement not only predicted the appropriate histologic group of the neoplasm, but also aided in the differential diagnosis of neoplasms without a characteristic delta Z value.

Noninvasive Evaluation of the Pediatric Airway: A Recent Advance

Visualization of the pediatric airway is now possible by new noninvasive radiologic methodology--the magnification high kilovoltage (Mag-high KV) technique. Clinical expamles of airway diseases are presented to show the ease and utility by which precise diagnoses can be made. The dynamic aspect of airway evaluation is discussed. The Mag-high KV technique is also valuable for the number of invasive procedures it prevents.

A Double Film Technique in Mammography

This report describes a technique in mammography for recording maximum contrast and detail over the wide range of radiographic opacity in the breast while minimising radiation to the patient. There is some difference of opinion and personal preference regarding the optimal kilovoltage, film type, positioning, and other technical factors in mammography, but most radiologists using this procedure have adopted some variation of a “low” kilovoltage (25–40) technique using a fine grain, non-screen film. After viewing over 2,000 such mammograms it was felt that in some instances all areas of the breast were not well demonstrated. The technique to be described was, therefore, adopted and may be used in conjunction with any of the “standard” low kilovoltage techniques. The variations in radiographic opacity which provide the subject contrast in mammography depend on two major factors: differences in tissue thickness due to the conical or globular contour of the breast and the differential radiation absorption of the tissues themselves (fat: atomic number about 6; and breast tissue: atomic number about 7·5; Siler, Garrett, Snyder, Laughlin and Sherman, 1962) which is greatly enhanced at low kilovoltages. These factors produce a variation in subject contrast which is too great to record on a single radiograph (Gershon-Cohen, 1960). If the areas of lesser radioopacity, fat and thinner superficial regions, are properly exposed, the areas of greater radio-opacity, glandular tissue and thicker regions near the base, are underexposed. Conversely, if the more radioopaque areas are properly exposed, those less radioopaque are overexposed (Fig. 2).

QUANTITATIVE ASSESSMENT OF THE MINERAL CONTENT OF BONE: PRELIMINARY INVESTIGATION.

A number of methods for determining the quantity of mineral in bones have been considered. The use of radioisotopes of calcium and strontium in uptake studies of bone lesions has been briefly reviewed. Comparative sensitivities of the radiographic and radioisotopic methods have been indicated, and the use of 47Ca for sequential studies on skeletal tumours has been mentioned as a possibility. High accuracy in determining bone mineral concentration can be achieved by the use of transmission dose techniques provided that low energy X rays are used, but measurements are restricted to regions with only small quantities of overlying soft tissue. The morphological technique affords the simplest approach to an assessment of the patient's clinical condition, but the technique cannot be considered to give a reliable estimate of the quantity of bone mineral present. Microradiography eliminates the effect of soft tissue by the use of biopsy and a low X-ray kilovoltage, but evaluation at the same site at successive time intervals is not possible. Some problems encountered in the radiographic densitometry technique, and their solution by a suitable experimental method, have been described. The possible use of a double kilovoltage technique (currently under investigation) in bypassing the limitations of a single kilovoltage method has been outlined, and future applications of the technique have been proposed.

GONAD DOSIMETRY IN DIAGNOSTIC RADIOLOGY WITH THE HIGH KILOVOLTAGE TECHNIQUE.

Extensive investigations were made on the effects of kilovoltage on gonad dose during diagnostic radiography at kilovoltages of 150 or higher. The superficial, exit, and scatter doses corresponding to the gonad dose were measured in a phantom at voltages ranging from 60 to 190 kv. Proof was obtained that the gonad dose decreases, both at short and long distances, when the tube potential is increased. The gonad dose was considerably higher at radiographic voltages from 60to 80 kv than in the 100 to 200 kv range. (C.H.)

RADIATION DOSE TO GONADS FROM DIAGNOSTIC X-RAY EXPOSURE

The doses of x-ray received by employees of the Oak Ridge National Laboratory were investigated for the purpose of estimating the total exposure to ionizing radiation received both within and outside the medical facilities of the ORNL. A manikin was constructed to permit measurement of the radiation received by skin and gonads during examinations of the chest, knee, abdomen, pelvis, and vertebral column. The frequency of the various types of examination was also studied. The average total gonadal dose per year was 0.013 rads for males and 0.035 rads for females. Although only 5% of the total male examinations were of the abdominal area, they contributed 81 % of the total male gonad dose. Minimizing the number of abdominal examinations is most important, particularly in children, but minimizing the gonad dose during each examination should not be overlooked. Three simple steps are emphasized: use a cone or diaphragm of minimum practicable size to reduce the dose to all areas outside the field of interest, use filtration at the source to reduce the amount of soft, scattered radiation, and use the highest kilovoltage and lowest milliamperage technique which is practicable. Personal diagnostic radiation exposure records as recommended by the National Academy of Sciences may possibly be kept by expanding the system of occupational exposure records now maintained in most industrial medical departments.

The effect of high kilovoltage on hard and soft tissue definition in lateral cephalometric roentgenograms

1. 1. The conventional radiation exposure technique (that is, 60 KVP, 20 Ma. for two and one-half seconds in cephalometric roentgenography) does not result, usually, in good soft tissue definition. 2. 2. Matter is composed of an element or combination of elements. Elements are composed of molecules and atoms. Molecules are composed of atoms. Atoms are composed of positively charged nuclei and negatively charged electrons. 3. 3. The electron is the smallest known particle in the universe, and the smallest unit of an electric current. Bodies, compounds, or elements, when charged with electricity or heated, emit electrons. A stream of electrons, also called cathode rays, generated in the x-ray tube, produces a form of energy upon bombardment of the opposite electrode, the anode. The form of energy is mostly heat and less than 2 per cent roentgen rays (x-rays). 4. 4. Roentgen rays are invisible and have the speed of light or electricity. Roentgen rays are characterized by their intensity and by their wave length. Intensity designates quantity of radiant energy, while wave length describes quality. In general, short wave lengths are more penetrating than long wave lengths. 5. 5. A x-ray machine more powerful than a dental x-ray machine is desirable. An x-ray should be so calibrated that the operator can manually control the milliamperage and kilovoltage. Such control is usually not incorporated in a dental x-ray machine. 6. 6. Milliamperage and kilovoltage are important factors in x-ray radiation. The milliamperage determines the density or blackness of a film. Kilovoltage brings out the contrast between hard and soft tissues. Milliamperage is the dangerous factor in x-ray radiation and should be reduced wherever feasible. The higher the kilovoltage, the greater the penetration. 7. 7. A high kilovoltage and a very low milliampere-second technique results in a better definition of soft tissues, at the same time retaining good hard tissue rendition. With this exposure factor there is a great reduction in exposure time and x-ray radiation hazard to both patient and operator. 8. 8. In this preliminary report the suggested high kilovoltage standardized technique for cephalometric roentgenography using focal-midline cephalostat distance of 60 inches, the exposure radiation factor in 90 KVP, 20 Ma. for 3 10 second for all orthodontic subjects, regardless of age. There seems to be very little difference in film densities of all anatomic landmarks at various age levels. 9. 9. More clinical experimentation is indicated to further improve this high kilovoltage technique. At the present time I am carrying on further investigations with the use of aluminum filters.