Computed tomography attenuation in differential diagnosis of transudative and exudative pleural effusions.

OBJECTIVE: Pleural effusion is a common medical problem. It is important to decide whether the pleural fluid is a transudate or an exudate. This study aims to measure the attenuation values of pleural effusions on thorax computed tomography and to investigate the efficacy of this measurement in the diagnostic separation of transudates and exudates. MATERIALS AND METHODS: 380 cases who underwent thoracentesis and thorax computed tomography with pleural effusion were classified as exudates or transudates based on Light's criteria. Attenuation measurements in Hounsfield units were performed through the examination of thorax computed tomography images. RESULTS: 380 patients were enrolled (39 % women), the mean age was 69.9 ± 15.2 years. 125 (33 %) were transudates whereas 255 (67 %) were exudates. The attenuation values of exudates were significantly higher than transudates (15.1 ± 5.1 and 5.0 ± 3.4) (p < 0.001). When the attenuation cut-off was set at ≥ 10 HU, exudates were differentiated from transudates at high efficiency (sensitivity is 89.7 %, specificity is 94.4 %, PPV is 97 %, NPV is 81.9 %). When the cut-off value was accepted as < 6 HU, transudates were differentiated from exudates with 97.2 % specificity. CONCLUSION: The attenuation measurements of pleural fluids can be considered as an efficacious way of differentiating exudative and transudative pleural effusions.

Single-Slice Hounsfield Unit (HU) Value of the Chinese Proximal Humerus on Routine Chest CT: A Study on Opportunistically Screening for Low Bone Density / Valor de Unidad Hounsfield (HU) de Corte Único del Húmero Proximal Chino en una Tomografía Computarizada de Tórax de Rutina: Un Estudio sobre la Detección Oportunista de Baja Densidad Ósea

SUMMARY: A Study on Relationship between Single-Slice Hounsfield Unit(HU) value of the Chinese proximal humerus and Bone Mineral Density(BMD) Using Routine Chest CT and Dual-energy X-ray Absorptiometry(DEXA) was performed. Data were collected from 240 individuals who underwent DEXA and routine chest CT scans (including full images of the proximal humerus) on the same day at 967 Hospitals between January 2019 and December 2021. The method of measuring single-slice HU values of the proximal humerus on routine chest CT scans exhibited high reliability and repeatability (intraclass correlation coefficient > 0.961, P < 0.001). A strong positive correlation was observed between single-slice HU values of the proximal humerus and DEXA results, with the 20-mm HU value demonstrating the highest correlation. Across different BMI groups, the Area Under Curve (AUC) for the 20-mm HU value was consistently the largest (AUC=0.701- 0.813, P< 0.05). Therefore, the 20-mm HU value can be considered a reliable reference for the opportunistic screening of low BMD, with reference values of -4HU for underweight individuals, -13HU for normal weight individuals, -7HU for overweight individuals, and -16HU for obese individuals. Values below these thresholds indicate a risk of low BMD. This study enriches the Chinese BMD data and offers a swift and effective approach for opportunistically screening low BMD.

Se realizó un estudio sobre la relación entre el valor de la Unidad Hounsfield (HU) de corte único del húmero proximal chino y la densidad mineral ósea (DMO) mediante TC de tórax de rutina y absorciometría de rayos X de energía dual (DEXA). Se recopilaron datos de 240 personas que se sometieron a DEXA y tomografías computarizadas de rutina de tórax (incluidas imágenes completas del húmero proximal) el mismo día en 967 hospitales entre enero de 2019 y diciembre de 2021. El método para medir los valores de HU de un solo corte del húmero proximal en las tomografías computarizadas de tórax mostraron alta confiabilidad y repetibilidad (coeficiente de correlación intraclase > 0,961, P < 0,001). Se observó una fuerte correlación positiva entre los valores de HU de un solo corte del húmero proximal y los resultados de DEXA, demostrando el valor de HU de 20 mm la correlación más alta. En diferentes grupos de IMC, el área bajo la curva (AUC) para el valor HU de 20 mm fue consistentemente el más grande (AUC = 0,701-0,813, P <0,05). Por lo tanto, el valor de HU de 20 mm puede considerarse una referencia fiable para el cribado oportunista de DMO baja, con valores de referencia de -4 HU para personas con bajo peso, -13 HU para personas con peso normal, -7 HU para personas con sobrepeso y -16 HU para personas obesas. Los valores por debajo de estos umbrales indican un riesgo de DMO baja. Este estudio es un aporte para los datos chinos sobre la DMO y ofrece un enfoque rápido y eficaz para detectar de forma oportunista la DMO baja.

Computed tomographic characterization of urinary stones in patients with urolithiasis from Southeast Mexico.

Urolithiasis (UL) is a severe public health concern in southeastern Mexico. Computed tomography (CT) is the first-line diagnostic method for patients with suspected UL. The present study aimed to characterize stones in the entire urinary system using CT and to contribute to personalized treatment in patients with UL. Patients >18 years of age with suspected UL were enrolled. Characteristics of UL included stone size, location (kidney, ureters, and bladder), composition of the stone in Hounsfield units (HU), presence of staghorn stone(s), and obstructive uropathy. Patients were stratified according to sex and age to determine whether stone size and HU were dependent on hormonal factors in females and on prostatic hyperplasia in males. The Mann-Whitney U test was used to compare median values. Frequencies are expressed as percentages and were analyzed using the Mantel-Haenszel chi-squared test. A total of 1150 patients were included in this study, of whom 744 (64.7 %) had UL in only 1 anatomical location in the urinary system, and 406 (35.3 %) had stones in ≥2 anatomical locations. Localization and stone size differed between males and females (p < 0.05). Additionally, males exhibited differences in HU (p = 0.024) and frequency of obstructive uropathy (p = 0.10) when stratified according to age (≤50 and > 50 years). In addition, females exhibited statistical differences in HU (p = 0.010) and kidney stone size (p = 0.047) dependent on age (≤47 and > 47 years). In conclusion, findings suggest that HU and stone size differ in different anatomical structures of the urinary system. In addition, differences in stone size and composition may be associated with age and sex.

Computed tomography attenuation in differential diagnosis of transudative and exudative pleural effusions

Abstract Objective: Pleural effusion is a common medical problem. It is important to decide whether the pleural fluid is a transudate or an exudate. This study aims to measure the attenuation values of pleural effusions on thorax computed tomography and to investigate the efficacy of this measurement in the diagnostic separation of transudates and exudates. Materials and methods: 380 cases who underwent thoracentesis and thorax computed tomography with pleural effusion were classified as exudates or transudates based on Light's criteria. Attenuation measurements in Houns-field units were performed through the examination of thorax computed tomography images. Results: 380 patients were enrolled (39 % women), the mean age was 69.9 ± 15.2 years. 125 (33 %) were transudates whereas 255 (67 %) were exudates. The attenuation values of exudates were significantly higher than transudates (15.1 ± 5.1 and 5.0 ± 3.4) (p< 0.001). When the attenuation cut-off was set at ≥ 10 HU, exudates were differentiated from transudates at high efficiency (sensitivity is 89.7 %, specificity is 94.4 %, PPV is 97 %, NPV is 81.9 %). When the cut-off value was accepted as < 6 HU, transudates were differentiated from exudates with 97.2 % specificity. Conclusion: The attenuation measurements of pleural fluids can be considered as an efficacious way of differentiating exudative and transudative pleural effusions.

Implementación de las curvas de densidad electrónica relativa al sistema de planificación de tratamiento en teleterapia mediante la calibración estequiométrica

Objetivos: el objetivo de este trabajo fue integrar curvas de densidad electrónica relativa al sistema de planificación de tratamiento CAT3D utilizando el método alternativo de la calibración estequiométrica. Métodos: se utilizó aluminio como material de calibración y un maniquí torácico con insertos y se consideraron 3 casos en la planificación del tratamiento: campo directo 10x10cm2, campo directo 20x20cm2 y campo lateral 10x10cm2 con cuña, donde se puso a prueba el sistema de planificación basado en el algoritmo Pencil Beam. Resultados: se encontró que el uso incorrecto de estas curvas afecta significativamente la dosis absorbida hasta en un 6% en regiones de cambios bruscos de densidad, excediendo la tolerancia recomendada de ±5% en la entrega de dosis adsorbida en regiones de equilibrio electrónico. Conclusiones: se concluyó que la implementación y uso correcto de estas curvas mejora la aproximación en medios heterogéneos, reduciendo la desviación de sus resultados.

Objectives: the objective of this work was to integrate relative electron density curves to the CAT3D treatment planning system using the alternative method of stoichiometric calibration. Methods: aluminum was usec as calibration material and a thoracic mannequin with inserts and 3 cases were considered in the treatment planning: direct field 10x10cm2, direct field 20x20cm2 and lateral field 10x10cm2 with wedge, where the planning system based on the Pencil Beam algorithm was tested. Results: it was found that incorrect use of these curves significantly affects the absorbed dose by up to 6% in regions of sudden changes in density exceeding the recommended tolerance of ±5% in the delivery of adsorbed dose in regions of electronic equilibrium. Conclusions: it was concluded that the implementation and correct use of these curves improves the approximation in heterogeneous media, reducing the deviation of their results.

Identification of Bone Mineral Density Deficit Using L1 Trabecular Attenuation by Opportunistic Multidetector CT Scan in Adult Patients.

BACKGROUND: Multidetector computer tomography (CT) has been used to diagnose pathologies such as osteoporosis via opportunistic screening, where the assessment of the bone structure and the measurement of bone mineral density (BMD) are of great relevance. PURPOSE: To construct reference BMD values based on the measurement of the attenuation of the L1 vertebral body by multidetector CT scan (in the soft tissue and bone windows) in adult patients and to establish normative ranges by sex and age of BMD values. MATERIALS AND METHODS: A retrospective cross-sectional study of 5080 patients who underwent multidetector CT scan between January and December 2021. Adult patients (≥18 years) with non-contrast multidetector CT scan of the abdomen or thorax-abdomen at a voltage 120 kV. The attenuation of the L1 vertebral body in Hounsfield units (HU) in both windows were compared using the Mann-Whitney U-test with α = 0.05. Additionally, the quartiles of the BMD were constructed (in both windows) grouped by sex and age. RESULTS: Only 454 (51.30 ± 15.89 years, 243 women) patients met the inclusion criteria. There is no difference in BMD values between windows (soft tissue: 163.90 ± 57.13, bone: 161.86 ± 55.80, p = 0.625), mean L1 attenuation decreased linearly with age at a rate of 2 HU per year, and the presence of BMD deficit among patients was high; 152 of 454 (33.48%) patients presented BMD values suggestive of osteoporosis, and of these, approximately half 70 of 454 (15.42%) corresponded to patients with BMD values suggestive of a high risk of osteoporotic fracture. CONCLUSIONS: From clinical practice, the bone mineral density (BMD) of a patient in either window below the first quartile for age- and sex-matched peers suggests a deficit in BMD that cannot be ignored and requires clinical management that enables identification of the etiology, its evolution, and the consequences of this alteration.

Implementation of a Technique Based on Hounsfield Units and Hounsfield Density to Determine Kidney Stone Composition.

Hounsfield units (HU) are a measure of radiodensity, related to the density of a tissue and the composition of kidney stones. Hounsfield density is what is related to the composition of kidney stones. In the standard acquisition method, these measures are arbitrary and dependent on the operator. This study describes the implementation of a technique based on the HU and Hounsfield density to predict the stone compositions of patients with nephrolithiasis. By conventional percutaneous nephrolithotomy, thirty kidney stone samples corresponding to the cortex, middle, and nucleus were obtained. The HU were obtained by CT scanning with a systematic grid. Hounsfield density was calculated as the HU value divided by the stone's greatest diameter (HU/mm). With that method and after analyzing the samples by IR-spectroscopy, anhydrous uric acid and ammonium magnesium phosphate were identified as the compounds of kidney stones. Additionally, anhydrous uric acid, magnesium ammonium phosphate, and calcium oxalate monohydrate were identified via Hounsfield density calculation. The study identified HU ranges for stone compounds using a systematic technique that avoids bias in its analysis. In addition, this work could contribute to the timely diagnosis and development of personalized therapies for patients with this pathology.

Valores de densidad en la escala de grises en Tomografía Computarizada de Haz Cónico: alcances y limitaciones / Grayscale Values in Cone Beam Computed Tomography: Scope and Limitations

ABSTRACT: Cone-beam computed tomography (CBCT) is a 3D imaging technique widely used in maxillofacial diagnosis. The grayscale value (GSV) is a number that represents the amount of attenuation of the X-ray beam by the material contained in each voxel or structural unit of the tomographic volume. Similarly, in computed tomography (CT) used in medical radiology, the attenuation values are standardized in the Hounsfield Unit (HU) scale. Although GSV may have interesting potential applications in maxillofacial diagnosis, it is essential to know that HU differ from GSV. The latter are susceptible to multiple technical factors during the tomographic acquisition, so their value can vary among different CBCT scanners or when technical parameters are modified. Hence, GSV should not be extrapolated between different CBCT machines, and their use should be cautious while more investigation is available considering various equipment and acquisition protocols.

RESUMEN: La tomografía computarizada de haz cónico (CBCT, por sus siglas en inglés) es una técnica de imagen 3D ampliamente usada en diagnóstico maxilofacial. El valor de densidad en la escala de grises (DEG) es una cifra que corresponde al grado de atenuación de los rayos x del material representado en cada vóxel o unidad estructural de la tomografía. De forma similar, en los sistema de tomografía computarizada de uso médico (CT) el valor de atenuación está estandarizado en las Unidades Hounsfield (UH). Aunque los valores de DEG pueden tener interesantes usos potenciales en el apoyo de diagnóstico en el área dentoalveolar, es importante conocer que los valores UH no son los mismos a los valores DEG, y que los valores de DEG son susceptibles a múltiples factores técnicos durante la adquisición de la tomografía, por lo que se pueden obtener resultados distintos entre equipos y al variar parámetros técnicos en las tomas. Por lo tanto sus valores no deben extrapolarse entre equipos y su uso debe ser cauteloso mientras se realiza mayor investigación específica para cada equipo y para cada protocolo de adquisición.

Lung radiofrequency ablation: post-procedure imaging patterns and late follow-up.

PURPOSE: To describe expected imaging features on chest computed tomography (CT) after percutaneous radiofrequency ablation (RFA) of lung tumors, and their frequency over time after the procedure. METHODS: In this double-center retrospective study, we reviewed CT scans from patients who underwent RFA for primary or secondary lung tumors. Patients with partial ablation or tumor recurrence during the imaging follow-up were not included. The imaging features were assessed in pre-defined time points: immediate post-procedure, ≤4 weeks, 5-24 weeks, 25-52 weeks and ≥52 weeks. Late follow-up (3 and 5 years after procedure) was assessed clinically in 48 patients. RESULTS: The study population consisted of 69 patients and 144 pulmonary tumors. Six out of 69 (9%) patients had primary lung nodules (stage I) and 63/69 (91 %) had metastatic pulmonary nodules. In a patient-level analysis, immediately after lung RFA, the most common CT features were ground glass opacities (66/69, 96 %), consolidation (56/69, 81 %), and hyperdensity within the nodule (47/69, 68 %). Less than 4 weeks, ground glass opacities (including reversed halo sign) was demonstrated in 20/22 (91 %) patients, while consolidation and pleural thickening were detected in 17/22 patients (77 %). Cavitation, pneumatocele, pneumothorax and pleural effusions were less common features. From 5 weeks onwards, the most common imaging features were parenchymal bands. CONCLUSIONS: Our study demonstrated the expected CT features after lung RFA, a safe and effective minimally invasive treatment for selected patients with primary and secondary lung tumors. Diagnostic and interventional radiologists should be familiar with the expected imaging features immediately after RFA and their change over time in order to avoid misinterpretation and inadequate treatments.

Sensitivity and Specificity of Computed Tomography in the Evaluation of Bone Mineral Density in Mexican Patients with Breast Cancer.

Introduction Breast cancer (BC) is the most frequently reported cancer among women - reported in 2012 as 25% of all cancers. BC has been related to the increased life and activity of osteoclasts, conferring a higher risk for osteoporosis/osteopenia. This study aimed to determine a cut-off point in Hounsfield units (HU) as well as the sensitivity and specificity of computed axial tomography (CT) in the diagnosis of osteoporosis/osteopenia in Mexican women with BC. Material and methods We included 108 patients with a histopathological diagnosis of BC treated at the ABC Medical Center in Mexico City. All patients were subjected to both dual X-ray densitometry and CT. The receiver operating characteristic (ROC) curve was used to identify the cutoff point and sensitivity and specificity were calculated, as were confidence intervals for the diagnoses of osteoporosis/osteopenia. Results The mean age was 58.49 ± 11.01 years. The cutoff point with the highest sensitivity (82%) and specificity (68%) was <157 HU for osteoporosis/osteopenia in patients with BC. Conclusions Women with BC are exposed to several risk factors for osteoporosis/osteopenia. The CT obtained for the general evaluation of these patients can also be used to evaluate bone mineral density, avoiding additional examinations and exposure to radiation, as well as the cost it confers, offering an earlier diagnosis of osteoporosis/osteopenia for its control.

Comportamiento dosimétrico de un sistema de planificación mediante curvas de calibración de densidades electrónicas relativas / Dosimetric behaviour of a planning system through calibration curves of relative electron density

En esta investigación se planteó como objetivo la verificación del comportamiento dosimétrico del Sistema de Planificación de Tratamiento (TPS) de Radioterapia mediante las curvas de calibración de Densidades Electrónicas Relativas (DER). Este estudio se realizó en el Hospital de la Sociedad de Lucha Contra el Cáncer (SOLCA) Núcleo Loja, usando un fantoma antropomorfo CIRS 062M y un tomógrafo Toshiba Activion 16. Para determinar la nueva curva de calibración DER se tomaron los valores de densidades electrónicas especificadas en el manual del fantoma y las Unidades Hounsfield de la imagen tomográfica. Se realizó controles de calidad dosimétricos y verificación dosimétrica en tres casos clínicos: tórax, pelvis y cráneo; para realizar las pruebas dosimétricas se utilizó un acelerador CLINAC CX, cámara de ionización PTW tipo Farmer con volumen sensible de 0,6 cm3 y un electrómetro PTW UNIDOS E. Los resultados mostraron que las medidas para cada inserto del fantoma en ningún caso excedieron los límites establecidos de ± 20 UH, para el tomógrafo y el TPS; las pruebas de control de calidad no superaron el límite máximo de desviaciones en el cálculo de dosis absorbida por el TPS y la obtenida por medición de ± 4 % establecida por la IAEA y las verificaciones dosimétricas en tórax, pelvis y cráneo, determinaron que las desviaciones en el cálculo de la dosis absorbida por el TPS y la obtenida por medición no superaban la tolerancia del ± 5 % establecida por la ICRU.

In this research, the aim was to verify the dosimetric behavior of the Radiotherapy Treatment Planning System (TPS) using the Relative Electron Density (DER) calibration curves. This study was carried out at the SOLCA (Society of Fight Against Cancer) hospital in Loja, using an CIRS model 062M anthropomorphic phantom and a Toshiba Activion 16 tomograph. To determine the new DER calibration curve, the values of the electron densities specified in the manual of the phantom and the Hounsfield Units of the tomographic image were taken. Dosimetric quality controls were made in the location of three clinical cases: thorax pelvis and skull; used a CLINAC CX accelerator was used to perform the dosimetric tests, PTW ionization chamber type Farmer with sensitive volume of 0.6 cm3 and a PTW UNIDOS E electrometer. The results showed that the measurements for each insert of the phantom in no case exceeded the established limits of ± 20 UH, for the tomograph and the TPS; the quality control tests did not exceed the maximum limit of deviations in the calculation of dose absorbed by the TPS and the one obtained by measurement of ± 4% established by the IAEA and the clinical planning in the thorax, pelvis and skull, determine that the deviations in the calculation of the dose absorbed by the TPS and that obtained by measurement, they do not exceed the tolerance of ± 5% established by the ICR.

Two findings of gallstones in archaeological mummies from Colombia.

Results involving the analysis of gallstones found in two pre-Hispanic Colombian mummies are presented. By applying SEM, X-ray diffraction (XRD), sectioning, and CT-scan Hounsfield Units, we were able to identify these choleliths as mainly formed by cholesterol. The number of reports on gallstones in archaeological human remains from South America is very small, making these two cases an important addition to what little is known about ancient gallstone disease on the continent.

Computed tomography is a feasible method for quantifying bone density in Macaca mulatta.

Osteopathologies are a result of advanced age and decreased bone density and represent a global health problem. It is therefore important to generate models for longitudinal studies of the pathophysiology in order to improve early diagnosis and develop preventive therapies. For this kind of research, the use of computed tomography (CT) to evaluate bone health offers advantages over other techniques since it provides more complete information. The aim of this prospective, pilot study was to obtain measurements of the left femur from a population in captivity of 32 rhesus monkeys (Macaca mulatta) in order to standardize the model for future research. Healthy subjects from 5 to 28 years old were chosen. Three groups with different ages were formed as follows: (1) 5-9 years, (2) 10-19 years, and (3) 20-28 years. Semi-automatic segmentation by threshold defined the regions of interest, which were subdivided in the range of 300-700 Hounsfield units (HU) for trabecular bone and >700 HU for cortical bone. Then, the proportional ratios of the volumes of trabecular bone and cortical bone were obtained. Significant differences (analysis of variance test) in the averages of Hounsfield units, cortical, and trabecular bone proportions from each age group proved that a decrease in bone density begins at approximately 20 years of age. The values presented here, as well as the method to obtain them from CT scans, can be used as a baseline in a primate model for long-term research in bone pathology diagnosis and treatment.