Article

Influencia del movimiento respiratorio sobre el contraste de las lesiones en estudios de perfusión pulmonar: simulación mediante el uso de un fantoma virtual.

Alasbimn Journal 01/2010;
Source: DOAJ

ABSTRACT ResumenEl movimiento respiratorio (MR) constituye un factor de degradación de las imágenes con potencial influencia sobre la capacidad de detección de lesiones tromboembólicas en estudios de perfusión pulmonar. El objetivo fue investigar la influencia del MR sobre el contraste de lesiones pulmonares, por medio de simulación con un fantoma virtual. Mediante un fantoma N-CAT se generó un modelo de perfusión pulmonar con SPECT; el modelo fue reconstruido produciendo cortes tomográficos y reproyección de los mismos en tres situaciones: sin MR, simulando MR con desplazamiento diafragmático de 2 cm, y con desplazamiento de 4 cm. Se instalaron en el modelo 7 “lesiones” hipocaptantes simulando la situación del tromboembolismo pulmonar (TEP) en situación superior, media y basal y se calculó el contraste de las lesiones en las 3 situaciones descriptas. Los resultados muestran que el contraste de las lesiones es menor con el MR, que se deteriora más cuanto mayor es la magnitud del MR, y que el MR afecta en mayor grado el contraste de las lesiones de ubicación basal. La corrección de MR podría mejorar la detectabilidad de algunos defectos de perfusión, especialmente los de ubicación basal, incrementando la sensibilidad de la técnica para el diagnóstico de TEP. AbstractRespiratory motion (RM) represents a major factor of image degradation with potential impact on the detection of embolic lesions in lung perfusion scintigraphy. The aim was to investigate the influence of RM on the contrast of pulmonary lesions through a simulation study with a virtual phantom. Using a N-CAT phantom, a SPECT lung perfusion model was generated; the model was reconstructed producing three sets of tomographic slices and image reprojection under different conditions: without RM, RM simulation with 2 cm diaphragmatic displacement, and RM simulation with 4 cm diaphragmatic displacement. Seven “cold” lesions were placed in the model resembling a typical pulmonary embolism (PE) situation in superior, medial and basal locations and image contrast was calculated. Results showed a decrease in lesion contrast proportional to the degree of RM, which was more pronounced for basal lesions. Motion correction could improve the detectability of some perfusión defects, especially those in basal locations, thus incrementing the sensitivity of the technique for the diagnosis of PE.

0 Bookmarks
 · 
93 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The development of positron emission tomography/computed tomography (PET/CT) scanners has allowed not only straightforward but also synergistic fusion of anatomical and functional information. Combined PET/CT imaging yields an increased sensitivity and specificity beyond that which either of the 2 modalities possesses separately and therefore provides improved diagnostic accuracy. Because attenuation correction in PET is performed with the use of CT images, with CT used in the localization of disease, accurate spatial registration of PET and CT image sets is required. Correcting for the spatial mismatch caused by respiratory motion represents a particular challenge for the requisite registration accuracy as a result of differences in temporal resolution between the 2 modalities. This review provides a brief summary of the materials, methods, and results involved in multiple investigations of the correction for respiratory motion in PET/CT imaging of the thorax, with the goal of improving image quality and quantitation. Although some schemes use respiratory-phase data selection to exclude motion artifacts, others have adopted sophisticated software techniques. The various image artifacts associated with breathing motion are also described.
    Seminars in Nuclear Medicine 06/2008; 38(3):167-76. · 3.82 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Pulmonary embolism (PE) can only be diagnosed with imaging techniques, which in practice is performed using ventilation/perfusion scintigraphy (V/P(SCAN)) or multidetector computed tomography of the pulmonary arteries (MDCT). The epidemiology, natural history, pathophysiology and clinical presentation of PE are briefly reviewed. The primary objective of Part 1 of the Task Group's report was to develop a methodological approach to and interpretation criteria for PE. The basic principle for the diagnosis of PE based upon V/P(SCAN) is to recognize lung segments or subsegments without perfusion but preserved ventilation, i.e. mismatch. Ventilation studies are in general performed after inhalation of Krypton or technetium-labelled aerosol of diethylene triamine pentaacetic acid (DTPA) or Technegas. Perfusion studies are performed after intravenous injection of macroaggregated human albumin. Radiation exposure using documented isotope doses is 1.2-2 mSv. Planar and tomographic techniques (V/P(PLANAR) and V/P(SPECT)) are analysed. V/P(SPECT) has higher sensitivity and specificity than V/P(PLANAR). The interpretation of either V/P(PLANAR) or V/P(SPECT) should follow holistic principles rather than obsolete probabilistic rules. PE should be reported when mismatch of more than one subsegment is found. For the diagnosis of chronic PE, V/P(SCAN) is of value. The additional diagnostic yield from V/P(SCAN) includes chronic obstructive lung disease (COPD), heart failure and pneumonia. Pitfalls in V/P(SCAN) interpretation are considered. V/P(SPECT) is strongly preferred to V/P(PLANAR) as the former permits the accurate diagnosis of PE even in the presence of comorbid diseases such as COPD and pneumonia. Technegas is preferred to DTPA in patients with COPD.
    European Journal of Nuclear Medicine 07/2009; 36(8):1356-70. · 4.53 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The aim of our study was to investigate the importance of attenuation correction (AC) in reconstructed and reprojected images on lung SPECT studies. Simulation studies were undertaken to evaluate the influence of AC on defect-to-normal ratios (D/N), to demonstrate the influence of errors in the correction map values and to detect lung boundaries used for AC. The use of a synthetic map (SM) for AC of the clinical data was also evaluated and the results compared with those obtained with data derived from CT (CTM). Additionally, the role of AC in reprojected SPECT data was assessed and level of noise on the 'planar-like' images was measured. Phantom studies showed that AC markedly affects the D/N ratio. However, variations in micro values typical of those found in clinical studies resulted in relatively small changes in results. Eroded and dilated conditions did not cause any significant effect on D/N. The level of noise in the reprojected images is reduced in comparison with real planar data. Clinical SPECT/CT data reconstructed with AC using CTM and SM showed an excellent correlation between the two methods. AC improves D/N in lung SPECT studies, thus potentially enhancing the diagnostic capability of the method. The use of a synthetic map for AC is feasible, avoiding the need for an additional procedure and the increased radiation dose involved. Planar-like images generated from reprojected SPECT data are well matched to normal planar images provided AC is performed and attenuation included in the reprojection.
    European Journal of Nuclear Medicine 03/2009; 36(7):1076-89. · 4.53 Impact Factor

Full-text (4 Sources)

View
34 Downloads
Available from
Jun 6, 2014