Question:

Which of the following is a measure of parenchymal density?
1. 3He magnetic resonance imaging (MRI) ventilation defect percent (VDP)
2. 3He MRI apparent diffusion coefficients (ADC)
3. Computed tomography (CT) measurement of the relative area of the lung with attenuation values -950HU (RA950)
4. Diffusing capacity of the lung for carbon monoxide (DLCO)
5. Residual volume (RV)





Answer:

The correct answer for the question "Which of the following is a measure of parenchymal density?" is:

3. Computed tomography (CT) measurement of the relative area of the lung with attenuation values -950HU (RA950)



Explanation
1. 3He MRI ventilation defect percent (VDP) measures 3He ventilation within the lung [3He MRI ventilation images were quantified to generate ventilation defect percent (VDP) which is the volume of the lung not participating in ventilation, normalized to total lung volume.]
2. 3He MRI apparent diffusion coefficients (ADC) are a measure of alveolar microstructure [which is the volume of the lung not participating in ventilation, normalized to total lung volume. For the generation of 3He ADC, diffusion-weighted images were acquired as previously described. To evaluate parenchymal microstructure, we adapted a method whereby D_L and D_T were defined as the longitudinal and transverse diffusion coefficients in the acinar ducts respectively. The structural dependency of D_L and D_T was modeled with R representing the outer radius and h the depth of the intra-acinar duct.]
3. CT measurement of the relative area of the lung with attenuation values -950HU (RA950) measures parenchyma density, lung tissue with attenuation values below -950HU are considered emphysematous [Thoracic CT was used to generate emphysema measurements including the relative area of the lung with attenuation values <-950HU (RA950), low attenuation clusters (LAC), and as well airway measurements including airway wall area percent (WA%) and lumen area (LA)]
4. Diffusing capacity of the lung for carbon monoxide (DLCO) is a measure of gas exchange within the lung and does not measure parenchymal density [In summary, quantitative thoracic imaging provides a way to non-invasively and regionally evaluate the critical structure-function relationships in an adult case of CLE in whom established measurements of pulmonary function (DLCO, FEV1) do not]
5. Residual volume (RV) is a measure of gas trapping within the lung and not parenchymal density [Spirometry, plethysmography and diffusing capacity of carbon monoxide (DLCO) measurements showed there was modestly abnormal forced expiratory volume in one second (FEV1, V1:V2 70%:75%), and highly abnormal residual volume (RV, V1:V2 125%:150%), and airways resistance (Raw, V1:V2 185%:180%), but normal DLCO (V1:V2 100%:115%).]



From the manuscript:
Pulmonary Imaging Abnormalities in an Adult Case of Congenital Lobar Emphysema
Radiology Case. 2015 Feb; 9(2):9-15


This article belongs to the Chest section.




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From the manuscript

Pulmonary Imaging Abnormalities in an Adult Case of Congenital Lobar Emphysema

Free full text article: Pulmonary Imaging Abnormalities in an Adult Case of Congenital Lobar Emphysema

Abstract
Congenital lobar emphysema is mainly diagnosed in infants, although rare cases are reported in adults. A 20-yr-old female with acute dyspnea, chest pain and left upper lobe (LUL) chest x-ray hyperlucency underwent 3He magnetic resonance imaging (MRI) for ventilation and apparent diffusion coefficient (ADC) measurements, as well as CT for emphysema and airway wall measurements. Forced expiratory volume in 1s, residual volume, and airways-resistance were abnormal, but there was normal carbon-monoxide-diffusing-capacity. The LUL relative area of the density histogram <-950 HU and airway morphology were highly abnormal compared with the other lobes and coincident with highly abnormal MRI-derived acinar duct dimensions. CT also identified bronchial atresia and congenital lobar emphysema as the source of symptoms in this case where there was also functional imaging evidence of collateral ventilation from the fissure (and not the abnormally terminated airway) into the emphysematous LUL.






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3. Hyperpolarized 3He

4. Magnetic Resonance Imaging

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6. Emphysema

7. Airways Disease


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