Blogs

Covid-19 CT Chest - Temporal Changes - V
September 18, 2020
This middle-aged individual had bad disease and was hospitalized for over a month. The first scan shows significant lung involvement. 3 weeks later, the lesions have started regressing / melting. Another 5 weeks later, there is some further improvement. The question remains. How much of this is permanent? Which of these lesions will eventually melt away / regress. The patient is improving clinically though slowly. Only time will tell as we see more and more patients coming f...
Covid-19 CT Chest - Temporal Changes - IV
September 18, 2020
This 52 years old man presented with mild disease that progressed in 3 days. He was Covid negative but breathless and a scan done 1 month later shows dense opacities with traction bronchiectasis. Is this fibrosis? Or resolving organizing pneumonia? Many of these tend to regress further as we shall see in future cases and unless there is frank honeycombing or volume loss, it may be difficult to label this as fibrosis. We just read them and describe them and mention whether th...
Covid-19 CT Chest - Temporal Changes - III
September 18, 2020
Then we have this 42-years old man with two scans done 9 days apart, who was mildly symptomatic at the time of the first scan and is asymptomatic at the time of the 2nd scan. The upper lobe lesions seen on the first scan have improved (green arrows), but there are new lesions in both lower lobes, especially the left (red arrows). So is this progressive disease? Or is it more likely that the lesions increased immediately after the first CT and have settled and this is now the...
Covid-19 CT Chest - Temporal Changes - II
September 18, 2020
On the other hand, this 34-years old patient had minimal subtle disease at presentation and then 13 days later landed up with extensive lung involvement, most of it likely related to angiopathy with an associated acute lung injury pattern. Some patients suddenly deteriorate like this. ...
Covid-19 CT Chest - Temporal Changes - I
September 18, 2020
This 43-years old man has typical changes of ground glass and crazy-paving at presentation. One week later, the lesions have resolved significantly with residual ground glass, reticular opacities and a thin band. Most patients follow this pattern. ...
Earliest Covid Signs on CT Chest
September 18, 2020
These are two asymptomatic individuals who tested positive, but sent for CT scan. Both patients show subtle opacities, which are predominantly perivascular, with ground glass or slightly denser appearance. Both of them had 4-5 such foci in thelungs. ...
Covid-19 CT Chest Patterns - VIII - Vasculopathy - IV - Thromboembolism & Bubble Lucencies
September 18, 2020
This is a 41-years old with severe disease. The red arrows show the “target sign”, one in the right lower lobe and the other in the left lower lobe. The patient has pulmonary thromboembolism (blue arrows), which is associated with increased morbidity and mortality. “Bubble lucencies” (yellow arrow) are seen on the soft tissue window images and generally imply hemorrhagic infarction. ...
Covid-19 CT Chest Patterns - VI - Vasculopathy - III - Target Sign
September 18, 2020
The target sign has been described to be a result of perivascular inflammation and organizing pneumonia. Whether there is also an element of infarction is uncertain. As seen in the video, the sign consists of the pin-point or sometimes thickened vessel in the center (red arrow), the perivascular opacity of inflammation (blue arrow), the relative “spared” halo (yellow arrow) and the ground glass halo (green arrow). Irrespective of the exact reason for the target sign, its pre...
Covid-19 CT Chest Patterns - VI - Vasculopathy - II - Vascular “Tree-in-Bud”
September 18, 2020
The vascular “tree-in-bud” appearance has been recently described by Brijesh Patel from the Royal Brompton in London and his colleagues. This refers to the presence of branching peripheral vessels, in a way, similar to the bronchial “tree-in-bud” (top left) we see with infectious bronchiolitis / tuberculosis. This vascular “tree-in-bud” (top right) is supposedly a marker of a thrombotic vasculopathy with angiogenesis and micro-thromboses. The presence of this sign in admitte...
Covid-19 CT Chest Patterns - V - Vasculopathy - I
September 18, 2020
One major difference between Covid-19 and other inflammatory / infective diseases of the lungs is the presence of a vasculopathy / angiopathy. While there is still debate about the exact pathophysiology behind the vascular involvement, there are radiology signs that allow us to identify the presence of a vasculopathy. Many patients show prominent / dilated proximal or intra-lesional vessels. This is perhaps the simplest sign of a vasculopathy, rarely seen outside of a Covid-...
Visualizing Ground Glass - Tips & Tricks
September 18, 2020
Ground glass (GG) foci are the commonest manifestation of Covid-19 and in subtle cases, may be difficult to diagnose. This difficulty may then turn a positive into a negative scan. Here are two ways to improve conspicuity of GG areas during interpretation.   1. Minimum Intensity Projection (minIP) images while scrolling on the workstation. I use a 3 mm sliding minIP and it allows quick pick-up of subtle lesions. In this case (top row), while a static image does not capture t...
Covid-19 CT Chest - Differential Diagnoses
September 18, 2020
None of the findings individually seen in patients with Covid-19 pneumonia are pathognomonic, except for some of the signs of angiopathy / vasculopathy that will be shown in subsequent posts. Organizing pneumonia patterns, crazy-paving patterns and ground glass can all occur in other situations as well, and before April 2020, we would consider all the conditions in these images in the differential diagnoses. Today in the setting of the pandemic, our first diagnosis is Covid-...
Covid-19 CT Chest Patterns - IV - Bands
September 18, 2020
Many patients show thin or thick curvilinear bands (purple arrows) usually in the lower lobes in the posterior and lateral basal segments. It is not clear what they represent. Some say that they are due to resolving pneumonia, but we have seen these bands at first presentation as well. Others believe they are due to sub-segmental atelectasis, because of their location and yet some others believe they represent fibrosis, though we have seen these bands resolve as well. Perhap...
Covid-19 CT Chest Patterns - III - Reticular Opacities
September 18, 2020
Reticular opacities present as thin short lines that are usually peripheral and subpleural. When the reticular lesions are predominant, resembling an NSIP pattern (blue arrow), this appearance is usually seen in resolving cases (top left). Some ground glass (yellow arrow) is almost always present. Reticular opacities can also be random (blue arrows) as seen in the top right image, accompanying areas of consolidation or ground glass. Septal thickening is also a type of reticu...
Covid-19 CT Chest Patterns - II - Consolidation
September 18, 2020
Unlike ground glass attenuation, which is increased attenuation that does not obscure the underlying vessels, consolidation obscures the underlying vessels and usually shows air bronchogram / bronchiolograms. This can also be subpleural or bronchocentric (red arrows), usually associated with ground glass (yellow arrow), which in turn either forms a halo or is at the center of a reverse halo, as shown yesterday or just randomly distributed together. The pattern of consolidati...
Covid-19 CT Chest Patterns - I - Ground Glass
September 18, 2020
Ground glass (GG) is the commonest sign. This can be subpleural or bronchocentric, with or without prominent vessels (green arrow), with reticular opacities / septal thickening (blue arrow) giving rise to the "crazy-paving pattern", as a halo around foci of consolidation (red arrow) or within the centre of a rim of consolidation (red arrow), producing a reverse ground glass halo or "atoll" sign. ...
CO-RADS 3/4 or Indeterminate
September 18, 2020
In the earlier days of reading CT scans for suspect Covid-19 cases, an image such as this would have been called suspicious for but not definitive for Covid-19 (CO-RADS 3/4) or “probable” as per the RSNA Consensus Statement. However, the presence of prominent vessels (red arrows) leading up to or within the areas of ground glass is a sign unique to Covid-19. When these are present, this appearance automatically gets classified as CO-RADS 5 or “typical” Covid-19 disease. ...
CO-RADS
September 18, 2020
In most CT scan reports of patients suspected to have Covid-19 pneumonia, there will be a mention of a CO-RADS score. This is used to communicate the extent of likelihood of the scan showing findings suggestive of Covid-19 or not. CO-RADS ClassificationCO-RADS 1 - Unlikely, CO-RADS 2 - Low, CO-RADS 3 - Indeterminate, CO-RADS 4 – Level of suspicion high, CO-RADS 5 – Classic findingsProkop M et al. Radiology 2020;Apr 27:online first. The image shows the various patterns of CO-...
Pediatric Pelvic Tumors - Classic Aneurysmal Bone Cyst (ABC) and a Simple Biopsy
August 14, 2020
This 6-years old girl presented with pain in the right hip. The radiograph shows an expansile osteolytic lesion involving the medial wall of the right acetabulum - there is a thin sclerotic rim, suggesting that this is a benign lesion. The MRI (PDFS coronal and T1FS contrast axial) shows a “cystic” lesion involving the ischium. Unfortunately, only films were available and though there were fluid levels, they are not well demonstrated. The contrast study shows enhancing septa...
Trans-Fissural Biopsies are Fine, if that's the Best Option
August 14, 2020
This 27-years old man presented with a left hilar mass, 13 years after amputation for a tibial osteosarcoma. The CT scan showed a left hilar mass with encasement of the left pulmonary artery with no other lung nodule. The question was whether this was a new primary or metastasis. The choice of biopsy was between a lateral decubitus approach versus a prone approach. Keeping in mind the position fo the vessels, I thought a prone approach was safer and better, even though that ...