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MRI and CT and 3D
MRI and CT and 3D
Hi there, a number of questions
Does MRI generate a sequence of parallel slices, similarly to what CT does?
I read that MRI slices can be along any plane. Since the machine has an
obvious doughnut shape like the CT machine, I doubt that the slices can
really be along any plane, they will probably be coplanar to the
doughnut..? I suppose for producing a slice along another plane, first
the slices coplanar to the doughnut are generated, then a 3D solid is
reconstructed from those, and then it is sliced again along another
plane by computation. Am I correct? If this is true, I suspect there is
a great deal of detail loss when you slice along a plane not coplanar to
the doughnut, right?
Are there places where after a CT or MRI scan they give you a CD with
the 3D reconstruction of the body? Or everywhere in the world they give
you just the bitmap images of the slices?
If yes, what is the file format of the 3D reconstruction? And what
viewer can be used?
If no, is there any software, possibly free of charge, that can be used
to obtain a 3D reconstruction from bitmap slices?
In angiographic MRI (the one with contrast), how is it possible that the
heart is really imaged? It moves too fast to obtain a MRI image...
Thank you
Hi there, a number of questions
Does MRI generate a sequence of parallel slices, similarly to what CT does?
I read that MRI slices can be along any plane. Since the machine has an
obvious doughnut shape like the CT machine, I doubt that the slices can
really be along any plane, they will probably be coplanar to the
doughnut..? I suppose for producing a slice along another plane, first
the slices coplanar to the doughnut are generated, then a 3D solid is
reconstructed from those, and then it is sliced again along another
plane by computation. Am I correct? If this is true, I suspect there is
a great deal of detail loss when you slice along a plane not coplanar to
the doughnut, right?
Are there places where after a CT or MRI scan they give you a CD with
the 3D reconstruction of the body? Or everywhere in the world they give
you just the bitmap images of the slices?
If yes, what is the file format of the 3D reconstruction? And what
viewer can be used?
If no, is there any software, possibly free of charge, that can be used
to obtain a 3D reconstruction from bitmap slices?
In angiographic MRI (the one with contrast), how is it possible that the
heart is really imaged? It moves too fast to obtain a MRI image...
Thank you
Re: MRI and CT and 3D
> Does MRI generate a sequence of parallel slices, similarly to what CT does?
Yes, but it aquires images differently.
> I read that MRI slices can be along any plane. Since the machine has an obvious doughnut shape like the CT machine, I doubt that the slices can really be along any plane, they will probably be coplanar to the doughnut..?
Cat Scan uses X-rays from an x-ray tube. The tube is circling around
the patient taking data as it turns around the patient, hence the
doughnut shape.
MRI on the other hand, uses RF waves and Magnetics. What the patient
is escentially doing is going inside an actual magnet. When the
magnet is "turned on", the magnetic field will cause certain molecules
and atoms in the body to point towards "north" or lay down flat. When
the magnet is "turned off", these molecules and atoms go back to their
original state. During both of these actions, they are giving off
energy in the form of RF waves, which the scanner picks up, and turns
into a visible image. The only reason for the "doughnut" is to put
the patient inside the magnet.
> I suppose for producing a slice along another plane, first the slices coplanar to the doughnut are generated, then a 3D solid is reconstructed from those, and then it is sliced again along another plane by computation. Am I correct? If this is true, I suspect there is a great deal of detail loss when you slice along a plane not coplanar to the doughnut, right?
Nope. That only occurs in CT. Since the tube has to circle the
patient, that's the only way that we can get the image. MRI will
physically aquire those images in that plane.
Detail loss used to be great when you reconstructed the different
planes in CT, but now with the new Multi-Slice scanners on the market,
the loss of detail is very minimal.
> Are there places where after a CT or MRI scan they give you a CD with the 3D reconstruction of the body? Or everywhere in the world they give you just the bitmap images of the slices?
Most places that do a 3D reconstruction for diagnostic purposes will
always save the images, and when the paitent asks for that study on a
CD, whatever images the radiologist used will be on the CD. 3D
imaging is not always used, and a lot of times, it's not what the
general population thinks it should look like. Many times 3D imaging
just means taking images from one plane and making more images in
another.
> If yes, what is the file format of the 3D reconstruction? And what viewer can be used?
All radiologic data comes in what is called DICOM format. It's a
standard (I believe world wide) for all imaging. Usually when you get
the CD, there should already be a DICOM viewer loaded onto the disk.
You just put the CD in the computer, and it should load up. If for
some reason it doesn't, there are DICOM viewers that can be downloaded
off the internet.
> In angiographic MRI (the one with contrast), how is it possible that the heart is really imaged? It moves too fast to obtain a MRI image...
Well firstly, MRI with contrast is not always angiographic.
Angiographic refers to the phase that the contrast is in. Generally
there are two phases of contrast enhancement: arterial and venous.
Most angiographic studies (CT and MRI) envolve the arterial phase.
As for the imaging of the heart, there is something called "cardiac
gaiting". Basically, (in CT at least, not 100% sure about MRI. SOME
HELP HERE GUYS!!) cardiac leads are placed on the patient, so that we
can aquire and EKG. There are places on that EKG where we can see
where the heart is at rest (even for a fracture of a second). While
the heart is at rest, we take our images. Depending on the scanner
used, sometimes we can image the heart constantly, and then pick and
choose the images we want.
Hope this helps.
Papa RT(R)(CT)
> Does MRI generate a sequence of parallel slices, similarly to what CT does?
Yes, but it aquires images differently.
> I read that MRI slices can be along any plane. Since the machine has an obvious doughnut shape like the CT machine, I doubt that the slices can really be along any plane, they will probably be coplanar to the doughnut..?
Cat Scan uses X-rays from an x-ray tube. The tube is circling around
the patient taking data as it turns around the patient, hence the
doughnut shape.
MRI on the other hand, uses RF waves and Magnetics. What the patient
is escentially doing is going inside an actual magnet. When the
magnet is "turned on", the magnetic field will cause certain molecules
and atoms in the body to point towards "north" or lay down flat. When
the magnet is "turned off", these molecules and atoms go back to their
original state. During both of these actions, they are giving off
energy in the form of RF waves, which the scanner picks up, and turns
into a visible image. The only reason for the "doughnut" is to put
the patient inside the magnet.
> I suppose for producing a slice along another plane, first the slices coplanar to the doughnut are generated, then a 3D solid is reconstructed from those, and then it is sliced again along another plane by computation. Am I correct? If this is true, I suspect there is a great deal of detail loss when you slice along a plane not coplanar to the doughnut, right?
Nope. That only occurs in CT. Since the tube has to circle the
patient, that's the only way that we can get the image. MRI will
physically aquire those images in that plane.
Detail loss used to be great when you reconstructed the different
planes in CT, but now with the new Multi-Slice scanners on the market,
the loss of detail is very minimal.
> Are there places where after a CT or MRI scan they give you a CD with the 3D reconstruction of the body? Or everywhere in the world they give you just the bitmap images of the slices?
Most places that do a 3D reconstruction for diagnostic purposes will
always save the images, and when the paitent asks for that study on a
CD, whatever images the radiologist used will be on the CD. 3D
imaging is not always used, and a lot of times, it's not what the
general population thinks it should look like. Many times 3D imaging
just means taking images from one plane and making more images in
another.
> If yes, what is the file format of the 3D reconstruction? And what viewer can be used?
All radiologic data comes in what is called DICOM format. It's a
standard (I believe world wide) for all imaging. Usually when you get
the CD, there should already be a DICOM viewer loaded onto the disk.
You just put the CD in the computer, and it should load up. If for
some reason it doesn't, there are DICOM viewers that can be downloaded
off the internet.
> In angiographic MRI (the one with contrast), how is it possible that the heart is really imaged? It moves too fast to obtain a MRI image...
Well firstly, MRI with contrast is not always angiographic.
Angiographic refers to the phase that the contrast is in. Generally
there are two phases of contrast enhancement: arterial and venous.
Most angiographic studies (CT and MRI) envolve the arterial phase.
As for the imaging of the heart, there is something called "cardiac
gaiting". Basically, (in CT at least, not 100% sure about MRI. SOME
HELP HERE GUYS!!) cardiac leads are placed on the patient, so that we
can aquire and EKG. There are places on that EKG where we can see
where the heart is at rest (even for a fracture of a second). While
the heart is at rest, we take our images. Depending on the scanner
used, sometimes we can image the heart constantly, and then pick and
choose the images we want.
Hope this helps.
Papa RT(R)(CT)
Re: MRI and CT and 3D
papa smurf wrote:
>
> As for the imaging of the heart, there is something called "cardiac
> gaiting". Basically, (in CT at least, not 100% sure about MRI. SOME
> HELP HERE GUYS!!) cardiac leads are placed on the patient, so that we
> can aquire and EKG. There are places on that EKG where we can see
> where the heart is at rest (even for a fracture of a second). While
> the heart is at rest, we take our images. Depending on the scanner
> used, sometimes we can image the heart constantly, and then pick and
> choose the images we want.
>
> Hope this helps.
>
> Papa RT(R)(CT)
We do a lot of "gated" studies in Nuc Med. ECG leads are placed on the
chest so that we can measure the R-R interval, or the time it takes for
one cardiac cycle to complete. That R-R interval is broken down into
"time bins" (usually 16 or 32). As the study is acquired, information is
recorded into those time bins in the correct sequence. That means that
information from the time that the heart is resting is always recorded
into the same frame. It's hard to explain without drawing a picture.
It really only works well on people who have nice steady heart rhythms.
Andrew Kerr M.R.T.(N.)
papa smurf wrote:
>
> As for the imaging of the heart, there is something called "cardiac
> gaiting". Basically, (in CT at least, not 100% sure about MRI. SOME
> HELP HERE GUYS!!) cardiac leads are placed on the patient, so that we
> can aquire and EKG. There are places on that EKG where we can see
> where the heart is at rest (even for a fracture of a second). While
> the heart is at rest, we take our images. Depending on the scanner
> used, sometimes we can image the heart constantly, and then pick and
> choose the images we want.
>
> Hope this helps.
>
> Papa RT(R)(CT)
We do a lot of "gated" studies in Nuc Med. ECG leads are placed on the
chest so that we can measure the R-R interval, or the time it takes for
one cardiac cycle to complete. That R-R interval is broken down into
"time bins" (usually 16 or 32). As the study is acquired, information is
recorded into those time bins in the correct sequence. That means that
information from the time that the heart is resting is always recorded
into the same frame. It's hard to explain without drawing a picture.
It really only works well on people who have nice steady heart rhythms.
Andrew Kerr M.R.T.(N.)
Re: MRI and CT and 3D
"Andrew Kerr" <apkerr@yahoo . com > ha scritto nel messaggio
news:A%sTi.9726$xa2.7978@read2.cgocable . net ...
> We do a lot of "gated" studies in Nuc Med. ECG leads are placed on the
> chest so that we can measure the R-R interval, or the time it takes for
> one cardiac cycle to complete. That R-R interval is broken down into "time
> bins" (usually 16 or 32). As the study is acquired, information is
> recorded into those time bins in the correct sequence. That means that
> information from the time that the heart is resting is always recorded
> into the same frame. It's hard to explain without drawing a picture.
>
> It really only works well on people who have nice steady heart rhythms.
absolutely with you.
We do the same in the hospital I work. This is a test with a Tecnethium
tracker and we split the exam ikn two separate times: stress and rest.
Usually we obtain good quality images showing ipoxiz areas in the 3 main
section of the heart and wa can also do lots of recontructions and analisys
such as EF and so on...
This is one of the most usual nuclear medicine test we perform daily...
sim1
"Andrew Kerr" <apkerr@yahoo . com > ha scritto nel messaggio
news:A%sTi.9726$xa2.7978@read2.cgocable . net ...
> We do a lot of "gated" studies in Nuc Med. ECG leads are placed on the
> chest so that we can measure the R-R interval, or the time it takes for
> one cardiac cycle to complete. That R-R interval is broken down into "time
> bins" (usually 16 or 32). As the study is acquired, information is
> recorded into those time bins in the correct sequence. That means that
> information from the time that the heart is resting is always recorded
> into the same frame. It's hard to explain without drawing a picture.
>
> It really only works well on people who have nice steady heart rhythms.
absolutely with you.
We do the same in the hospital I work. This is a test with a Tecnethium
tracker and we split the exam ikn two separate times: stress and rest.
Usually we obtain good quality images showing ipoxiz areas in the 3 main
section of the heart and wa can also do lots of recontructions and analisys
such as EF and so on...
This is one of the most usual nuclear medicine test we perform daily...
sim1
Re: MRI and CT and 3D
"1316" <1316@1110 . com > ha scritto nel messaggio
news:471c6d53$0$90430$892e0abb@auth.newsreader.octanews . com ...
> Hi there, a number of questions
>
> Does MRI generate a sequence of parallel slices, similarly to what CT
> does?
MRI is a multiplanar imaging technique. for this reason you can acquire
slices in 3 different planes (sagittal, axial and coronal) and also with
oblique prjections mixing these 3 patterns of planes.
> I read that MRI slices can be along any plane. Since the machine has an
> obvious doughnut shape like the CT machine, I doubt that the slices can
> really be along any plane, they will probably be coplanar to the
> doughnut..? I suppose for producing a slice along another plane, first the
> slices coplanar to the doughnut are generated, then a 3D solid is
> reconstructed from those, and then it is sliced again along another plane
> by computation. Am I correct? If this is true, I suspect there is a great
> deal of detail loss when you slice along a plane not coplanar to the
> doughnut, right?
well, as a technologist I can tell you how I usually work with the machine
at work.
Tipically I acquire a scout view with all the 3 planes and, on this 3 plane
acquisition I set up the different views. I, for istance, can set the
sagittal on the axial and so on...
> Are there places where after a CT or MRI scan they give you a CD with the
> 3D reconstruction of the body? Or everywhere in the world they give you
> just the bitmap images of the slices?
In Italy we are starting to give patients the cd with the exam saved on
dicom format.
> If yes, what is the file format of the 3D reconstruction? And what viewer
> can be used?
I think any dicom viewer...
> If no, is there any software, possibly free of charge, that can be used to
> obtain a 3D reconstruction from bitmap slices?
I don't know, sorry...
> In angiographic MRI (the one with contrast), how is it possible that the
> heart is really imaged? It moves too fast to obtain a MRI image...
well, tricky question :-)
actually I think in MRI the imaging is based on the flow of contrast in the
veins or arthery. For this reason is not so correct of call the mri an
angiographic exam. On the other hand the modern CT SCAN with 16 slices bank+
are connected with EKG leads and sincronyzed with the actual beat oh the
heart. I have to say that CT Scans of the heart are, in Italy, a very rare
kind of exam as we prefer to do Nuclear Medicine exam or Coronarography.
I hope I might be helpful :-)
sim1
"1316" <1316@1110 . com > ha scritto nel messaggio
news:471c6d53$0$90430$892e0abb@auth.newsreader.octanews . com ...
> Hi there, a number of questions
>
> Does MRI generate a sequence of parallel slices, similarly to what CT
> does?
MRI is a multiplanar imaging technique. for this reason you can acquire
slices in 3 different planes (sagittal, axial and coronal) and also with
oblique prjections mixing these 3 patterns of planes.
> I read that MRI slices can be along any plane. Since the machine has an
> obvious doughnut shape like the CT machine, I doubt that the slices can
> really be along any plane, they will probably be coplanar to the
> doughnut..? I suppose for producing a slice along another plane, first the
> slices coplanar to the doughnut are generated, then a 3D solid is
> reconstructed from those, and then it is sliced again along another plane
> by computation. Am I correct? If this is true, I suspect there is a great
> deal of detail loss when you slice along a plane not coplanar to the
> doughnut, right?
well, as a technologist I can tell you how I usually work with the machine
at work.
Tipically I acquire a scout view with all the 3 planes and, on this 3 plane
acquisition I set up the different views. I, for istance, can set the
sagittal on the axial and so on...
> Are there places where after a CT or MRI scan they give you a CD with the
> 3D reconstruction of the body? Or everywhere in the world they give you
> just the bitmap images of the slices?
In Italy we are starting to give patients the cd with the exam saved on
dicom format.
> If yes, what is the file format of the 3D reconstruction? And what viewer
> can be used?
I think any dicom viewer...
> If no, is there any software, possibly free of charge, that can be used to
> obtain a 3D reconstruction from bitmap slices?
I don't know, sorry...
> In angiographic MRI (the one with contrast), how is it possible that the
> heart is really imaged? It moves too fast to obtain a MRI image...
well, tricky question :-)
actually I think in MRI the imaging is based on the flow of contrast in the
veins or arthery. For this reason is not so correct of call the mri an
angiographic exam. On the other hand the modern CT SCAN with 16 slices bank+
are connected with EKG leads and sincronyzed with the actual beat oh the
heart. I have to say that CT Scans of the heart are, in Italy, a very rare
kind of exam as we prefer to do Nuclear Medicine exam or Coronarography.
I hope I might be helpful :-)
sim1
