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CTA imaging Uncategorized Venous venous aneurysm venous intervention

3D VR Images from CT Data Very Useful in Open Surgical Planning: Popliteal Venous Aneurysm

ct-3dvr-planning

Patient is a middle aged man with history of DVT and PE who in preoperative workup for another operation was found to have a popliteal venous aneurysm affecting his right leg. Unlike the recently posted case (link) which was fusiform, this aneurysm was saccular (CT above, duplex below). Popliteal venous aneurysms have a high risk of pulmonary embolism because: they tend to form clot in areas of sluggish flow and once loaded with clot, will eject it when compressed during knee flexion.

preop-duplex

When I perform open vascular surgery, I tend to get a CTA not just because it is minimally invasive and convenient, but because it gives important information for operative planning. The volume rendering function, which takes the 3 dimensional data set from a spiral CT scan, and creates voxels (3 dimensional pixels) of density information and creates stunning images such as the one featured on the current September 2016 issue of the Journal of Vascular Surgery. But these are not just pretty pictures.

In fact, I use these images to plan open surgery, even to the location of incisions. Vital structures are seen in 3D and injuries are avoided. Take for example the CT Venogram on the panel below. By adjusting the window level, you have first the venographic information showing the saccular popliteal venous aneurysm on the left panel, you can also see where it is in reference to the muscles in the popliteal fossa. The greater saphenous vein and varicose veins below are well seen.

ct-3dvr-planning

By adjusting the level, subcutaneous structures are better seen including the small saphenous vein which could be harvested to create a patch or a panel graft from a posterior approach. A final adjustment of the window level on the right shows the skin, and I can now plan the curvilinear incision.

By changing the orientation, I can also recreate the surgeon’s eye view of the leg in the prone position (below).

or-view_1

And you can see how well it matches up to the actual operation shown below:

Intraop Photo.png

This was treated with plication of the saccular aneurysm and unlike the fusiform aneurysm, I did not sew over a mandrill (a large 24F foley) inserted through a transverse venotomy, but rather ran a Blalock type stitch under and over a clamp.

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The several weeks postoperatively showed no further trace of the saccular aneurysm.

postop-duplex

The volume rendering software grew out of the 3D gaming industry. The voxel data that paints flesh and bone on skeletons and costumes and weapons is far more complex than what is applied for the 3DVR packages that are available. The images shown for this post comes from TeraRecon/Aquarius, but they are also available as open source software from Osirix, Vitrea, and various software packages sold with CT scanners. While those that are tied to the scanners are often tied to dedicated workstations -limiting you to going to Radiology and taking over their workstation, many will work in the cloud for both the DICOM data and for virtual desktop access through mobile. Contrast is not necessary if the patient has kidney dysfunction -the vessels can be manually centerlined -ie. a line can be dropped in the center of the artery to illustrate its course when viewing the VR images.

I will plan the surgery while in the clinic with the patient, actually tracing out the incisions and dissections necessary to achieve success. It is a wonderful teaching tool for trainees. But most critically, it helps me imagine the operation and its successful completion.

Categories
AIOD CTA imaging techniques

3DVR -Very Helpful in Planning Open Surgical Cases

3DVR CIA Endart

The images above show a patient with on isolated occlusion of his left common iliac artery. He was young, in his forties, but was a heavy smoker and suddenly developed claudication of his left leg which interfered with his work. He quit smoking and did not progress with exercise. Discussion involving possible stenting was made and initially offered but he turned it down because erroneously he assumed that his father’s coronary stents were the same as an iliac stent in terms of longevity. I do think that common iliac and aortoiliac occlusive disease is well treated with stents, but I felt it was possible to do a common iliac endarterectomy. We went over these images together and he settled on proceeding with endarterectomy.

The images show how well the 3D Volume Rendering, which I mentally┬ácall Virtual Reality, of CTA makes it possible to plan out operations and exposures virtually. The bottom left image shows the surgeon’s eye view of the exposed vessel.

Below, the virtual and the actual are juxtaposed.

3DVR CIA Endart Exposure

The outline on the virtual image (volume rendered) shows the areas of retraction -for the trainees, the retractor systems work to make quadrilaterals out of linear incisions, and as a rule, the incision should be twice the length of the square that you want to expose. The end points of the endarterectomy were at the aortic and iliac bifurcations.

SAMSUNG DIGITAL CAMERA

The arteriotomy was repaired with a patch at the iliac bifurcation -the common iliac was large and was repaired primarily.

SAMSUNG DIGITAL CAMERA

The specimen below was fibrocalcific. The thing about this disease is that the plaque truly has no endpoint -intimal thickening and mild plaque was present that could be taken all the way to the aortic root and to the feet on the other end!

SAMSUNG DIGITAL CAMERA

This patient did very well and had palpable pulses. He did not develop neointimal hyperplasia and successfully quit smoking.

One of the exciting developments is the ongoing development of wearable virtual reality and display solutions -particularly from the gaming industry. The gaming industry ironically drives all computer imaging because that is where the money is at. The advances in imaging trickle down to medicine -the VR images seen here are the result of the same algorithms that drive first person shooting games. It would be great to see this displayed intraop on a HoloLens, on a virtually positioned screen behind the assistant!

Categories
CTA imaging PAD techniques training

Intuition Aquarius (TeraRecon) Trick -Applying Virtual Reality to Operative Planning

I have used many different flavors of image post processing software including Osiris, Vitrea, and now Aquarius, aka TeraRecon. But I notice that outside of endovascular planning, people rarely use the virtual 3D reconstructed images (the pretty pictures) for anything other than posting images for publication in JVS, and even there I think we have reached saturation.

I have found 3D reconstruction to be especially useful for open surgical planning, and that is by doing two things. First, on viewing the 3DVR data, I reorient and center on the surgeon’s perspective, using left button to rotate the picture around the zero at the center of the screen, and the right mouse button to grab the whole image and recenter as necessary.

Window Leveling.001
Surgeon’s eye OR view

I then window-level in tissue density -this is done by pressing both the right and left mouse buttons, but you can choose this off the menu.

Window Leveling.002

I can plan the incisions and exposures from any angle -in this case, I can see the saphenous vein and its relative proximity to the CFA to perform an in site bypass to the AK POP. And I see the loci of the tributaries that I may need to ligate.

Window Leveling.004

This is a powerful tool that is often overlooked.