Do you need IV contrast to see Masses on Head CT?

[waterski232002]

I had a patient today with a headache for 1 month, constant, small relief with OTC pain meds. no other symptoms, no neuro deficits on exam. He was worried about brain cancer (although I wasn't worried about an intracranial mass). His CT head w/o contrast was normal. I realize that in order to visualize intracranial masses a CT with contrast is the imaging modality of choice. My question is... will most masses still show up on a non-contrast CT (or will there be some secondary changes which may indicate a mass)? What percent of masses, or what size masses will be missed on a non-contrast CT as opposed to a contrast CT?

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[tangosierra]

I don't think the brain tumor should be on the top of your differential diagnosis, there can be numerous other causes of a h/a esp. w/o neuro deficit. If he's obsessed with the tumor (or cancer for that matter) send him to a neurologist.

 

[waterski232002]

As I said above... I wasn't worried about a brain tumor. Nevertheless, it should be considered in the differential of a patient with a persistent HA lasting over over 4 weeks. Other more serious etiologies need to be ruled out (SAH, SDH, EDH, Meningitis, pseudotumor cerebrei). Although it would be nice, it is not imperative that a brain tumor be ruled out in the emergency department. If a brain tumor was at the top of my differential or the patient was sick (neuro deficits, signs of elevated ICP), I most certainly would have infused the CT.

My question was how good is a non-contrast CT at visualizing tumors? Are most picked up? Do they have to be very large?

 

[Wrigleyville]

The non-contrast is mostly for emergencies, like bleeds. It really has no place in the evaluation of masses, as you won't be able to see them unless they are big enough to cause changes like midline shift or effacement of the gyri/sulci (b/c the tumor has the same density as the surrounding tissue).

I don't know the percent that will show up on non-contrast, but the bottom line is that you'll see "the big ones", in the sense that you'll see there is "something there" that shouldn't be.

This is a common way that brain tumors are picked up -- person goes to ER for headache, gets noncontrast CT to r/o bleed, the radiologist sees some mass effect, and asks for a contrast-enhanced study that reveals the mass.

 

[Docxter]

I realize that in order to visualize intracranial masses a CT with contrast is the imaging modality of choice.

No. Currently, the imaging modality of choice for detecting an intracranial mass is an MRI protocol that includes triple-dose gadolinium (not FDA approved) with magnetization transfer in three planes+high resolution FLAIR+diffusion, preferably on a 3T magnet.

Regular contrast MRI, noncontrast MRI, contrast CT, and noncontrast CT are other ways to look for masses, in decreasing order of overall sensitivity.

My question is... will most masses still show up on a non-contrast CT (or will there be some secondary changes which may indicate a mass)?

Both.

What percent of masses, or what size masses will be missed on a non-contrast CT as opposed to a contrast CT?

No good answer here. It depends on a combination of size, relative density of tumor, exact location within the brain or surrounding structures (some places are harder and some places easier to visualize), and the amount of surrounding edema, mass effect, etc.

As I said above... I wasn't worried about a brain tumor. Nevertheless, it should be considered in the differential of a patient with a persistent HA lasting over over 4 weeks. Other more serious etiologies need to be ruled out (SAH, SDH, EDH, Meningitis, pseudotumor cerebrei).

EDH is not in the differential of HA of 4 weeks. SAH would also be quite rare to have this presentation.

My question was how good is a non-contrast CT at visualizing tumors? Are most picked up? Do they have to be very large?

Pretty good, but one can always make the argument that it's not good enough. Yes, most are picked up, except for small lesion, those with minimal edema, posterior fossa lesions, cortical lesions.

Some neuroradiologists, neurologists, and neurosurgeons even believe that outside of the ED, if you're thinking of brain mass, you do an MRI and not a CT, even at the start. Most of the head CTs (contrast or no contrast) we get outside of emergent situations are from primary care doctors. Neurologists and neurosurgeons just go straight to MRI.

 

[Docxter]

This is a common way that brain tumors are picked up -- person goes to ER for headache, gets noncontrast CT to r/o bleed, the radiologist sees some mass effect, and asks for a contrast-enhanced study that reveals the mass.

If you suspect a mass on noncontrast CT, you go straight to contrast MRI. Getting a contrast CT is a waste of time.

 

[poloace]

given the presentation of your story, i am assuming that this patient is not a child. in the case of a child, you'd go straight to MR for diagnosis as tumors in the posterior fossa do not show up well on CT. also, agree with above post, CT w or w/out contrast is NOT the best choice for brain mass. we use it primarily for screening in the ED - but, if you want a more definitive diagnosis - go with MR, hands down.

 

[waterski232002]

Docxter... Thanks for your response. This was an adult pt I saw in the ED yesterday. As you said, MRI is not realistic in the ED setting, particularly for this case, that's why I didn't even consider it in my imaging modalities of choice.

So would you have recommended a non-contrast or contrast CT for the patient above (adult w/ 4wk HA)?

What about an HIV pt w/ AMS presenting in the ED when you're considering lymphoma, toxo, meningitis, encephalitis, etc? or a known cancer patient you suspect may have metastatic disease presenting in the ED? Contrast, Non-contrast, or W + W/O?

Thanks for you responses...

 

[waterski232002]

EDH is not in the differential of HA of 4 weeks. SAH would also be quite rare to have this presentation.

Agreed... I was merely listing the things we need to rule out in the ED, not necessarily what I suspected this patient to have. I was really only concered with a SDH b/c he was an alcoholic.

 

[Docxter]

Docxter... Thanks for your response. This was an adult pt I saw in the ED yesterday. As you said, MRI is not realistic in the ED setting, particularly for this case, that's why I didn't even consider it in my imaging modalities of choice. So would you have recommended a non-contrast or contrast CT for the patient above (adult w/ 4wk HA)?

Either one would have worked. Noncontrast CT is an excellent screening tool and the imaging of choice for this patient in the ED setting. A negative CT is very reassuring in a headache patient without other symptoms and negative neuroexam and is a very good choice. In the rare instance that the patient has ongoing symptoms, he will follow-up with someone or return and then more work-up can be done.

What about an HIV pt w/ AMS presenting in the ED when you're considering lymphoma, toxo, meningitis, encephalitis, etc? or a known cancer patient you suspect may have metastatic disease presenting in the ED? Contrast, Non-contrast, or W + W/O?

Thanks for you responses...

The sensitivity of CT is low for these conditions and they will need MRI and likely a whole slew of laboratory tests, LP with CSF special studies (PCR, etc.), and maybe even biopsy. But again, noncontrast CT is a good initial test to rule out any emergent or potential life-threatening conditions that are in the differential of these conditions and also to look for possible changes that may be seen in CT in these diseases.

The exception is a patient with known metastatic cancer with neurological changes that can be attributed to brain mets. I would do a contrast CT in the ED for this indication.

Overall, the overall indications and utility of contrast CT someone who does not have contraindications to MRI is not a lot. Mostly it is done in low-probability cancer patients for staging or follow-up of known MRI findings. Depending on what you you're investigating, often either a noncontrast CT or an MRI is performed.

 

[f_w]

As for imaging in patients presenting to the ED with headache:

-- The negative non-contrast CT is typically sufficient to r/o any mass that could kill the patient between the ED visit and the neurologist appointment (--> causing herniation or a threat of herniation).
-- The negative contrast CT done on a latest generation scanner is typically sufficient to r/o most masses big enough to cause a headache (--> hydrocephalus or meningeal stretching. mass effect on brain parenchyma alone will not cause a headache).
-- The triple dose 3T extravaganza read by an expert neuroradiologist is certainly the 'test of choice' to r/o any ill that can befall the brain and leaves an imaging correlate (However, the only situation I am aware of a clinical benefit of the triple dose contrast is the setting of suspected brain-mets where the yeah/nay answer makes a difference in treatment planning for an extracranial tumor.)

And here is the reason why doing the head-CT can be a good idea:

CPT 70450 (CT head wo contrast) : $202.11
CPT 70470 (CT head w/wo contrast) : $302.70

CPT 70553 (MRI brain w/wo contrast) : $960.19

(And this is medicare funny-money. The number on the bill that the patient receives is typically about about twice that. Doesn't matter so much as long as you are in academia. But I run into our patients at the local coffee-shop and I don't want them to have the feeling they got gouged by the hospital.)

 

[stephew]

I had a patient today with a headache for 1 month, constant, small relief with OTC pain meds. no other symptoms, no neuro deficits on exam. He was worried about brain cancer (although I wasn't worried about an intracranial mass). His CT head w/o contrast was normal. I realize that in order to visualize intracranial masses a CT with contrast is the imaging modality of choice. My question is... will most masses still show up on a non-contrast CT (or will there be some secondary changes which may indicate a mass)? What percent of masses, or what size masses will be missed on a non-contrast CT as opposed to a contrast CT?

the answer is you can NOT rule out a tumro without contrast. while some will show becaus eof bleed, edema or just differences in the plane from normal tissue, some will be completely hidden without contrast. indeed some can't be seen without MRI.