Radiopharmaceutical, Dose, and Technique of Administration
Patient Position and Image Field:
The camera MUST be positioned as close to the patient as possible. THIS IS IMPERATIVE if you want crisp, clear pictures. This is one of the biggest mistakes made across the U.S. We must say this again--it cannot be over-emphasized... the camera MUST be as close to the patient as possible!!
Sestamibi Scan Preferred Views:
This is the most important information on this page! We perform nearly 1400 sestamibi scans per year, and our volume of cases dictates that we review nearly 2500 scans per year that have been performed at outside institutions. This fact means that Dr. Norman has seen far more sestamibi scans than any other physician... so we know what works and what does not. The following list is very dear to our hearts and we feel very strongly that these simple changes will make dramatic changes in both the sensitivity and specificity of these scans.
Our standard protocol (which we rarely follow - but we do recommend highly for institutions that do not perform hundreds of these scans per year) is to obtain 5 early and 4 delayed views (if the patient is not going to the operating room): Ant neck, Ant neck with marker (early only), Ant mediastinum, LAO, and RAO. Each image is obtained at 8cm or less. The camera MUST be nearly touching the patient! Early views are obtained about 5 minutes after injection. Delayed views are obtained between 1.25 to 2.5 hours. The mediastinal view must show at least the top half of the heart. NONE of the other views should show more than a small sliver of the heart. If too much heart is showing it will decrease your quality! Without mediastinal imaging down to the level of the heart 4 to 5% of adenomas will be missed. Only a small sliver of the heart is to be included in LAO and RAO views. If performing immediately prior to performing a minimal parathyroidectomy, the timing is more critical -- see below. If the adenoma shows within the neck on the early view (most common scenario) then we do not get a delayed mediastinal view to save time and effort. Also note, the delay protocol changes according to how the early films look. If they look good, we speed things up. Better for the nuclear medicine department, better for the patient, and better for the surgeon if the patient is going directly to the OR (this is the ideal situation...the nuclear medicine department takes part in the treatment of this disease rather than playing just a diagnostic role.
IMPORTANT... nearly 98% of scans that are positive will be positive with the first three pictures (an AP, and a LAO, RAO). This is all we do on ALL patients going to the operating room. Also, this is all we do on about 90% of ALL patients that we scan. Delayed scanning only helps with about 2% of patients. THUS... if a criteria for positivity is that a hot spot stays on delayed images while the thyroid washes out... you will MISS at least 20% of positive scans. Yes, differential washout during delayed imaging CAN be helpful... it should NEVER be a necessary criteria for calling a scan positive!!!). We see at least 1 scan per week that was performed at an outside hospital that is a clear positive scan but is read as negative because the parathyroid tumor washes out at the same rate as the thyroid. This is NOT a criteria for a parathyroid tumor!!!
Acquisition Protocol:March '06
We acquire each view for a fixed time rather than a fixed number of counts. This way we find more uniformity with all images (early and delayed) which makes comparisons easier and subtle findings more apparent. You cannot have too much of the heart and/or liver in the field. This will wash out the thyroid/parathyroid. You should see just a sliver of the top of the heart (ventricles).
Early Images: Anterior, ant + mediastinum, LAO, and RAO views at 5 minutes, (one anterior with markers and one without). Markers are placed on the sternal notch, and 2 laterally along the lateral border of the SCM muscle 4 cm apart (distance guide). Note... since we do 8 of these scans every day, we no longer perform scans with markers...UNLESS 1) the tumor is displaced from the thyroid (in the chest or near the clavicles, for example), or 2) the patient has had their thyroid removed already and thus the thyroid is not available as an anatomical landmark.
Delayed Images: Timing discussed below. Anterior, ant + mediastinum, LAO, and RAO views are obtained. The lateral oblique views are at 31 degrees with the patient's head midline. Note: often we do the delayed films earlier (see below) if the adenoma shows up on the initial scan. Why 31 degrees? This is a frequently asked question. We have found that rotating the camera any further than this means that the patient's shoulder gets in the way, necessitating moving the camera further away from the patient's neck. This means that all the scans will not be obtained at the same distance from the patient's neck (as noted above, we aim to maintain the same distance for all views). We have done enough to know that 31 degrees is about all you can rotate the camera without pushing the patient's shoulder. DO NOT PERFORM OBLIQUE IMAGES BY ROTATING THE PATIENT'S HEAD. YOU WILL NOT GET THE SAME RESULT. EXTREMELY IMPORTANT!!!
Lateral views are NEVER required. The importance of the LAO and RAO views is that they allow the parathyroid adenoma to be localized in three dimensions in relationship to the thyroid gland. If the adenoma is located at the level of the thyroid (in depth from the skin) then it will appear to "move" in the neck when comparing the right and left views. If the adenoma is located deep to the thyroid, it is almost always in the tracheoesophageal groove. In this case, the position of the adenoma will appear to be the same on the LAO and RAO views while the thyroid "rotates" from side to side. This 3-dimensional localization will help the surgeon by giving a good estimate of the adenoma depth.
The use of a Pin-hole collimator is absolutely the worst thing you can do and is the second most common problem we see in scans from across the US. DO NOT DO THIS! It will destroy all the fine details that you can achieve by placing the camera very close to the patient. Trust us... and try it. You will be amazed how you are destroying your detail with this technique!!!! DON'T DO IT!
Delayed Images and SPECT Imaging
There are very few indications for delayed images after 2.5 hours. Occasionally (rarely) thyroid activity can be a bit hot and re-scanning at 3 hours may be helpful. We do NOT think this is a common occurrence...in fact, it is extremely rare.
We had (past tense) been using SPECT imaging for all patients in which there is a questionable adenoma (about one in 20). We used to think that SPECT analysis could increase sensitivity and specificity several percent, and therefore, used it selectively. If the standard views suggest single gland disease but cannot definitively say yes or no, then we would (in the past) perform a SPECT immediately after the delayed films. We strongly believe that SPECT adds NOTHING that the LAO / RAO views don't already give us. In fact, the ONLY time we do SPECT is when the tumor is located deep in the chest next to the heart. In our review of 6,500 scans from across the US, those that had a SPECT were typically graded LOWER than those that obtained planar images only. Remember, even patients that have a negative scan still has the highest likelihood of having a SINGLE adenoma, but the chances of having 4 gland disease have been increased from 3% to about 7% (depending on how good your scans are). Some centers perform a SPECT on all patients. We think this is overkill and unnecessary almost all of the time and, is usually NOT as good as doing simple planar with LAO / RAO views. THIS SHOULD NEVER BE DONE! Furthermore, if the patient is being taken directly to the OR, this wastes valuable time. We NEVER get SPECT scans unless it is in the chest. To summarize on our feelings of SPECT... 1) there is no reason to do SPECT only and this should NEVER be done. 2) Routine use of SPECT in addition to planar imaging is unnecessary and will always be un-helpful if the planar images are performed as outlined on this page. Most uses of SPECT fall into this category and this really should STOP!. 3) SPECT can be helpful in SOME re-operation... but limited to only those that are displaced from the thyroid (such as those that are deep in the chest), or when a previous thyroidectomy has been performed). We perform about 1000 parathyroid operations per year, and we use SPECT about 15-20 times per year... on deep chest operations. The only reason to do SPECT is so the radiology department and radiologist can bill an additional $1000. This MUST STOP.
Information about Probes used for Radioguided Surgery
REMEMBER!!! A good parathyroid probe used in the operating room is MUCH better at finding a hot spot of radioactivity than is the camera. HOWEVER, using a probe designed for breast surgery or melanoma will NOT provide this high degree of sensitivity and specificity. Radioguided surgery for breast and melanoma is VERY DIFFERENT... In these cases, the probe is designed to detect a hot radioactive lymph node within a cold background. Of course, in parathyroid surgery, the probe needs to detect a 'very hot' parathyroid from within a 'hot' background (or a near-similarly hot thyroid gland). Thus, if your surgeon is trying to perform radioguided parathyroid surgery and he/she is using a Neoprobe, or any other probe (C-tract, Navigator, etc) that is NOT fitted with a specific 'Norman Parathyroid Probe' which is specifically collimated for use during parathyroid surgery (hot vs. hotter), then it WILL NOT WORK! Again, only parathyroid probes are designed to distinguish hot from hotter, and the probes that are designed to work with breast and melanoma lymph node mapping WILL NOT WORK on some cases where the parathyroid is in close proximity to the thyroid. We have seen malpractice law suits filed because a surgeon used the wrong probe. Don't make this mistake.
If Performing Sestamibi
Scanning Prior to Intra-operative Nuclear Mapping for
Minimal Parathyroid Surgery:
UPDATED: 2006. We VERY RARELY do any delayed imaging at
all on the day of surgery. The scan will
take about 10 to 20 minutes (two, three, or four views) and off to the OR they go.
About 25% of patients have such a beautiful scan at 10 minutes (two views)
that this is all they get. About 55% are clearly positive including
estimates on depth of the tumor within the neck (obtained by oblique
views) after three views that this is all they get. Only about 20% of
patients have a fourth view (always an AP) which will often show the tumor
when compared against the very first view (also an AP). Thus, on about 25% we simply to an AP and one oblique. The oblique provides depth
information to the surgeon. IMPORTANT... if you do the scans
right, 98% of positive scans will be positive within the first 15
minutes... delayed scanning will only get you another 2%! AGAIN.....
Delayed scans beyond the first 15 minutes will give you only very
incremental improvements in positivity.... if you are doing the scans
right in the first place. If you are waiting to see the thyroid wash out
completely leaving only a single focus...... then you are missing the true
value of this test and need to re-think it. THIS IS NOT CORRECT!
This technical page on Sestamibi Scanning for Parathyroid Disease was written and these techniques have been developed by Hemant Chheda, MD, Brandi Reardon, and James Norman, MD who interpret over 4000 parathyroid scans per year.
ABOUT THE AUTHOR: Dr Chheda is a Clinical Associate Professor of Radiology at the University of South Florida and Medical Director of Nuclear Medicine at Tampa General Hospital where he has performed more than 350 sestamibi scans each year since 1995 (when radioguided parathyroid surgery was developed with his assistance). By 2006, he averages overseeing more than 2000 Sestamibi scans per year performed for Dr Norman's patients. Dr. Chheda is the nuclear radiologist for the Norman Parathyroid Clinic and he gets daily written feedback from Dr Norman with the results of every operation so as a team, their accuracy is extremely high.
The Chief Technologist is Brandi Reardon who performs the vast majority of Sestamibi scans, and is considered by many to be one of the world's foremost experts on the technical aspects of Sestamibi scanning for parathyroid disease. The extremely high accuracy of scans performed by the Norman Parathyroid Clinic and Tampa General Hospital nuclear medicine department is due in large part to Brandi's expertise and constant attention to detail which allows our scans to get better year after year.
Dr James Norman has seen and reviewed more sestamibi scans than anybody else in the world. He currently performs about 1800 parathyroid operations per year and the vast majority of these patients come with scans performed at another hospital. About 85% of outside scans are performed with substandard techniques and about 75% of these are read as negative because of the poor techniques used. Poor sestamibi scan techniques are STANDARD in the US, and the big university hospitals are NOT any better at it than the small community hospitals. It all depends on technique. Dr Norman has the opportunity to review about 4,500 sestamibi scans per year--from all over the US and many foreign countries. Dr Norman has seen every possible parathyroid scan and every technique ever used. Our excellent scans are a result of dedication to this disease, tremendous volume, and a great team.
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