Ultrasound Evaluation of the Parathyroid - SD

Objectives of the Study

The objectives of this study include to describe the scanning technique and sonographic appearance of parathyroid adenoma, to understand the role of color doppler in assessing parathyroid adenoma, and to understand the role of nuclei in parathyroid imaging.

Anatomic Location of the Parathyroids

This slide describes the anatomic location of the parathyroids. As we all know, there are four parathyroid glands, two superior and two inferior, and 25% are located in the superior mediastinum in the event they are ectopic and location.

This slide just demonstrates the location of the parathyroids posteriorly. This is from the net diagram.

Blood Supply to the Parathyroid Glands

This slide demonstrates the blood supply to the superior and inferior parathyroid gland. Superior parathyroid gland derives its blood supply from the superior thyroid artery and the inferior parathyroid gland derives its blood supply from the inferior thyroidal artery.

When parathyroid glands are ectopic, they usually lie in the lower neck or in the anterior mediastinum, and inferior parathyroid glands have a higher chance of being ectopic.

The parathyroids can also be classified depending upon their location. They can be normal in location within media tum, retro pharyngeal or intra horal.

Indications for Parathyroid Imaging

We know that parathyroid imaging is usually indicated or asked for when patients present with hyperparathyroidism. The primary parathyroidism hyperparathyroidism is usually secondary to ary adenoma, and 10 to 15% is secondary to hyperplasia and only less than 4% is secondary to parathyroid carcinoma.

The secondary hyperparathyroidism is predominantly by secondary to renal failure and rarely secondary to paraneoplastic syndrome.

There is high association of hyperparathyroidism in patients with men one syndrome. As shown in this slide, more than 90% have hyperparathyroidism in men one syndrome, and approximately 10 to 30% have hyperparathyroidism in men. Two, A syndrome.

Ultrasound Technique for Evaluation of Parathyroid

The ultrasound technique for the evaluation of parathyroid involves utilization of a high frequency linear transducer of 10 to 14 megahertz with broadband capability and color flow. Upper capability scan is performed in transverse plane from hide bone to the thoracic inlet, and we know that the normal parathyroid cannot be seen by ultrasound as they are less than four millimeter in size, and there are many other entities in that location, which could be mistaken for parathyroid gland such as esophagus or lymph node, and will go over these false negative and positives in the next coming slides.

Ultrasound Appearance of Parathyroid Lesions

The ultrasound appearance of parathyroid adenoma or carcinoma or hyperplastic parathyroid gland is similar on ultrasound as described on this slide, and ultrasound cannot differentiate between benign or malignant lesions.

This is an example in gray scale showing a right lower pole parathyroid adenoma, predominantly hypo quake and appearance.

This is another example of a parathyroid adenoma in the left parathyroid gland in the inferior pole, and the maximum size of this is about two centimeters.

Role of Color Flow Doppler Sonography

Is there a role of color flow doppler sonography in the evaluation of parathyroid gland? Yes, there is a definite role of color flow doppler sonography in its evaluation. In a study by Wolf RJAA all which was published in JUM in 1994, they described the presence of an arc between 90 degree and 270 degree of the parathyroid mass, and it was seen in 20 of 32 patients.

This is an example describing the peripheral arc. You can see the first slide is a gray scale image of a hypo quake mass, which is confirmed parathyroid adenoma with a rol dopplar demonstrating the arc sign.

The additional sign of an extra thyroidal artery was described by MJ AAL and was published in a JR in 1998, and it was seen in 35 of the 42 adenomas in their study.

Additionally, polar vascular and vascular Ari of the thyroid gland can be seen as shown in this slide. And this was published by Scott b reader in JUM in 2002.

This is an example of a polar distribution of color flow. The first two images show the gray scale appearance of a parathyroid adenoma, and this color flow shows the polar sign as we described in the previous slide.

This is an additional example of color flow doppler polar sign.

This is an additional image describing the polar sign.

Pitfalls in Parathyroid Evaluation

Once again, as we mentioned before, there are many reasons a false positive examination. When you evaluate parathyroid gland, the commonness cause actually is esophagus. We'll see the examples. Cervical lymph nodes can be mistaken for this gland, long COI muscle or thyroid nadu.

There are false negative results and they are usually secondary to minimally enlarged adenoma, multinodular thyroid greater and ectopic location of the parathyroid adenoma.

This is an example demonstrating the esophagus posteriorly, which has a classic gut signature, which may give rise to a false positive result. And this should not be mistaken for parathyroid adenoma.

This case is interesting as you can see, the first slide CT where it shows a large mass with a well-defined margin. It was called to be parathyroid adenoma or a mass. Subsequently ultrasound was performed. You can see on a gray scale this is arising from the thyroid gland and is not a parathyroid. It is, it was confirmed to be an extrophy collide nodule.

Parathyroid Carcinoma

I certainly want to mention about parathyroid carcinoma, which is an unusual entity. However, when present it is usually of a larger size and maybe palable in one third of the cases. And other characteristics of this are mentioned in this slide.

And I just want to emphasize that parathyroidectomy is not always successful.

Parathyroid Cyst

Parathyroid cyst can be seen and their origin is attributed to various reasons as described in this slide. But if you can do a fine needle aspiration and demonstrate PTH, that can certainly diagnose the cyst and its origin.

Limitations of Ultrasound Evaluation

What are the limitations of a ultrasound evaluation of the parathyroid gland and why are they number one? Ultrasound is not able to detect the ectopic nodules. It is unable to characterize the intra parathyroid nodules. And if there is a concomitant presence of thyroid disease, which is seen in up to 40% of patients with parathyroid disease, it's very difficult to identify parathyroid adenomas.

The sensitivity of ultrasound is about 34 to 92%. It is very, very variable because the manufacturer are involved in it, such as the experience of the operator, ectopic location and the presence of the thyroid disease. Specificity is very consistent, is about 92 to 97%.

Nuclear Scintigraphy

Nucleus synography is an additional technique which is also performed to evaluate parathyroid gland disease processes in older times. Subtraction of thallium 2001 chloride from technician 99 M per technic eight was done, which is no more performed.

The community standard is a double phase in with technician 99 system maybe. And the current clinical practice is routine use of planar and spec imaging at 10 minutes and two hours.

Now, the technician 99 system maybe is taken up by both thyroid and the disease parathyroid gland. The normal washout from thyroid and parathyroid is in about 30 minutes, and the peak activity is in four to six minutes. The washout from the disease parathyroid is delayed because the mitochondria rich oxil cell content as a tumor. Therefore, there is a differential washout between the thyroid and parathyroid, and that is how the system may be is utilized for diagnosing the disease.

This is just to summarize. The clearance time is based upon the differential washout. The mechanism is mitochondrial. Physical half-life of system may be a six hours. The four on energy is one 40 KV and imaging protocol is at 10 minutes and delayed images at two to three hours.

This is an example demonstrating the presence of a ectopic parathyroid adenoma.

This is an additional patient which you can see on a pinhole, a two hour image on the left hand side, the parathyroid adenoma can be seen. Uh, so well, pinhole images are useful to see and improve the resolution of these images.

What are false positives in nucleus synography, multi no lag Hashimoto thyroiditis and thyroid carcinoma, including the uptake by lymph nodes and false negatives as given below in this slide.

How good is nuclei? You can see the sensitivity is about 89 to 95% in patients who are undergoing or prior to the surgery. And only about 59% of those who are undergoing repeat surgery.

This is an example. You can see the parathyroid ectopic adenoma in a CT and corresponding system may be image demonstrates the ectopic location.

Comparison of Ultrasound and Nuclear Scintigraphy

What are the differences in cost? The Ultrasound is non-ionizing and certainly system maybe is ionizing. Ultrasound is much cheaper as compared to the system. AB study ultrasound has severe anato resolution and does not need appointment, whereas in nucleus study, the anatomic resolution is poor and appointments are necessity.

This was a very interesting study which was done by Maria Laura and was published in radiology in 2000 and they were able to identify 23 after 24 parathyroid art duals utilizing a combination of ultrasound and synography. I thought it was worthwhile presenting that into this discussion.

And they did high five of six cases where ultrasound was positive and synography was negative, but that involved not due less than one CM in size. And there was one case utilizing both techniques which provided negative result, and that was secondary to a large hyperplastic gland with wide cystic and necrotic areas.

So overall sensitivity in this study combining the ultrasound and graph was 96% versus 67% for ultrasound alone and 71% fori alone. The specificity of the combination of ultrasound and synography was 83%.

Minimally Invasive Radio-Guided Parathyroidectomy

The presentation would not be complete without mention of a minimally invasive radio guided parathyroidectomy procedure, which is nowadays the standard of care on average takes about 17 minutes, is performed through a three fourth inch to one inch incision. Patient goes home in one to two hours and there are no stitches to remove.

This is a live image of a patient. The first image shows the how the patient is prepped and draped second shows the suture going through the inferior thyroid artery. And the third image demonstrate the removal of the parathyroid gland.

How does the surgeon know that they have removed the parathyroid adenoma after removal of the adenoma? They perform the PTH blood level, and after about 15 minutes, there is a 50% fall in the PTH level. That is how they get to know that the surgery was successful.

But how do they localize this? They, as I mentioned, patient comes to the department and gets a system, maybe injection then goes to the or, and then they use the nuclear probe to localize the uptake of the system, maybe by the parathyroid gland, and they make incision over it.

And this principle is because we know that most of the hyperparathyroidism involves only one gland and not all the glands.

Conclusion

In conclusion, I would say that ultrasound is operator dependent and results are variable. RO doppler helps in localization. Ultrasound cannot differentiate parathyroid adenoma and carcinoma technician. 99 dual phase imaging is better. In imaging, the ectopic parathyroid gland and combined ultrasound imaging and nucleus angiography have better results.

Thank you for your time.