Hyperparathyroidism CT
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Anmol Pitliya, M.B.B.S. M.D.[2]
Overview
Good quality preoperative evaluation favors post operative results. 4-dimentional CT scan is an investigation for preoperative localizing of hyper-functioning parathyroid gland. 4D-CT is significantly more sensitive than Tc-99m sestamibi scintigraphy and ultrasound for precise (quadrant) localization of hyper-functioning parathyroid glands. 4D-CT is required to be performed with three phases including non-contrast, arterial, and delayed phase imaging. 4D-CT provides extremely detailed images of neck in multiple planes and enables the visualization of difference in hyper-functioning parathyroid gland compared with normal parathyroid glands and other structures in the neck on the basis on perfusion characteristics ( rapid uptake and washout). 4D-CT is particularly useful in cases of re-operation. The major disadvantage of 4D-CT is significant radiation exposure associated with scanning the patient multiple times.
CT scan
- 4-Dimentional CT scan is an investigation for preoperative localizing of hyper-functioning parathyroid gland.[1]
- 4D-CT may be used for preoperative localization of hyper-functioning parathyroid glands in hyperparathyroidism. 4D-CT is significantly more sensitive than Tc-99m sestamibi imaging and ultrasound for precise (quadrant) localization of hyper-functioning parathyroid glands.[2]
- The name 4D-CT refers to 3-dimensional CT scanning plus additional dimension of changes observed with respect to time as perfusion of contrast occurs. The principle is similar to CT angiography.
- 4D-CT is required to be performed with three phases:[3]
- Non-contrast phase imaging
- Arterial phase imaging
- Delayed phase imaging
- The characteristic enhancement of parathyroid lesions relative to thyroid tissue peaks at arterial phase. There is washout of contrast material from arterial to delayed phase. Images of parathyroid lesion are lower attenuated compared to thyroid tissue in non-contrast enhanced phase.[4]
- The enhancement pattern on 4D-CT scans can be grouped into three types on the basis of relative attenuation of hyper-functioning parathyroid glands relative to thyroid gland.
| Type of pattern | Attenuation of parathyroid lesions relative to thyroid tissue | ||
|---|---|---|---|
| Arterial phase | Delayed phase | Non-contrast phase | |
| Type A pattern | Higher | -- | -- |
| Type B pattern | Not higher | Lower | -- |
| Type C pattern | Not higher | Not lower | Higher |
| Type B pattern is most common type of pattern (approximately half of lesions). | |||
- At least 3 phases are required due to the following reasons:
- On arterial phase, only 20% of parathyroid lesions are higher attenuation than thyroid tissue.
- 22% of parathyroid adenomas have the similar enhancement to the thyroid tissue on both arterial and delayed phase and could be missed without the non-contrast imaging.
- 4D-CT provides extremely detailed images of neck in multiple planes and enables the visualization of difference in hyper-functioning parathyroid gland compared with normal parathyroid glands and other structures in the neck on the basis on perfusion characteristics ( rapid uptake and washout).
- 4D-CT has a sensitivity of 88% in preoperative lateralizing hyper-functioning parathyroid glands to one side of neck.[5]
- 4D-CT has a sensitivity of 79-88% in preoperative localizing the hyper-functioning parathyroid gland to the correct quadrant of the neck (right inferior, right superior, left inferior, or left superior).[6]
- 4D-CT has a specificity of 75-100% in preoperative localizing the hyper-functioning parathyroid glands.[7]
- A modified technique of 4D-CT/ultrasound (Mod 4D-CT/US) has a sensitivity of 94% and specificity of 96% for lateralizing the hyperfunctioning parathyroid glands to one side of the neck. Mod 4D-CT/US has a sensitivity of 82% and specificity of 93% for localizing the hyper-functioning parathyroid glands to the correct quadrant of the neck (right inferior, right superior, left inferior, or left superior). Mod 4D-CT/US has a positive predictive value of 92% for single-gland disease and 75% for multi-gland disease. Mod 4D-CT/US has a negative predictive value of 73% for single-gland disease and 92% multi-gland disease.[8]
Advantages of 4D-CT over other imaging techniques
- Difficult subgroups: 4D-CT is superior than Tc-99m sestamibi scintigraphy and ultrasound in following subgroups of patients:[2][9]
- Small lesions
- Ectopic lesions
- Multigladular disease
- Preoperative planning: 4D-CT enables an improved preoperative planning, particularly in case of re-operation. 4D-CT provides high-resolution images in multiple planes. There is better visualization of size of the parathyroid adenoma, polar vessel to the adenoma and surrounding structures on 4D-CT. [10]
- Grading diagnostic confidence: Diagnostic confidence is important in pre-operative planning for minimally invasive parathyroidectomy as all four parathyroid glands are not visualized intra-operatively. High diagnostic confidence of 4D-CT may eliminate the need of additional diagnostic modality thereby increasing the cost effectiveness.[3][11]
- Cost-effective: A single imaging modality followed by 4D-CT when traditional modality fails to identify the lesion is more cost-effective than other protocols. This cost-effectiveness is due to the fact that proper localization leads to minimally invasive surgery which is a less costly than bilateral neck exploration and failed surgery.[12][13]
Disdvantages of 4D-CT over other imaging techniques
- The major disadvantage of 4D-CT is significant radiation exposure associated with scanning the patient multiple times.The effective dose (ED) of radiation is 28 mSv for 4D-CT when compared with 12 mSv for Tc-99m sestamibi scintigraphy. In exposed patients, lifetime attributable risk for cancer incidence is approximately 193 cancers/100,000 patients and and 68 cancers/100,000 patients for 4D-CT and Tc-99m sestamibi scintigraphy respectively. 4D-CT leads to a 0.52% increase in lifetime incidence of cancer over baseline compared to 0.19% increase in lifetime incidence of cancer over baseline for Tc-99m sestamibi scintigraphy.[14]
References
- ↑ Hunter GJ, Schellingerhout D, Vu TH, Perrier ND, Hamberg LM (2012). "Accuracy of four-dimensional CT for the localization of abnormal parathyroid glands in patients with primary hyperparathyroidism". Radiology. 264 (3): 789–95. doi:10.1148/radiol.12110852. PMID 22798226.
- ↑ 2.0 2.1 Rodgers SE, Hunter GJ, Hamberg LM, Schellingerhout D, Doherty DB, Ayers GD; et al. (2006). "Improved preoperative planning for directed parathyroidectomy with 4-dimensional computed tomography". Surgery. 140 (6): 932–40, discussion 940-1. doi:10.1016/j.surg.2006.07.028. PMID 17188140.
- ↑ 3.0 3.1 Bahl M, Sepahdari AR, Sosa JA, Hoang JK (2015). "Parathyroid Adenomas and Hyperplasia on Four-dimensional CT Scans: Three Patterns of Enhancement Relative to the Thyroid Gland Justify a Three-Phase Protocol". Radiology. 277 (2): 454–62. doi:10.1148/radiol.2015142393. PMID 26024308.
- ↑ Hoang, Jenny K.; Sung, Won-kyung; Bahl, Manisha; Phillips, C. Douglas (2014). "How to Perform Parathyroid 4D CT: Tips and Traps for Technique and Interpretation". Radiology. 270 (1): 15–24. doi:10.1148/radiol.13122661. ISSN 0033-8419.
- ↑ Eichhorn-Wharry LI, Carlin AM, Talpos GB (2011). "Mild hypercalcemia: an indication to select 4-dimensional computed tomography scan for preoperative localization of parathyroid adenomas". Am J Surg. 201 (3): 334–8, discussion 338. doi:10.1016/j.amjsurg.2010.08.033. PMID 21367374.
- ↑ Griffith B, Chaudhary H, Mahmood G, Carlin AM, Peterson E, Singer M; et al. (2015). "Accuracy of 2-Phase Parathyroid CT for the Preoperative Localization of Parathyroid Adenomas in Primary Hyperparathyroidism". AJNR Am J Neuroradiol. 36 (12): 2373–9. doi:10.3174/ajnr.A4473. PMID 26359149.
- ↑ Beland MD, Mayo-Smith WW, Grand DJ, Machan JT, Monchik JM (2011). "Dynamic MDCT for localization of occult parathyroid adenomas in 26 patients with primary hyperparathyroidism". AJR Am J Roentgenol. 196 (1): 61–5. doi:10.2214/AJR.10.4459. PMID 21178047.
- ↑ Kutler DI, Moquete R, Kazam E, Kuhel WI (2011). "Parathyroid localization with modified 4D-computed tomography and ultrasonography for patients with primary hyperparathyroidism". Laryngoscope. 121 (6): 1219–24. doi:10.1002/lary.21783. PMID 21557243.
- ↑ Galvin, Leo; Oldan, Jorge D.; Bahl, Manisha; Eastwood, James D.; Sosa, Julie A.; Hoang, Jenny K. (2016). "Parathyroid 4D CT and Scintigraphy". Otolaryngology-Head and Neck Surgery. 154 (5): 847–853. doi:10.1177/0194599816630711. ISSN 0194-5998.
- ↑ Kukar M, Platz TA, Schaffner TJ, Elmarzouky R, Groman A, Kumar S; et al. (2015). "The use of modified four-dimensional computed tomography in patients with primary hyperparathyroidism: an argument for the abandonment of routine sestamibi single-positron emission computed tomography (SPECT)". Ann Surg Oncol. 22 (1): 139–45. doi:10.1245/s10434-014-3940-y. PMID 25074663.
- ↑ Bahl M, Muzaffar M, Vij G, Sosa JA, Choudhury KR, Hoang JK (2014). "Prevalence of the polar vessel sign in parathyroid adenomas on the arterial phase of 4D CT". AJNR Am J Neuroradiol. 35 (3): 578–81. doi:10.3174/ajnr.A3715. PMID 23945223.
- ↑ Lubitz CC, Stephen AE, Hodin RA, Pandharipande P (2012). "Preoperative localization strategies for primary hyperparathyroidism: an economic analysis". Ann Surg Oncol. 19 (13): 4202–9. doi:10.1245/s10434-012-2512-2. PMC 3680347. PMID 22825773.
- ↑ Wang TS, Cheung K, Farrokhyar F, Roman SA, Sosa JA (2011). "Would scan, but which scan? A cost-utility analysis to optimize preoperative imaging for primary hyperparathyroidism". Surgery. 150 (6): 1286–94. doi:10.1016/j.surg.2011.09.016. PMID 22136852.
- ↑ Hoang JK, Reiman RE, Nguyen GB, Januzis N, Chin BB, Lowry C; et al. (2015). "Lifetime Attributable Risk of Cancer From Radiation Exposure During Parathyroid Imaging: Comparison of 4D CT and Parathyroid Scintigraphy". AJR Am J Roentgenol. 204 (5): W579–85. doi:10.2214/AJR.14.13278. PMID 25905965.