How to Order a 4D Parathyroid CT in Epic
To order a 4D parathyroid CT in Epic, search for "CT Neck Without and With IV Contrast" or "4D-CT Parathyroid" in your institution's order entry system, ensuring the protocol specifies noncontrast, arterial, and venous phases for optimal parathyroid localization. 1
Understanding What You're Ordering
A 4D parathyroid CT is technically a CT Neck Without and With IV Contrast that uses a multiphase technique (noncontrast, arterial, and venous phases) to differentiate parathyroid tissue from thyroid tissue and lymph nodes based on enhancement patterns. 1, 2
The "4D" terminology refers to the addition of temporal (time-based) contrast enhancement as the fourth dimension beyond the three spatial dimensions. 1
Specific Ordering Instructions in Epic
In Epic's order entry system, navigate to the imaging orders section and search for "CT Neck" or "Parathyroid CT" depending on your institution's nomenclature. 1
Ensure the order specifies all three phases: noncontrast, arterial phase with IV contrast, and delayed venous phase with IV contrast—omitting the noncontrast phase reduces sensitivity from 79% to 55% for single-gland disease. 1, 2
If your Epic system has integrated order sets, look for "Parathyroid Imaging" or "Hyperparathyroidism Workup" order sets that may include the properly protocoled 4D-CT. 1
Clinical Context for Ordering
Order 4D-CT when ultrasound and sestamibi scintigraphy are negative, discordant, or equivocal in patients with biochemically confirmed primary hyperparathyroidism who are surgical candidates. 1, 2, 3
4D-CT achieves 79-92% sensitivity for single-gland disease and 43-67% sensitivity for multigland disease, with positive predictive values of 88-92%. 1, 2
This study is particularly valuable in obese patients, reoperative cases, or when multigland disease is suspected, as it outperforms traditional imaging in these scenarios. 3, 4, 5
Common Pitfalls to Avoid
Do not order 4D-CT as the initial imaging study—it should be reserved as second-line imaging after ultrasound ± sestamibi due to radiation exposure (approximately 6.7 mSv effective dose). 2, 3
Verify the protocol includes the noncontrast phase—22% of parathyroid lesions have enhancement patterns similar to thyroid on arterial and venous phases alone and will be missed without the baseline noncontrast images. 1
Ensure proper IV contrast administration timing—the arterial phase must be properly timed to capture peak parathyroid enhancement, which differs from standard neck CT protocols. 1, 6
Coordination with Radiology
Contact your radiology department or use Epic's secure messaging to confirm they have a dedicated 4D parathyroid CT protocol before placing the order, as not all institutions use standardized protocols. 1
Include relevant clinical information in the order indication field: "Primary hyperparathyroidism, preoperative localization, prior imaging nonlocalizing" to ensure radiologists apply the correct protocol and interpretation approach. 1, 2