Parathyroid Imaging What is best Mike Avison Bradford
Why me? I m honoured to be asked to present this. There is no killer paper or text which clearly proves the best methodology. Bradford has performed a lot of these studies developing our protocols, auditing and occasionally publishing the results. I hope to be able to convince you that we have found out enough to offer some useful advice.
Hyperparathyroidism Hyperparathyroidism can be insidious Bones, Stones and Groans Bone fractures (osteoporosis) Kidney stones Depression, irritability, headache, Fatigue, forgetfulness, skin irritation Gastro-oesophageal reflux Left ventricular hypertrophy, arrhythmia Cancer risk breast, prostate, colon, kidney It can also be asymptomatic
Hyperparathyroidism The primary diagnosis is made using Parathyroid hormone concentration (PTH) Adjusted calcium level (Ca++) Patient history Symptoms Renal function Other endocrine conditions (such as MEN1 and MEN2)
Hyperparathyroidism 1. Benign adenomas secrete excess PTH and cause bone mineral loss with increase serum calcium:- primary hyperparathyroidism 2. Renal failure causes parathyroid hyperplasia: secondary hyperparathyroidism Normal parathyroid glands are not visualised on scintigraphy Scintigraphy gives pre-op localisation Enables minimally invasive surgery
Options MIBI or Tetrofosmin Activities? Washout 60, 90, 120 min? Subtraction With pertechnetate With iodine-123 Collimator Pinhole LEHR SPECT-CT Planar Approx 64 different protocols
History at Bradford 1980 s 199?-2010 2011-2012 2013-2016 Tracer THALLIUM Tc-MIBI Tc-MIBI Tc-MIBI Subtraction 99m TcO 4 99m TcO 4 123 I 123 I Planar washout phases No 1, 2, 3hr 1, 2, 3hr 1.5hr sometimes Collimator for planar LEHR LEHR LEHR PINHOLE 3D none Occasional SPECT Occasional SPECT SPECT-CT Accuracy 25 81 In progress
What the literature says There are a wide range of findings. Taken together it is difficult to find a clear consensus on technique.
Our Current Audit Work in progress 105 patients identified primary or hyperplasia 2 referring hospitals, so far data only from one. Surgical results 33 primary 8 hyperplasia Fourth audit First one with pinhole planar SPECT-CT
Our Current Procedure Inject 20 MBq 123 sodium iodide Wait 3 to 4 hours Set windows Tc symmetric iodine asymmetric Inject 900MBq 99m Tc-SESTAMIBI Acquire 10 minute ANT static with pinhole collimators Review Either repeat at 90 minutes followed by SPECT-CT or go straight to SPECT-CT All acquisitions are dual energy. All scanned on Brightview XCT
Whether to perform late statics Late statics All suspected hyperplasia Equivocal focus of activity Skip late statics Known primary And clear focus/foci of uptake Rationale If you have found an adenoma (or 2) on early planar imaging it is unlikely you will find another on delayed, but you may fail to localise the known gland(s) on SPECT-CT due to early washout.
Data Capture Scint images from Intellispace or PACS Ca++ and PTH pre and post surgery from result server (ICE) Scint and US reports from result server or PACS Histology on resected glands from ICE Clinical history from ICE egfr from ICE. On previous audits we had to obtain patient notes much more trouble.
Results:- Primary HPT All patients (n=105) At least one gland identified in 104/105 cases Results with surgical findings (n=33) 33/33 resected glands were identified on planar subtraction 5/33 PTH did not normalise but did fall. No second gland was identified scintigraphically in these cases, no later surgery performed.
Pinhole planar vs SPECT-CT Early pinhole planar subtraction Planar pinhole washout Definitive Equivocal Failed 32/33 (97%) 1/33 (3%) 0 (0%) 13/22 (59%) 2/22 (9%) 7/22 (32%) SPECT-CT 21/30 (70%) 7/30 (23%) 2/30 (7%)
Specificity In 1/33 a second focus of uptake was called No second parathyroid adenoma was resected PTH normalised Status of these findings uncertain. Possibly a thyroid nodule hot on MIBI, cold on iodine. See images on next slide
Early planar subtraction SPECT (no CT available) MIBI Iodine
Hyperplasia (secondary HPT) More difficult to know how to audit this. Depends on the intention of the referrer Referred to find most active glands? Success is showing them hot glands, confirmed on histology Referred to find all glands so surgeon can choose Success is n/4 (assuming patient has 4 glands)
Glands on Scint Hyperplasia Matching glands resected Additional glands resected Glands on Scint not resected 1 1 1 0 2 2 0 0 1 1 0 0 2 2 1 0 3 3 1 0 2 2 2 0 1 1 0 0 Per gland analysis: Sensitivity 70% Specificity 100% 6/7 (86%) PTH normalised
scan surgery scan surgery Some examples from the audit..this is what should happen
scan Clinical History : Elevated calcium, but normal PTH. Primary hyperparathyroidism? No surgery yet Normal PTH hyperparathyroidism is a known entity
LEHR planar comparison
Parathyroid adenoma identified and resected surgery
Seen on pinhole planar, not on SPECT-CT
CT incidental sequel Single parathyroid adenoma seen on planar and SPECT-CT Slight opacity on lung in SPECT-CT Had lung CT with contrast Which showed slight abnormality in colon Had colonoscopy Negative Successful parthyroidectomy!