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Letters to the Editor |
and
Darcy L. Kasner, 
Department of Radiology–Nuclear Medicine Section,* Radiation Safety Office, and Marshfield Medical Research Foundation, Marshfield Clinic, 1000 North Oak Avenue, H-1-NM, Marshfield, WI 54449 e-mail: spiethm@mfldclin.edu
Editor:
We read with interest the article by Dr van Dalen and colleagues in the September 2001 issue of Radiology (1). However, we strongly disagree with the authors’ opinion that conventional scintigraphy is "not well suited for selecting patients for the minimally invasive surgical procedure" because of "poor image resolution and anatomic information obtained." In accordance with the findings of many other studies (2–5) and those of our studies in press, this is simply not true.
Multiple imaging modalities used to help localize parathyroid adenomas preoperatively include magnetic resonance (MR) imaging, computed tomography (CT), ultrasonography (US), and scintigraphy. No single technique is ideal. By combining imaging techniques, the sensitivity and specificity increase. In 53 surgically proven cases at our institution, preoperative US and scintigraphy had sensitivities and specificities of 71% and 77% and 71% and 82%, respectively. By combining these techniques, the sensitivities and specificities increased to 85% and 86%, respectively. Since an experienced oncology surgeon was added to the staff at our institution, the sensitivity and positive predictive values have increased to 97% and 93%, respectively, and conventional surgical neck exploration time was reduced from 2 to 4 hours to an average of 22 minutes. We now localize adenomas that are smaller than 120 mg with both techniques.
Other advantages of parathyroid scintigraphy are ectopic gland localization, intrathyroidal parathyroid adenoma localization, and thyroid lesion detection. All parts of the mediastinum are depicted, and the depiction differs from that with US. Without preoperative or intraoperative localization of ectopic parathyroid adenomas, they could be easily overlooked at surgery. Current statistics show that parathyroid scintigraphy has a sensitivity and specificity of 90% and 95%, respectively, for parathyroid adenomas larger than 1 g (6). We also found incidental concurrent thyroid carcinoma.
As you can see, the sensitivity, specificity, and positive predictive values obtained in our study with the combined use of US and scintigraphy, or what you term a technique "not well suited" for parathyroid imaging, are almost identical to the values obtained in your study. Your comment is unfounded.
REFERENCES
and
Eduard E. de Lange, MD
Department of Radiology, Diaconessenhuis Meppel, Hoogeveenseweg 38, 7943 KA Meppel, the Netherlands* e-mail: albertvandalen@planet.nl
Department of Surgery, University Medical Center Utrecht, the Netherlands
Department of Radiology, University of Virginia Health Sciences System, Charlottesville, Va
We thank Dr Spieth and colleagues for their comments about our article (1). We agree that multiple imaging modalities are used to help localize parathyroid adenomas and that no single technique is ideal. As mentioned in our article, scintigraphy has been used for identification of parathyroid adenomas, with results that are comparable to those with US and CT (2). There is no doubt that, on the basis of scintigraphic findings, surgical neck exploration can be restricted to the side or area of the neck where a parathyroid adenoma is depicted, which results in a considerable reduction in the extent of surgery and surgical time. Furthermore, as was mentioned in our article, a minimally invasive procedure is also possible with intraoperative use of a small gamma probe to help localize adenomas that have sufficient uptake of a radiopharmaceutical (3,4).
In their letter, Dr Spieth and colleagues indicate that the combined use of scintigraphy and US resulted in high sensitivity and positive predictive value for preoperative imaging of parathyroid adenomas and that the information led to a substantial reduction in surgical time. However, no information was given about the type of surgical procedure performed. As we stated in our article, the minimally invasive procedure used in our study began with a 2-cm incision in the neck, a site that was determined with US and through which the adenoma was removed. In order for this surgical approach to be successful, "high accuracy is required in diagnosing and localizing the solitary lesion. In addition, accurate determination of its relationship with the surrounding structures is needed..." (1). In our study, we found that in more than two-thirds of patients, the required information for successful minimally invasive surgery could be obtained with US alone, which is a patient-friendly, easily accessible, and low-cost imaging modality. In some of these cases, additional CT was performed, exclusively for road mapping, at the request of the surgeon.
The anatomic information, which included the location of the adenoma and its relationship with the surrounding structures, provided with scintigraphy was, in the opinion of our endocrine surgeons, insufficient for successful application of the minimally invasive procedure used in our study. Therefore, in our opinion, conventional scintigraphy as the primary technique is not well suited for selecting patients for the minimally invasive procedure used in our study. In addition, compared with US, scintigraphy involves the use of ionizing radiation, is relatively expensive, and may not be readily available. The potential role of scintigraphy as an imaging modality supplemental to US was not investigated in our study.
REFERENCES
This article has been cited by other articles:
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  N. A. Johnson, M. E. Tublin, and J. B. Ogilvie Parathyroid Imaging: Technique and Role in the Preoperative Evaluation of Primary Hyperparathyroidism Am. J. Roentgenol., June 1, 2007; 188(6): 1706 - 1715. [Abstract] [Full Text] [PDF]
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