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Head and Neck Imaging |
1 From the Departments of Radiology (A.v.D.) and Surgery (C.P.S., T.J.M. V.v.V.), and the Julius Center for General Practice and Patient Oriented Research (H.B.), University Medical Center Utrecht, the Netherlands; and the Department of Radiology, University of Virginia Health Sciences System, Charlottesville (E.E.d.L.). Received May 24, 2000; revision requested July 7; final revision received March 19, 2001; accepted March 30. Address correspondence to A.v.D., Department of Radiology, Diaconessenhuis Meppel, Hoogeveenseweg 38, 7943 KA Meppel, the Netherlands (e-mail: albertvandalen@planet.nl).
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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MATERIALS AND METHODS: US and CT were performed in 61 consecutive patients with primary hyperparathyroidism (part 1) to identify and localize solitary adenomas for resection by means of minimally invasive surgery and to provide a surgical road map. In part 2, involving 33 consecutive patients, CT was performed only when no solitary adenoma was identified with US or for road map information. Minimally invasive surgery was considered successful when serum calcium levels normalized and remained stable.
RESULTS: In part 1, 46 definite solitary adenomas were found with US and two additional ones with CT. Minimally invasive surgery was successful in 45 patients and failed once. In part 2, US helped identify 23 solitary adenomas, and CT helped to find one. Minimally invasive surgery was successful in 22 patients and failed in two. Combined results in 94 patients demonstrated successful minimally invasive surgery in 67 (71%), with 64 of them selected with US alone (95% CI: 61, 80). The sensitivity of US in the diagnosis of solitary adenoma was 78% (95% CI: 67%, 86%), with a positive predictive value of 96% (95% CI: 88%, 99%).
CONCLUSION: US examination of patients with primary hyperparathyroidism allowed successful selection for minimally invasive surgery in more than two-thirds of the cases, with additional CT useful chiefly for surgical road mapping.
Index terms: Parathyroid, CT, 274.12112, 274.12115 • Parathyroid, hyperparathyroidism, 274.531 • Parathyroid, neoplasms, 274.363 • Parathyroid, US, 274.1298, 274.12983
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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The common treatment of primary hyperparathyroidism is conventional neck exploration (6). With this procedure, the neck is explored to identify all parathyroid glands and to remove the enlarged ones. Conventional neck exploration is a time-consuming and surgically demanding procedure because of the many vulnerable structures of the neck that need to be explored to allow identification of the parathyroid glands. Nevertheless, in experienced hands, conventional neck exploration is curative in 95% of cases, with few reported complications (6–8).
Recently, we introduced minimally invasive surgery by use of ultrasonography (US) and computed tomography (CT) to treat primary hyperparathyroidism caused by a solitary adenoma, and in this earlier report (9), which included 61 patients of the current study, we highlighted the clinical aspects of this method. During minimally invasive surgery, the surgeon, guided by means of an imaging-based road map, carefully approaches the lesion through a small incision in the skin and removes the lesion with minimal damage to the vulnerable structures of the neck. Advantages of minimally invasive surgery compared with conventional neck exploration include reduction in surgical time and hospital stay, with subsequent decreased costs, improved cosmetic results, and restriction of postoperative fibrosis to the immediate area of the removed gland, which facilitates repeat surgery in cases of disease recurrence (10).
The typical adenoma is small, is usually not palpable because its consistency is equal to that of fat, and is often hidden among the structures of the neck. Consequently, high accuracy is required in diagnosing and localizing the solitary lesion. In addition, accurate determination of its relationship with the surrounding structures is needed to perform minimally invasive surgery successfully.
The purpose of the current study was to investigate prospectively the role of US as the primary imaging modality for identification and localization of parathyroid adenomas in patients with primary hyperparathyroidism who undergo minimally invasive surgery. As the surgical technique was relatively new when we initiated this study and we were uncertain about the full potential of US in facilitating the surgery, we used CT as a supplemental test to increase confidence in lesion diagnosis and to provide an operator-independent road map for the surgeon.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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Two distinct diagnostic strategies were followed. In part 1 (61 patients [12 men and 49 women; age range, 17–84 years; mean age, 59 years]), which took place from October 1994 through April 1997, all patients underwent both US and CT of the neck. In part 2 (33 patients [nine men, 24 women; age range, 28–82 years; mean age, 58 years]), which took place from May 1997 through April 1998, all patients underwent US, and supplemental CT was performed only when no solitary adenoma was identified with US or when requested by the surgeon for additional road mapping. Eighty-nine of the 94 US examinations were performed and interpreted by one radiologist (A.v.D.). This radiologist also interpreted the US findings in the remaining five patients whose examinations were performed by an experienced sonographer. In all cases, the US findings were interpreted without knowledge of any prior imaging studies, if present. All CT images were interpreted by the same radiologist with knowledge of the US findings, and the final diagnosis was based on the combined results.
When the final preoperative diagnosis of a definite solitary adenoma was made, the patient was scheduled for minimally invasive surgery, and in all other cases conventional neck exploration was performed. The study was approved by the institutional review board, and informed patient consent was obtained in all cases. Immediately prior to surgery, all patients who were scheduled for minimally invasive surgery underwent a repeat US examination with the neck extended in the position in which surgery was going to be performed. The previously diagnosed solitary adenoma was then localized again in the presence of the surgeon, the surgical approach was assessed, and the optimal incision site was marked on the skin of the patient.
US Imaging
Real-time units with 4–7-MHz and 5–10-MHz transducers (HDI 900 and 3000; Advanced Technology Laboratory, Bothell, Wash) were used. Examination was performed with the patient supine with the neck extended. The area from the carotid bifurcation to the deepest accessible part of the mediastinum was scanned in longitudinal and transverse planes. Graded compression was used to improve depiction of the deep paratracheal and paraesophageal areas, and, in case of doubt, to differentiate between an intra- or extrathyroidal location of a lesion. When a possible parathyroid lesion was identified, color Doppler US was used to determine the vascularity of the lesion and/or to identify a vascular pedicle favoring the diagnosis of a parathyroid adenoma. Lesion mobility during swallowing and/or deep breathing was also observed to allow differentiation from structures such as paracarotid cervical lymph nodes or the longus colli muscle. The thyroid gland was also evaluated and assessed for disease. The initial US examination required approximately 15 minutes, and the preoperative repeat examination required 5 minutes.
Spiral CT Imaging
Contrast medium–enhanced CT was performed with the patient supine and the neck in slight extension, with the shoulders pulled down as much as possible. Ninety milliliters of nonionic contrast medium (iotrolan, Isovist; Schering, Berlin, Germany) was administered intravenously at a rate of 2 mL/sec. Imaging was initiated 25 seconds after the beginning of the administration of the contrast medium. In a single breath hold, the volume from the level of the mandibular angle to that of the aortic root was scanned. A table speed of 5 mm/sec, section thickness of 5 mm, gantry rotation time of 1 second, and reconstruction index of 3 mm were used. The images obtained were evaluated on hard copy and in cine loop by using a dedicated computer workstation (EASYVISION, release 2.1; Philips Medical Systems, Best, the Netherlands).
Grading of Adenomas with US and CT
US.—Normal parathyroid glands are oval or bean shaped and measure on average 6 mm in length, with a mean weight of 40 mg (11). They contain a considerable amount of stromal fat (11) and are generally not depicted with current US equipment (12). A typical definite adenoma was diagnosed at US when a lesion was depicted with a homogeneous hypoechoic reflection pattern relative to that of thyroid tissue (Fig 1) and showed the following characteristics. Typically, the shape varied from round or oval to elongated with alignment in a craniocaudal orientation, with a diameter of at least 8 mm when round or as much as 3 cm long when elongated (5,13–15). In addition, the typical adenoma was located close to the thyroid gland or more caudad in the paratracheal or paraesophageal space. Essential for the diagnosis of a parathyroid adenoma was that the lesion retained its relationship with the thyroid gland during swallowing and deep breathing and did not show a central hilum.
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A patient was considered to have a definite solitary adenoma when a definite adenoma as described earlier was the only identified lesion. In all other instances (ie, when an equivocal solitary lesion, definite or equivocal multiple lesions, or no lesions were found), the diagnosis of no definite solitary adenoma was made. When the solitary adenoma was located posterior to the thyroid lobe near the middle portion, it was considered an adenoma of the superior type (Fig 1). It was considered of an inferior type when it was located near the lower pole of a thyroid lobe or inferior to it and having, at least in part, a close relationship with the anterior muscular wall of the neck (Fig 2). Any other location was considered aberrant.
CT.—The images were analyzed with knowledge of US findings. In the case of a definite adenoma at US, the diagnosis was not changed when the CT and US findings were compatible; otherwise, the final diagnosis was equivocal adenoma. Criteria were that either the adenoma was depicted at CT as an enhancing lesion in the same location and with the same size as that seen with US or, in the case of a close relationship with the thyroid gland at US, the lesion was recognized only as a local bulge of the contour of the thyroid gland at the same location as that seen with US.
When a lesion was diagnosed at US as an equivocal adenoma because of poor depiction, it was considered a definite adenoma when it was depicted at CT as an enhancing lesion in the same location and with the same size as that seen with US. In the case of a lesion well depicted at US but diagnosed as an equivocal adenoma because it did not fulfill the other criteria described earlier, the US diagnosis was not changed by the CT findings.
When at CT an enhancing lesion that had a size and location compatible with that of a parathyroid adenoma was found and it was not depicted at US, it was considered a definite adenoma only if it was located in an area not well accessible to US examination, such as the deep paraesophageal and mediastinal regions. Otherwise, the lesion was considered an equivocal adenoma.
Surgery, Histopathologic Examination, and Follow-up
With guidance from the imaging-based road map, minimally invasive surgery was begun with a 2-cm transverse incision at the medial border of the sternocleidomastoid muscle at the site of the skin marking. After lateral mobilization of the muscle, internal jugular vein, and common carotid artery and medial mobilization of the strap muscles and thyroid gland, the tracheoesophageal groove was entered, and the enlarged gland was identified and removed (Fig 1). If during minimally invasive surgery no lesion could be identified, the surgery was changed to conventional neck exploration. Surgical results were qualified as successful when the serum calcium levels normalized within 24 hours and remained stable for at least 6 months. The surgical specimens were weighed in the pathology department, and histopathologic examination was performed by the pathologist to assess the presence of parathyroid tissue. The lesions were considered to represent adenoma when parathyroid tissue was found at histologic evaluation. Histologic differentiation between adenoma and hyperplasia was not made at our institution (University Medical Center Utrecht, the Netherlands) (16).
Statistical Analysis
The data were analyzed statistically by using two approaches. The first analyses were performed while considering the patients as the units of analysis. As only definite solitary adenomas were considered eligible for minimally invasive surgery, the imaging results were categorized according to the preoperative diagnosis of solitary adenoma or no solitary adenoma. In other words, the imaging was used as a screening test yielding either solitary adenoma with the patient eligible for minimally invasive surgery or no solitary adenoma with the patient not eligible for minimally invasive surgery. To obtain sensitivity, specificity, and predictive values of this screening test, a reference standard test indicating whether a patient in reality was suitable for minimally invasive surgery is required. In this study, the latter could only be established with confidence after surgery and follow-up. Therefore, the final diagnosis served as the reference standard in this study.
The final diagnosis was based on the findings during surgery combined with the course of postsurgical serum calcium levels. If at surgery a single adenoma was removed and calcium levels normalized and remained stable as described earlier, the final diagnosis was solitary adenoma. In all other cases, the final diagnosis was no solitary adenoma.
By using this approach, the sensitivity of US denotes, for a final diagnosis of solitary adenoma, the probability of a US diagnosis of a solitary adenoma at the same location as that observed at surgery. The positive predictive value of US denotes, among patients with a solitary adenoma at US, the probability of a final diagnosis of solitary adenoma at the predicted location. The negative predictive value denotes, among patients with no solitary adenoma at US, the probability of a final diagnosis of no solitary adenoma. Specificity denotes, among patients with a final diagnosis of no solitary adenoma, the probability of no solitary adenoma at US. All probabilities from this analysis are presented as percentages with exact binomial 95% CIs (17).
We also carried out analyses with adenomas as units of analysis. Because in this situation the number of no solitary adenoma diagnoses at both US and surgery is undefined, only sensitivity and positive predictive value were calculated. By using this approach, the sensitivity denotes the probability that an adenoma found at surgery had also been identified at that site with US, and the positive predictive value is defined as the probability that an adenoma identified at US was present at surgery at the same location. Because in this analysis the observations may not be independent within patients, confidence limits were omitted.
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RESULTS |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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Calcium levels did not normalize in one of the 46 patients, and histologic examination of the specimen in this case revealed normal thyroid tissue without parathyroid components. In retrospect, the lesion that was diagnosed as a definite solitary adenoma at US with confirmation at CT appeared to be an accessory thyroid gland located 2 cm inferior to the right lobe of the thyroid gland (Fig 4a, 4b). Conventional neck exploration performed 2 days after the initial surgery revealed a small (274-mg) intrathyroidal parathyroid adenoma located subcapsularly in the left lobe (Fig 4c, 4d). In another patient undergoing successful minimally invasive surgery, the depicted lesion consisted of two abutting adenomas rather than one solitary lesion, and the final postoperative diagnosis in this case was, therefore, multiple adenomas.
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In two of the 24 patients, however, serum calcium levels did not normalize after minimally invasive surgery. At subsequent conventional neck exploration, a large (900-mg) second adenoma was found in one patient at the same location from which initially a small (230-mg) adenoma was removed during minimally invasive surgery. In this case, only the large adenoma had been identified at imaging. In the other one, conventional neck exploration revealed a large part of an adenoma at the same location where during prior minimally invasive surgery fragments of an adenoma were removed, with a total weight of 1,020 mg. In this case, a much larger lesion (44 x 22 x 11 mm, with estimated weight of 6,000 mg) had been diagnosed with the initial US examination. Thus, 22 of the 24 minimally invasive surgeries were successful, which resulted in a 92% success rate.
In six of 23 cases, additional CT was performed at the request of the surgeons, particularly by one who was new on the team and who therefore had less experience with the US-guided minimally invasive surgery. In these patients, the CT scans were used exclusively for road mapping in cases of deep paraesophageal location of the adenoma at US (n = 3), severe enlargement of the thyroid gland because of goiter (n = 2), or when there was an extremely large parathyroid adenoma diagnosed at US (n = 1; weight of the specimen, 16,020 mg). However, in these cases, CT findings were not used for lesion diagnosis.
In parts 1 and 2 combined, 69 definite solitary adenomas were diagnosed at US; in three of these, the diagnosis was incorrect. Of the 66 solitary adenomas correctly diagnosed at US, 34 were in a superior location, 27 were inferior, and five were aberrant (intrathyroidal [n = 1], paraesophageal [n = 3], and cephalad to the thyroid gland [n = 1]).
Histopathologic Results
At histopathologic examination, parathyroid tissue was identified in all 107 surgical specimens, with the exception of one in which only normal thyroid tissue was found. The median weight of the parathyroid specimens was 610 mg (range, 90–16,020 mg).
Statistical Results
The combined results of parts 1 and 2 in selecting patients with a solitary adenoma at US for minimally invasive surgery are depicted in Table 2. Eighty-five (90%) of the 94 patients had a solitary adenoma according to the reference standard (ie, the final surgical results and change of the serum calcium levels). The sensitivity of US for the diagnosis and localization of solitary parathyroid adenomas was 78% (66 of 85; 95% CI: 67%, 86%), and the specificity was also 78% (seven of nine; 95% CI: 40%, 97%). The positive predictive value was 96% (66 of 69; 95% CI: 88%, 99%), and the negative predictive value was 28% (seven of 25; 95% CI: 12%, 49%). In two of the three false-positive cases, there was multiglandular disease as described before, and in one there was a solitary adenoma that was not located at the predicted site.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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The combined results of parts 1 and 2 demonstrate that US is an excellent tool for selecting patients with primary hyperparathyroidism in whom successful minimally invasive surgery can be performed. In the 70 completed minimally invasive surgeries, three cases were selected by means of CT and thus 67 by means of US alone. Three of the 70 minimally invasive surgeries were unsuccessful, which resulted in a 96% (67 of 70) success rate for the surgical procedure. On the basis of selection with US alone, 64 of 67 (96%) minimally invasive surgeries were successful. These success rates for minimally invasive surgery are similar to those reported for primary conventional neck exploration performed by experienced surgeons in patients who did not undergo preoperative imaging (6–8). Thus, if we consider the results of the entire group of 94 patients, preoperative imaging was of major benefit in more than two-thirds (71% [67 of 94]) of the patients in our study because they were able to undergo limited but equally successful surgery for treatment of primary hyperparathyroidism instead of an extensive complicated conventional surgical procedure.
It is well recognized, in cases of ectopic adenomas with mediastinal or deep paratracheal and/or paraesophageal location, that US is of limited value because the lesions are generally inaccessible to the ultrasound beam; however, in these cases, they are usually well depicted at CT (3,5,13,14,18). Nevertheless, in selecting patients for minimally invasive surgery, the added value of CT was limited in our study because it aided in identifying only three additional definite solitary adenomas out of the entire group of 25 patients with no solitary adenoma diagnosed at US. In two of these, the adenoma was located deeply in an area inaccessible to US, and in one the US diagnosis of an equivocal lesion was changed to a definite solitary adenoma. Although in both cases of deep location the adenoma was depicted at repeat US with knowledge of the CT findings, it is conceivable that depiction may have been impossible at repeat US. In such a situation, minimally invasive surgery could still be considered; however, the deep location of the lesion and the absence of preoperative localization of the adenoma, including lack of determination of the optimal incision site may make a surgical approach through a small opening in the skin very difficult, if not impossible.
In our study, we used CT exclusively as an adjunctive test, and we did not evaluate its role as a primary imaging tool. However, in our experience, use of spiral CT with cine loop presentation of images allows easy identification of a number of lesions and provides an excellent display of the depicted adenoma in its surrounding anatomic structures. Therefore, CT could potentially also be used as the primary test for selecting patients for minimally invasive surgery. However, the cost of CT is generally much higher than that of US, and the modality involves the use of ionizing radiation to a vulnerable area (thyroid gland), with associated risks (19). For these reasons, together with its good results, we prefer to use US as the primary modality for selection of patients for minimally invasive surgery. Nevertheless, in selected cases the surgeon may still want to use additional CT for road mapping, as has been our experience, particularly in cases in which the lesion is located deeply or the thyroid gland is enlarged.
Magnetic resonance (MR) imaging and scintigraphy have also been used for identification of parathyroid adenomas, with results comparable with US and CT (4,20). In our study, we preferred to use CT as an additional modality rather than MR imaging for reasons of availability and cost, and therefore the role of this modality in selecting patients for minimally invasive surgery was not determined. Conventional scintigraphy is, in our opinion, not well suited for selecting patients for the minimally invasive surgical procedure used in our study because of the relatively poor image resolution and anatomic information obtained. Recent study results (21,22) have shown, however, that a minimally invasive surgical procedure is possible in cases in which the uptake of the administered radiopharmaceutical is sufficient to allow localization of the parathyroid adenoma intraoperatively with a small gamma probe.
In one patient with two contiguous adenomas simulating one lesion at imaging, minimally invasive surgery was successfully performed because during the surgery a discrepancy was noted between the size of the lesion that was first removed and the size predicted by means of imaging. Technically, minimally invasive surgery allows removal of multiple lesions through the same incision; however, since in case of multiglandular disease all parathyroid glands may be involved and identification at US is less successful due to the small average size of the enlarged glands (13), it is important that all glands be surgically inspected. Therefore, we prefer to perform conventional neck exploration in case enlargement of more than one gland has been diagnosed.
In three patients, minimally invasive surgery was unsuccessful. One of these treatment failures was caused by incorrect imaging diagnosis, in which an accessory thyroid gland was misinterpreted as being a parathyroid adenoma. In another case, there were two adenomas close to each other in the same anatomic location, and only the largest was depicted at preoperative imaging. However, in this case, minimally invasive surgery was terminated after removal of the smaller adenoma because no notice was made of the discrepancy between the size of the removed adenoma and that of the larger one depicted at US and found later at conventional neck exploration. In the third case, the surgeon initially removed only a part of the predicted large adenoma, and the remainder was left behind, which was later removed at conventional neck exploration.
These experiences emphasize the importance of correlating the size of the removed adenoma during minimally invasive surgery with the size predicted at imaging. Use of a test that allows rapid determination of the parathyroid hormone level in the blood at the end of the surgical procedure may also alert the surgeon to incomplete resection or the presence of a second adenoma in the patient if the hormone level remains elevated. Such a test, which takes only 40 minutes to complete, was recently introduced at our institution as a routine procedure, which allowed another surgery within an hour in case of initial failure (23).
US showed an overall sensitivity of 74% (solitary and multiple adenomas combined) in identifying parathyroid adenomas. Although in our conservative approach we considered all equivocal adenomas as negative findings, these results are within the range (65%–85%) of those reported by others (13,15,18,20,24) in identifying parathyroid adenomas with US imaging. However, our positive predictive value of 98% in diagnosing parathyroid adenomas, and thus the nature of the lesions, at US was high compared with that of others (range, 80%–97%) (13,15,18,20,24). Because of the high accuracy in determining the nature of the lesions, we were also able to diagnose solitary parathyroid adenomas with high consistency (positive predictive value of 96%), something that is of crucial importance for successful minimally invasive surgery. In our study, fewer than 10% (nine of 94) of the patients had multiglandular disease, which supports the suggestion by some authors (25) that the true frequency of multiglandular involvement is lower than the 15% that is usually reported (3–5).
In our experience, characterizing the location of the solitary adenomas as superior, inferior, or aberrant was very useful in communicating with the surgeon because it gave essential information about the anatomic location of the lesion with its surrounding structures, which is necessary for the implementation of minimally invasive surgery. Our approach to diagnosing a definite solitary adenoma was conservative to minimize the number of unsuccessful minimally invasive surgeries. Whether a definite adenoma was diagnosed or not, in all patients with the imaging findings of one or more equivocal lesions, primary conventional neck exploration was performed. If we had considered the equivocal lesions to be all definite adenomas or all negative, in both instances we would have been able to perform a greater number of successful minimally invasive surgeries; however, this would have been at the expense of a substantially greater number of surgical failures.
A limitation of our study is that the patient groups were taken as convenience samples (group 1 came before group 2). As a result, temporal effects on the results cannot be excluded. For instance, in group 2 the clinicians could have been more familiar with the advantages of minimally invasive surgery compared with conventional neck exploration. They may therefore have lowered their threshold by referring patients with minimal or no clinical symptoms of primary hyperparathyroidism for group 2 of the study. Such patients are more likely to have relatively small adenomas that are more difficult to diagnose with imaging and are also more difficult to find at surgery. On the other hand, learning effects may have resulted in superior diagnostic and surgical performance in group 2, although a new surgeon without previous experience with US-guided minimally invasive surgery joined the team during part 2 of the study. As the magnitudes of these effects are unknown, results of parts 1 and 2 of the study should be compared cautiously. However, the goal of our study was not to compare the results of the two patient groups but to determine the overall role of US as the primary imaging modality for identification and localization of parathyroid adenomas in patients with primary hyperparathyroidism to undergo minimally invasive surgery.
In conclusion, minimally invasive surgery is an imaging-guided surgical technique for treatment of parathyroid adenomas that has considerable advantages compared with conventional neck exploration. We have demonstrated that by using the outlined criteria, US permitted successful selection of patients with primary hyperparathyroidism for minimally invasive surgery in more than two-thirds of the cases. The adjunctive diagnostic use of spiral CT allowed the selection of only a few more patients for minimally invasive surgery, and therefore the added diagnostic value of CT may not have been worth the effort, cost, and risk of radiation hazard. However, in selected cases, CT may play an important role in providing an operator-independent road map for the surgeon. Close cooperation between surgeon and radiologist is essential, because minimally invasive surgery can be performed successfully only when the surgeon is informed in detail about the location and size of the adenoma to be removed.
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FOOTNOTES |
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REFERENCES |
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TOPABSTRACTINTRODUCTIONMATERIALS AND METHODS RESULTSDISCUSSIONREFERENCES |
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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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 G Abikhzer, M Levental, and C Rush High resolution MRI in the detection of an intrathymic parathyroid adenoma. Br. J. Radiol., September 1, 2006; 79(945): e78 - e80. [Abstract] [Full Text] [PDF]
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 K. Sejean, S. Calmus, I. Durand-Zaleski, P. Bonnichon, P. Thomopoulos, C. Cormier, P. Legmann, B. Richard, X. Y Bertagna, and G. M Vidal-Trecan Surgery versus medical follow-up in patients with asymptomatic primary hyperparathyroidism: a decision analysis Eur. J. Endocrinol., December 1, 2005; 153(6): 915 - 927. [Abstract] [Full Text] [PDF]
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F Lumachi, A Tregnaghi, P Zucchetta, M C Marzola, D Cecchin, P Marchesi, F Fallo, and F Bui Technetium-99m sestamibi scintigraphy and helical CT together in patients with primary hyperparathyroidism: a prospective clinical study Br. J. Radiol., February 1, 2004; 77(914): 100 - 103. [Abstract] [Full Text] [PDF]
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 M. E. Spieth, J. Gough, D. L. Kasner, A. van Dalen, T. J. M. V. van Vroonhoven, and E. E. de Lange Role of US with Supplemental CT for Localization of Parathyroid Adenomas * Dr van Dalen and colleagues respond: Radiology, June 1, 2002; 223(3): 878 - 879. [Full Text] [PDF]
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