Pediatric skeletal scintigraphy: applications of pinhole magnification

Use of intraoperative bone scintigraphy for resection of spinal osteoid osteoma

BACKGROUND

The location and proximity to the spinal cord in spinal osteoid osteoma can increase the likelihood of an incomplete resection. Intraoperative bone scintigraphy (IOBS) can be used to verify location and complete surgical resection.

OBJECTIVE

To review our experience using IOBS for resection of intraspinal osteoid osteoma.

METHODS

IRB approved, retrospective review of IOBS-guided resection over 10 years. Patients underwent injection of 200 uCi/kg (1-20 mCi) 99mTc-MDP 3-4 h prior surgery. Portable single-headed gamma camera equipped with a pinhole collimator (3- or 4-mm aperture) was used. Images were obtained pre-operatively, at the start of the procedure, and intraoperatively. Operative notes were reviewed. Evaluation of recurrence and clinical follow-up was performed.

RESULTS

Twenty IOBS-guided resections were performed in 18 patients (median age 13.5 years, 6-22 years, 12 males). Size ranged 5-16 mm, with 38.9% (7/18) cervical, 22.2% (4/18) thoracic, 22.2% (4/18) lumbar, and 16.7% (3/18) sacral. In all cases, IOBS was able to localize the lesion. After suspected total excision, IOBS altered the surgical plan in 75% of cases (15/20), showing residual activity prompting further resection. Median length of follow-up was 6 months (range 1-156 months) with 90% (18/20) showing complete resection without recurrence. Two patients had osteoid osteoma recurrence at 7 and 10 months following the original resection, requiring re-intervention.

CONCLUSIONS

IOBS is a useful tool for real-time localization and assessment of spinal osteoid osteoma resection. In all cases, IOBS was able to localize the lesion and changed surgical planning in 75% of cases. Ninety percent of patients achieved complete resection and remain recurrence free.

Radioguided Biopsy of Osteoid Osteoma: Usefulness of Imaging Probe

Aims and Background

When removal of osteoid osteoma is performed with open biopsy, the surgeon can be guided by radioactivity of 99mTc-MDP (methylene D- phosphonate) acquired by a probe.

Material and methods

We compared the performance of a commercially available ZnCdTe probe (Neoprobe 2000) and a one-square-inch-field-of-view imaging probe (IP) on two patients undergoing open biopsy for osteoid osteoma. Triphasic bone scintigraphy was performed before operation and Neoprobe as well as IP were used in the operating room by two nuclear physicians. When the surgeon asked for guidance, each nuclear physician had to indicate a precise direction.

Results

The surgeon asked for guidance once in the first operation, on a patient with osteoid osteoma of the femur, and four times in the second operation, for osteoid osteoma of the acetabulum. The indications provided by IP were correct 5/5 times, whereas the commercial probe was correct 3/5 times. Both devices were able to assess the surgical radicality. After biopsy, bone samples were divided into high-count and low-count samples. Pathological examination confirmed the presence of osteoid osteoma in high-count samples.

Conclusions

IP has already been used to guide biopsy, but only in breast disease. The present work confirms its good performance also in orthopedics as a portable mini gamma camera that can be used in the operating room.

Size measurement of the thyroid gland on a magnified pinhole thyroid scan using an ultrasonic device measuring distance from the pinhole to the thyroid gland

PURPOSE

Pinhole has been used for magnification of gamma camera images and is valuable for imaging of small organs, such as thyroid; however, size of the organ cannot be measured on the image due to variable degree of magnification by distance between the pinhole and the organ. The aim of this study was to develop a true size measuring system (TSM system) on magnified pinhole thyroid scan using an ultrasonic sensor.

METHODS

An ultrasonic device capable of measuring the distance from the pinhole to the skin overlying the thyroid gland was manufactured using a ~40 kHz piezoelectric-transducer-based sensor, and its accuracy was tested. An interface program was developed and fused with the ultrasonic device for development of the TSM system. Accuracy of the TSM system for measuring size was tested with phantom images and 35 thyroid scans.

RESULTS

The ultrasonic device accurately measured the distance from the pinhole to the skin over the thyroid gland and the measured values were highly reproducible (6 cm; 6.02 ± 0.04 cm, 8 cm; 8.00 ± 0.05 cm, 10 cm; 10.00 ± 0.05 cm). Distance on the phantom image corrected by the TSM system was almost the same as the true distance. Size of the thyroid on the pinhole image was larger (+67.3 to 103.1 %) than the true thyroid size on the parallel-hole image and the magnification decreased by increase of the distance between the pinhole and the skin over the thyroid gland. However, size of the thyroid obtained using the TSM system was almost equal (-2.1 to +3.6 %) to the true thyroid size on the parallel-hole image.

CONCLUSIONS

We developed the TSM system for magnified pinhole images using a distance measuring ultrasonic sensor. Size of the thyroid on the magnified pinhole image obtained using the system was almost the same as the true thyroid size. The TSM system can be applied to obtain accurate size of the thyroid gland or lesions in the thyroid gland on pinhole thyroid scan.

Comparison of pinhole and high-resolution parallel-hole imaging for nodular thyroid disease

INTRODUCTION AND OBJECTIVE

Pinhole has been the main standard collimator to be used for thyroid imaging. There has been a gradually increasing trend to replace pinhole with the use of high-resolution low-energy parallel-hole collimator with zoom in thyroid imaging. The objective of this study is to compare parallel-hole collimator acquisition of thyroid gland with that obtained by pinhole collimator to find the effect on the diagnostic information in nodular thyroid disease.

MATERIAL AND METHODS

A total of 29 patients, 24 women and 5 men, aged 18 to 70 years who were routinely referred for thyroid imaging for the assessment of nodular disease were studied. Each patient was injected with 185 MBq (5 mCi) of Tc-99m sodium pertechnetate intravenously. After 20 minutes, acquisition using pinhole followed by parallel-hole collimators was obtained. For pinhole acquisition, a 3-mm insert was used, and 3 images were obtained in the anterior and anterior oblique projections. For parallel-hole acquisition, anterior view was obtained for 250 K. The collimator was placed as close as possible to the patient. The image quality, number, and definition of nodules were evaluated by 2 independent, qualified nuclear medicine physicians. Differences were resolved by consensus.

RESULTS

There were 14 patients who had nodular patterns and 15 had no apparent nodules. There were 40 nodules of different sizes detected by pinhole imaging. Only 10 (25%) of these nodules were observed on parallel-hole images.

CONCLUSION

Pinhole imaging must be used for thyroid imaging particularly in patients suspected of having nodular disease.

[Bone scintigraphy in evaluation of bone vascularisation at wrist and hand]

Diphosphonate bone scintigraphy is used since the 1970s for studying bone pathology; it is increasingly common because of increased physical activity of the population. The disphosphonate uptake in bone requires the preservation of bone vascularity and reflects osteoblastic activity; it allows studying the viability of bone. Using data from the literature and our experience, we tried to take stock of its main uses in routine emphasizing the study of vascular and describe its use in fractures of the scaphoid and in the study of vascularised bone transfers. If the value of scintigraphy is well known, the use made by means of pinhole collimator and the market entry of new and more sensitive detectors with better resolution could allow the side of the imaging anatomy of improving the study of the vascularisation of small bone transfers which are increasingly used, particularly at wrist and hand.

Serial bone scintigraphy in Legg-Calvé-Perthes disease: correlation with the Catterall and Herring classification

Radiographic classifications in Legg-Calvé-Perthes disease are difficult to use in the early stage of the disease. Changes on bone scintigraphy (revascularization versus recanalization pathway) precede the radiographic changes. Our purpose was to study the correlation between serial bone scintigraphy and radiographic classifications in Legg-Calvé-Perthes disease. In 86 patients, 95 hips that presented with Legg-Calvé-Perthes disease in the early stage were followed with serial bone scintigraphy and radiographs. Forty-four hips showed recanalization: pathway A on bone scintigraphy. Of these hips 96% were classified as Herring A or B and 66% as Catterall 2. Thirty-five hips showed revascularization: pathway B on bone scintigraphy. Of this group 82.8% were classified as Herring C and 17.1% as Herring B. All pathway B hips have Catterall 3 or 4. Sixteen hips showed pathway C: regression from pathway A to pathway B. They presented in 56% of cases with Herring B, 44% with Herring C, and in 81% with Catterall 3 or 4 classifications. We can conclude that there is a significant correlation between the vascularization pattern and the radiographic classification of Herring and Catterall.

Benign bone tumors in children

When children present for evaluation of bone tumor, great anxiety often occurs among the family. Usually the diagnosis of a benign bone tumor can be made easily with plain radiographs without biopsy. Most have a good outcome. However, occasionally, serious complications can develop. Moreover, the physician must be aware of the possibility of the malignant tumors. To avoid errors in the evaluation and treatment of this heterogeneous group of tumors, the clinician should have a good knowledge base of common bone neoplasms and correlate the clinical, radiographic, and pathologic findings. In this article, history, diagnosis, evaluation, treatment, and management of common types of benign tumors of bone commonly seen in children and adolescents are reviewed in the light of current literature.

Importance of positioning and technical factors in anatomic localization of sporting injuries in scintigraphic imaging

Sports medicine is becoming increasingly important as more people take up exercise for health and well-being. It is adding to the spectrum of acute and chronic injuries that have traditionally been seen in elite or professional athletes. Because of its high sensitivity and lesion contrast, bone scintigraphy has traditionally played a key role in the detection of such injuries. This role has been reduced in recent times by the increased use of magnetic resonance imaging (MRI), which has functional capability, high-contrast resolution, and high-spatial resolution. Bone scintigraphy has the capability of detecting early cortical ligament avulsion and enthesopathic disease before the onset of edema or changes in bone marrow that are detected by MRI. If this capability is added to more precise anatomic localization of lesions, we may see a resurgence in its use in sports medicine. A number of techniques are presented in this article, encompassing positioning, special views, and tomographic reconstructions, that can significantly improve the accuracy of localization of scintigraphic abnormalities with reference to anatomic models or sources of cross-sectional anatomy.