Muscular sarcoidosis: Ga-67 scintigraphy and magnetic resonance imaging

Ga-67 scintigraphy is helpful in the assessment of active extrapulmonary sarcoidosis. Muscular involvement of sarcoidosis is often asymptomatic or nonspecific, and laboratory examinations do not provide convincing evidence of muscular involvement. The authors report a case of muscular sarcoidosis detected by Ga-67 scintigraphy. In a patient who had fever and arthralgia of both knee joints, Ga-67 scintigraphy showed mediastinal and hilar involvement of sarcoidosis with unexpected extensive muscular uptake. Magnetic resonance imaging revealed in detail intramuscular infiltration of sarcoid granuloma. Ga-67 scintigraphy is useful in detecting inflammatory muscular involvement of sarcoidosis and other multiorgan involvement.     

Whole-body magnetic resonance imaging for detecting bone metastases: comparison with bone scintigraphy

Purpose

The aim of the study was to assess the reliability of whole-body magnetic resonance imaging (WB-MRI) in detecting skeletal metastasis and to compare the results with those of bone scintigraphy (BS).

Materials and methods

Thirty-three patients (21 women, 12 men, median age 58 years, range 27–78) were enrolled. Histological proof of malignancy was obtained in all cases. The primary tumour was unknown in 1 patient. BS and WB-MRI were performed as staging procedures in 15 patients, during the follow-up in 6 and to investigate pain in 9 and neurological symptoms in 3. Bone metastases were recorded for 8 different skeletal segments (ribs, skull, cervicothoracic spine, lumbosacral spine, clavicle-scapula-sternum, pelvis, upper extremities and lower extremities) in all patients, for a total of 264 examined areas.

Results

Bone metastases were detected in 18 patients (55%). In 15/33 patients, WB-MRI and BS were concordantly negative. BS revealed focal metastatic uptake in 72%, whereas WB-MRI was positive in 89%. Results differed in seven patients. WB-MRI was positive but BS was negative in five cases. Two patients with negative WB-MRI had focal and intense uptake in the ribs on BS. Out of 264 examined areas, bone metastases were detected in 34 (13%). WB-MRI revealed tumour spread in 26/34 areas (76%) and BS in 21/34 areas only (62%).

Conclusions

WB-MRI is a reliable method for screening patients with suspected skeletal metastases, although BS still remains a useful tool. WB-MRI is also advantageous because it reveals extraskeletal and soft tissue metastases.     

Detectability of metastatic bone tumor by Ga-67 scintigraphy

Ga-67 scintigrams in patients with malignant diseases sometimes reveal uptake of the tracer in the bone metastases. Detectability of Ga-67 scintigraphy for metastatic bone tumors and benign bone lesions was compared with that of Tc-99m bone scintigraphy. Countable bone metastases detected by bone scintigraphy were evaluated whether the lesion showed apparent, faint, or negative Ga-67 uptake. Of 47 lesions 23 (49%) showed apparent uptake and 17 (36%) showed negative uptake. On the other hand, of 71 benign bone lesions, only 7 (10%), mostly fracture/osteotomy, showed apparent uptake of the tracer. Uptake in the other benign lesions such as trauma of the ribs, spondylosis deformans, and arthrosis deformans was rather faint. In patients with multiple bone metastases, 9 patients (82%) out of 11 showed more prominent abnormal findings in Tc-99m MDP bone scintigraphy than in Ga-67 scintigraphy; that is, Ga-67 scintigraphy was not able to reveal all metastatic bone lesions. In patients with untreated or recurrent tumors, relation between Ga-67 uptake in the tumors and that in the bone metastases was evaluated. Of 7 patients with negative Ga-67 uptake in the primary tumors, 5 showed positive Ga-67 uptake in the bone metastases; that is, there seemed to be little relation between Ga-67 affinity to the primary tumors and that to the bone metastases. Mechanisms of the Ga-67 uptake in the bone metastases were discussed. Not only the tumor cells or tissues in the bone metastases but also bone mineral or osteoclasts might be the deposition sites of Ga-67.     

Indium-111-chloride and three-phase bone scintigraphy: a comparison for imaging experimental osteomyelitis

To investigate the utility of indium-111-chloride (111In-Cl) imaging in detecting osteomyelitis complicating surgical or fracture sites, the proximal tibia of 11 dogs were experimentally infected with Staphylococcus aureus after creation of a cortical defect. The contralateral limb served as a sham-operated control. Animals were serially imaged by radiography, three-phase technetium-99m-methylene diphosphonate (99mTc-MDP) scintigraphy, and 111In-Cl scintigraphy. There was a significant difference between infected (1.93) and noninfected (1.32) limb's tibia/femur count density ratios on 24-hr (p = 0.0001) and 72-hr (p = 0.0001) 111In-Cl images. A smaller difference was found for 99mTc-MDP bone-phase tibia/femur ratios (p = 0.0199). Using receiver operator characteristic analysis of tibia/femur ratios, a sensitivity of 61%, specificity of 88%, and positive (75%) and negative (79%) predictive values were determined for the 24-hr 111In-Cl images. Indium-111-chloride was superior to 99mTc-MDP in differentiating infected and noninfected operative sites.     

Acute osteomyelitis in children: combined Tc-99m and Ga-67 imaging

This retrospective study was done to determine the value of combined bone (technetium-99m methylene-diphosphonate) and gallium-67 citrate imaging in selected children with complicated clinical situations. Thirty-one children were evaluated for suspected osteomyelitis by bone scan followed within 4 days by a gallium scan. These 31 children represented a subpopulation in whom the Tc-99m scan is known to be potentially unreliable in diagnosing acute osteomyelitis. Eight children had acute osteomyelitis by strict criteria, while 23 did not. The bone scan successfully identified five of the eight with osteomyelitis but was positive in ten of the other 23. The gallium scan correctly identified all eight with osteomyelitis but was positive in seven of the other 23. The gallium scan was significantly less specific when the suspected lesion was in the extremities compared with central locations; causes of false-positive gallium scans included fracture and juvenile rheumatoid arthritis. Combined gallium and bone scanning increased accuracy of the scintigraphic diagnosis of acute osteomyelitis. Both tests may, however, be abnormal in conditions other than osteomyelitis. These findings emphasize the importance of correlating all imaging studies in detection of osteomyelitis.     

Chronic post-traumatic osteomyelitis of the lower extremity: comparison of magnetic resonance imaging and combined bone scintigraphy/immunoscintigraphy with radiolabelled monoclonal antigranulocyte antibodies

Objective. A retrospective study of the validity of combined bone scintigraphy (BS) and immunoscintigraphy (IS) using ^99mTc-labelled murine antigranulocyte antibodies (MAB) and magnetic resonance imaging (MRI) in chronic post- traumatic osteomyelitis. Design and patients. The results of MRI and combined BS/IS of 19 lesions in 18 patients (13 men, 5 women; mean age 45 years, range 27–65 years) were independently evaluated by two radiologists and one nuclear medicine physician with regard to bone infection activity and extent. The patient group was a highly selective collection of clinical cases: the average number of operations conducted because of relapsing infection was eight (range 2–27), the average time interval between the last surgical intervention and the present study was 6.5 years (range 3 months to 39 years), and from the first operation was 14 years (range 1.5–42 years). Interobserver agreement on MRI was measured by kappa statistics. Sensitivity, specificity, accuracy, positive predictive value (PPV) and negative predictive value (NPV) were calculated for MRI and the nuclear medicine studies. Results. For MRI/nuclear medicine, a sensitivity of 100%/77%, a specificity of 60%/50%, an accuracy of 79%/61%, a PPV of 69%/58% and a NPV of 100%/71% were calculated. Four MR examinations were false positives because of postsurgical granulation tissue. A high degree of interobserver agreement was found on MRI (κ=0.88). A low-grade infection was missed on two scintigrams, while four were false positive because of ectopic haematopoietic bone marrow, and in one examination the anatomical distortion resulted in an inaccurate assignment of the uptake leading to false positive findings. Image analysis was frequently hindered by susceptibility artefacts due to residual abrasions of metallic implants after removal of orthopaedic devices (15/18 patients); this led to limited assessment in 17% (3/18 patients). Conclusion. Acute activity in a chronic osteomyelitis can be excluded with high probability if the MRI findings are negative. In the first postoperative year fibrovascular scar cannot be distinguished accurately from reactivated infection on MRI and scintigraphy may improve the accuracy of diagnosis. MRI is more sensitive in low-grade infection during the later course than combined BS/IS. Scintigraphic errors due to ectopic, peripheral, haematopoietic bone marrow can be corrected by MRI. Received: 17 December 1999 Revision requested: 25 January 2000 Revision received: 15 March 2000 Accepted: 4 April 2000     

Diffusion-weighted magnetic resonance imaging of spinal bone marrow

Diffusion-weighted (DW) imaging is an alternative source of image contrast. DW imaging enables to measure the random motion of free water protons on a molecular basis by using different imaging sequences including steady-state free precession imaging, navigated spin-echo DW imaging, and single-shot echo planar imaging. Analysis of intravoxel incoherent motion of water protons is a promising tool that has shown to be of value in the differential diagnosis between benign and malignant spontaneous vertebral fractures. Acute benign osteoporotic fractures show hypo- or isointense signal on DW sequences that reflects persistent free water proton mobility. With increasing diffusion strength a substantial signal loss is found. Metastatic fractures show hyperintensity compared with normal surrounding bone marrow probably due to altered water proton mobility within neoplasm. The ability of the different methods for DW imaging to differentiate other bone marrow alterations needs to be investigated in further studies.     

Clinical evaluation of Ga-67 DFO-DAS-fibrinogen scintigraphy

Gallium-67 DFO-DAS-fibrinogen scintigraphy was performed in four patients for the detection of tumor and thrombosis. No adverse reactions were noted. Scintigrams in a patient with bronchogenic carcinoma accompanied with atelectasis showed abnormal uptake not only in the cancerous region but also in the whole atelectatic region as well. In a patient with hepatoma after TAE, a slight uptake of tracer was noted in the area surrounding the tumorous region, indicating accumulation of the tracer in the microthrombi. In two patients with venous thrombosis, no abnormal uptake was seen. The long interval from the onset of thrombus formation and the commencement of anticoagulant therapy prior to scintigraphy may have caused the false-negative scans in these cases. Further evaluation is necessary with regard to the usefulness of this technique in clinical practice.     

Negative scintigraphy with positive magnetic resonance imaging in bone metastases

We report three patients with known primary tumor in whom radionuclide skeletal imaging for metastatic disease was normal with or without clinical symptomatology referable to this area. Magnetic resonance imaging (MRI) of the spine demonstrated focal areas of abnormal signal intensity in the vertebral bodies of these patients. In all three patients, biopsy confirmed metastatic disease. All the patients received radiation or chemotherapy depending upon the etiology. These preliminary data suggest that MR imaging may be useful in evaluating patients with known primary tumor in whom clinical suspicion persists despite a negative radionuclide bone scan.     

Primary Ewing sarcoma: follow-up with Ga-67 scintigraphy

While avid accumulation of gallium-67 citrate and technetium-99m methylene diphosphonate (MDP) occurs initially in most cases of primary Ewing sarcoma, uptake after therapy is less well defined. Thirty patients with Ewing sarcoma who underwent Ga-67 and bone scintigraphy at diagnosis, at completion of therapy, and at relapse from 1978 to 1988 were evaluated. All 30 patients showed less primary site Ga-67 activity following therapy. Twenty-three of 28 patients who underwent corresponding bone scintigraphy showed less uptake, but residual activity was usually more intense than with Ga-67. Avid reaccumulation of Ga-67 occurred in four of five patients with primary site relapse, while patients who underwent bone scintigraphy showed less change. It was concluded that a greater decrease in Ga-67 than in Tc-99m MDP uptake often occurs in patients successfully treated for primary Ewing sarcoma. Information obtained at Ga-67 scintigraphy is most likely to be helpful if results of bone scintigraphy remain abnormal or if occult relapse is suspected.