Current role of gallium scanning in the management of lymphoma

[Basic Study for the Purpose of Developing a Quantitative 67Ga-SPECT Measurement Method]

PURPOSE

⁶⁷Ga-single photon emission computed tomography (SPECT) images vary according to the imaging time and image display methods. The calculation of an index, such as the standardized uptake value used in positron emission tomography, from ⁶⁷Ga-SPECT images would enable the accurate evaluation of the region of accumulation. The purpose of this study was to elucidate the conversion formula, the lower detection limit (LDL), and recovery coefficient (RC) for quantifying the radiation concentration in the ⁶⁷Ga accumulation site.

METHODS

After chronologically obtaining SPECT/CT images at a radiation concentration of 1.0-442.4 kBq/mL with 27 bottles (diameter: 48 mm, 100 mL), the radiation concentration conversion formula was calculated using the successive approximation reconstruction method. The conversion coefficient was then calculated from the relationship between the count rate and the radiation concentration, and the LDL was determined. To compensate for the partial volume effect, the recovery curve was calculated using the mean SPECT count for six bottles (diameter: 9, 18, 29, 38, 48, and 94 mm).

RESULTS

There was a linear relationship between the radiation concentration and the count rate with a good correlation (r=0.99). The LDL was 1.0 kBq/mL. The recovery curve reached a plateau at a diameter of at least 48 mm.

CONCLUSION

The calculation of the absorbed dose index was possible using the radiation concentration conversion formula and the RC.

Revisiting gallium-67 imaging: investigation of the energy photopeaks

BACKGROUND

Ga-67 has multiple energy emissions of different abundances and the quality of images is affected by these inhomogeneous energy distributions. Thus the purpose of this study was to investigate whether two or three energy peaks of Ga-67 would be the most appropriate setting in terms of γ-camera performance and image quality measurements.

MATERIALS AND METHODS

The physical performance of the γ-camera using Ga-67 has been tested; in particular, the effect of different gallium energy settings (two vs. three energy photopeaks) on the extrinsic and intrinsic uniformity and resolution of the γ-camera. The multicontrast/resolution phantom (OPRAXMEDICAL model 74-345) has been used to compare the two energy settings. The average contrast of the lesions and the contrast-to-noise ratio were measured and the significance of the result was determined using the paired Student's t-test. To test the effects of size and contrast on the detectability of defects, contrast detail curves have been generated for both the acquisition energy settings. For the optimization of the energy window, multiple static liver phantom images were acquired using the dual-energy photopeak acquisition method. However, each image was taken at different symmetric energy window combinations and the window settings were (5, 10, 15, and 20%) for 92 and 184 keV, respectively.

RESULTS

For the two energy window acquisitions, the intrinsic uniformity calculated by the integral and differential equations for the useful field of view was 2.26 and 1.39%, respectively. However, for the three energy windows, the values were 3.04 and 1.81%, respectively. The integral and differential values for the dual-energy flood images were 10.97 and 3.75%, respectively, whereas the integral and differential values for the triple-energy flood images were 13.3 and 4.13%, respectively. A slight improvement in the system's intrinsic spatial resolution was observed in the dual-window setting with a full width at half maximum of 9.24 mm compared with 10.42 mm for the triple-energy acquisition. The full width at half maximum was not drastically increased in the three window acquisitions, but the full width at tenth maximum was found to be larger. The two energy acquisitions yielded a significant improvement by 20.5 and 22% in the mean contrast of the planar images of the phantom filled with 2 and 5 mCi of Ga-67, respectively (P value <0.01). Single-photon emission computed tomography images acquired for the liver phantom showed an improvement in the mean contrast by 29 and 27.6% using two windows (P<0.001) for 2 and 5 mCi activity concentration, respectively. Unlike planar imaging, single-photon emission computed tomography images yielded a 45% increase in the contrast-to-noise ratio using the two window acquisitions with a mean CNR of 5.24±3.47 and 2.9±2.23 for two and three windows respectively; P value less than 0.05. The contrast detail curves showed better detectibality for small-sized lesions and lower contrast when using dual-energy settings. The best contrast, on average, was achieved using 10% for 92 keV and 5, 10, 15, and 20% for 184 keV, respectively, and it was improved by 16, 24, and 35% compared with other settings.

CONCLUSION

A significant improvement in image quality can be achieved by simply applying different window widths over the different photopeaks. Our results indicated that two photopeaks with optimized window widths can significantly outperform three windows in terms of spatial and contrast resolution and lesion detectability with a relatively negligible reduction of count sensitivity.

Role of serial quantitative gallium-67 tumor uptake in assessing response rates for chemotherapy in lymphoma patients

PURPOSE

To evaluate in serial gallium-67 scans (GS) the role of semiquantitative tumor-to-background (Tm/Bg) and tumor-to-liver ratios in assessing response rates to chemotherapy, in Hodgkin's disease and non-Hodgkin's lymphoma.

MATERIALS AND METHODS

Twenty-seven consecutive patients (15 Hodgkin's disease and 12 non-Hodgkin's lymphoma patients) with an average age of 30 (range, 5-60) years underwent GS at prechemotherapy, early chemotherapy (after first cycle), and postchemotherapy. Average tumor, background, and liver region of interest counts obtained and Tm/Bg, tumor-to-liver, and liver region to background ratios were derived for each patient on serial GS. All patients were assessed by visual and quantitative GS and followed up clinically for more than 7 years.

RESULTS

At early visual GS, 70% (19 of 27) of the patients showed rapid response, 15% (four of 27) showed delayed response (negative at post-GS), and 15% showed no response. Mean early-GS Tm/Bg ratio of disease-free patients (1+/-0.04) was significantly different from relapsed (1.4+/-0.2) (P<0.025) and progressive disease (1.8+/-0.7) patients. A significant difference was noted (P<0.01) in serial paired comparisons of Tm/Bg ratios between pretherapy and early-therapy scans in relapsed patients, whereas progressive disease patients showed no significant change during the same time. At early-GS, 15 patients showed quantitative rapid response (Tm/Bg ratio 1.04), nine patients showed quantitative delayed response (Tm/Bg ratio >1.04 with significant serial change between pretherapy and early-therapy GS), and three patients showed quantitative no response (Tm/Bg ratio >1.04 with nonsignificant serial change between pretherapy and posttherapy GS).

CONCLUSION

Quantitative GS is an effective tool in the detection of early response to chemotherapy. Quantitative response rates after the first cycle can more reliably identify patients who are most likely to be disease-free or relapse after first-line therapy or those that will show no response to therapy as compared with visual analysis alone.

[Scintigraphic image in a case of atypical presentation of Burkitt lymphoma. The role of the scintigraphy with 67Ga SPECT in the diagnosis and post-treatment control]

We present a case of Burkitt's disease with bone (thoracic wall, femur) and lymph node involvement. The patient had symptoms of fever with thoracic wall and femur pain. Lymph node involvement was detected by clinical exploration. A chest X-ray showed rib abnormalities. 99mTc-DPD scan showed thoracic wall (one rib) and femur involvement. 67Gallium SPECT and CT were performed at diagnosis. 67Gallium SPECT showed thoracic wall (one rib more) and abdominal lymph node involvement that was not detected by planar images. A CT scan did not show metastatic disease in mediastinal and abdominal lymph node chains but did show it in one rib and femur. After 6 chemotherapy sessions a new 67gallium scan and CT scan were performed. 67Gallium SPECT showed involvement in the thoracic wall (one rib) that was not detected in planar images. The CT scan was considered normal.

Gallium-67 scintigraphy: a cornerstone in functional imaging of lymphoma

Until recently, gallium-67 scintigraphy (GS) has been the best available functional imaging modality for evaluating patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). The diagnostic accuracy of GS in detecting lymphoma is based on optimisation of the imaging protocol, knowledge of potential physiological and benign sites of (67)Ga uptake, and the Ga avidity characteristics of the individual lymphoma. As (67)Ga is a tumour viability agent, the role of GS is primarily at follow-up. A residual mass persisting on CT after treatment poses a common clinical dilemma: it may indicate the presence of viable lymphoma, which requires further treatment, or it can be benign, consisting of only fibrotic and necrotic tissues. GS can successfully differentiate between these conditions. Routine follow-up with GS may allow early diagnosis of recurrence and early institution of treatment. Reversion of a positive GS to a negative test, and the rapidity with which this occurs has a high predictive value for the outcome of the individual patient. Lymphoma showing a normal GS early during treatment has a better prognosis than lymphoma with persistence of pathological findings. Other tumour-seeking single-photon emitting agents, such as thallium-201, technetium-99m methoxyisobutylisonitrile and indium-111 octreotide, have been investigated in lymphoma, primarily as an alternative to GS in specific clinical settings, but are of limited value. The role of radioimmunoscintigraphy is gaining importance in conjunction with radioimmunotherapy. Fluorine-18 fluorodeoxyglucose (FDG) imaging of lymphoma using either dedicated or camera-based PET systems is gradually replacing GS for assessment of lymphoma. FDG overcomes some of the limitations of GS while sharing its tumour viability characteristics. The extensive clinical knowledge and experience accumulated over three decades with GS in lymphoma provides a solid background as well as a model for the assessment of new functional imaging techniques.

Differentiation of low-grade gastric MALT lymphoma and high-grade gastric MALT lymphoma: the clinical value of Ga-67 citrate scintigraphy--a pilot study

Ga-67 citrate scintigraphy has been routinely and extensively used to evaluate non-Hodgkin's lymphoma (NHL) for more than 20 years. Gastric lymphoma of mucosa-associated lymphoid tissue (MALT) is by far the most common extranodal primary NHL. Gastric MALT lymphoma can be classified as low-grade (LG) or high-grade (HG). Low-grade gastric MALT lymphoma can be cured by eradication of Helicobacter pylori; but radiotherapy and/or chemotherapy and/or surgery are the major methods of treatment for the HG gastric MALT lymphoma. However, it is difficult to differentiate these two groups by clinical parameters and endoscopic findings. The purpose of this study was to determine whether Ga-67 citrate scintigraphy can distinguish the LG gastric MALT lymphoma from the HG gastric MALT lymphoma. Twenty-one patients (11 men and 10 women ranging in age from 38 to 83 years) with histologically confirmed gastric MALT lymphoma were enrolled. Twelve patients had LG and nine patients had HG. All 21 patients underwent Ga-67 citrate scintigraphy before treatment. The results of Ga-67 citrate scintigraphy were classified as positive or negative. In the LG group, nine patients had negative results and three patients had positive results. In the HG group of nine patients, all patients had positive results. Among the three patients who had positive results in the LG group, the uptake of gastric MALT lymphoma was lower than that of the liver. The Ga-67 citrate scintigraphy is of good clinical value for the differentiation of the LG gastric MALT lymphoma and the HG gastric MALT lymphoma. We think that the major value of Ga-67 citrate scintigraphy will be in following the patients with HG gastric MALT lymphoma after treatment to assess response of therapy and to detect possible recurrence and perhaps in determining transformation from the LG to HG gastric MALT lymphoma. However, further investigation is needed to understand the relationship between the uptake of Ga-67 citrate in gastric MALT lymphoma and transformation.

[Malignant lymphoma of the thyroid gland]

INTRODUCTION

Malignant lymphoma of the thyroid gland can be defined as a lymphoma arising from the thyroid gland. Lymphomas of the thyroid gland represent less than 5% of primary thyroid neoplasms and are two to three times more common in women than in men, whereas the median age is usually close to 60 years. Majority of thyroid lymphomas are diffuse, large-cell lymphomas. The incidence of thyroid lymphomas in patients with Hashimoto thyroiditis has markedly increased and this phenomenon is probably related to their pathogenesis.

CLINICAL PRESENTATION

Unlike most other thyroid neoplasms, lymphomas are usually rapidly enlarging masses and local symptoms are common: pain, hoarseness, dysphagia, and dyspnea or stridor.

DIAGNOSIS

To evaluate the extent of disease, a chest x-ray and CT scans of the head and neck, chest, abdomen, and pelvis are necessary. An excisional or large-needle biopsy may also be necessary to make the correct diagnosis. Occasionally, these tumors can be confused with anaplastic thyroid carcinomas, which can lead to serious mistakes in management. A gallium scan or a positron emission tomography (PET) scan can help later to establish whether any residual abnormality, observed on x-ray studies after treatment, contains active lymphoma or scar tissue. After diagnosis, patients are clinically staged (without surgery) using appropriate computed tomography scans or magnetic resonance imaging.

THERAPY

Assessment of the extent of thyroid lymphomas is crucial for prognosis and treatment. Total thyroidectomy may improve the prognosis in patients with intrathyroidal disease only. It is very important to identify patients with favorable prognostic factors and to treat them with standard chemotherapy (CHOP) and radiotherapy protocols. Patients with diffuse large-cell primary thyroid lymphomas should not be treated with radiation therapy alone.

CONCLUSION

The best treatment results for malignant lymphomas of the thyroid gland are achieved using a combined-modality therapy.

Gallium avid breast carcinoma

Primary breast carcinomas are generally thallium (Tl-201) avid but uncommonly accumulate gallium (GA-67). Therefore, GA-67 scans are not routinely performed in patients with suspected breast cancer. We report a rare case of a primary breast carcinoma with bone marrow metastases where the primary lesion was GA-67 avid but did not accumulate Tl-201. The case also illustrated an unusual presentation of aggressive metastatic breast adenocarcinoma with pancytopenia or bone marrow failure. The extensive bone marrow metastases of the primary breast carcinoma were evident on both the Tl-201 and GA-67 scans.

Technetium-99m Tetrofosmin Imaging in Malignant Lymphomas

Aim

To assess the utility of 99mTc tetrofosmin (TF) scintigraphy as a diagnostic modality in lymphomas.

Methods

Seventeen patients (14 with Hodgkin's disease and three with non-Hodgkin's lymphomas; age range, 10-59 years) were investigated. Planar and SPECT images of the supradiaphragmatic region (including neck and chest) were obtained. All patients were untreated at the time of the first scintigraphy. Follow-up scans after therapy were acquired in six patients (in five twice), so a total of 28 scintigraphic studies were performed. Mediastinal, pulmonary, cervical, supraclavicular and axillary activity was evaluated and results were compared in a blinded fashion with those of CT.

Results

TF imaging demonstrated pathological focal uptake at 38 sites (16 in the mediastinum, eight in the lungs, four in the axillae, eight in the supraclavicular region and two in the cervical region) in 16 of 17 untreated patients; CT identified 24 lesions (16 in the mediastinum, two in the lungs, two in the axillae, two in the supraclavicular and two in the cervical region) in 17 patients. Scintigraphy detected 22 of the 24 lesions demonstrated by CT and revealed 16 unknown tumor sites in 10 patients. The only negative pre-treatment scintigraphy result was found in a patient with axillary lymph node involvement. On the first post-treatment scintigrams there was a reduction in the number of visualized pathological sites (seven vs 16) in five of the six patients examined. The second follow-up study demonstrated only two lesions in two of the five patients examined.

Conclusions

Our preliminary results indicate that TF imaging is effective in depicting supradiaphragmatic lymphoma lesions in untreated patients and suggest that serial scintigraphic studies may be suitable for monitoring response to treatment. However, larger series are needed to better define the possible role of TF scintigraphy in the follow-up of the response to therapy.

Fluorine-18 fluorodeoxyglucose positron emission tomography, gallium-67 scintigraphy, and conventional staging for Hodgkin's disease and non-Hodgkin's lymphoma

PURPOSE

To compare fluorine-18 fluorodeoxyglucose positron emission tomography (PET) and gallium scanning with each other and with conventional staging, for patients with Hodgkin's disease or non-Hodgkin's lymphoma.

SUBJECTS AND METHODS

Fifty patients had PET, gallium scanning, and conventional staging of newly diagnosed or progressive Hodgkin's disease or non-Hodgkin's lymphoma. Disease sites, stage, and treatment plans were assessed retrospectively.

RESULTS

Positron emission tomography and gallium scanning each upstaged 14% of patients (n = 7). Management was altered by PET in 9 cases (18%) and by gallium scanning in 7 (14%, P = 0.6). Disease was evident in 117 sites in 42 patients. The case positivity rate for conventional assessment was 90%; for PET, 95%; for gallium scanning, 88%; for conventional assessment plus PET, 100%; and for conventional assessment plus gallium scanning, 98%. Site positivity rates for conventional assessment were 68%; for PET, 82%; for gallium scanning, 69% (conventional vs. PET, P = 0.01; conventional vs. gallium scanning, P = 0.9; PET vs. gallium scanning, P = 0.01); for conventional assessment plus PET, 96%; and for conventional assessment plus gallium scanning, 94%. Positron emission tomography and gallium scanning were entirely concordant in 31 patients; in the other 19 patients, PET identified 25 sites missed by gallium scanning, whereas gallium scanning identified 10 sites missed by PET.

CONCLUSION

In this retrospective study, PET demonstrated a higher site positivity rate than did gallium scanning, with similar case positivity rates. These data support the use of PET in place of gallium scanning for the staging of patients with Hodgkin's disease or non-Hodgkin's lymphoma.

Thoracic imaging of pediatric lymphomas

Lymphoma (Hodgkin and non-Hodgkin types) is the most common intra-thoracic neoplasm in the pediatric age group. Diagnostic strategies and treatment approaches for these tumors are largely determined by protocols established by one of the large, multi-institutional cooperative groups. In this paper, Hodgkin and non-Hodgkin lymphoma is discussed in the context of these cooperative group protocols. The basic biology, patterns of primary and metastatic disease distribution, treatment approaches, imaging follow-up, and areas of active research are discussed.

Radionuclide evaluation of patients with lymphoma

Nuclear medicine imaging techniques allow us to peer into physiologic processes, avoiding the need to wait until anatomic changes are detectable, and allowing for prompt, informed management decisions. Recognition of normal, abnormal, and post-therapy scan patterns is critical to achieve the necessary sensitivity and specificity needed for patient management. Gallium scintigraphy using updated techniques has an important continuing role in management of patients with lymphoma. Gallium scintigraphy can contribute to patient management primarily by detecting residual disease or relapse after treatment, monitoring response during therapy, and providing prognostic information. FDG and PET cameras, especially dedicated ring systems, offer high resolution and high-contrast images, thereby demonstrating additional sites of disease. Although preliminary evidence looks promising that FDG can provide all information that Ga-67 has been shown to do in the past, additional data are required. Further studies will show whether FDG-PET can provide prognostic information and predict disease-free and overall survival, the availability of both FDG and PET scanners, and issues of cost. Patient accessibility will undoubtedly also play a role in when, or whether, FDG-PET will totally replace Ga-67 scintigraphy in the management of patients with lymphoma.

Value of combined 67Ga and 99Tc(m)-human immunoglobulin G whole-body scanning in malignant lymphoma

Human immunoglobulin G labelled with 99Tc(m) (99Tc(m)-HIG) is an agent introduced for the localization of inflammatory lesions. There is also a limited number of reports concerning the uptake of this agent by malignant lesions. The aim of this study was to evaluate the uptake of 99Tc(m)-HIG by lymphoma. Twenty-three patients (five female, 18 male) with known Hodgkin's or non-Hodgkin's lymphoma for a period of 2-6 years (mean 4.2 years) and which, by using computed tomography (CT), showed recurrence, were included in the study. The patients were aged between 32 and 68 years (mean 38 +/- 5 years). No evidence of inflammation or infection was seen in any of these patients. CT, 99Tc(m)-HIG and a 67Ga scan were performed in the same week. CT showed abdominal involvement in 17 patients, pelvic involvement in 11, and thorax involvement in 11. 99Tc(m)-HIG showed higher sensitivity (94.1%) in the abdomen, a similar sensitivity (63.6%) in thorax, but lower (18.1%) in pelvic area than for 67Ga. 99Tc(m)-HIG was found to be more useful for the evaluation of abdominal involvement compared to 67Ga due to gastrointestinal excretion of the latter. The resolution of 67Ga was better than 99Tc(m)-HIG in thorax and pelvis. Using 99Tc(m)-HIG and 67Ga together in lymphoma may increase sensitivity.

Resolution of Ga-67 citrate uptake in the left neck mass of Hodgkin's disease and reversion of double scoliosis of cervical-thoracic and lower lumbar vertebrae

A 6-yr-old boy underwent a total body Ga-67 citrate imaging study because of a large mass of Hodgkin's lymphoma in the left neck and the left anterior chest wall region. The images showed intense uptake in the left neck extending anteroinferiorly to the left upper chest wall corresponding to the left neck and chest region. In addition, there was mild cervical-upper thoracic scoliosis with convexity to the right and mild scoliosis of the lower lumbar scoliosis with concavity to the left. After three cycles of chemotherapy, in the follow-up Ga-67 citrate total body images seven months after his first Ga-67 citrate imaging, the intense uptake in the left neck and the left upper chest wall had been resolved and the scoliosis of the cervical-thoracic and lower lumbar spine had also been reversed to normal. This case shows that a Ga-67 citrate imaging study is useful for first diagnosis and subsequent monitoring of the therapeutic effects in a follow-up imaging. Also Ga-67 citrate imaging provided evidence that the scoliosis had been reversed.

Effect of filtering on the detection and localization of small Ga-67 lesions in thoracic single photon emission computed tomography images

Tumor detection can be significantly affected by filtering so determining an optimal filter is an important aspect of establishing a clinical reconstruction protocol. The purpose of this study was to identify the cut-off frequency of a Butterworth filter used in a filtered backprojection (FBP) reconstruction that maximized the detection and localization accuracy of 1 cm spherical lesions in Ga-67 citrate, thoracic SPECT images. Image quality was evaluated by means of a localization receiver operating characteristic (LROC) study using computer simulated images. Projection data were generated using the mathematical cardiac-torso digital phantom with a clinically realistic background source distribution. The images were reconstructed using FBP with multiplicative Chang attenuation correction and fifth-order Butterworth filtering. The cut-off frequencies considered were 0.25, 0.32, 0.47, and 0.79 cm(-1) for the case of three-dimensional (3D) post-filtering and 0.25, 0.32, and 0.47 cm(-1) for two-dimensional (2D) post-filtering. The images were read by three research scientists and one board certified nuclear medicine clinician. The area under the LROC curve and the localization accuracy for all test conditions were compared using Scheffé's multiple comparisons test. It was found that 3D post-filtering using filters with cut-off frequencies of 0.32 and 0.47 cm(-1) resulted in the highest lesion detectability and localization accuracy. These two test conditions did not differ significantly from each other but were significantly better (p<0.05) than all of the 2D, and the 3D 0.79 cm(-1) cut-off frequency cases.

Tl-201 and Ga-67 scintigraphy in non-Hodgkin's lymphoma

Ga-67 scintigraphy is routinely used to stage and monitor non-Hodgkin's lymphoma (NHL). It is highly sensitive in high-grade NHL but less so in intermediate- and low-grade NHL. Several studies have reported the use of Tl-201 in the low and intermediate grades of NHL and found it superior in low-grade NHL. In this study, the authors evaluated the utility of combined Ga-67 and Tl-201 scintigraphy in low, intermediate, and unusual types of NHL. Combined Tl-201 and Ga-67 scintigraphy were done in 33 patients (18 women, 15 men; age range, 21-91 years; mean age, 56 years). Tl-201 and Ga-67 had similar overall patient sensitivity in the 33 patients studied. However, the use of both agents increased the overall patient sensitivity from 67% (for Ga-67 only) to 82% and improved the overall site detection from 59 positive sites with Ga-67 to 81 abnormal sites with both Tl-201 and Ga-67. The combined use of Tl-201 and Ga-67 scintigraphy in low- and intermediate-grade NHL resulted in increased disease and site detection and is beneficial for clinical follow-up.

Gallium-67 scintigraphy in the treatment and prognosis of acute adult T-cell lymphoma

The case of a 77-year-old male patient who complained of left upper quadrant pain and progressive vomiting. Laboratory examination showed extremely high lactic acid dehydrogenase (LDH) and adult T-cell leukemia antibody (ATLA). The anatomical studies CT, MRI, US and upper GI series substantiated an omental lymphadenopathy which was causing a circumferential compression of portions of the duodenum and jejunum. Gallium-67 citrate (Ga-67) scintigraphy showed high uptake at LUQ. Ultrasound guided biopsy failed to confirm the diagnosis. Irradiation was performed. Ga-67 scintigraphy had a contributory role in clinical subtyping of the disease, planning of treatment, posttreatment assessment and prognostication of adult T-cell lymphoma.

Clinical applications of fusion imaging in oncology

Recent developments in tumor imaging, made possible by advances in instrumentation and radiopharmaceuticals, has led to an increasing need for accurate anatomic correlation of single photon emission computed tomography (SPECT) and positron emission tomography (PET) images. Fusion imaging permits the functional strengths of SPECT and PET to be combined with the anatomic resolution of computed tomography (CT) and magnetic resonance imaging (MRI). Clinical applications of fusion imaging include the evaluation of brain tumors, lymphoma, hepatic lesions and monoclonal antibody studies. The continued development of these techniques will eventually allow fusion imaging to become a routine part of nuclear medicine practice.

Gallium-67-citrate imaging in nuclear oncology

Gallium-67-citrate is one of the most useful radiopharmaceuticals to detect tumors, stage extent of the disease, monitor response to treatment and distinguish recurrent disease from post-treatment changes. Gallium is likewise very sensitive to detect and locate infections and inflammatory foci. This application is extremely important in the management of immunocompromised cancer patients. Image interpretation should be tempered with full knowledge of the patients clinical condition, anatomic alterations due to prior surgery and correct timing of image acquisition. Early imaging at 4-6 h is useful to detect gastrointestinal infections, whereas 24 h imaging is used to evaluate chest infections. Although gallium-67 is a non-specific agent, the identification of the etiology of the inflammation may be improved by adequate clinical and laboratory information as well as correlation with other imaging modalities such as sonography and computerized x-ray tomography (CT). High dose (10 mCi) gallium-67 single photon emission computed tomography (SPECT) imaging with image co-registration is important for accurate uptake localization.

Current role of gallium scan and magnetic resonance imaging in the management of mediastinal Hodgkin lymphoma

BACKGROUND

A residual mediastinal mass after treatment represents a common diagnostic problem in the management of patients with Hodgkin lymphoma (HD). Conventional diagnostic radiology, computed tomography (CT), or ultrasonography (US) do not adequately reflect changes as fibrosis or necrosis. Gallium-67 (67Ga) imaging has been proven to be useful for the evaluation of HD in the mediastinum. The authors compared the ability of gallium scan and magnetic resonance imaging (MRI) to evaluate the mediastinal disease in the follow-up of patients with HD.

METHODS

Thirty-four patients previously treated for HD were investigated with gallium scan, MRI, and all the other investigations to evaluate the mediastinal region. Sixteen patients were in restaging after treatment, and 18 were investigated for suspected radiologic recurrence in the mediastinum (follow-up, 9-75 months). The results of gallium scan and MRI were matched with clinical findings during the follow-up.

RESULTS

A sensitivity of 85.7% for 67Ga and 92.8% for MRI was found, while the specificity was 100% for the scan and 80.6% for MRI. The predictive positive value that resulted was 100% for 67Ga and 68.4% for MRI.

CONCLUSIONS

Both examinations were accurate in assessing the activity of residual masses in the mediastinum after treatment. 67Ga showed a lower sensitivity in comparison with MRI, but 67Ga frequently overestimates the presence of pathologic tissue. The authors acknowledge the complementary role of these two tests, but if only one of these examinations can be performed for logistic or economic reasons, then gallium scan represents the single most adequate diagnostic procedure.

Genitourinary tract nuclear oncology

Currently available routine radionuclide procedures and on-going investigational scintigraphic studies of genitourinary tract tumors were reviewed. Emphasis was focused on the most commonly encountered tumors located in the kidneys, bladder, and prostate. Other imaging modalities, such as computed tomography (CT), magnetic resonance imaging (MRI), and sonography have replaced many of the routine radionuclide imaging procedures providing high-resolution images and anatomic details. The advantages of radionuclide procedures with their simple, uninvasive, and functioning nature will continue play important role in our management of tumors of the genitourinary tract.

A comparison of gallium-67 single photon emission computed tomography and computed tomography in mediastinal Hodgkin's disease

The role of gallium-67 single photon emission computed tomography (Ga-67 SPECT) in the assessment of mediastinal Hodgkin's disease was evaluated prospectively. Ga-67 SPECT and computed tomography (CT) were compared and correlated with clinical findings at initial presentation in 30 patients, 6 weeks after treatment, and 6 months later in 20 of the 30 patients. At initial presentation, active disease was detected on both imaging modalities on all occasions. 6 weeks after treatment CT showed residual mediastinal abnormality in 7 patients, whereas Ga-67 SPECT showed abnormal mediastinal tracer uptake in 3 patients. 6 months later CT showed residual mediastinal abnormality in 5 patients whereas all the Ga-67 SPECT studies were negative. Ga-67 SPECT imaging is a useful tool in assessing response to therapy in mediastinal Hodgkin's disease.