Whole-body Planar Scans Research Articles

Radiation exposure of the spleen during (177)Lu-DOTATATE treatment and its correlation with haematological toxicity and spleen volume.

BackgroundSomatostatin analogue-based radionuclide therapy with 177Lu-DOTATATE is an important treatment option for patients with advanced neuroendocrine tumours overexpressing somatostatin receptors. In addition to the kidneys, the bone marrow is a major dose-limiting organ. The correlation between developed haematological toxicity and absorbed dose to the bone marrow is poor, which indicates that other factors affect haematological response. The spleen has an important role in the haematopoetic system, including being a reservoir for blood cells. It is also the organ that receives the highest mean absorbed dose during 177Lu-DOTATATE treatment. The aim of this study was to analyse mean absorbed dose to the spleen and its correlation with haematological toxicity, and to explore changes in splenic volume.The study included 41 patients treated with 7.2 GBq (3.5–8.3 GBq) of 177Lu-DOTATATE on two to five occasions. Following each fraction, planar whole-body scans were acquired at 2, 24, 48, and 168 h, and a SPECT/CT at 24 h post-injection. Mean absorbed spleen dose was calculated utilising planar images for time-activity data and SPECT to adjust activity amounts. Splenic volume information was collected from diagnostic CT scans at baseline and follow-up.ResultsMedian and total absorbed spleen doses were estimated to 4.5 and 15 Gy, respectively. Total absorbed spleen dose correlated with decrease in Hb (p = 0.02), but not WBC (p = 0.31) or PLT (p = 0.65) counts. For patients without bone metastases, mean absorbed spleen dose correlated with decrease in PLT (p = 0.04) but not Hb (p = 0.16) or WBC (p = 0.42) counts. The spleen volume was reduced to 75 % (p < 0.001) of original values (200 vs. 260 ml) at a mean follow-up of 36 months.ConclusionsHaematological toxicity according to Hb counts was moderately but significantly correlated with total absorbed spleen dose. This supports the possibility that radiation exposure of the spleen affects overall haematological response during 177Lu-DOTATATE treatment.

A 3D Monte Carlo Method for Estimation of Patient-specific Internal Organs Absorbed Dose for (99m)Tc-hynic-Tyr(3)-octreotide Imaging.

Single-photon emission computed tomography (SPECT)-based tracers are easily available and more widely used than positron emission tomography (PET)-based tracers, and SPECT imaging still remains the most prevalent nuclear medicine imaging modality worldwide. The aim of this study is to implement an image-based Monte Carlo method for patient-specific three-dimensional (3D) absorbed dose calculation in patients after injection of 99mTc-hydrazinonicotinamide (hynic)-Tyr3-octreotide as a SPECT radiotracer. 99mTc patient-specific S values and the absorbed doses were calculated with GATE code for each source-target organ pair in four patients who were imaged for suspected neuroendocrine tumors. Each patient underwent multiple whole-body planar scans as well as SPECT imaging over a period of 1-24 h after intravenous injection of 99mhynic-Tyr3-octreotide. The patient-specific S values calculated by GATE Monte Carlo code and the corresponding S values obtained by MIRDOSE program differed within 4.3% on an average for self-irradiation, and differed within 69.6% on an average for cross-irradiation. However, the agreement between total organ doses calculated by GATE code and MIRDOSE program for all patients was reasonably well (percentage difference was about 4.6% on an average). Normal and tumor absorbed doses calculated with GATE were slightly higher than those calculated with MIRDOSE program. The average ratio of GATE absorbed doses to MIRDOSE was 1.07 ± 0.11 (ranging from 0.94 to 1.36). According to the results, it is proposed that when cross-organ irradiation is dominant, a comprehensive approach such as GATE Monte Carlo dosimetry be used since it provides more reliable dosimetric results.

In vivo quantification of (177)Lu with planar whole-body and SPECT/CT gamma camera imaging.

BackgroundAdvances in gamma camera technology and the emergence of a number of new theranostic radiopharmaceutical pairings have re-awakened interest in in vivo quantification with single-photon-emitting radionuclides. We have implemented and validated methodology to provide quantitative imaging of 177Lu for 2D whole-body planar studies and for 3D tomographic imaging with single-photon emission computed tomography (SPECT)/CT.MethodsWhole-body planar scans were performed on subjects to whom a known amount of [177Lu]-DOTA-octreotate had been administered for therapy. The total radioactivity estimated from the images was compared with the known amount of the radionuclide therapy administered. In separate studies, venous blood samples were withdrawn from subjects after administration of [177Lu]-DOTA-octreotate while a SPECT acquisition was in progress and the concentration of the radionuclide in the venous blood sample compared with that estimated from large blood pool structures in the SPECT reconstruction. The total radioactivity contained within an internal SPECT calibration standard was also assessed.ResultsIn the whole-body planar scans (n = 28), the estimated total body radioactivity was accurate to within +4.6 ± 5.9 % (range −17.1 to +11.2 %) of the correct value. In the SPECT reconstructions (n = 12), the radioactivity concentration in the cardiac blood pool was accurate to within −4.0 ± 7.8 % (range −16.1 to +7.5 %) of the true value and the internal standard measurements (n = 89) were within 2.0 ± 8.5 % (range −16.3 to +24.2 %) of the known amount of radioactivity contained.ConclusionsIn our hands, state-of-the-art hybrid SPECT/CT gamma cameras were able to provide accurate estimates of in vivo radioactivity to better than, on average, ±10 % for use in biodistribution and radionuclide dosimetry calculations.

123I]Iodometomidate Imaging in Adrenocortical Carcinoma

Imaging with [¹²³I]iodometomidate ([¹²³I]IMTO) has been shown to diagnose adrenocortical lesions with high sensitivity and specificity. Our objective was to evaluate the clinical utility of [¹²³I]IMTO imaging in adrenocortical carcinoma (ACC). We conducted a prospective monocentric diagnostic study and a prospective case series at a single tertiary referral center. Fifty-eight patients with histologically confirmed ACC, all European Network for the Study of Adrenal Tumors stage IV (with distant metastases), received 185 MBq [¹²³I]IMTO. Sequential planar whole-body scans until 24 hours post injection and single photon emission computed tomography/computed tomography (SPECT/CT) hybrid imaging 4 to 6 hours post injection were performed. Outcome measures included uptake of [¹²³I]IMTO in ACC lesions, sensitivity and specificity of [¹²³I]IMTO imaging compared with conventional imaging, and number of patients eligible for [¹³¹I]IMTO therapy. Of 430 lesions detected by conventional imaging, 30% showed strong, 8% moderate, and 62% no tracer accumulation. [¹²³I]IMTO detected both primary and metastatic lesions of ACC. However, a substantial percentage of lesions failed to show [¹²³I]IMTO uptake. The overall sensitivity and specificity values were 38% and 100%, respectively. Thirty-four patients (59%) had at least 1 [¹²³I]IMTO-positive lesion. Cortisol and aldosterone secretion by ACC was positively correlated to [¹²³I]IMTO uptake (P = .01); cytotoxic chemotherapy and mitotane treatment presumably did not influence tracer uptake. Twenty-one patients (36.2%) had radiotracer uptake in all lesions ≥ 2 cm and therefore were potential candidates for targeted systemic radiotherapy with [¹³¹I]IMTO. About one-third of patients with ACC show specific retention of [¹²³I]IMTO in metastatic lesions. This study provides support for the conduct of a prospective trial to determine whether the first molecular informed therapy using [¹³¹I]IMTO will be of value to patients with metastatic ACC.

Functional Characterization of Adrenal Lesions Using [123I]IMTO-SPECT/CT

Adrenal tumors are highly prevalent and represent a wide range of different pathological entities. Conventional imaging often provides only limited information on the origin of these lesions. Novel specific imaging methods are, therefore, of great clinical interest. We evaluated [(123)I]iodometomidate ([(123)I]IMTO) imaging for noninvasive characterization of adrenal masses. This was a prospective monocentric diagnostic study in a tertiary care center. A total of 51 patients with an adrenal lesion underwent [(123)I]IMTO imaging after injection of 185 MBq of [(123)I]IMTO. Sequential planar whole-body scans until 24 hours postinjection and single photon emission computed tomography (SPECT)/computed tomography imaging 4 to 6 hours postinjection were performed. Sensitivity and specificity of [(123)I]IMTO imaging for the noninvasive characterization of adrenal lesions were measured. Adrenocortical tissue showed high and specific tracer uptake with a short investigation time and low radiation exposure. Qualitative analysis of SPECT/computed tomography data resulted in a sensitivity of 89% and a specificity of 85% for differentiating adrenocortical tumors from lesions of nonadrenocortical origin. Receiver-operating characteristic analysis of semiquantitative data revealed a sensitivity of 83% and a specificity of 86% for identification of adrenocortical lesions at a cutoff value of tumor to liver ratio of 1.3. [(123)I]IMTO is a highly specific radiotracer for imaging of adrenocortical tissue with a short investigation time and low radiation exposure. Because of the general availability of SPECT technology, [(123)I]IMTO scintigraphy has the potential to become a widely used tool to noninvasively characterize the biology of adrenal lesions.

I-131 SPECT/CT Elucidates Cryptic Findings on Planar Whole-Body Scans and Can Reduce Needless Therapy with I-131 in Post-Thyroidectomy Thyroid Cancer Patients

Interpreting I-131 whole-body scans (WBSs) after thyroidectomy for thyroid cancer is not simple. There are scans in which interpretation is speculative because of cryptic findings (CF). Complexity is added in scans that are done a week after an ablative or therapeutic dose of I-131 because not only is I-131-labeled thyroxine (T4) distributed throughout the body, but inorganic I-131 that is derived from the de-iodination of T4 may be also detected. We present our observations regarding the analysis of CF on WBS using I-131 single-photon emission computed tomography (SPECT) in fusion with noncontrast computed tomography (CT), referred to here and elsewhere as I-131 SPECT/CT. Forty of 184 WBSs in 38 thyroidectomized thyroid cancer patients were followed up with I-131 SPECT/CTs. The SPECT/CT images were acquired after a tracer dose of I-131 (n=82) or a week after an ablative or therapeutic dose of I-131 (n=102). Among 184 WBSs, 40 (22%) had CF. In 35 patients the WBS was negative for metastatic disease except for the CF and 5 patients had evidence of thyroid cancer in addition to the CF. There were 49 CF in the planar scans that were localized by SPECT/CT. These were characterized as physiological uptake in gingiva, thymus, gall bladder, menstrual blood, uterine fibroid, recto-sigmoid, colon, and bladder. Also observed was uptake in sites that represented nonthyroidal pathology including dental abscess, hiatal hernia, renal cyst, and struma ovarii. SPECT/CT suggested that 10 of the CF were actually of thyroid origin. In 40 SPECT/CT scans, the images contributed to interpreting the scan. In 15 of 40 patients the SPECT/CT analysis of WBS was performed with tracer doses of I-131 and was important for determining whether to administer ablative I-131 treatment. In another 25 patients, in whom SPECT/CT was performed after ablative or therapeutic doses of 131-I, information regarding the characterization of CF by SPECT/CT was useful in determining if thyroid cancer metastases or thyroid remnants were present. I-131 SPECT/CT is a useful tool to characterize atypical or CF on WBS by differentiating thyroid remnant or cancer from physiologic activity or nonthyroid pathology. In the past, uptake on a WBS that was not explicable as physiologic activity was identified as putative or possible thyroid cancer and generally was treated with I-131. Now, by identifying activity in some possible cancer sites as not thyroid cancer, SPECT/CT can reduce inappropriate treatment with I-131. SPECT/CT of WBS performed after ablative doses of 131-I is useful in determining the nature of CF and therefore likely providing prognostic information.

Should we stop performing nuclear medicine procedures?

Should we stop performing nuclear medicine procedures?

Five months’ follow-up of patients with and without iodine-positive lymph node metastases of thyroid carcinoma as disclosed by 131I-SPECT/CT at the first radioablation

In differentiated thyroid carcinoma (DTC), (131)I-SPECT/CT is more accurate in identifying radioiodine-positive lymph node metastases (LNM) than planar whole-body scans (WBS). The purpose of this study was to investigate the value of (131)I-SPECT/CT performed at the first radioablation to predict the occurrence and/or persistence of cervical radioiodine-positive LNM 5 months later. The study included 81 DTC patients that had had SPECT/ spiral CT after radioablation of thyroid remnants after thyroidectomy. The patients were re-examined 5 months later using (131)I-WBS performed at TSH stimulation. In addition, SPECT/CT of the neck was performed in patients with iodine-positive cervical foci to distinguish between thyroid remnant and LNM. The outcome variable of the study was the detection or exclusion of iodine-positive cervical LNM. Of 61 patients without a SPECT/CT diagnosis of (131)I-positive LNM at radioablation, 60 had no (131)I-positive LNM at follow-up. In the remaining patient of this group, a new radioiodine-positive LNM was detected. In 17 of 20 patients with a SPECT/CT diagnosis of (131)I-positive LNM (n = 19) or an indeterminate lesion (n = 1) at first radioablation, no (131)I-positive LNM were detected 5 months later. Radioiodine-positive LNM persisted in three patients of this group. (131)I-SPECT/CT has a high negative predictive value with regard to the occurrence of radioiodine-positive cervical LNM 5 months after initial therapy. The majority of iodine-positive LNM diagnosed by SPECT/CT at radioablation disappear within 5 months. These findings motivate further research into the value of (131)I-SPECT/CT of the neck for predicting recurrence and planning surgical reintervention in DTC.

Technetium-99m RP527, a GRP analogue for visualisation of GRP receptor-expressing malignancies: a feasibility study.

Gastrin-releasing peptide (GRP) receptor scintigraphy could allow prediction of response to GRP receptor-targeted treatment options, early non-invasive diagnosis and in vivo prognostic stratification of GRP receptor-positive tumours. This study reports on the imaging characteristics and efficacy for tumour detection of technetium-99m RP527, a 99mTc chelated targeting peptide derived from bombesin, which binds GRP receptors with high affinity. Ten patients (four men and six women, mean age 56.4 years) either suffering from metastasised prostate (n, number of patients = 4) or breast carcinoma (n=1) or presenting with a clinical diagnosis highly suggestive for breast carcinoma (n=5) were included in the study. In the latter five patients, 99mTc-RP527 scintigraphy was performed prior to diagnostic, e.g. biopsy, and staging examinations. Final diagnosis in these patients was breast carcinoma in all five. In all patients, whole-body planar scans and tomographic images were acquired 1 h and 5-6 h post injection of 555 MBq 99mTc-RP527 and tumour to normal tissue (T/N) ratios determined. 99mTc-RP527 showed specific uptake in four of six breast and one of four prostate carcinomas. T/N ratios derived from planar and tomographic images increased significantly (P<0.01) from 1.65 (SD 1.53) and 3.35 (SD 3.04) to 2.58 (SD 1.26) and 7.23 (SD 8.46), respectively. T/N ratios derived from tomographic images were consistently higher (P<0.01). The data presented suggest that 99mTc-RP527 results in specific tumour localisation and exhibits good imaging characteristics with a good T/N ratio that may be further enhanced by single-photon emission tomography.

Benign versus malignant osseous lesions in the lumbar vertebrae: differentiation by means of bone SPET

Bone scanning is a well-accepted and frequently performed diagnostic procedure with a high sensitivity, especially when single-photon emission tomography (SPET) acquisitions are added. However, the differentiation of benign from malignant osseous lesions often poses difficulty. The purpose of this study was to find out whether the particular localisation of an intraosseous lesion in a lumbar vertebra is an indicator of its aetiology. Bone scintigraphy including planar whole-body scans as well as SPET imaging of the lumbar spine was performed in 109 patients. The diagnoses of osseous lesions in the lumbar vertebrae were made strictly on the basis of the findings of magnetic resonance imaging, computed tomography or plain radiography. Sixteen patients had to be excluded from the study because they did not undergo adequate radiological examination. To determine the particular localisation of vertebral lesions in the bone scan, two experienced nuclear medicine physicians examined the studies independently while blinded to the radiological results. Four anatomical regions were differentiated within the vertebra: the vertebral body, the pedicle, the facet joints and the spinous process. Clopper-Pearson analysis, which takes into account the number of examinations, yielded the following probability intervals for the malignancy of intraosseous lesions in the lumbar spine: vertebral body 36.8%-57.3%, pedicle 87.7%-100%, facet joints 0.8%-21.4% and spinous process 18.7%-81.3%. It was concluded that lesions affecting the pedicle are a strong indicator for malignancy, whereas involvement of the facet joints is usually related to benign disease. Lesions affecting the vertebral body or the spinous process do not show a clear tendency towards either malignancy or benignity. In contrast to other studies, a significant probability of malignancy (35.6%) was observed in lesions affecting exclusively the vertebral body.

Detection efficiency of colorectal carcinoma recurrence using technetium pertechnetate-anti-carcinoembryonic antigen monoclonal antibody BW 431/26.

A new anti-carcinoembryonic antigen (CEA) antibody, BW 431/26 (Scintimun, Behring-Werke, Marburg, Germany), labeled with technetium pertechnetate (Tc-99m), is an intact immunoglobulin G1 monoclonal antibody that has been used to image colorectal cancer (CRC). This report is part of a prospective multicenter clinical trial initiated by the International Atomic Energy Agency to evaluate the role of this antibody in radioimmunoimaging of patients with suspected disease recurrence. A group of 31 consecutive patients underwent radioimmunoimaging with Tc-99m-BW 431/26 after resection of their primary CRC. Patient referral was based on either a persistent rise in serum CEA levels of unknown origin and/or questionable findings by other imaging studies. Whole-body planar scans and single photon emission computed tomography scans of selected body regions (e.g., chest, abdomen) were performed up to 24 hours after the intravenous antibody injection. Pathologic antibody concentration localizations by radioimmunoimaging were correlated with surgical, clinical, and other imaging modality findings to validate the accuracy of radioimmunoimaging in detecting CRC recurrence. A total of 75 detected tumoral lesions was evaluated: 26 of 75 were of known origin (36%), and 49 of 75 were of unknown origin (65%). There were four true-negative lesions, one false-negative lesion, and no false-positive lesions; all others were true-positive lesions. Sensitivity was 96.8%, specificity 100%, and accuracy 98.6%. The study was easy to perform, without untoward side effects on patients after antibody administration. Anti-CEA antibody radioimmunoimaging is a highly reliable diagnostic procedure in detecting CRC recurrence and is useful especially for the diagnosis of patients with rising CEA blood levels of unknown origin, thereby significantly affecting patient management. Radioimmunoimaging should become part of the diagnostic workup of patients suspected of having CRC recurrence.

Gallium scans in patients with mediastinal Hodgkin's disease treated with chemotherapy.

To determine the predictive value of gallium scans in patients with mediastinal Hodgkin's disease treated with chemotherapy or combined modality treatment. A retrospective study was performed of 48 patients with mediastinal Hodgkin's disease treated with chemotherapy or combined modality therapy. Patients were monitored with whole-body planar scans (34 patients) or chest single-photon-emission computed tomography (SPECT) plus planar abdominal imaging studies (14 patients). Scans were performed at diagnosis, following three to eight cycles of chemotherapy, and after the end of treatment. The value of gallium scans in modifying treatment and predicting outcome was assessed. All patients studied at the time of diagnosis had abnormal gallium accumulation in the mediastinum. After chemotherapy, four patients had residual mediastinal activity; two patients with persistent activity on planar scans failed to enter remission and died of disease; two other patients with abnormal activity only seen on SPECT had therapy modified and remain in remission. After chemotherapy, 44 patients had a normal gallium scan. Twelve patients with negative scans relapsed, including nine patients with recurrence above the diaphragm. The use of gallium scans after several courses of chemotherapy resulted in a modification of treatment in four patients, including two patients who are apparently cured. However, after negative scans, 20% of patients relapsed above the diaphragm. These results suggest that gallium imaging, including SPECT, is of limited value in predicting disease sterilization, although the number of patients studied with SPECT was small. At present, the major value of gallium scans is to identify patients who may benefit from a modification of treatment.