Optimal Time for 124I PET/CT Imaging in Metastatic Differentiated Thyroid Cancer.

BACKGROUND: The objective of this study was to determine the optimal time for 124I PET/CT imaging to maximize the detection of locoregional and/or distant metastases of differentiated thyroid cancer. METHODS: Differentiated thyroid cancer patients suspected of having metastatic disease were prepared with low-iodine diet and appropriate thyroid-stimulating hormone stimulation. 124I PET and low-dose localization CT were performed over 4 days after oral administration of 31.5 or 62.9 MBq (0.85 or 1.7 mCi) of 124I. Each scan was independently reviewed by 2 nuclear medicine physicians. All foci of activity were categorized, and the visual intensity of uptake was scored by a semiquantitative 3-point grading system (1: mild uptake, 2: moderate uptake, 3: intense uptake). Lesion volumes were determined on the CT image or on the PET images. Background (bkg) was also measured for each lesion and on each individual PET image. For each lesion, the mean activity concentration rate per unit administered activity (ACRmean/AA) and lesion-to-bkg ratios were compared across the 5 different time points. The semiquantitative grade and the quantitative measurements were compared. RESULTS: A total of 45 124I PET/CT scans were reviewed for 9 patients. In the visual assessment, a total of 31 foci suggestive for or highly suggestive of metastasis were identified on 124I PET/CT. Of these, 6 were seen on the 2-h, 18 on the 24-h, 27 on the 48-h, 24 on the 72-h, and 20 on the 96-h scan. There was a significant difference between the 24- and 48-h scans in the total number of foci (ie, locoregional and distant metastasis) (P < 0.05) and in the number of distant metastases (P < 0.05). The 24-, 48-, and 72-h scans identified the same number of locoregional foci. The 48-h scan visualized more of the distant metastases than any other time point. 124I PET/CT with dual-time-point imaging was superior to single-time-point imaging (97% vs 87%). In the quantitative analysis, the median ACRmean/AA was highest at 24 and 48 h, and the median lesion-to-bkg ratio was variable for different lesion locations. For lung metastases, the highest median lesion-to-bkg ratio was at 72 and 96 h. CONCLUSIONS: 124I PET/CT with dual-time-point imaging was superior to any single-time-point imaging (P < 0.10). Based on the visual assessment, dual time points at 48 + 72 h or 48 + 96 h yielded the highest lesion detection rate, whereas for single-time-point imaging, the 48-h images had the highest lesion detection rate. If the 48-h scan is completely negative or has negative 124I uptake in the region of interest, then a 72- or 96-h scan may be valuable. If lung metastases are suspected, then one should consider additional imaging at 72 or 96 h.

Recombinant Human Thyroid-Stimulating Hormone Versus Thyroid Hormone Withdrawal in 124I PET/CT-Based Dosimetry for 131I Therapy of Metastatic Differentiated Thyroid Cancer.

Patients with metastatic differentiated thyroid cancer (DTC) may be prepared using either thyroid-stimulating hormone withdrawal (THW) or recombinant human thyroid-stimulating hormone (rhTSH) injections before 131I administration for treatment. The objective of this study was to compare the absorbed dose to the critical organs and tumors determined by 124I PET/CT-based dosimetry for 131I therapy of metastatic DTC when the same patient was prepared with and imaged after both THW and rhTSH injections. Methods: Four DTC patients at MedStar Washington Hospital Center were first prepared using the rhTSH method and imaged by 124I PET/CT at 2, 24, 48, 72, and 96 h after administration of approximately 30-63 MBq of 124I. After 5-8 wk, the same patients were prepared using the THW method and imaged as before. The 124I PET/CT images acquired as part of a prospective study were used to perform retrospective dosimetric calculations for 131I therapy for the normal organs with the dosimetry package 3D-RD. The absorbed doses from 131I for the lungs, liver, heart, kidneys, and bone marrow were obtained for each study (rhTSH and THW). Twenty-two lesions in 3 patients were identified. The contours were drawn on each PET image of each study. Time-integrated activity coefficients were calculated and used as input in OLINDA/EXM sphere dose calculator to obtain the absorbed dose to tumors. Results: The THW-to-rhTSH organ absorbed dose ratio averaged over 5 organs for the first 3 patients was 1.5, 2.5, and 0.64, respectively, and averaged over 3 organs for the fourth patient was 1.1. The absorbed dose per unit administered activity to the bone marrow was 0.13, 0.086, 0.33, and 0.068 mGy/MBq after rhTSH and 0.11, 0.14, 0.22, and 0.080 mGy/MBq after THW for each patient, respectively. With the exception of 3 lesions of 1 patient, the absorbed dose per unit administered activity of 131I was higher in the THW study than in the rhTSH study. The ratio of the average tumor absorbed dose after stimulation by THW compared with stimulation by rhTSH injections was 3.9, 27, and 1.4 for patient 1, patient 2, and patient 3, respectively. The ratio of mean tumor to bone marrow absorbed dose per unit administered activity of 131I, after THW and rhTSH, was 232 and 62 (patient 1), 12 and 0.78 (patient 2), and 22 and 11 (patient 3), respectively. Conclusion: The results suggest a high patient variability in the overall absorbed dose to the normal organs per MBq of 131I administered, between the 2 TSH stimulation methods. The tumor-to-dose-limiting-organ (bone marrow) absorbed dose ratio, that is, the therapeutic index, was higher in the THW-aided than rhTSH-aided administrations. Additional comparison for tumor and normal organ absorbed dose in patients prepared using both methods is needed before definitive conclusions may be drawn regarding rhTSH versus THW patient preparation methods for 131I therapy of metastatic DTC.

Effects of Dosimetrically Guided I-131 Therapy on Hematopoiesis in Patients With Differentiated Thyroid Cancer.

OBJECTIVE: The objective of the study was to evaluate the effects of dosimetrically guided I-131 prescribed activities on hematopoiesis reflected by changes in complete blood counts (CBCs). DESIGN: This was a retrospective analysis. SETTING: The study was conducted at an academic center. PATIENTS: A total of 152 patients with differentiated thyroid cancer who had 185 dosimetrically guided I-131 treatments. INTERVENTIONS: There were no interventions. MAIN OUTCOME MEASURES: Repeated-measure ANOVA was used for the analysis of the differences in the averages of CBCs that were documented at baseline and 1, 6, 12, 24­36, and 48­60 months after I-131 treatment. RESULTS: All parameters decreased to their respective nadir at 1 month and then gradually returned toward baseline values. White blood cells (WBCs) and platelets (PLTs) were the most significantly affected cells. At 1 month, the decrease was 29.6% (P < .0001) for WBCs and 25% (P < .0001) for PLTs, whereas at 12 months, the decrease was 15.5% (P < .0001) and 13% (P < .0001), respectively. Lymphocytes appeared to be more susceptible to I-131 than neutrophils (ANCs). The decreases were small in absolute numbers for red blood cells, hematocrit and hemoglobin not surpassing 10%. Multivariate analysis demonstrated that the ratio of administered prescribed activity-to-maximum tolerated activity was associated with the decreases in WBCs (P = .0038), ANCs (P = .0063), and red blood cells (P = .029), with borderline significance for PLTs (P = .057) and hemoglobin (P = .057). CONCLUSIONS: Dosimetrically guided I-131 resulted in statistically significant decreases in CBC parameters, which were more prominent in WBCs and PLTs. Lymphocytes were more severely affected than ANCs, whereas all parameters reached a nadir at 1 month and then gradually returned toward baseline values over the 5-year follow-up of our study.

Validation of a Simple Thyroid Cancer Dosimetry Model Based on the Fractional Whole-Body Retention at 48 Hours Post-Administration of (131)I.

BACKGROUND: Standard dosimetric methods to determine the maximum tolerated activity (MTA) of (131)I for the treatment of metastatic, well-differentiated thyroid cancer (DTC) are time-consuming and require complex analysis. As a result, reliable, accurate, and simplified methods are desirable. The objective of this study was to evaluate the validity of a simple regression dosimetry model. METHOD: Previously, the authors reported a bi-exponential model for estimating the MTA of (131)I for the treatment of metastatic DTC based on a limit of 2 Gy to the blood. This model uses the patient's body surface area (BSA) along with the fractional whole-body retention (WBR) at 48 hours following oral administration of a diagnostic dosage of (131)I. A bi-exponential regression model was developed between the MTA normalized to the patient's BSA and the percent retention value at the 48-hour time point (R): MTA (GBq)/BSA (m(2)) = (13.91 · e(-0.0387R) + 42.33 · e(-0.8522R)). In this study, the same model was applied to a different set of adult patients referred for dosimetry and possible (131)I treatment of DTC under conditions of thyroid hormone withdrawal or recombinant human thyrotropin (rhTSH) stimulation. All patients (n = 170; 96 female) referred to the authors' clinic for dosimetry and possible (131)I treatment for metastatic DTC during the collection period were included in this study, apart from those undergoing renal dialysis. The MTA predicted (MTAp) using the model described above was compared to the measured MTA (MTAm), with statistical analysis performed using ProStat v4.5. RESULTS: In this group, the MTAm ranged from 2.3 to 41.1 GBq. The linear correlation between the MTAp and MTAm was excellent (r = 0.96), with an average deviation of only ± 1.2%. However, to avoid overdosing a patient on the basis of the MTAp, a weighting factor (<1.0) should be applied (e.g., using a value of 0.7 would result in only one patient receiving a prescribed activity of (131)I that exceeded the MTAm [<3%]). CONCLUSIONS: The % 48-hour WBR as determined by the bi-exponential function noted herein with reasonable restrictions has been validated as a reliable simplified dosimetry model.

Recombinant human thyroid-stimulating hormone versus thyroid hormone withdrawal in the identification of metastasis in differentiated thyroid cancer with 131I planar whole-body imaging and 124I PET.

UNLABELLED: Various studies have compared the detection of functioning residual thyroid tissue after thyroidectomy using radioiodine whole-body (WB) imaging following preparation of patients with injections of recombinant human thyroid-stimulating hormone (rhTSH) and thyroid hormone withdrawal (THW). However, metastases may have radiopharmacokinetics different from normal thyroid tissue. The objective of this study was to evaluate these 2 methods of patient preparation for the detection of metastases from differentiated thyroid cancer (DTC) using (131)I WB imaging and (124)I PET. METHODS: A prospective study approved by the institutional review board was conducted at Washington Hospital Center from 2006 to 2010 recruiting patients who had DTC, were suspected of having metastasis from DTC (e.g., elevated thyroglobulin level without thyroglobulin antibodies, positive results on recent fine-needle aspiration, suspected enlarging mass, and abnormal findings suggesting metastasis on a diagnostic study) and were referred for (131)I WB dosimetry. All patients subsequently underwent both (131)I WB imaging and (124)I PET performed using the same preparation. All foci of uptake identified on these scans were categorized in a masked manner by consensus of 2 physicians in the following manner: 1, definite physiologic uptake or artifact; 2, most likely physiologic uptake or artifact; 3, indeterminate; 4, most likely locoregional metastases in the neck bed; 5, most likely distant metastases; or 6, definite distant metastases. Foci categorized as 4, 5, and 6 were considered positive for functioning metastases. RESULTS: Of 40 patients evaluated, 24 patients were prepared with rhTSH and 16 with THW. No statistical difference was noted between the 2 groups for any of the parameters evaluated, including serum thyroglobulin. The percentages of patients with positive foci detected on the rhTSH (131)I and THW (131)I WB scans were 4% (1/24) and 63% (10/16), respectively (P < 0.02). The number of foci detected on the rhTSH (131)I and THW (131)I WB scans were 2 and 58, respectively (P < 0.05). When (124)I PET was used for imaging, the percentages of patients with foci detected on the rhTSH and THW scans were 29% (7/24) and 63% (10/16), respectively (P < 0.03). The number of foci detected on the rhTSH and THW scans were 17 and 117, respectively (P < 0.03). CONCLUSION: Significantly more foci of metastases of DTC may be identified in patients prepared with THW than in patients prepared with rhTSH.

Efficacy of dosimetric versus empiric prescribed activity of 131I for therapy of differentiated thyroid cancer.

BACKGROUND: The optimal management of high-risk patients with differentiated thyroid cancer (DTC) consists of thyroidectomy followed by radioiodine ((131)I) therapy. The prescribed activity of (131)I can be determined using two approaches: 1) empiric prescribed activity of (131)I (E-Rx); and 2) dosimetry-based prescribed activity of (131)I (D-Rx). AIM: The aim of the study was to compare the relative treatment efficacy and side effects of D-Rx vs. E-Rx. METHODS: A retrospective analysis was performed of patients with distant metastases and/or locoregionally advanced radioiodine-avid DTC who were treated with either D-Rx or E-Rx. Response to treatment was based on RECIST (Response Evaluation Criteria in Solid Tumors) 1.1 criteria. RESULTS: The study group consisted of 87 patients followed for 51 ± 35 months, of whom 43 were treated with D-Rx and 44 with E-Rx. Multivariate analysis, controlling for age, gender, and status of metastases revealed that the D-Rx group tended to be 70% less likely to progress (odds ratio, 0.29; 95% confidence interval, 0.087-1.02; P = 0.052) and more likely to obtain complete response (CR) compared to the E-Rx group (odds ratio, 8.2; 95% confidence interval, 1.2-53.5; P = 0.029). There was an association in the D-Rx group between the observed CR and percentage of maximum tolerable activity given as a first treatment of (131)I (P = 0.030). The advantage of D-Rx was specifically apparent in the locoregionally advanced group because CR was significantly higher in D-Rx vs. E-Rx in this group of patients (35.7 vs. 3.3%; P = 0.009). The rates of partial response, stable disease, and progression-free survival, as well as the frequency of side effects, were not significantly different between the two groups. CONCLUSION: Higher efficacy of D-Rx with a similar safety profile compared to E-Rx supports the rationale for employing individually prescribed activity in high-risk patients with DTC.

Radiopharmacokinetics of radioiodine in the parotid glands after the administration of lemon juice.

BACKGROUND: The ability of sialagogues to increase or decrease radiation induced-sialoadenitis and/or xerostomia after therapeutic administration of ¹³¹I is controversial. To evaluate this we measured the radiopharmacokinetics of ¹²³I in the parotid glands (PGs) after its administration of lemon juice (LJ). METHODS: A retrospective review was performed on all patients who had a salivary gland scan performed before ¹³¹I therapy between July 2008 and April 2009 at the Washington Hospital Center. Two hours after ¹²³I was given orally, dynamic scintigraphy was initiated. Five milliliters of LJ was given 5 minutes later. Then, the patient was imaged for 1 hour (phase 1) at which point the sequence was repeated (phase 2). Twenty-three patients were studied. For each PG, the presence or absence of uptake was assessed, and based on background corrected counts, the mean, range, and standard deviation were determined for multiple radiopharmacokinetic parameters such as (i) percent radioiodine washout, (ii) time from LJ administration to re-accumulation of radioiodine to pre-LJ activity, and (iii) percent reduction in radiation absorbed dose to the PGs if LJ had been re-administered at the time the radioiodine activity re-accumulated to the pre-LJ activity. RESULTS: The mean ± one standard deviation and range for percent washout were 84% ± 18% (35%-100%) and 83% ± 21% (37%-100%) in phase 1 and 2, respectively. The times from LJ to re-accumulation of the radioiodine to the pre-LJ activity were 21 ± 10 minutes (4-45 minutes) and 40 ± 14 minutes (12-62 minutes) for phase 1 and 2, respectively. The estimated percent reduction in radiation absorbed dose to the PGs following the first and second administration of LJ was 37% ± 14% (13%-93%) and 47% ± 16% (21%-97%), respectively. CONCLUSIONS: The washout of radioiodine from the PGs is rapid but transient. Early repeat administration may result in continued and cumulative reduction of radiation absorbed dose in the PGs.

(124)I positron emission tomography versus (131)I planar imaging in the identification of residual thyroid tissue and/or metastasis in patients who have well-differentiated thyroid cancer.

BACKGROUND AND OBJECTIVE: (124)I emits a positron and can be imaged with a positron emission tomography (PET) scanner. The objective of this study was to compare the ability of diagnostic (124)I PET images versus (131)I planar whole-body imaging in detecting residual thyroid tissue and/or metastatic well-differentiated thyroid cancer (WDTC). METHODS: Patients were recruited prospectively for this study who (i) had WDTC, (ii) were suspected of having metastatic WDTC, and (iii) were referred for (131)I whole-body dosimetry. The prescribed activity was 1-2 mCi (37-74 MBq) and 1.7 mCi (62.9 MBq) for (131)I and (124)I, respectively. For each image, one blinded reader (D.V.N.) categorized every focus of (131)I and (124)I radioiodine uptake as 1 = definite physiological uptake/artifact, 2 = most likely physiological uptake/artifact, 3 = indeterminate, 4 = residual thyroid tissue/metastases in the neck/bed, 5 = most likely metastases, or 6 = definite metastases. Foci categorized as 4, 5, or 6 were considered positive. When available, foci categorized as 4, 5, or 6 were correlated with other diagnostic studies. RESULTS: Of the 25 patients, 8 patients (32%) had more positive foci on (124)I images than on (131)I, of which 3 patients to date have had metastases confirmed in one or more of the additional positive (124)I foci. (124)I demonstrated the same number of foci as on (131)I in 16 patients (14 with no positive foci, and 2 with two positive and five positive foci each). One patient had one additional positive focus on (131)I not seen on (124)I, which has not yet been confirmed as a metastasis. A total of 97 positive foci were identified on either (124)I or (131)I. (124)I identified 49 positive foci not seen with (131)I, and (131)I identified one positive focus not seen with (124)I. CONCLUSION: Relative to (131)I planar whole-body imaging, (124)I PET identified as many as 50% more foci of radioiodine uptake suggestive of additional residual thyroid tissue and/or metastases in as many as 32% more patients who had WDTC.

Effective reduction of brown fat FDG uptake by controlling environmental temperature prior to PET scan: an expanded case series.

INTRODUCTION: Brown fat uptake of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) on a positron emission tomography (PET) scan may limit the ability to assess for cancer. Previously, Garcia et al. demonstrated in ten patients a significant decrease in brown fat uptake of 2-deoxy-2-[F-18]fluoro-D: -glucose (FDG) after controlling the patient's environmental temperature. OBJECTIVE: The objective of the current study is to validate the effectiveness of controlled environmental temperature (CET) to reduce physiologic brown fat (BF) FDG uptake on a PET scan in a larger series. METHOD: A retrospective review was performed from January 2002 to October 2007 of patients who had (1) a pattern of FDG uptake on PET scan consistent with BF, (2) no evidence of cancer by computed tomography in the regions of interest noted below, (3) repeat scan with CET within 4 months of the 1st PET scan, and (4) no use of drugs reported to reduce BF FDG uptake (e.g., benzodiazepine, beta-blockers, reserpine) unless they were used identically prior to and during both studies. The FDG-PET and controlled environmental temperature-positron emission tomography (CET-PET) scans were performed as per protocol. The non-CET and CET-PET images were blinded/randomized, and three physicians assessed three regions (right neck, left neck, and paraspinal area) semiquantitatively using the following scale: "0" (background [bkgd]), 1 + (> bkgd < liver), 2 + (equal to liver), 3 + (> liver). Standard uptake value (SUV) data was recorded. Results were analyzed using a two-tailed t test. RESULTS: Of 8,640 FDG-PET scans performed, 30 patients (four male, 26 female) met the above criteria. The median age was 36 years (range, 12-60 years). The mean (± 1 standard deviation) of differences in the scores between the two studies for right neck, left neck, and paraspinal regions, respectively, were for reader 1:(2.1 ± 1.37), (1.95 ± 1.43), and (1.85 ± 1.26); reader 2 (2.3 ± 1.40), (1.70 ± 1.13), and (1.77 ± 1.13); reader 3 (2.17 ± 1.17), (2.20 ± 1.18), and (0.50 ± 1.30); for maximum SUV score (3.4 ± 2.9), (3.3 ± 2.9), and (1.77 ± 1.13). All p values were <0.001. CONCLUSION: In this larger series, CET effectively reduced the false-positive (18)FDG uptake in BF on PET scans without the use of drugs.

Utility of the radioiodine whole-body retention at 48 hours for modifying empiric activity of 131-iodine for the treatment of metastatic well-differentiated thyroid carcinoma.

BACKGROUND: Dosimetry has been used to help identify when empiric dosages of 131-I treatment for suspected metastatic well-differentiated thyroid carcinoma (WDTC) may be increased or should be decreased, but dosimetry is complex, and easier approaches would be useful. The three objectives of this study were to assess the utility of the percent whole-body retention of 131-I at 48 hours (%WBR(48hr)) in identifying patients with WDTC in whom the therapeutic empiric prescribed activity of 131-I might be increased/decreased, to evaluate the thresholds proposed by Sisson et al. in 2003 for increasing or decreasing activity, and to determine the relationship between %WBR(48hr) and maximum tolerated activity (MTA). METHOD: A retrospective review was conducted of patients who had WDTC, total thyroidectomy, suspected metastatic disease, thyroid hormone withdrawal, and 131-I dosimetry. The %WBR(48hr) was determined based on the Benua-Leeper dosimetry protocol, and the four thresholds and recommendations of Sisson et al., 2003 for the use of %WBR(48hr) were evaluated relative to an empiric activity (EA) of 7.4 GBq of 131-I. A biexponential equation was determined from the %WBR(48hr) data. RESULTS: Of 142 patients, 47 patients had a %WBR(48hr) of <9%, and all could have received more than the EA of 7.4 GBq with an average of 21.0 GBq (incremental range of 6.8-23.2 GBq). Ten patients had a %WBR(48hr) < or = 5%, and all could have had their EA of 7.4 GBq safely increased by at least 250%. Conversely, if the %WBR(48hr) was >24.8%, then 7 of 14 of these patients would have exceeded the MTA by 0.37-3.18 GBq with an EA of 7.4 GBq. Finally, for patients with a %WBR(48hr) > 40%, five of six patients would have exceeded the MTA by 0.85-3.18 GBq. A biexponential regression equation is presented. CONCLUSION: We conclude that, with respect to the treatment of metastatic epithelial cell thyroid cancer, the %WBR(48hr) of 131-I helps identify those patients in whom the empiric therapeutic prescribed activity of 131-I may be increased or should be decreased so as not to exceed the MTA and that Sisson et al.'s thresholds published in 2003 are applicable. We favor a biexponential regression model using the %WBR(48hr) and a lower limit threshold as a potentially useful method for determining how much an empiric therapeutic prescribed activity of 131-I can be increased or decreased.

Salivary gland protection with sialagogues: a case study.

BACKGROUND: To decrease the severity and frequency of radiation sialoadenitis, postponement of the use of sialagogues has been proposed for the first 24 hours after (131)I treatment for well-differentiated thyroid cancer. One proposed mechanism is that sialagogues increased salivation and salivary blood flow resulting in greater radioiodine uptake in the salivary glands-a rebound effect. This case study demonstrates no rebound effect. METHODS: A 33-year-old woman with well-differentiated thyroid cancer desired to know whether she would have a rebound effect if she used sialagogues during the 24-hour period after her (131)I treatment. Salivary images of the parotid glands were initiated 2 hours after the administration of (131)I for her whole body scan. Lemon juice was administered. Background corrected time-activity curves were obtained for both parotid glands. The potential reduction in radiation absorbed dose to the parotid glands secondary to the administration of lemon juice was calculated. RESULTS: The time-activity curves demonstrated that the (131)I in the right and left parotid glands decreased rapidly after lemon juice by 87% and 83%, respectively, with return to pre-lemon juice levels by 30 and 13 minutes in the right and left parotid glands, respectively. However, at no time during the 1 hour of imaging did the uptake in either parotid gland significantly exceed the pre-lemon juice levels of activity. The potential reduction of radiation absorbed dose to the parotid glands secondary to the use of lemon juice ranged from as much as 30% to 67%. CONCLUSION: This case study demonstrates 1) an approach to assess whether an individual patient will have increased or decreased radioiodine uptake in the salivary glands after administration of sialagogues without the administration of any additional radioiodine, 2) a decrease of radioiodine uptake in the salivary glands after lemon juice without a rebound effect, and 3) a potential reduction of radiation absorbed dose with administration of sialagogues.

The utility of radioiodine scans prior to iodine 131 ablation in patients with well-differentiated thyroid cancer.

BACKGROUND: The utility of radioiodine (RAI) scans prior to (131)I ablation is controversial. The objective of this study was to evaluate the utility of RAI scans prior to (131)I ablation in patient with well-differentiated thyroid cancer. METHOD: All RAI scans performed prior to (131)I ablation from July 2000 to November 2006 at Washington Hospital Center were reviewed retrospectively. Patients were excluded who were suspected of having 1) loco-regional disease, 2) distant metastases, and/or 3) physiological uptake that might alter management prior to the pre-ablation RAI scans. RAI scans were performed either 24 hours after dosing with 37-148 MBq of (123)I or 48 hours after dosing with 37-148 MBq of (131)I with imaging of the whole body, the thyroid bed/neck with a pinhole collimator, and the neck and chest with a parallel-hole collimator. One reviewer blindly evaluated each set of scans using six criteria, and for the purpose of this study, the thresholds for each criterion for which the patient's management may have been altered prior to (131)I ablation are noted in parentheses: 1) the number of foci of RAI uptake in thyroid bed/neck (0 or > or =6), 2) the location(s) of these foci in the thyroid bed/neck (outside the thyroid bed), 3) the size of the largest foci in thyroid bed/neck (> or =1 lobe), 4) the percent uptake in the thyroid bed/neck (> or =15%), 5) uptake suggestive of distant metastases, and 6) significant altered biodistribution (e.g., any breast, marked salivary gland, or marked gastrointestinal uptake). RESULTS: Of 355 sets of scans reviewed, 53% of patients had findings on the RAI scans that might have altered the patient's management prior to their (131)I ablation. The data grouped by the criteria noted above were 1) 12% with six or more foci suggesting local metastases and 6% (22) with no focal uptake, 2) 14% with suggestion of lymph node metastases, 3) 1.1% with at least one focus > or =1 lobe, 4) 8% with > or =15% uptake, 5) 4% with distant metastases, 6) 16% demonstrating altered distribution with 6% breast, 3% salivary, 10% GI, and 0.3% urinary bladder. CONCLUSION: Pre-ablation RAI scans demonstrate a significant number of findings that may alter the management of patients with well-differentiated thyroid cancer prior to (131)I ablation.

Utility of PET/neck MRI digital fusion images in the management of recurrent or persistent thyroid cancer.

BACKGROUND: Approximately 30% of thyroid cancer patients present with reappearing disease within 40 years of initial diagnosis. Hence, sensitive postsurgical monitoring techniques are imperative to successful long-term care. The objective of this study was to assess the added clinical utility of a combined positron emission tomography/magnetic resonance imaging (PET/MRI) of the neck in conjunction with standard imaging in the detection of recurrent thyroid carcinoma. We define standard imaging as a neck sonogram, 131I scan, computed tomography, and MRI. METHODS: This study included 34 patients treated for thyroid cancer at Washington Hospital Center. All patients had previously undergone near-total or total thyroidectomy, standard follow-up imaging studies, and laboratory studies. Twenty-nine of thirty-four patients had received at least one 131I treatment prior to the study. Each patient received a PET and MRI scan, and these images were subsequently digitally fused. RESULTS: Individually and blinded, four endocrinologists retrospectively reviewed all information in patient charts prior to PET and PET/MRI coregistration. A clinical assessment and treatment plan were devised with these data. Following the initial assessment, the endocrinologists were provided results from the PET and PET/MRI fusion studies and asked to make a revised assessment and treatment plan. For each patient, the physicians categorized PET/MRI fusion results as providing new information that altered the initial treatment plan, providing new information that confirmed the initial treatment plan, or providing no additional information. On average, PET/MRI coregistration provided additional information that altered the treatment plan in 46% of the cases, provided additional information that confirmed the treatment plan in 36% of cases, and did not provide any additional information in 18% of cases. CONCLUSION: The combination of structural and functional data that PET/neck MRI fusion offers provided further information in an overwhelming majority of thyroid cancer patients in this study. Thus PET/MRI can be a useful tool in surgical planning, radioactive iodine therapy decisions, and determining the level of follow-up necessary for each patient.

Radioiodine therapy for thyroid cancer and hyperthyroidism in patients with end-stage renal disease on hemodialysis.

Treatment with radioactive iodine ((131)I) may be necessary for thyroid cancer or for hyperthyroidism in patients with end-stage renal disease who require hemodialysis. Because (131)I is cleared mainly by the kidneys in patients with normal renal function, many issues arise in patients who require (131)I treatment but who are on hemodialysis. This paper presents a case report of a patient on dialysis who required treatment with (131)I for thyroid cancer. We describe a mathematical model, which suggests that the treatment dose of (131)I for a patient with thyroid cancer on hemodialysis would be approximately 13%-28% of a typical empiric dose of (131)I for a patient with normal renal function. Also, we present a comprehensive review and discussion of the literature on patients who are receiving hemodialysis who were treated with (131)I for either thyroid cancer or hyperthyroidism. Using a multidisciplinary approach and special precautions, (131)I therapy can be administered safely and effectively for patients with thyroid cancer or hyperthyroidism who are receiving hemodialysis.

Measuring the impact of passenger restrictions on new teenage drivers.

Passenger restrictions for new teenage drivers that became law in 1998 in California provide an opportunity to study the effectiveness of such laws in reducing the number of passengers as well as the influence of teenage passengers on novice drivers. Using fatal and injury crash data from California's Statewide Integrated Traffic Records System, this study found that teenage passengers are a causal factor in crashes of 16-year-old drivers and that in the three years following implementation of the new law, the average number of teenage passengers carried by 16-year-olds decreased by approximately 25%. Without considering the beneficial effect of a decrease in the crash rate, the decrease in the number of teenage passengers in actual crashes resulted in an estimated saving of eight lives and the prevention of 684 injuries over a three-year period.

Standardization and quantification of radionuclide solid gastric-emptying studies.

UNLABELLED: The purposes of this investigation were to standardize and validate a simple quantitative method for performing radionuclide solid gastric emptying that can be used for any dual-head gamma-camera and to establish reference values. METHODS: After eating a solid meal (egg sandwich) labeled with a radionuclide, 20 healthy volunteers (9 male, 11 female) underwent a 90-min gastric-emptying study performed with a triple-head gamma-camera. Two sets of 3 simultaneous projections were acquired sequentially for 30 s each: anterior, right posterior oblique (RPO), left posterior oblique (LPO), posterior, left anterior oblique (LAO), and right anterior oblique (RAO), and this sequence was repeated continuously for 90 min. Time-activity curves were generated using a gastric region of interest for each of the views as well as the conjugate-view geometric mean (GM) data for the anterior/posterior, LAO/RPO, and RAO/LPO combinations. Quantitative parameters were determined: percentage gastric emptying (%GE) at 90 min, half-time (min) based on an exponential fit, and clearance rate (%/min) based on a linear fit. Reference values were determined on the basis of a 95% confidence interval of the t distribution. The results were statistically analyzed and compared. RESULTS: The %GE reference values were greater for the anterior/posterior GM (>or=33%) than for the LAO (>or=31%) and anterior (>or=30%) GMs. The 3 %GE GM methods, the 3 exponential-fit GM methods, and the 3 linear-fit GM methods had high correlation coefficients (r >or= 0.874), and with only a single exception, there was no statistical difference among them. The LAO method and LAO/RPO GM mean method correlated strongly (r = 0.900) and had similar mean values (52% vs. 51%) and reference values (29% vs. 30%). All 3 methods of GM quantification also correlated strongly, and there was no significant difference among them. CONCLUSION: We have described and validated a simple method for radionuclide solid gastric emptying that can be used with a dual-head gamma-camera. We recommend the anterior/posterior GM method and have established reference values (>or=33%).

Dosimetrically determined doses of radioiodine for the treatment of metastatic thyroid carcinoma.

In the absence of definitive studies relating radioiodine dose to outcomes, selection of a dose of radioiodine to treat metastatic thyroid carcinoma is problematic, and several approaches have been used. These include empiric fixed doses and doses used on dosimetric approaches specific for each patient. This paper is a review of the rationale and technique for dosimetrically-determined doses of radioiodine for the treatment of metastatic thyroid carcinoma. This review (1) discusses the alternatives for selection of a dose, (2) discusses the two major approaches for determining radioiodine doses dosimetrically, (3) briefly reviews several modifications of these approaches, (4) reviews the literature regarding the results, (5) discusses the side effects of these different approaches, and (6) concludes with recommendations for patient management and future research. This review does not address use of dosimetrically-determined doses of radioiodine for the initial ablation of thyroid tissue postoperatively.