24-hour Imaging Research Articles

Effect of Distal Embolization on Myocardial Perfusion Reserve After Percutaneous Coronary Intervention

Studies have shown that a subset of patients demonstrate persistent impairment in microcirculatory function after percutaneous coronary intervention (PCI). Distal embolization of plaque contents has been postulated as the main mechanism for this. We sought to investigate this further by evaluating PCI-induced changes in myocardial perfusion reserve index (MPRI) over time in segments with "distal-type" procedure-related myonecrosis using high-resolution quantitative cardiovascular magnetic resonance imaging. Forty patients undergoing PCI were studied with pre-PCI and 24-hour post-PCI delayed-enhancement magnetic resonance imaging and first-pass perfusion magnetic resonance imaging at rest and stress. Twenty patients underwent a third magnetic resonance imaging scan at 6 months. For perfusion imaging, 3 short-axis images were acquired during every heartbeat with a T1-weighted turboFLASH sequence. MPRI was calculated as the ratio of hyperemic to resting myocardial blood flow and subdivided according to the presence and location of new delayed hyperenhancement. Twenty-one patients demonstrated new distal hyperenhancement after PCI. Mean MPRI in revascularized myocardial segments not demonstrating new HE was significantly increased after the procedure (2.06 [95% CI, 1.99 to 2.13] before PCI and 2.52 [95% CI, 2.42 to 2.62] after PCI; P<0.001). In contrast, MPRI in segments with distal hyperenhancement was reduced after PCI (2.16 [95% CI, 1.95 to 2.37] before PCI; 2.00 [95% CI, 1.82 to 2.19] after PCI; mixed-model z=-4.82; P<0.001). Changes in mean MPRI 24 hours after PCI in segments upstream to new injury were not significantly different compared with perfusion changes in remote myocardium (z=-0.68; P=0.50). At 6 months after the procedure, mean MPRI in segments with new injury improved significantly compared with MPRI measured in these segments at 24 hours after PCI. MPRI is reduced in myocardial segments that demonstrate new distal irreversible injury at 24 hours after PCI. These reductions are confined to the segments with injury and do not affect the entire supply territory of the culprit vessel.

Hepatobiliary Scintigraphy With SPECT in Infancy

Hepatobiliary scintigraphy (HBS) is an important investigation for the diagnosis of biliary atresia (BA) and its differentiation from causes of conjugated hyperbilirubinemia that do not require surgical intervention. Delayed imaging at 24 hours and phenobarbitone augmentation for 5 days has been required to achieve high sensitivity and specificity with current techniques. This study explores whether adding single photon emission computed tomography (SPECT) performs as well as existing methods without requiring delayed 24-hour imaging and whether the phenobarbitone premedication is necessary in all cases. A retrospective analysis of 105 HBS studies on 94 patients was performed. HBS included SPECT at 4 to 6 hours postinjection when no tracer was seen in the gastrointestinal tract in the first 60 minutes. This was done in 80 patients. Gastrointestinal activity was seen in 14 patients within 60 minutes. For 4- to 6-hour studies, standard HBS and HBS with SPECT data showed a sensitivity of 100% for the diagnosis of BA. The specificity, accuracy, and positive likelihood ratios (PLR) were 67%, 75%, and 3 (confidence interval [CI]=2.03-4.16) for planar imaging at 4 to 6 hours and 90%, 93%, and 10 (CI=4.42-19) for 4- to 6-hour planar and SPECT imaging. When the 11 patients who had phenobarbitone stimulation were included, the results improved to 97%, 98%, and 30 (CI=7.06-80). The addition of SPECT 4 to 6 hours postinjection of tracer significantly improves the diagnostic accuracy of hepatobiliary scintigraphy compared with planar imaging alone. This accuracy is as good as HBS performed after phenobarbitone stimulation. The combined technique of HBS with SPECT and phenobarbitone has the highest accuracy. Delayed imaging at 24 hours is usually not necessary.

Cost-Effectiveness of Intravenous Thrombolysis With Alteplase Within a 3-Hour Window After Acute Ischemic Stroke

The aim of this study was to assess the costs and cost-effectiveness of intravenous thrombolysis treatment with alteplase (Actilyse) of acute ischemic stroke with 24-hour in-house neurology coverage and use of magnetic resonance imaging. A health economic model was designed to calculate the marginal cost-effectiveness ratios for time spans of 1, 2, 3 and 30 years. Effect data were extracted from a meta-analysis of six large-scale randomized and placebo-controlled studies of thrombolytic therapy with alteplase. Cost data were extracted from thrombolysis treatment at Aarhus Hospital, Denmark, and from previously published literature. The calculated cost-effectiveness ratio after the first year was $55,591 US per quality-adjusted life-year (base case). After the second year, computation of the cost-effectiveness ratio showed that thrombolysis was cost-effective. The long-term computations (30 years) showed that thrombolysis was a dominant strategy compared with conservative treatment given the model premises. A high-quality thrombolysis treatment with 24-hour in-house neurology coverage and magnetic resonance imaging might not be cost-effective in the short term compared with conservative treatment. In the long term, there are potentially large-scale health economic cost savings.

In-111 DTPA-D-Phe1-Octreotide SPECT in a Rare Case of Anorectal Small-Cell Undifferentiated Neuroendocrine Carcinoma

In-111 DTPA-D-Phe1-octreotide (In-111 pentetreotide) is a widely used radiotracer for somatostatin receptor (SSTR) in- vestigations in neuroendocrine (NE) pathology. Cellular SSTR den- sity is directly related to the degree of NE cellular differentiation. Poorly differentiated cell lines show a surface reduction of SSTRs, which may lead to misinterpreting the In-111 pentetreotide scintig- raphy results as negative. A case of anorectal small-cell undifferen- tiated neuroendocrine carcinoma is reported. This pathologic finding is rare, highly aggressive, and associated with a dramatic prognosis. The patient was investigated with In-111 pentetreotide SPECT and low-dose computed tomography (CT) for anatomic reference. De- spite its low degree of differentiation, the tumor showed high tracer uptake characterized by a positive incremental trend as shown by comparison of the 4-hour and 24-hour SPECT images, suggesting specific receptorial binding of In-111 pentetreotide.

Diaphragmatic Paralysis Simulating Pulmonary Infection on Gallium-67 Scan

Ga-67 is a useful agent for imaging infection, especially in the chest, but is not so reliable in the abdomen because of physiological bowel activity. A 64-year-old man with fever of unknown origin received a Ga-67 scan for survey of any occult infection focus. Focal Ga-67 accumulation was noted in the left lower chest region on the 24-hour image, but a different pattern of radioactivity was shown on the 48-hour image after bowel cleansing. On review of the chest radiographs and history, we found bowel activity in the left lower chest secondary to diaphragmatic paralysis masqueraded as pulmonary infection. Diaphragmatic paralysis should be considered as a differential diagnosis of abnormal activity in the chest on Ga-67 scan.

Covered Versus Bare Self-Expanding Stents for Endovascular Treatment of Carotid Artery Stenosis:A Stopped Randomized Trial

To investigate whether filter-protected carotid artery stenting (CAS) using a covered self-expanding stent reduces the risk of cerebral embolization. Fourteen asymptomatic patients (13 men; median age 77 years, IQR 73-83) were enrolled in a randomized pilot trial comparing the rates of cerebral microembolism during and after filter-protected CAS using either a self-expanding covered (n=8) or a bare (n=6) carotid stent. Transcranial Doppler (TCD) monitoring was done during and for 90 minutes after the procedure. Diffusion-weighted magnetic resonance imaging (DW-MRI) was performed before and 24 hours after CAS. Patients were followed for 6 months for neurological events and occurrence of restenosis. A significant reduction in ipsilateral microembolic signals by TCD was observed with the covered (median 1, IQR 0-4) versus the bare stent (median 6, IQR 3-8; p=0.043). Comparison of the preprocedural and 24-hour postprocedural DW-MRI images showed no new ipsilateral lesions but 1 new lesion in the contralateral hemisphere in the covered stent group, resulting in an overall 7% (95% CI 0%-20%) rate of new ischemic lesions. No neurological complications occurred up to 6 months. Restenosis (>70%) occurred in 3 (38%) of 8 patients with the covered versus none of the bare stents (p=0.21). The trial was stopped when the third restenosis of a covered stent was detected. Self-expanding covered stents potentially reduce the risk of cerebral microembolism during and after carotid stenting. However, the problem of in-stent restenosis has to be resolved before these devices can be considered for further investigation.

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Diagnosis of Septic Joint in an Immunosuppressed Patient by Twenty-Four Hour Delayed Imaging with Tc-99m HMPAO Labeled White Blood Cell Scan

A 64-year-old male with a history of allogeneic bone marrow transplantation for lymphoma 10 months earlier presented for evaluation of bacteremia. The white blood cell count was 4,400 cells/microliter with 76% neutrophils. A tagged white blood cell scan was performed to localize the infection. Images obtained 4 hours postinjection of radiolabeled leukocytes displayed no focus of infection, but delayed 24-hour images demonstrated the interval development of markedly increased activity in the left shoulder. Arthrocentesis yielded purulent fluid. We hypothesize that delayed leukocyte migration in this immunosuppressed patient might have accounted for the significant disparity between the standard and delayed scans.

Randomized, double-blind, placebo-controlled trial of vaginal misoprostol for management of early pregnancy failures

To determine whether misoprostol medical management of early pregnancy failures is more effective than expectant management. Patients diagnosed with early pregnancy failures, closed cervix, and minimal vaginal bleeding were randomized to 800 microg of misoprostol or placebo placed vaginally. Patients were evaluated by ultrasound imaging 24 hours and 48 hours after study drug administration, with repeat administration if 24-hour imaging showed a persistent gestational sac. Treatment success was defined as expulsion of uterine contents within 48 hours. Patient follow-up occurred 2 weeks after expulsion of uterine contents. Treatment success occurred in 15 of 18 (83%) misoprostol patients and 2 of 16 (13%) placebo patients (P < .0001). Side effects were similar between groups except for vaginal bleeding, which was more common in the misoprostol group (P = .001). Patient satisfaction and pain perception were similar between groups. Misoprostol appears to be highly effective for treating early pregnancy failures, with few side effects and high patient satisfaction.

Focal lesions of the cerebral white matter in patients with arterial hypertension as evidenced by 5-year prospective study

Studies were conducted in 58 patients (33 males and 25 females) aged 36 to 59 years who had arterial hypertension. 24-hour blood pressure (BP) monitoring and brain magnetic resonance imaging were performed in all the patients before and 5 years after the studies. Focal cerebral white matter lesions (FCWML) that had been absent before was found to appear in 15 (25%) patients; FCWML showed no changes in 12 (21%) patients. There was an increase in the number of FCWML in 17 (30%). The patients in whom FCWML appeared had significantly higher baseline values of BP and its time indices and, on repeated examination, they had only significantly higher time indices of BP. The findings suggest that arterial hypertension is a factor that enhances the likelihood of GCWML and that the use of 24-hour BP monitoring permits identification of a group of patients having a high risk for their appearance.

When is Medical Prophylaxis Cost-effective for Recurrent Calcium Stones?

Medical management is generally recommended for recurrent calcium stones to prevent future episodes. However, in this era of extracorporeal shock wave lithotripsy and outpatient ureteroscopy it is not known whether medical prophylaxis is more cost-effective than treatment of recurrent stone episodes. The cost of medical prophylaxis was compared with the cost of clinically managing recurrent stone episodes, and the stone recurrence rate without prophylaxis (stone frequency) at which these 2 treatment approaches became cost equivalent was determined. An international cost survey was conducted in 10 countries to compare costs of medical prophylaxis and managing recurrent acute stone episodes. Costs of an acute stone episode included an emergency room visit, associated radiographic imaging to confirm diagnosis of a symptomatic stone and outpatient treatment of upper urinary tract stones that did not pass spontaneously. Costs of medical management included an initial limited metabolic evaluation, drug therapy, a followup office visit every 6 months that included a 24-hour urinalysis and radiographic imaging of the kidneys, ureters and bladder once a year. Costs of medical prophylaxis and managing an acute stone episode varied significantly from country to country. The stone frequency at which costs of these management options became equivalent ranged from 0.3 to 4 stone episodes a year. Medical management of a first stone episode is not cost-effective. Cost analysis should be individualized for specific health care plans to determine which practice patterns are most cost-effective for a particular patient with recurrent calcium stone formation.

Twenty-four-hour Tl-201 delayed scan underestimates myocardial viability in patients with acute myocardial infarction after percutaneous transluminal coronary angioplasty.

Myocardial viability in area at risk of acute myocardial infarction (AMI) after reperfusion therapy may be underestimated by the 24-hour images due to reverse redistribution (r-RD). Subjects were 37 AMI patients in whom Tc-99m pyrophosphate (PYP)/Tl-201 dual-isotope SPECT was positive. The 24-hour delayed scan was performed with only a Tl window. One month later, follow up rest Tl SPECT was performed to evaluate myocardial viability. In early (at PYP/Tl-201 dual-isotope SPECT), 24-hour, and one month follow up Tl studies, Tl uptake in the area of AMI was scored into four grades: 3 as normal to 0 as severely reduced. The scores were evaluated. Among the 37 AMI lesions, there were 16 r-RD, 3 RD, 16 fixed defect (FD) and 2 normal (positive PYP and normal Tl). Mean Tl scores were early; 1.4 +/- 1.1, 24-hr; 0.9 +/- 0.9 and one month; 1.3 +/- 1.1. The 24-hour Tl score was lower than the early and one month Tl scores (p < 0.01). Reverse redistribution is frequently observed in an area at risk where PYP SPECT was positive. Nuclear medicine physicians should be aware of the existence of frequent r-RD in Tl scan to avoid the underestimation of myocardial viability in the acute phase after PTCA.

Long-term effect of irradiation on lymph node uptake of interstitially delivered nanoparticulate contrast media.

To characterize the long-term effects of therapeutic doses of ionizing radiation on the uptake and distribution of percutaneously delivered particulate contrast media in normal lymph nodes. Two milliliters of an iodinated nanoparticle suspension (76 mg I/mL) was injected subcutaneously or submucosally into nine normal adult beagles. Region of interest analysis was used to estimate the volume, attenuation, and iodine concentration of opacified targeted lymph nodes and nonopacifled contralateral nodes on 24-hour postinjection CT images. All lymph nodes were then irradiated with 50 Gy in 25 fractions of 2 Gy/d. Contrast-enhanced quantitative CT was repeated 12 months after irradiation. Contrast-enhanced nodes averaged 2.3+/-0.8 times the volume of nonenhanced contralateral nodes before irradiation. The mean attenuation of contrast-enhanced nodes increased to 305 to 380 Hounsfield units from a pre-enhancement value of approximately 25 Hounsfield units. Opacified node volumes after irradiation averaged 61% to 86% of preirradiation volumes but were generally not statistically different. Contrast uptake assessed by average attenuation and iodine concentration decreased significantly by an average of 17% to 22% after irradiation and was significantly less than preirradiation uptake. Qualitatively, irradiated nodes generally appeared smaller than nonirradiated nodes, but the distribution pattern of contrast media did not appear to be appreciably altered. Lymph node irradiation resulted in only minimal decreases in contrast media uptake and node volume at 12 months. These effects presumably would not appreciably alter the potential clinical value of indirect lymphography for evaluating patients undergoing radiation therapy.

Gammagrafía miocárdica con doble isótopo (201Tl en reposo/99mTc-tetrofosmin en esfuerzo) en la detección de hipoperfusión reversible

The dual-isotope technique (rest 201Tl and stress 99mTc-sestamibi) is useful to assess myocardial perfusion in coronary disease patients. 99mTc-labeled tetrofosmin is a radiopharmaceutical whose characteristics are similar to sestamibi. Thus, we decided to use it to detect reversible myocardial hypoperfusion in patients with a background of myocardial infarction and ischemia. A sequential dual-isotope scintigraphy (3 mCi rest 201Tl and 25 mCi stress 99mTc-tetrofosmin) with 24-hour 201Tl redistribution (RD) was performed in 20 patients with previously confirmed myocardial infarction and clinical and ergometric signs of ischemia. Each patient also underwent a stress-redistribution protocol with redistribution at 4 and 24 hours post injection with 201Tl scintigraphy within two weeks of the first study. The qualitative uptake analysis showed no significant differences in the number of myocardial segments with severe reduction of tracer uptake on stress that improved at rest or in RD images, even if 24-hour RD images were considered. The quantitative global uptake analysis showed a similar defect reversibility with both protocols; however if 24-hour RD images were considered the uptake improvement was significant only when compared with the rest 201Tl images in dual-isotope scintigraphy protocol (75+/-8% vs. 81+/-9% of peak activity, rest vs. 24-hour RD; p<0.01) and not when compared with the 4-hour RD in the 201Tl scintigraphy. On the other hand, when only the segments with severely reduced uptake (<50% of peak activity) were analyzed, the 24-hour RD improved myocardial uptake significantly (p<0.001 vs. rest and vs 4-hour RD) in both protocols. We conclude that a sequential dual-isotope rest 201Tl/stress 99mTc-tetrofosmin scintigraphy is comparable with stress-redistribution 201Tl scintigraphy to detect reversible myocardial hypoperfusion; however in both cases, the addition of 24-hour images increases its usefulness in severely hypoperfused segments, if the uptake of the radiopharmaceutic is quantified.

Thallium-201 for Detection of Myocardial Viability: Comparison of Early Postexercise Reinjection and Imaging with 4 and 18–24 Hours Redistribution Imaging

To evaluate the efficacy of an early ²⁰¹Tl reinjection and imaging protocol for reducing the need for conventional 4-hour or optimal 24-hour redistribution imaging (RI) and detecting of myocardial viability, we compared the results of early postexercise Tl reinjection and imaging with those of 4- and 24-hour RI in 74 consecutive patients aged 55 ± 9 years (mean ± SD) who were assessed for myocardial ischemia. One millicurie of Tl was injected promptly after completion of the initial postexercise imaging (PEX) and three additional sets of images were acquired 1, 4 and 18–24 h later. A total of 2,368 segments were evaluated. On PEX, 390 (17%) segments showed defects, of which 287 (74%) showed enhanced Tl uptake at 1-hour RI; 89 (23%) did not change and 14 (4%) showed reverse redistribution. Of the 103 persistent defects, only 27 (7%) showed further fill-in of Tl; 62 (16%) segments showed reverse redistribution at 4-hour RI while at 18- to 24-hour RI 17 (4%) and 47 (12%) segments showed further fill-in of Tl and reverse redistribution, respectively. Finally, after analysis of 4- and 18- to 24-hour RI, the diagnosis changed from myocardial necrosis to ischemia in only 2 (3%) patients. In conclusion, these results suggest that by eliminating the need for an additional delayed set of images for detection of myocardial viability, this protocol reduces the total investigation procedure, is more convenient for the patient, increases patient turnover and expedites the decision-making process.

The 24-hour Tl-201 image in dual isotope myocardial perfusion scintigraphy: clinical utility and prognostic significance.

This study assessed the effect on clinical decision making and the possible prognostic significance of the 24-hour Tl-201 image in patients undergoing Tl-201-MIBI dual-isotope myocardial scintigraphy. The records of all patients who underwent 24-hour Tl-201 imaging as part of their myocardial perfusion study from 1994 to 1996 were reviewed. Follow-up evaluations were obtained from the referring physician or by direct patient contact. Fifty-six patients underwent a total of 57 studies; four patients were lost to follow-up. Of the 53 studies evaluated, 29 showed no change between the standard rest images and the 24-hour images; these patients were reported to have myocardial scar. Of these 29 patients, 25 were treated medically without further evaluation; 24 of these 25 patients remained stable. Four of the 29 patients had further evaluation; 2 patients had coronary artery bypass graft, 1 had a stent placed, and 1 remained stable. Twenty-four patients showed definite improvement or normalization of their study results by 24 hours; they were reported as ischemic. Of these 24 patients, 11 were treated medically without further evaluation; 9 remained stable, whereas 2 had adverse events. The remaining 13 patients required further evaluation; 4 remained stable, whereas 9 had adverse events (4 = increasing angina; 1 = stent; 1 = rotoblator; 2 = percutaneous transluminal coronary angioplasty; 1 = death). Twenty-four-hour imaging contributes to clinical decision making and may identify a subset of patients at risk for subsequent complications.

Manganese-metalloporphyrin (ATN-10) as a tumor-localizing agent: magnetic resonance imaging and inductively coupled plasma atomic emission spectroscopy study with experimental brain tumors.

We examined whether selective tumor accumulation of a novel manganese-metalloporphyrin (ATN-10) occurs in Fisher rats bearing intracerebral 9L gliomas. After intravenous administration of ATN-10, magnetic resonance imaging of brains with tumors or nontumoral vasogenic brain edema was performed. Tissue manganese concentrations were measured by inductively coupled plasma atomic emission spectroscopy until 48 hours after administration of ATN-10, to evaluate its uptake in tumor, normal brain, and peritumoral brain tissue. In magnetic resonance imaging scans, early enhancement was observed in both tumor tissue and regions of nontumoral vasogenic brain edema at 5 minutes after ATN-10 administration. However, delayed enhancement was noted only in tumor tissue, at 24 hours after intravenous injection of ATN-10. Comparison of rat brain specimens and 24-hour magnetic resonance imaging scans revealed that only the viable portions of tumors were enhanced with ATN-10; necrotic regions and areas of peritumoral brain tissue and nontumoral vasogenic edema were not. Significantly greater uptake of ATN-10 was found in tumor samples, compared with normal and peritumoral brain tissue, at 24 hours. A high tumor/normal brain tissue ratio (10.4) was achieved at 24 hours. ATN-10, a manganese-metalloporphyrin, is a potentially useful tumor-localizing agent that accumulates and is preferentially retained in viable tumor tissue.

Is there any advantage to the acquisition of 24-hour thallium images, in the presence of persistent perfusion defects at 4 h after reinjection?

We determined the incidence of delayed 24-h reversibility post thallium-201 reinjection and imaging at 4 h, as well as the prognostic and significance of such delayed reversibility. We studied 46 consecutive patients with persistent thallium-201 perfusion or incompletely reversible single-photon emission tomography (SPET) perfusion defects acquired within 10 min after reinjection performed 4 h after stress. In 38 of 46 patients (82%) 24-h images showed no further reversibility beyond the post-reinjection 4-h study (group A). Eight of 46 patients (17%) demonstrated reversibility on 24-h imaging (group B). Of these eight, three patients showed no improvement compared with the post-stress images, with a mean perfusion score of the abnormal segments of 1. 25+/-0.50 on the 4-h images, and of 3.00 on the 24-h images, where normal is 4. Four patients presented with nine mixed regions. Four of these regions showed an improvement in the mean perfusion score of 2.50+/-0.58 on 4- and 24-h images. Two of them, with moderate/severe defects, demonstrated complete reversibility at 4-h post-reinjection imaging. In addition, five other regions presented no improvement at 4-h imaging, but showed an improvement in the mean perfusion score from 0.80+/-0.84 at 4-h to 3.30+/-0.89 at 24-h imaging. Two of these regions in one patient showed a severe perfusion score of 0 at 4 h, and complete reversibility at 24 hours, with a mean score improvement of 4. Another patient had three severe perfusion defects; two of them redistributed partially at 4 h and completely at 24 h. The remaining segment with a perfusion score of 0 at 4 h, presented complete reversibility with a score of 4 at 24 h. Two (4%) patients revealed significant reversibility at 24 h in a region that was severely underperfused after post-reinjection imaging at 4 h. Among group B patients, 75% (6/8) had recent acute ischemic syndrome, compared with only 13% (5/38) in group A (P = 0. 001). Among 11 patients with unstable angina, six (55%) had evidence of delayed 24-h reversibility, compared with 2 of 35 (6%) patients without clinically acute ischemia (P = 0.001). On follow-up, there were seven (17%) cardiac deaths among the 38 group A patients but three (38%) among the eight group B patients (P = 0.3). These findings suggest that although the presence of delayed 24-h 201Tl, post-reinjection reversibility is infrequent, it has potential clinical importance. Thus, delayed 24-h imaging should be considered in the context of unstable angina or other acute coronary syndromes.

Use of Iodine-123 as a Diagnostic Tracer for Neck and Whole-Body Scanning in Patients with Well-Differentiated Thyroid Cancer

To determine whether 123 I can be used as a safe and effective alternative tracer to 131 I for imaging remnant tissue and for searching for metastatic lesions of well-differentiated thyroid cancer. We studied a series of 16 patients (10 women and 6 men; 29 to 73 years of age) who had well-differentiated thyroid cancer and had undergone thyroidectomy and subsequent radioiodine treatment. Diagnostic 10 mCi (either preablation or postablation) were compared with the 5- to 7-day 131 I posttherapy scans (doses, 75 to 200 mCi). Scans were jointly interpreted by nuclear medicine and endocrinology staff members. Of the 16 patients, 15 had concordant findings between the 123 I diagnostic images and the corresponding 131 I posttherapy scans. Only one patient had additional lesions noted on the posttherapy 131 I scan, which was attributed to the higher dose the patient received during radioiodine treatment (a 6% discordance rate). This discordance, however, would not have changed the patient treatment. No advantage was noted for delayed imaging at 48 hours; the 24-hour images were satisfactory. The 123 I scans were of higher resolution than the 131 I scans. Diagnostic 123 I scans are an acceptable alternative to 131 I scanning for whole-body imaging in well-differentiated thyroid cancer and demonstrate adequate imaging of thyroid remnant tissue or metastatic lesions from thyroid carcinoma comparable to the post-therapy scans. 123 I scans also offer greater convenience to patients because they do not have to return for 48- or 72-hour scans. Furthermore, they facilitate earlier institution of therapy by decreasing the interval between diagnostic scanning and radioiodine treatment.

Regional thickening on gated tomography for detection of reversible ischemia in severe stress perfusion defects: A comparison with resting and 24-hour redistribution thallium images

Regional thickening on gated tomography for detection of reversible ischemia in severe stress perfusion defects: A comparison with resting and 24-hour redistribution thallium images