Comparative study of fast MR imaging: quantitative analysis on image quality and efficiency among various time frames and contrast behaviors

The purpose of this study is to quantitatively compare the image quality and efficiency provided by widely available fast MR imaging pulse sequences. A composite phantom with various T1 and T2 values and subjected to periodic motion was imaged at 1.5 T. The fast MRI sequences evaluated included fast spin-echo (FSE), single shot fast spin-echo (SSFSE), echo-planar imaging (EPI), multi-slice gradient recalled (MPGR), fast MPGR (FMPGR), and fast multi-slice spoiled gradient echo (FMPSPGR). T1-weighted (T1WI), T2-weighted (T2WI), proton-density-weighted (PDWI), and T2*-weighted (T2*WI) images were evaluated in breath-hold and non-breath-hold time frames. Analysis included measurement of image signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), nonuniformity, ghosting ratio, SNR per unit time and CNR per unit time. Among fast T2WI sequences, FSE with breath-hold time frame resulted in the highest image quality and in superior SNR and CNR efficiency by a factor of 5 or 6 as compared with conventional spin echo sequence. Among fast T1WI sequences, FMPGR and FMPSPGR both with non-breath-hold time frame produced the highest image quality and SNR and CNR efficiency by a factor of greater than 5 as compared with conventional spin echo. Among fast PDWI and T2*WI sequences, FSE produced the highest SNR and CNR, and was maximally efficient with a factors of greater than 6 as compared with conventional spin echo.     

The value of specific MRI features in the evaluation of suspected placental invasion

OBJECTIVE: The objective of this study was to determine imaging features that may help predict the presence of placenta accreta, placenta increta or placenta percreta on prenatal MRI scanning. SUBJECTS AND METHODS: A retrospective review of the prenatal MR scans of 10 patients with a diagnosis of placenta accreta, placenta increta or placenta percreta made by pathologic and clinical reports and of 10 patients without placental invasion was performed. Two expert MRI readers were blinded to the patients' true diagnosis and were asked to score a total of 17 MRI features of the placenta and adjacent structures. The interrater reliability was assessed using kappa statistics. The features with a moderate kappa statistic or better (kappa > .40) were then compared with the true diagnosis for each observer. RESULTS: Seven of the scored features had an interobserver reliability of kappa > .40: placenta previa (kappa = .83); abnormal uterine bulging (kappa = .48); intraplacental hemorrhage (kappa = .51); heterogeneity of signal intensity on T2-weighted (T2W) imaging (kappa = .61); the presence of dark intraplacental bands on T2W imaging (kappa = .53); increased placental thickness (kappa = .69); and visualization of the myometrium beneath the placenta on T2W imaging (kappa = .44). Using Fisher's two-sided exact test, there was a statistically significant difference between the proportion of patients with placental invasion and those without placental invasion for three of the features: abnormal uterine bulging (Rater 1, P = .005; Rater 2, P = .011); heterogeneity of T2W imaging signal intensity (Rater 1, P = .006; Rater 2, P = .010); and presence of dark intraplacental bands on T2W imaging (Rater 1, P = .003; Rater 2, P = .033). CONCLUSIONS: MRI can be a useful adjunct to ultrasound in diagnosing placenta accreta prenatally. Three features that are seen on MRI in patients with placental invasion appear to be useful for diagnosis: uterine bulging; heterogeneous signal intensity within the placenta; and the presence of dark intraplacental bands on T2W imaging.     

Medial tibial pain: a dynamic contrast-enhanced MRI study.

The purpose of this study was to compare the sensitivity of different magnetic resonance imaging (MRI) sequences to depict periosteal edema in patients with medial tibial pain. Additionally, we evaluated the ability of dynamic contrast-enhanced imaging (DCES) to depict possible temporal alterations in muscular perfusion within compartments of the leg. Fifteen patients with medial tibial pain were examined with MRI. T1-, T2-weighted, proton density axial images and dynamic and static phase post-contrast images were compared in ability to depict periosteal edema. STIR was used in seven cases to depict bone marrow edema. Images were analyzed to detect signs of compartment edema. Region-of-interest measurements in compartments were performed during DCES and compared with controls. In detecting periosteal edema, post-contrast T1-weighted images were better than spin echo T2-weighted and proton density images or STIR images, but STIR depicted the bone marrow edema best. DCES best demonstrated the gradually enhancing periostitis. Four subjects with severe periosteal edema had visually detectable pathologic enhancement during DCES in the deep posterior compartment of the leg. Percentage enhancement in the deep posterior compartment of the leg was greater in patients than in controls. The fast enhancement phase in the deep posterior compartment began slightly slower in patients than in controls, but it continued longer. We believe that periosteal edema in bone stress reaction can cause impairment of venous flow in the deep posterior compartment. MRI can depict both these conditions. In patients with medial tibial pain, MR imaging protocol should include axial STIR images (to depict bone pathology) with T1-weighted axial pre and post-contrast images, and dynamic contrast enhanced imaging to show periosteal edema and abnormal contrast enhancement within a compartment.     

Chorioangioma: antenatal diagnosis with fast MR imaging

We report a case of chorioangioma of the placenta, in which fast magnetic resonance imaging (MRI) was useful adjunct to ultrasonography for the antenatal diagnosis. MRI allowed clear demonstration of 6.8 x 6.0 cm solid placental mass along with hydramnios and anatomically normal fetus. On T(1)-weighted breath-hold spoiled gradient-echo (fast low-angle shot [FLASH]) images, chorioangioma was mostly isointense to the placenta, but had an area of high signal intensity near the base and at the periphery, suggestive of hemorrhage. On T(2)-weighted half-Fourier single-shot fast spin echo (HASTE) images, the mass showed heterogeneous high signal intensity, but had an area of low signal intensity near the surface.     

MRI appearance of placenta percreta and placenta accreta.

The purpose of this paper is to describe the magnetic resonance imaging (MR) features of placenta accreta and percreta. We retrospectively reviewed MRI findings in four cases of placenta accreta/percreta to determine features which assist in identifying the presence and extent of placental implantation abnormality. All patients had ultrasound (US) examinations. Pathologic correlation was available in all cases. There were two cases of placenta percreta and two cases of placenta accreta. All cases were treated by hysterectomy. In the two cases of placenta percreta, the placenta demonstrated transmural extension through the uterus (percreta) on MRI. In the two cases of placenta accreta, the location of thinning in the uterine wall correlated with the location of placental invagination into the myometrium at pathology. US correlation was available in all four cases. Gray scale US did not demonstrate placental invasion in any of the four cases of placenta accreta/percreta, however, in two of three cases in which color Doppler was performed, there was flow at the uterine margin suspicious for implantation abnormality. In conclusion, MRI is useful for identifying the presence and extent of placenta accreta/percreta.     

MR imaging of radiation osteitis in the sacroiliac joints

The purpose of this study was to analyze magnetic resonance (MR) images of radiation osteitis of sacroiliac joints, retrospectively. Seven patients with radiation osteitis, which was diagnosed by pelvic plain radiographs and CT images, underwent MRI. T(1)-weighted spin echo images and T(2)-weighted fast spin echo images were obtained in all patients. Four patients were examined after gadolinium injection. Major signal changes of radiation osteitis were distributed on the iliac side. T(1)-weighted images showed diffuse low intensity both in sacral and iliac sides. T(2)-weighted images showed very low intensity adjacent to sacroiliac joints, but mixed intensity was illustrated apart from joints, and high intensity in the peripheral areas. Radiation osteitis showed slight to mild, but irregular enhancement in four patients after gadolinium administration. MRI can illustrate abnormal bone change distribution and is useful for diagnosing this entity by characteristic intensity patterns on T(1)-weighted images with and without gadolinium and T(2)-weighted image. However, the diagnosis of accompanied insufficiency fractures in the area of radiation osteitis is occasionally difficult with conventional MRI.     

A fast screening protocol for carotid plaques imaging using 3D multi-contrast MRI without contrast agent

PurposeTo implement a fast (~ 15 min) MRI protocol for carotid plaque screening using 3D multi-contrast MRI sequences without contrast agent on a 3 Tesla MRI scanner.Materials and methods7 healthy volunteers and 25 patients with clinically confirmed transient ischemic attack or suspected cerebrovascular ischemia were included in this study. The proposed protocol, including 3D T1-weighted and T2-weighted SPACE (variable-flip-angle 3D turbo spin echo), and T1-weighted magnetization prepared rapid acquisition gradient echo (MPRAGE) was performed first and was followed by 2D T1-weighted and T2-weighted turbo spin echo, and post-contrast T1-weighted SPACE sequences. Image quality, number of plaques, and vessel wall thicknesses measured at the intersection of the plaques were evaluated and compared between sequences.ResultsAverage examination time of the proposed protocol was 14.6 min. The average image quality scores of 3D T1-weighted, T2-weighted SPACE, and T1-weighted magnetization prepared rapid acquisition gradient echo were 3.69, 3.75, and 3.48, respectively. There was no significant difference in detecting the number of plaques and vulnerable plaques using pre-contrast 3D images with or without post-contrast T1-weighted SPACE. The 3D SPACE and 2D turbo spin echo sequences had excellent agreement (R = 0.96 for T1-weighted and 0.98 for T2-weighted, p < 0.001) regarding vessel wall thickness measurements.ConclusionThe proposed protocol demonstrated the feasibility of attaining carotid plaque screening within a 15-minute scan, which provided sufficient anatomical coverage and critical diagnostic information. This protocol offers the potential for rapid and reliable screening for carotid plaques without contrast agent.     

Exophytic benign tumors of the liver: appearance on MRI.

The purpose of our study was to determine the MR imaging appearance of exophytic benign liver tumors on precontrast and postgadolinium images. We reviewed our 9.5 year experience with MRI of the liver with dynamic gadolinium enhanced imaging to identify four patients with five histologically proven exophytic benign liver tumors. The histological diagnoses were cavernous hemangioma (2), focal nodular hyperplasia (FNH) (1), and hepatocellular adenoma (HCA) (2 exophytic adenomas in a patient with adenomatosis of the liver). All MRI studies were performed at 1.5 T and included: in-phase and out-of-phase T1-weighted spoiled gradient echo (SGE), T2-weighted fat-suppressed echo train spin echo, single shot T2-weighted sequences, and serial postgadolinium T1-weighted SGE sequences without and with fat-suppression. Prospective interpretations were reviewed and retrospective consensus readings of all MR images were performed assessing location, size, origin, morphology, visibility of the connection to the liver, signal characteristics on precontrast T1-weighted and T2-weighted images, and enhancement patterns on serial postgadolinium images. Three of the five tumors were pedunculated and connected to the liver by a thin stalk, which was prospectively identified in one patient. On precontrast and serial postgadolinium images, all exophytic tumors showed signal characteristics comparable to imaging features of standard intraparenchymal benign liver tumors. Our findings illustrate that the characteristic T1, T2, and postgadolinium imaging findings of these tumors permit correct identification of their liver origin despite their exophytic location, even if their connection with liver is not visualized.     

Recurrent hepatocellular carcinoma versus radiation-induced hepatic injury: differential diagnosis with MR imaging

The objective of this study was to assess the value of MR imaging in the differentiation between a recurrent hepatocellular carcinoma (HCC) and a radiation-induced hepatic injury. Nine male patients with suspected recurrence after radiotherapy for HCC underwent T(2)-, T(1)-weighted imaging and Gd-DTPA enhanced dynamic studies. T(2) relaxation times, signal intensity ratios in T(1)-weighted images (WI) and the relative enhancement of the dynamic study were calculated. Recurrent tumors and the irradiated area showed similar image characteristics: hypointense in T(1)-WI and hyperintense in T(2)-WI. T(2) values and signal intensity ratios in the T(1)-WI were not significantly different. In the gadolinium-enhanced dynamic study, a recurrent HCC showed early enhancement, followed by a rapid washout. However, the irradiated liver parenchyma showed hyperintensity from an early phase, and contrast enhancement tended to be more prominent and prolonged at the end of the dynamic studies. The characteristic findings of the dynamic MR study enable us to distinguish between a recurrent HCC and a radiation-induced hepatic injury.     

Hepatic alveolar echinococcosis: MRI findings

The purpose of this study was to describe the magnetic resonance imaging (MRI) appearance of hepatic alveolar echinococcosis (HAE) on T(1)-weighted, T(2)-weighted and postgadolinium images. A total of 13 lesions were demonstrated in 13 patients. All patients underwent MR examination at 1 T imager. MR examinations included precontrast T(1)-weighted breathing averaged spin echo (SE), breath-hold spoiled gradient echo, T(2)-weighted TSE sequences with and without fat suppression, and T(1)-weighted breath-hold spoiled gradient echo (SGE) sequence following i.v. after gadolinium administration. All lesions were confirmed with histopathology. HAE hepatic lesions revealed geographic patterns of variable signal intensities on noncontrast T(1)- and T(2)-weighted images. Slightly hyperintense, iso- and hypointense signal on T(1)-weighted images corresponded to calcified regions, which appeared hypo-isointense signal on T(2)-weighted images. Necrotic areas were hypointense signal on T(1)-weighted and hyperintense signal on T(2)-weighted images. On postgadolinium images, lesions did not reveal enhancement. Dilatation of intrahepatic bile ducts distal to HAE abscesses were observed in five patients and portal vein invasion or compression was observed in four patients, lobar atrophy of the liver was coexistent finding in cases with portal vein compression. The MRI appearance of HAE abscesses included large irregularly marginated masses with heterogenous signal on T(1)- and T(2)-weighted images and lack of enhancement with gadolinium.     

Giant hemangioma of the liver: MR imaging characteristics in 24 patients

We retrospectively reviewed the magnetic resonance imaging (MRI) of giant hemangiomas in 24 patients. MRI studies comprised T1-weighted, T2-weighted and serial gadolinium-enhanced spoiled gradient echo (SGE) images. Morphologic features, signal characteristics and enhancement patterns were assessed. Histopathologic evaluation was obtained in nine patients. On T2-weighted images all lesions (size 5.7-24 cm) were hyperintense relative to the spleen and two dominant patterns of heterogeneity were demonstrated: a central heterogeneous area of either bright, dark, or mixed signal intensity, and a network of multiple fibrous septa of low signal intensity. Histopathologic evaluation of two lesions with a central bright area demonstrated the presence of hypocellular myxoid tissue. Central enhancement (9 lesions) and an irregular flame-shaped peripheral pattern of enhancement (12 lesions) were present in lesions with a mean diameter greater than 10 cm. Although giant hemangiomas show greater variability in their MR imaging appearance, an accurate diagnosis can be made through still characteristic features of high signal intensity on T2-weighted images and discontinuous peripheral enhancement.     

MR imaging findings of infectious cholangitis

The purpose of this study was to evaluate the appearance of infectious cholangitis on MRI. The MR images of 13 patients (9 women, 4 men; age range, 14-79 years) with clinically confirmed infectious cholangitis, who represent our complete 9.5 year experience with this entity, were retrospectively evaluated. All MR studies were performed at 1.5 T and included: in-phase and out-of-phase T(1)-weighted spoiled gradient echo (SGE), T(2)-weighted fat-suppressed echo train spin echo, single shot T(2)-weighted sequences, and serial postgadolinium T(1)-weighted SGE sequences without and with fat-suppression. The biliary ductal system was evaluated regarding presence of dilatation, stenosis, wall irregularities, wall thickening, and gadolinium enhancement of duct walls. The liver parenchyma was evaluated regarding focal signal abnormalities on precontrast and serial postgadolinium images. Biliary ductal dilatation was observed in 100% of patients. Mild to moderate thickening of bile duct walls combined with increased enhancement on postgadolinium images was observed in 92% of patients. The liver parenchyma showed periportal or wedge-shaped areas of hyperintense signal on T(2)-weighted images in 69% of patients. On T(1)-weighted images, 54% of patients showed areas of hypointense signal and 15% of patients showed wedge-shaped hyperintense areas. Areas with increased enhancement on immediate postgadolinium SGE were observed in 58% of patients, and in 42% of patients increased enhancement persisted on 2 min postgadolinium fat-suppressed images. Distinctive MRI findings on pre- and postgadolinium images are appreciated for infectious cholangitis.     

Hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide-enhanced magnetic resonance imaging in cirrhosis or chronic hepatitis: comparison of four magnetic resonance sequences for lesion conspicuity

Purpose

The aim of this study was to determine the adequate MR sequence for the lesion conspicuity of hepatocellular lesions with increased iron uptake on superparamagnetic iron oxide (SPIO)-enhanced MRI.

Materials and Methods

SPIO-enhanced MRI was performed using a 1.5-T system. Among 25 patients with hypovascular hepatocellular nodules on contrast-enhanced dynamic CT (no early enhancement at arterial phase and hypoattenuation at equilibrium phase), 39 lesions with increased iron uptake on SPIO-enhanced MRI were evaluated. SPIO-enhanced MRI included (1) T1-weighted in-phase gradient recalled echo (GRE) images, (2) T2-weighted fast spin echo (FSE) images, (3) T2*-weighted GRE with moderate TE (7 ms) and (4) long TE (12 ms). The lesion-to-liver contrast-to-noise ratios of the hepatocellular nodule and the signal-to-noise ratio (SNR) of the hepatic parenchyma were calculated by one radiologist for a quantitative assessment. MR images were reviewed retrospectively by two independent radiologists to compare the subjective lesion conspicuity in each image set based on a four-point rating scale.

Result

The mean lesion-to-liver contrast-to-noise ratios with T2*-weighted GRE with moderate TE (7 ms) was highest (5.79±3.71) and was significantly higher than those with T1-weighted, in-phase images (3.79±3.23, P<.01), T2-weighted images (2.72±1.52, P<.001) and T2*-weighted GRE with long TE (12 ms) (3.93±2.69, P<.05). The subjective rating of lesion conspicuity was best on the T2*-weighted GRE with moderate TE (7 ms), followed by that on the T2*-weighted GRE with moderate TE (7 ms; P<.05).

Conclusion

T2*-weighted GRE sequence with moderate TE (7 ms) showed high lesion-to-liver contrast-to-noise ratios in hepatocellular lesions with increased iron uptake on SPIO-enhanced MRI, indicating better lesion conspicuity of hypointense hepatocellular nodules in cirrhosis or chronic hepatitis.     

Granulomatous hepatitis: MRI findings.

The purpose of this study was to describe the magnetic resonance imaging findings of granulomatous hepatitis on T1-weighted, T2-weighted and postgadolinium images. Eight patients with histopathological diagnosis of granulomatous hepatitis were evaluated in this study. MRI examinations included precontrast T1-weighted breath-hold spoiled gradient echo, breathing independent STIR sequences, and T1-weighted breath-hold spoiled gradient-echo sequence following after i.v. gadolinium administration in arterial, intermediate and late phases. Diffuse nodular liver involvement was visualized in all patients. Nodules were consistent with granulomas and were 0.5-4.5 cm in diameter. Caseating granulomas were intermediate and high signal on T2-weighted, low signal on T1-weighted images. They revealed no enhancement in two patients, and enhanced in one patient. Noncaseating granulomas revealed intermediate signal on T1, and T2-weighted images and increased enhancement on arterial phase images with persisting enhancement in late phase images. Portal lymph nodes were visible in five patients. Splenomegaly was present in five patients. Granulomatous hepatitis has spectrum of MRI features, to be considered in differential diagnosis with other diffuse nodular liver pathologies.     

High density barium sulfate suspension for MRI: optimization of concentration for bowel opacification.

In this in vitro study of a potential oral MRI contrast agent, barium sulfate suspension (BSS), the object was to examine the effect of varying barium sulfate concentration on signal intensity while keeping suspension additives the same; and to optimize the concentration of a specific preparation of BSS. A phantom was used to test suspensions with concentrations of barium sulfate ranging from 90% to 220% w/v. T1-weighted, T2-weighted, and gradient echo sequences all showed a decrease in signal as concentration was increased to 170%. Between 170% and 220%, the signal intensity was constant on the T1-weighted and T2-weighted sequences. With the proton density and gradient echo sequences, there was a slower rate of decline in the signal intensity in the 170 to 220% range of BSS concentrations. We conclude that BSS with a concentration in the range of 170% to 220% w/v is optimum for the specific preparation used. We speculate that the behavior of the signal-to-noise ratio with changing concentration is explained by factors including proton density, T1 relaxation enhancement, diffusion effects, and magnetic field inhomogeneity, depending on the particular pulse sequence used.     

Dynamic contrast-enhanced MRI of Implanted VX2 tumors in rabbit muscle: comparison of Gd-DTPA and NMS60

We studied the dynamics of injected contrast enhancement in implanted VX2 tumors in rabbit thigh muscle. We compared two contrast agents Gd-DTPA and NMS60, a novel gadolinium containing trimer of molecular weight 2.1 kd. T1-weighted spin echo images were acquired preinjection and at 5-60 min after i.v. injection of 0.1 mmol/kg of agent. Dynamic T1-weighted SPGR images (1.9 s/image) were acquired during the bolus injection. Male NZW rabbits (n = 13) were implanted with approximately 2 x 10(6) VX2 tumor cells and grew tumors of 28+/-27 mL over 12 to 21 days. NMS60 showed significantly greater peak enhancement in muscle, tumor rim, and core compared to DTPA in both T1-weighted and SPGR images. NMS60 also showed delayed peak enhancement in the dynamic scans (compared to Gd-DTPA) and significantly reduced leakage rate constant into the extravascular space for tumor rim (K21 = 5.1 min(-1) vs. 11.5 min(-1) based on a 2 compartment kinetic model). The intermediate weight contrast agent NMS60 offers greater tumor enhancement than Gd-DTPA and may offer improved regional differentiation on the basis of vascular permeability in tumors.     

Water-selective spectral-spatial contrast-enhanced breast MRI for cancer detection in patients with extracapsular and injected free silicone

OBJECTIVE: This study investigates the use of contrast-enhanced, T1-weighted, water-selective spectral-spatial 3D gradient echo magnetic resonance imaging (MRI) with magnetization transfer (3DSSMT) for detecting breast cancer in patients with intraparenchymal silicone. CONCLUSION: Water-selective 3DSSMT provides superior fat and silicone suppression in patients with free silicone as compared with conventional fat saturation. It enables direct, high-quality, high-spatial-resolution, T1-weighted breast MRI of contrast enhancement without the need for subtraction processing and aids diagnosis of cancer in the breast with free silicone.     

Hemorrhagic cerebral metastases from thyroid cancer on T2*-weighted gradient echo MRI

We report a case of multiple hemorrhagic cerebral metastases from papillary thyroid cancer, with reference to T(2)*-weighted gradient echo (GRE) magnetic resonance imaging (MRI). Small metastatic nodules were recognized as round nodules with signal loss on T(2)*-weighted GRE MRI, and were more pronounced compared with other sequences. Lesions were later confirmed as hemorrhagic on T(1)- and T(2)-weighted MRI. T(2)*-weighted GRE MRI was a sensitive tool for early detection of metastases displaying hemorrhagic changes.     

Magnetic resonance imaging of the uterus at an ultra low (0.02 T) magnetic field.

In vivo pelvic imaging of 39 women and in vitro relaxation time measurements of four uterine specimens were performed using an ultra low field (0.02 T) MRI unit. Average T1 times measured in vitro at 37 degrees C for the myometrium and endometrium were 206 ms (SD 47 ms) and 389 ms (SD 21 ms), respectively. Corresponding T2 times were 95 ms (SD 20 ms) and 167 ms (SD 13 ms). The proton relaxation of almost all myometrial specimens proved to be biexponential, but of all endometrial specimens was monoexponential. Contrast measurements between endometrium versus myometrium and myometrium versus the junctional zone were performed after imaging 18 volunteer women using different pulse sequence parameters. Normal uterine structures were optimally demonstrated by SE 700/70. Relatively short repetition times could be used, because spin-lattice relaxation times were short at the low magnetic field. Consequently, the short repetition times allowed averaging of four excitations to create adequate images within an acceptable scanning time. In addition to T2-weighted images a T1-weighted inversion recovery sequence with a short inversion time of 50 ms (IR 1000/50/40) adequately differentiated the three uterine zones. Although pathologic lesions of the uterus including leiomyomas, anomalies and carcinomas were well demonstrated, especially with the T2-weighted spin echo pulse sequence, further investigations are needed to evaluate the optimal technique for ultra low field MR imaging of uterine tumors.     

MRI characterization of residual mediastinal masses in Hodgkin's disease: long-term follow-up

Our purpose was to evaluate the role of MRI in distinguishing fibrous from active residual masses in treated Hodgkin's disease. Forty patients with residual mediastinal mass larger than 1.5 cm underwent MRI 1, 3, 6, and 12 months after the end of cycles of prescribed chemotherapy or combined chemoradiotherapy. The MRI examinations were performed on a 0.5 and a 1.5 T systems, using T(1) before and after gadolinium injection and T(2)-weighted sequences. Each time the residual mass was evaluated in size and signal intensity on spin echo (SE) T(2)-weighted images and on SE T(1)-weighted images after contrast medium. Low signal intensity and low contrast enhancement were considered signs of inactive residues; homogeneous high signal intensity and high contrast enhancement were indicative of active residual disease; heterogeneous signal intensity and heterogeneous contrast enhancement were indicative of partial remission or necrotic/inflammatory phenomena. MR showed high diagnostic accuracy in the evaluation of Hodgkin's mediastinal residues after treatment, if performed at least 6 months after the end of therapy, reaching the highest sensitivity and specificity values at 12 month follow-up (considering the three parameters-T(2) signal intensity, contrast-enhancement, and size-all together). If we consider the single parameters individually, we can observe that size variation remains the more valuable parameter to predict or to exclude a relapse. MR diagnostic accuracy at the 6-month follow-up was lower due to the higher incidence of inhomogeneous pattern. The accuracy of MR performed at 1 and at 3 months after the end of therapy was not satisfying. This represents a clinical problem because the most important clinical decisions have to be taken just in this early post-treatment phase.