Alkylphosphocholine analogs incorporating a chelating moiety that is chelated to gadolinium are disclosed herein. The alkylphophocholine analogs are compounds having the formula: ##STR00001## or a salt thereof. R.sub.1 includes a chelating agent that is chelated to a gadolinium atom; a is 0 or 1; n is an integer from 12 to 30; m is 0 or 1; Y is H, OH, COOH, COOX, OCOX, or OX, wherein X is an alkyl or an arylalkyl; R.sub.2 is N.sup.+H.sub.3, N.sup.+H.sub.2Z, N.sup.+HZ.sub.2, or N.sup.+Z.sub.3, wherein each Z is independently an alkyl or an aroalkyl; and b is 1 or 2. The compounds can be used to detect solid tumors or to treat solid tumors. In detection/imaging applications, the gadolinium emits signals that are detectable using magnetic resonance imaging. In therapeutic treatment, the gadolinium emits tumor-targeting charged particles when exposed to epithermal neutrons.